system/linux
system/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux synced 2024-11-05 18:23:50 +00:00
Code Issues Projects Releases Packages Wiki Activity
linux/mm/filemap.c
Matthew Wilcox (Oracle) 5d74b2ab2c mm: make lock_folio_maybe_drop_mmap() VMA lock aware 
Patch series "Handle more faults under the VMA lock", v2.

At this point, we're handling the majority of file-backed page faults
under the VMA lock, using the ->map_pages entry point.  This patch set
attempts to expand that for the following siutations:

 - We have to do a read.  This could be because we've hit the point in
   the readahead window where we need to kick off the next readahead,
   or because the page is simply not present in cache.
 - We're handling a write fault.  Most applications don't do I/O by writes
   to shared mmaps for very good reasons, but some do, and it'd be nice
   to not make that slow unnecessarily.
 - We're doing a COW of a private mapping (both PTE already present
   and PTE not-present).  These are two different codepaths and I handle
   both of them in this patch set.

There is no support in this patch set for drivers to mark themselves as
being VMA lock friendly; they could implement the ->map_pages
vm_operation, but if they do, they would be the first.  This is probably
something we want to change at some point in the future, and I've marked
where to make that change in the code.

There is very little performance change in the benchmarks we've run;
mostly because the vast majority of page faults are handled through the
other paths.  I still think this patch series is useful for workloads that
may take these paths more often, and just for cleaning up the fault path
in general (it's now clearer why we have to retry in these cases).


This patch (of 6):

Drop the VMA lock instead of the mmap_lock if that's the one which
is held.

Link: https://lkml.kernel.org/r/20231006195318.4087158-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20231006195318.4087158-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-10-18 14:34:14 -07:00

4292 lines
121 KiB
C
Raw Blame History

// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/mm/filemap.c
*
* Copyright (C) 1994-1999 Linus Torvalds
*/
/*
* This file handles the generic file mmap semantics used by
* most "normal" filesystems (but you don't /have/ to use this:
* the NFS filesystem used to do this differently, for example)
*/
#include <linux/export.h>
#include <linux/compiler.h>
#include <linux/dax.h>
#include <linux/fs.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
#include <linux/capability.h>
#include <linux/kernel_stat.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/syscalls.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/error-injection.h>
#include <linux/hash.h>
#include <linux/writeback.h>
#include <linux/backing-dev.h>
#include <linux/pagevec.h>
#include <linux/security.h>
#include <linux/cpuset.h>
#include <linux/hugetlb.h>
#include <linux/memcontrol.h>
#include <linux/shmem_fs.h>
#include <linux/rmap.h>
#include <linux/delayacct.h>
#include <linux/psi.h>
#include <linux/ramfs.h>
#include <linux/page_idle.h>
#include <linux/migrate.h>
#include <linux/pipe_fs_i.h>
#include <linux/splice.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include "internal.h"
#define CREATE_TRACE_POINTS
#include <trace/events/filemap.h>
/*
* FIXME: remove all knowledge of the buffer layer from the core VM
*/
#include <linux/buffer_head.h> /* for try_to_free_buffers */
#include <asm/mman.h>
#include "swap.h"
/*
* Shared mappings implemented 30.11.1994. It's not fully working yet,
* though.
*
* Shared mappings now work. 15.8.1995 Bruno.
*
* finished 'unifying' the page and buffer cache and SMP-threaded the
* page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
*
* SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
*/
/*
* Lock ordering:
*
* ->i_mmap_rwsem (truncate_pagecache)
* ->private_lock (__free_pte->block_dirty_folio)
* ->swap_lock (exclusive_swap_page, others)
* ->i_pages lock
*
* ->i_rwsem
* ->invalidate_lock (acquired by fs in truncate path)
* ->i_mmap_rwsem (truncate->unmap_mapping_range)
*
* ->mmap_lock
* ->i_mmap_rwsem
* ->page_table_lock or pte_lock (various, mainly in memory.c)
* ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
*
* ->mmap_lock
* ->invalidate_lock (filemap_fault)
* ->lock_page (filemap_fault, access_process_vm)
*
* ->i_rwsem (generic_perform_write)
* ->mmap_lock (fault_in_readable->do_page_fault)
*
* bdi->wb.list_lock
* sb_lock (fs/fs-writeback.c)
* ->i_pages lock (__sync_single_inode)
*
* ->i_mmap_rwsem
* ->anon_vma.lock (vma_merge)
*
* ->anon_vma.lock
* ->page_table_lock or pte_lock (anon_vma_prepare and various)
*
* ->page_table_lock or pte_lock
* ->swap_lock (try_to_unmap_one)
* ->private_lock (try_to_unmap_one)
* ->i_pages lock (try_to_unmap_one)
* ->lruvec->lru_lock (follow_page->mark_page_accessed)
* ->lruvec->lru_lock (check_pte_range->isolate_lru_page)
* ->private_lock (page_remove_rmap->set_page_dirty)
* ->i_pages lock (page_remove_rmap->set_page_dirty)
* bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
* ->inode->i_lock (page_remove_rmap->set_page_dirty)
* ->memcg->move_lock (page_remove_rmap->folio_memcg_lock)
* bdi.wb->list_lock (zap_pte_range->set_page_dirty)
* ->inode->i_lock (zap_pte_range->set_page_dirty)
* ->private_lock (zap_pte_range->block_dirty_folio)
*/
static void page_cache_delete(struct address_space *mapping,
struct folio *folio, void *shadow)
{
XA_STATE(xas, &mapping->i_pages, folio->index);
long nr = 1;
mapping_set_update(&xas, mapping);
xas_set_order(&xas, folio->index, folio_order(folio));
nr = folio_nr_pages(folio);
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
xas_store(&xas, shadow);
xas_init_marks(&xas);
folio->mapping = NULL;
/* Leave page->index set: truncation lookup relies upon it */
mapping->nrpages -= nr;
}
static void filemap_unaccount_folio(struct address_space *mapping,
struct folio *folio)
{
long nr;
VM_BUG_ON_FOLIO(folio_mapped(folio), folio);
if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(folio_mapped(folio))) {
pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
current->comm, folio_pfn(folio));
dump_page(&folio->page, "still mapped when deleted");
dump_stack();
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
if (mapping_exiting(mapping) && !folio_test_large(folio)) {
int mapcount = page_mapcount(&folio->page);
if (folio_ref_count(folio) >= mapcount + 2) {
/*
* All vmas have already been torn down, so it's
* a good bet that actually the page is unmapped
* and we'd rather not leak it: if we're wrong,
* another bad page check should catch it later.
*/
page_mapcount_reset(&folio->page);
folio_ref_sub(folio, mapcount);
}
}
}
/* hugetlb folios do not participate in page cache accounting. */
if (folio_test_hugetlb(folio))
return;
nr = folio_nr_pages(folio);
__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr);
if (folio_test_swapbacked(folio)) {
__lruvec_stat_mod_folio(folio, NR_SHMEM, -nr);
if (folio_test_pmd_mappable(folio))
__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr);
} else if (folio_test_pmd_mappable(folio)) {
__lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr);
filemap_nr_thps_dec(mapping);
}
/*
* At this point folio must be either written or cleaned by
* truncate. Dirty folio here signals a bug and loss of
* unwritten data - on ordinary filesystems.
*
* But it's harmless on in-memory filesystems like tmpfs; and can
* occur when a driver which did get_user_pages() sets page dirty
* before putting it, while the inode is being finally evicted.
*
* Below fixes dirty accounting after removing the folio entirely
* but leaves the dirty flag set: it has no effect for truncated
* folio and anyway will be cleared before returning folio to
* buddy allocator.
*/
if (WARN_ON_ONCE(folio_test_dirty(folio) &&
mapping_can_writeback(mapping)))
folio_account_cleaned(folio, inode_to_wb(mapping->host));
}
/*
* Delete a page from the page cache and free it. Caller has to make
* sure the page is locked and that nobody else uses it - or that usage
* is safe. The caller must hold the i_pages lock.
*/
void __filemap_remove_folio(struct folio *folio, void *shadow)
{
struct address_space *mapping = folio->mapping;
trace_mm_filemap_delete_from_page_cache(folio);
filemap_unaccount_folio(mapping, folio);
page_cache_delete(mapping, folio, shadow);
}
void filemap_free_folio(struct address_space *mapping, struct folio *folio)
{
void (*free_folio)(struct folio *);
int refs = 1;
free_folio = mapping->a_ops->free_folio;
if (free_folio)
free_folio(folio);
if (folio_test_large(folio))
refs = folio_nr_pages(folio);
folio_put_refs(folio, refs);
}
/**
* filemap_remove_folio - Remove folio from page cache.
* @folio: The folio.
*
* This must be called only on folios that are locked and have been
* verified to be in the page cache. It will never put the folio into
* the free list because the caller has a reference on the page.
*/
void filemap_remove_folio(struct folio *folio)
{
struct address_space *mapping = folio->mapping;
BUG_ON(!folio_test_locked(folio));
spin_lock(&mapping->host->i_lock);
xa_lock_irq(&mapping->i_pages);
__filemap_remove_folio(folio, NULL);
xa_unlock_irq(&mapping->i_pages);
if (mapping_shrinkable(mapping))
inode_add_lru(mapping->host);
spin_unlock(&mapping->host->i_lock);
filemap_free_folio(mapping, folio);
}
/*
* page_cache_delete_batch - delete several folios from page cache
* @mapping: the mapping to which folios belong
* @fbatch: batch of folios to delete
*
* The function walks over mapping->i_pages and removes folios passed in
* @fbatch from the mapping. The function expects @fbatch to be sorted
* by page index and is optimised for it to be dense.
* It tolerates holes in @fbatch (mapping entries at those indices are not
* modified).
*
* The function expects the i_pages lock to be held.
*/
static void page_cache_delete_batch(struct address_space *mapping,
struct folio_batch *fbatch)
{
XA_STATE(xas, &mapping->i_pages, fbatch->folios[0]->index);
long total_pages = 0;
int i = 0;
struct folio *folio;
mapping_set_update(&xas, mapping);
xas_for_each(&xas, folio, ULONG_MAX) {
if (i >= folio_batch_count(fbatch))
break;
/* A swap/dax/shadow entry got inserted? Skip it. */
if (xa_is_value(folio))
continue;
/*
* A page got inserted in our range? Skip it. We have our
* pages locked so they are protected from being removed.
* If we see a page whose index is higher than ours, it
* means our page has been removed, which shouldn't be
* possible because we're holding the PageLock.
*/
if (folio != fbatch->folios[i]) {
VM_BUG_ON_FOLIO(folio->index >
fbatch->folios[i]->index, folio);
continue;
}
WARN_ON_ONCE(!folio_test_locked(folio));
folio->mapping = NULL;
/* Leave folio->index set: truncation lookup relies on it */
i++;
xas_store(&xas, NULL);
total_pages += folio_nr_pages(folio);
}
mapping->nrpages -= total_pages;
}
void delete_from_page_cache_batch(struct address_space *mapping,
struct folio_batch *fbatch)
{
int i;
if (!folio_batch_count(fbatch))
return;
spin_lock(&mapping->host->i_lock);
xa_lock_irq(&mapping->i_pages);
for (i = 0; i < folio_batch_count(fbatch); i++) {
struct folio *folio = fbatch->folios[i];
trace_mm_filemap_delete_from_page_cache(folio);
filemap_unaccount_folio(mapping, folio);
}
page_cache_delete_batch(mapping, fbatch);
xa_unlock_irq(&mapping->i_pages);
if (mapping_shrinkable(mapping))
inode_add_lru(mapping->host);
spin_unlock(&mapping->host->i_lock);
for (i = 0; i < folio_batch_count(fbatch); i++)
filemap_free_folio(mapping, fbatch->folios[i]);
}
int filemap_check_errors(struct address_space *mapping)
{
int ret = 0;
/* Check for outstanding write errors */
if (test_bit(AS_ENOSPC, &mapping->flags) &&
test_and_clear_bit(AS_ENOSPC, &mapping->flags))
ret = -ENOSPC;
if (test_bit(AS_EIO, &mapping->flags) &&
test_and_clear_bit(AS_EIO, &mapping->flags))
ret = -EIO;
return ret;
}
EXPORT_SYMBOL(filemap_check_errors);
static int filemap_check_and_keep_errors(struct address_space *mapping)
{
/* Check for outstanding write errors */
if (test_bit(AS_EIO, &mapping->flags))
return -EIO;
if (test_bit(AS_ENOSPC, &mapping->flags))
return -ENOSPC;
return 0;
}
/**
* filemap_fdatawrite_wbc - start writeback on mapping dirty pages in range
* @mapping: address space structure to write
* @wbc: the writeback_control controlling the writeout
*
* Call writepages on the mapping using the provided wbc to control the
* writeout.
*
* Return: %0 on success, negative error code otherwise.
*/
int filemap_fdatawrite_wbc(struct address_space *mapping,
struct writeback_control *wbc)
{
int ret;
if (!mapping_can_writeback(mapping) ||
!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
return 0;
wbc_attach_fdatawrite_inode(wbc, mapping->host);
ret = do_writepages(mapping, wbc);
wbc_detach_inode(wbc);
return ret;
}
EXPORT_SYMBOL(filemap_fdatawrite_wbc);
/**
* __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
* @mapping: address space structure to write
* @start: offset in bytes where the range starts
* @end: offset in bytes where the range ends (inclusive)
* @sync_mode: enable synchronous operation
*
* Start writeback against all of a mapping's dirty pages that lie
* within the byte offsets <start, end> inclusive.
*
* If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
* opposed to a regular memory cleansing writeback. The difference between
* these two operations is that if a dirty page/buffer is encountered, it must
* be waited upon, and not just skipped over.
*
* Return: %0 on success, negative error code otherwise.
*/
int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
loff_t end, int sync_mode)
{
struct writeback_control wbc = {
.sync_mode = sync_mode,
.nr_to_write = LONG_MAX,
.range_start = start,
.range_end = end,
};
return filemap_fdatawrite_wbc(mapping, &wbc);
}
static inline int __filemap_fdatawrite(struct address_space *mapping,
int sync_mode)
{
return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
}
int filemap_fdatawrite(struct address_space *mapping)
{
return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
}
EXPORT_SYMBOL(filemap_fdatawrite);
int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
loff_t end)
{
return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
}
EXPORT_SYMBOL(filemap_fdatawrite_range);
/**
* filemap_flush - mostly a non-blocking flush
* @mapping: target address_space
*
* This is a mostly non-blocking flush. Not suitable for data-integrity
* purposes - I/O may not be started against all dirty pages.
*
* Return: %0 on success, negative error code otherwise.
*/
int filemap_flush(struct address_space *mapping)
{
return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
}
EXPORT_SYMBOL(filemap_flush);
/**
* filemap_range_has_page - check if a page exists in range.
* @mapping: address space within which to check
* @start_byte: offset in bytes where the range starts
* @end_byte: offset in bytes where the range ends (inclusive)
*
* Find at least one page in the range supplied, usually used to check if
* direct writing in this range will trigger a writeback.
*
* Return: %true if at least one page exists in the specified range,
* %false otherwise.
*/
bool filemap_range_has_page(struct address_space *mapping,
loff_t start_byte, loff_t end_byte)
{
struct folio *folio;
XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
pgoff_t max = end_byte >> PAGE_SHIFT;
if (end_byte < start_byte)
return false;
rcu_read_lock();
for (;;) {
folio = xas_find(&xas, max);
if (xas_retry(&xas, folio))
continue;
/* Shadow entries don't count */
if (xa_is_value(folio))
continue;
/*
* We don't need to try to pin this page; we're about to
* release the RCU lock anyway. It is enough to know that
* there was a page here recently.
*/
break;
}
rcu_read_unlock();
return folio != NULL;
}
EXPORT_SYMBOL(filemap_range_has_page);
static void __filemap_fdatawait_range(struct address_space *mapping,
loff_t start_byte, loff_t end_byte)
{
pgoff_t index = start_byte >> PAGE_SHIFT;
pgoff_t end = end_byte >> PAGE_SHIFT;
struct folio_batch fbatch;
unsigned nr_folios;
folio_batch_init(&fbatch);
while (index <= end) {
unsigned i;
nr_folios = filemap_get_folios_tag(mapping, &index, end,
PAGECACHE_TAG_WRITEBACK, &fbatch);
if (!nr_folios)
break;
for (i = 0; i < nr_folios; i++) {
struct folio *folio = fbatch.folios[i];
folio_wait_writeback(folio);
folio_clear_error(folio);
}
folio_batch_release(&fbatch);
cond_resched();
}
}
/**
* filemap_fdatawait_range - wait for writeback to complete
* @mapping: address space structure to wait for
* @start_byte: offset in bytes where the range starts
* @end_byte: offset in bytes where the range ends (inclusive)
*
* Walk the list of under-writeback pages of the given address space
* in the given range and wait for all of them. Check error status of
* the address space and return it.
*
* Since the error status of the address space is cleared by this function,
* callers are responsible for checking the return value and handling and/or
* reporting the error.
*
* Return: error status of the address space.
*/
int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
loff_t end_byte)
{
__filemap_fdatawait_range(mapping, start_byte, end_byte);
return filemap_check_errors(mapping);
}
EXPORT_SYMBOL(filemap_fdatawait_range);
/**
* filemap_fdatawait_range_keep_errors - wait for writeback to complete
* @mapping: address space structure to wait for
* @start_byte: offset in bytes where the range starts
* @end_byte: offset in bytes where the range ends (inclusive)
*
* Walk the list of under-writeback pages of the given address space in the
* given range and wait for all of them. Unlike filemap_fdatawait_range(),
* this function does not clear error status of the address space.
*
* Use this function if callers don't handle errors themselves. Expected
* call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
* fsfreeze(8)
*/
int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
loff_t start_byte, loff_t end_byte)
{
__filemap_fdatawait_range(mapping, start_byte, end_byte);
return filemap_check_and_keep_errors(mapping);
}
EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors);
/**
* file_fdatawait_range - wait for writeback to complete
* @file: file pointing to address space structure to wait for
* @start_byte: offset in bytes where the range starts
* @end_byte: offset in bytes where the range ends (inclusive)
*
* Walk the list of under-writeback pages of the address space that file
* refers to, in the given range and wait for all of them. Check error
* status of the address space vs. the file->f_wb_err cursor and return it.
*
* Since the error status of the file is advanced by this function,
* callers are responsible for checking the return value and handling and/or
* reporting the error.
*
* Return: error status of the address space vs. the file->f_wb_err cursor.
*/
int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
{
struct address_space *mapping = file->f_mapping;
__filemap_fdatawait_range(mapping, start_byte, end_byte);
return file_check_and_advance_wb_err(file);
}
EXPORT_SYMBOL(file_fdatawait_range);
/**
* filemap_fdatawait_keep_errors - wait for writeback without clearing errors
* @mapping: address space structure to wait for
*
* Walk the list of under-writeback pages of the given address space
* and wait for all of them. Unlike filemap_fdatawait(), this function
* does not clear error status of the address space.
*
* Use this function if callers don't handle errors themselves. Expected
* call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
* fsfreeze(8)
*
* Return: error status of the address space.
*/
int filemap_fdatawait_keep_errors(struct address_space *mapping)
{
__filemap_fdatawait_range(mapping, 0, LLONG_MAX);
return filemap_check_and_keep_errors(mapping);
}
EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
/* Returns true if writeback might be needed or already in progress. */
static bool mapping_needs_writeback(struct address_space *mapping)
{
return mapping->nrpages;
}
bool filemap_range_has_writeback(struct address_space *mapping,
loff_t start_byte, loff_t end_byte)
{
XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
pgoff_t max = end_byte >> PAGE_SHIFT;
struct folio *folio;
if (end_byte < start_byte)
return false;
rcu_read_lock();
xas_for_each(&xas, folio, max) {
if (xas_retry(&xas, folio))
continue;
if (xa_is_value(folio))
continue;
if (folio_test_dirty(folio) || folio_test_locked(folio) ||
folio_test_writeback(folio))
break;
}
rcu_read_unlock();
return folio != NULL;
}
EXPORT_SYMBOL_GPL(filemap_range_has_writeback);
/**
* filemap_write_and_wait_range - write out & wait on a file range
* @mapping: the address_space for the pages
* @lstart: offset in bytes where the range starts
* @lend: offset in bytes where the range ends (inclusive)
*
* Write out and wait upon file offsets lstart->lend, inclusive.
*
* Note that @lend is inclusive (describes the last byte to be written) so
* that this function can be used to write to the very end-of-file (end = -1).
*
* Return: error status of the address space.
*/
int filemap_write_and_wait_range(struct address_space *mapping,
loff_t lstart, loff_t lend)
{
int err = 0, err2;
if (lend < lstart)
return 0;
if (mapping_needs_writeback(mapping)) {
err = __filemap_fdatawrite_range(mapping, lstart, lend,
WB_SYNC_ALL);
/*
* Even if the above returned error, the pages may be
* written partially (e.g. -ENOSPC), so we wait for it.
* But the -EIO is special case, it may indicate the worst
* thing (e.g. bug) happened, so we avoid waiting for it.
*/
if (err != -EIO)
__filemap_fdatawait_range(mapping, lstart, lend);
}
err2 = filemap_check_errors(mapping);
if (!err)
err = err2;
return err;
}
EXPORT_SYMBOL(filemap_write_and_wait_range);
void __filemap_set_wb_err(struct address_space *mapping, int err)
{
errseq_t eseq = errseq_set(&mapping->wb_err, err);
trace_filemap_set_wb_err(mapping, eseq);
}
EXPORT_SYMBOL(__filemap_set_wb_err);
/**
* file_check_and_advance_wb_err - report wb error (if any) that was previously
* and advance wb_err to current one
* @file: struct file on which the error is being reported
*
* When userland calls fsync (or something like nfsd does the equivalent), we
* want to report any writeback errors that occurred since the last fsync (or
* since the file was opened if there haven't been any).
*
* Grab the wb_err from the mapping. If it matches what we have in the file,
* then just quickly return 0. The file is all caught up.
*
* If it doesn't match, then take the mapping value, set the "seen" flag in
* it and try to swap it into place. If it works, or another task beat us
* to it with the new value, then update the f_wb_err and return the error
* portion. The error at this point must be reported via proper channels
* (a'la fsync, or NFS COMMIT operation, etc.).
*
* While we handle mapping->wb_err with atomic operations, the f_wb_err
* value is protected by the f_lock since we must ensure that it reflects
* the latest value swapped in for this file descriptor.
*
* Return: %0 on success, negative error code otherwise.
*/
int file_check_and_advance_wb_err(struct file *file)
{
int err = 0;
errseq_t old = READ_ONCE(file->f_wb_err);
struct address_space *mapping = file->f_mapping;
/* Locklessly handle the common case where nothing has changed */
if (errseq_check(&mapping->wb_err, old)) {
/* Something changed, must use slow path */
spin_lock(&file->f_lock);
old = file->f_wb_err;
err = errseq_check_and_advance(&mapping->wb_err,
&file->f_wb_err);
trace_file_check_and_advance_wb_err(file, old);
spin_unlock(&file->f_lock);
}
/*
* We're mostly using this function as a drop in replacement for
* filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
* that the legacy code would have had on these flags.
*/
clear_bit(AS_EIO, &mapping->flags);
clear_bit(AS_ENOSPC, &mapping->flags);
return err;
}
EXPORT_SYMBOL(file_check_and_advance_wb_err);
/**
* file_write_and_wait_range - write out & wait on a file range
* @file: file pointing to address_space with pages
* @lstart: offset in bytes where the range starts
* @lend: offset in bytes where the range ends (inclusive)
*
* Write out and wait upon file offsets lstart->lend, inclusive.
*
* Note that @lend is inclusive (describes the last byte to be written) so
* that this function can be used to write to the very end-of-file (end = -1).
*
* After writing out and waiting on the data, we check and advance the
* f_wb_err cursor to the latest value, and return any errors detected there.
*
* Return: %0 on success, negative error code otherwise.
*/
int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
{
int err = 0, err2;
struct address_space *mapping = file->f_mapping;
if (lend < lstart)
return 0;
if (mapping_needs_writeback(mapping)) {
err = __filemap_fdatawrite_range(mapping, lstart, lend,
WB_SYNC_ALL);
/* See comment of filemap_write_and_wait() */
if (err != -EIO)
__filemap_fdatawait_range(mapping, lstart, lend);
}
err2 = file_check_and_advance_wb_err(file);
if (!err)
err = err2;
return err;
}
EXPORT_SYMBOL(file_write_and_wait_range);
/**
* replace_page_cache_folio - replace a pagecache folio with a new one
* @old: folio to be replaced
* @new: folio to replace with
*
* This function replaces a folio in the pagecache with a new one. On
* success it acquires the pagecache reference for the new folio and
* drops it for the old folio. Both the old and new folios must be
* locked. This function does not add the new folio to the LRU, the
* caller must do that.
*
* The remove + add is atomic. This function cannot fail.
*/
void replace_page_cache_folio(struct folio *old, struct folio *new)
{
struct address_space *mapping = old->mapping;
void (*free_folio)(struct folio *) = mapping->a_ops->free_folio;
pgoff_t offset = old->index;
XA_STATE(xas, &mapping->i_pages, offset);
VM_BUG_ON_FOLIO(!folio_test_locked(old), old);
VM_BUG_ON_FOLIO(!folio_test_locked(new), new);
VM_BUG_ON_FOLIO(new->mapping, new);
folio_get(new);
new->mapping = mapping;
new->index = offset;
mem_cgroup_migrate(old, new);
xas_lock_irq(&xas);
xas_store(&xas, new);
old->mapping = NULL;
/* hugetlb pages do not participate in page cache accounting. */
if (!folio_test_hugetlb(old))
__lruvec_stat_sub_folio(old, NR_FILE_PAGES);
if (!folio_test_hugetlb(new))
__lruvec_stat_add_folio(new, NR_FILE_PAGES);
if (folio_test_swapbacked(old))
__lruvec_stat_sub_folio(old, NR_SHMEM);
if (folio_test_swapbacked(new))
__lruvec_stat_add_folio(new, NR_SHMEM);
xas_unlock_irq(&xas);
if (free_folio)
free_folio(old);
folio_put(old);
}
EXPORT_SYMBOL_GPL(replace_page_cache_folio);
noinline int __filemap_add_folio(struct address_space *mapping,
struct folio *folio, pgoff_t index, gfp_t gfp, void **shadowp)
{
XA_STATE(xas, &mapping->i_pages, index);
int huge = folio_test_hugetlb(folio);
bool charged = false;
long nr = 1;
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio);
mapping_set_update(&xas, mapping);
if (!huge) {
int error = mem_cgroup_charge(folio, NULL, gfp);
if (error)
return error;
charged = true;
}
VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
xas_set_order(&xas, index, folio_order(folio));
nr = folio_nr_pages(folio);
gfp &= GFP_RECLAIM_MASK;
folio_ref_add(folio, nr);
folio->mapping = mapping;
folio->index = xas.xa_index;
do {
unsigned int order = xa_get_order(xas.xa, xas.xa_index);
void *entry, *old = NULL;
if (order > folio_order(folio))
xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index),
order, gfp);
xas_lock_irq(&xas);
xas_for_each_conflict(&xas, entry) {
old = entry;
if (!xa_is_value(entry)) {
xas_set_err(&xas, -EEXIST);
goto unlock;
}
}
if (old) {
if (shadowp)
*shadowp = old;
/* entry may have been split before we acquired lock */
order = xa_get_order(xas.xa, xas.xa_index);
if (order > folio_order(folio)) {
/* How to handle large swap entries? */
BUG_ON(shmem_mapping(mapping));
xas_split(&xas, old, order);
xas_reset(&xas);
}
}
xas_store(&xas, folio);
if (xas_error(&xas))
goto unlock;
mapping->nrpages += nr;
/* hugetlb pages do not participate in page cache accounting */
if (!huge) {
__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);
if (folio_test_pmd_mappable(folio))
__lruvec_stat_mod_folio(folio,
NR_FILE_THPS, nr);
}
unlock:
xas_unlock_irq(&xas);
} while (xas_nomem(&xas, gfp));
if (xas_error(&xas))
goto error;
trace_mm_filemap_add_to_page_cache(folio);
return 0;
error:
if (charged)
mem_cgroup_uncharge(folio);
folio->mapping = NULL;
/* Leave page->index set: truncation relies upon it */
folio_put_refs(folio, nr);
return xas_error(&xas);
}
ALLOW_ERROR_INJECTION(__filemap_add_folio, ERRNO);
int filemap_add_folio(struct address_space *mapping, struct folio *folio,
pgoff_t index, gfp_t gfp)
{
void *shadow = NULL;
int ret;
__folio_set_locked(folio);
ret = __filemap_add_folio(mapping, folio, index, gfp, &shadow);
if (unlikely(ret))
__folio_clear_locked(folio);
else {
/*
* The folio might have been evicted from cache only
* recently, in which case it should be activated like
* any other repeatedly accessed folio.
* The exception is folios getting rewritten; evicting other
* data from the working set, only to cache data that will
* get overwritten with something else, is a waste of memory.
*/
WARN_ON_ONCE(folio_test_active(folio));
if (!(gfp & __GFP_WRITE) && shadow)
workingset_refault(folio, shadow);
folio_add_lru(folio);
}
return ret;
}
EXPORT_SYMBOL_GPL(filemap_add_folio);
#ifdef CONFIG_NUMA
struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order)
{
int n;
struct folio *folio;
if (cpuset_do_page_mem_spread()) {
unsigned int cpuset_mems_cookie;
do {
cpuset_mems_cookie = read_mems_allowed_begin();
n = cpuset_mem_spread_node();
folio = __folio_alloc_node(gfp, order, n);
} while (!folio && read_mems_allowed_retry(cpuset_mems_cookie));
return folio;
}
return folio_alloc(gfp, order);
}
EXPORT_SYMBOL(filemap_alloc_folio);
#endif
/*
* filemap_invalidate_lock_two - lock invalidate_lock for two mappings
*
* Lock exclusively invalidate_lock of any passed mapping that is not NULL.
*
* @mapping1: the first mapping to lock
* @mapping2: the second mapping to lock
*/
void filemap_invalidate_lock_two(struct address_space *mapping1,
struct address_space *mapping2)
{
if (mapping1 > mapping2)
swap(mapping1, mapping2);
if (mapping1)
down_write(&mapping1->invalidate_lock);
if (mapping2 && mapping1 != mapping2)
down_write_nested(&mapping2->invalidate_lock, 1);
}
EXPORT_SYMBOL(filemap_invalidate_lock_two);
/*
* filemap_invalidate_unlock_two - unlock invalidate_lock for two mappings
*
* Unlock exclusive invalidate_lock of any passed mapping that is not NULL.
*
* @mapping1: the first mapping to unlock
* @mapping2: the second mapping to unlock
*/
void filemap_invalidate_unlock_two(struct address_space *mapping1,
struct address_space *mapping2)
{
if (mapping1)
up_write(&mapping1->invalidate_lock);
if (mapping2 && mapping1 != mapping2)
up_write(&mapping2->invalidate_lock);
}
EXPORT_SYMBOL(filemap_invalidate_unlock_two);
/*
* In order to wait for pages to become available there must be
* waitqueues associated with pages. By using a hash table of
* waitqueues where the bucket discipline is to maintain all
* waiters on the same queue and wake all when any of the pages
* become available, and for the woken contexts to check to be
* sure the appropriate page became available, this saves space
* at a cost of "thundering herd" phenomena during rare hash
* collisions.
*/
#define PAGE_WAIT_TABLE_BITS 8
#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
static wait_queue_head_t folio_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
static wait_queue_head_t *folio_waitqueue(struct folio *folio)
{
return &folio_wait_table[hash_ptr(folio, PAGE_WAIT_TABLE_BITS)];
}
void __init pagecache_init(void)
{
int i;
for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
init_waitqueue_head(&folio_wait_table[i]);
page_writeback_init();
}
/*
* The page wait code treats the "wait->flags" somewhat unusually, because
* we have multiple different kinds of waits, not just the usual "exclusive"
* one.
*
* We have:
*
* (a) no special bits set:
*
* We're just waiting for the bit to be released, and when a waker
* calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up,
* and remove it from the wait queue.
*
* Simple and straightforward.
*
* (b) WQ_FLAG_EXCLUSIVE:
*
* The waiter is waiting to get the lock, and only one waiter should
* be woken up to avoid any thundering herd behavior. We'll set the
* WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue.
*
* This is the traditional exclusive wait.
*
* (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM:
*
* The waiter is waiting to get the bit, and additionally wants the
* lock to be transferred to it for fair lock behavior. If the lock
* cannot be taken, we stop walking the wait queue without waking
* the waiter.
*
* This is the "fair lock handoff" case, and in addition to setting
* WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see
* that it now has the lock.
*/
static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
{
unsigned int flags;
struct wait_page_key *key = arg;
struct wait_page_queue *wait_page
= container_of(wait, struct wait_page_queue, wait);
if (!wake_page_match(wait_page, key))
return 0;
/*
* If it's a lock handoff wait, we get the bit for it, and
* stop walking (and do not wake it up) if we can't.
*/
flags = wait->flags;
if (flags & WQ_FLAG_EXCLUSIVE) {
if (test_bit(key->bit_nr, &key->folio->flags))
return -1;
if (flags & WQ_FLAG_CUSTOM) {
if (test_and_set_bit(key->bit_nr, &key->folio->flags))
return -1;
flags |= WQ_FLAG_DONE;
}
}
/*
* We are holding the wait-queue lock, but the waiter that
* is waiting for this will be checking the flags without
* any locking.
*
* So update the flags atomically, and wake up the waiter
* afterwards to avoid any races. This store-release pairs
* with the load-acquire in folio_wait_bit_common().
*/
smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN);
wake_up_state(wait->private, mode);
/*
* Ok, we have successfully done what we're waiting for,
* and we can unconditionally remove the wait entry.
*
* Note that this pairs with the "finish_wait()" in the
* waiter, and has to be the absolute last thing we do.
* After this list_del_init(&wait->entry) the wait entry
* might be de-allocated and the process might even have
* exited.
*/
list_del_init_careful(&wait->entry);
return (flags & WQ_FLAG_EXCLUSIVE) != 0;
}
static void folio_wake_bit(struct folio *folio, int bit_nr)
{
wait_queue_head_t *q = folio_waitqueue(folio);
struct wait_page_key key;
unsigned long flags;
wait_queue_entry_t bookmark;
key.folio = folio;
key.bit_nr = bit_nr;
key.page_match = 0;
bookmark.flags = 0;
bookmark.private = NULL;
bookmark.func = NULL;
INIT_LIST_HEAD(&bookmark.entry);
spin_lock_irqsave(&q->lock, flags);
__wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
while (bookmark.flags & WQ_FLAG_BOOKMARK) {
/*
* Take a breather from holding the lock,
* allow pages that finish wake up asynchronously
* to acquire the lock and remove themselves
* from wait queue
*/
spin_unlock_irqrestore(&q->lock, flags);
cpu_relax();
spin_lock_irqsave(&q->lock, flags);
__wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
}
/*
* It's possible to miss clearing waiters here, when we woke our page
* waiters, but the hashed waitqueue has waiters for other pages on it.
* That's okay, it's a rare case. The next waker will clear it.
*
* Note that, depending on the page pool (buddy, hugetlb, ZONE_DEVICE,
* other), the flag may be cleared in the course of freeing the page;
* but that is not required for correctness.
*/
if (!waitqueue_active(q) || !key.page_match)
folio_clear_waiters(folio);
spin_unlock_irqrestore(&q->lock, flags);
}
static void folio_wake(struct folio *folio, int bit)
{
if (!folio_test_waiters(folio))
return;
folio_wake_bit(folio, bit);
}
/*
* A choice of three behaviors for folio_wait_bit_common():
*/
enum behavior {
EXCLUSIVE, /* Hold ref to page and take the bit when woken, like
* __folio_lock() waiting on then setting PG_locked.
*/
SHARED, /* Hold ref to page and check the bit when woken, like
* folio_wait_writeback() waiting on PG_writeback.
*/
DROP, /* Drop ref to page before wait, no check when woken,
* like folio_put_wait_locked() on PG_locked.
*/
};
/*
* Attempt to check (or get) the folio flag, and mark us done
* if successful.
*/
static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
struct wait_queue_entry *wait)
{
if (wait->flags & WQ_FLAG_EXCLUSIVE) {
if (test_and_set_bit(bit_nr, &folio->flags))
return false;
} else if (test_bit(bit_nr, &folio->flags))
return false;
wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE;
return true;
}
/* How many times do we accept lock stealing from under a waiter? */
int sysctl_page_lock_unfairness = 5;
static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
int state, enum behavior behavior)
{
wait_queue_head_t *q = folio_waitqueue(folio);
int unfairness = sysctl_page_lock_unfairness;
struct wait_page_queue wait_page;
wait_queue_entry_t *wait = &wait_page.wait;
bool thrashing = false;
unsigned long pflags;
bool in_thrashing;
if (bit_nr == PG_locked &&
!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
delayacct_thrashing_start(&in_thrashing);
psi_memstall_enter(&pflags);
thrashing = true;
}
init_wait(wait);
wait->func = wake_page_function;
wait_page.folio = folio;
wait_page.bit_nr = bit_nr;
repeat:
wait->flags = 0;
if (behavior == EXCLUSIVE) {
wait->flags = WQ_FLAG_EXCLUSIVE;
if (--unfairness < 0)
wait->flags |= WQ_FLAG_CUSTOM;
}
/*
* Do one last check whether we can get the
* page bit synchronously.
*
* Do the folio_set_waiters() marking before that
* to let any waker we _just_ missed know they
* need to wake us up (otherwise they'll never
* even go to the slow case that looks at the
* page queue), and add ourselves to the wait
* queue if we need to sleep.
*
* This part needs to be done under the queue
* lock to avoid races.
*/
spin_lock_irq(&q->lock);
folio_set_waiters(folio);
if (!folio_trylock_flag(folio, bit_nr, wait))
__add_wait_queue_entry_tail(q, wait);
spin_unlock_irq(&q->lock);
/*
* From now on, all the logic will be based on
* the WQ_FLAG_WOKEN and WQ_FLAG_DONE flag, to
* see whether the page bit testing has already
* been done by the wake function.
*
* We can drop our reference to the folio.
*/
if (behavior == DROP)
folio_put(folio);
/*
* Note that until the "finish_wait()", or until
* we see the WQ_FLAG_WOKEN flag, we need to
* be very careful with the 'wait->flags', because
* we may race with a waker that sets them.
*/
for (;;) {
unsigned int flags;
set_current_state(state);
/* Loop until we've been woken or interrupted */
flags = smp_load_acquire(&wait->flags);
if (!(flags & WQ_FLAG_WOKEN)) {
if (signal_pending_state(state, current))
break;
io_schedule();
continue;
}
/* If we were non-exclusive, we're done */
if (behavior != EXCLUSIVE)
break;
/* If the waker got the lock for us, we're done */
if (flags & WQ_FLAG_DONE)
break;
/*
* Otherwise, if we're getting the lock, we need to
* try to get it ourselves.
*
* And if that fails, we'll have to retry this all.
*/
if (unlikely(test_and_set_bit(bit_nr, folio_flags(folio, 0))))
goto repeat;
wait->flags |= WQ_FLAG_DONE;
break;
}
/*
* If a signal happened, this 'finish_wait()' may remove the last
* waiter from the wait-queues, but the folio waiters bit will remain
* set. That's ok. The next wakeup will take care of it, and trying
* to do it here would be difficult and prone to races.
*/
finish_wait(q, wait);
if (thrashing) {
delayacct_thrashing_end(&in_thrashing);
psi_memstall_leave(&pflags);
}
/*
* NOTE! The wait->flags weren't stable until we've done the
* 'finish_wait()', and we could have exited the loop above due
* to a signal, and had a wakeup event happen after the signal
* test but before the 'finish_wait()'.
*
* So only after the finish_wait() can we reliably determine
* if we got woken up or not, so we can now figure out the final
* return value based on that state without races.
*
* Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive
* waiter, but an exclusive one requires WQ_FLAG_DONE.
*/
if (behavior == EXCLUSIVE)
return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR;
return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR;
}
#ifdef CONFIG_MIGRATION
/**
* migration_entry_wait_on_locked - Wait for a migration entry to be removed
* @entry: migration swap entry.
* @ptl: already locked ptl. This function will drop the lock.
*
* Wait for a migration entry referencing the given page to be removed. This is
* equivalent to put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE) except
* this can be called without taking a reference on the page. Instead this
* should be called while holding the ptl for the migration entry referencing
* the page.
*
* Returns after unlocking the ptl.
*
* This follows the same logic as folio_wait_bit_common() so see the comments
* there.
*/
void migration_entry_wait_on_locked(swp_entry_t entry, spinlock_t *ptl)
__releases(ptl)
{
struct wait_page_queue wait_page;
wait_queue_entry_t *wait = &wait_page.wait;
bool thrashing = false;
unsigned long pflags;
bool in_thrashing;
wait_queue_head_t *q;
struct folio *folio = page_folio(pfn_swap_entry_to_page(entry));
q = folio_waitqueue(folio);
if (!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
delayacct_thrashing_start(&in_thrashing);
psi_memstall_enter(&pflags);
thrashing = true;
}
init_wait(wait);
wait->func = wake_page_function;
wait_page.folio = folio;
wait_page.bit_nr = PG_locked;
wait->flags = 0;
spin_lock_irq(&q->lock);
folio_set_waiters(folio);
if (!folio_trylock_flag(folio, PG_locked, wait))
__add_wait_queue_entry_tail(q, wait);
spin_unlock_irq(&q->lock);
/*
* If a migration entry exists for the page the migration path must hold
* a valid reference to the page, and it must take the ptl to remove the
* migration entry. So the page is valid until the ptl is dropped.
*/
spin_unlock(ptl);
for (;;) {
unsigned int flags;
set_current_state(TASK_UNINTERRUPTIBLE);
/* Loop until we've been woken or interrupted */
flags = smp_load_acquire(&wait->flags);
if (!(flags & WQ_FLAG_WOKEN)) {
if (signal_pending_state(TASK_UNINTERRUPTIBLE, current))
break;
io_schedule();
continue;
}
break;
}
finish_wait(q, wait);
if (thrashing) {
delayacct_thrashing_end(&in_thrashing);
psi_memstall_leave(&pflags);
}
}
#endif
void folio_wait_bit(struct folio *folio, int bit_nr)
{
folio_wait_bit_common(folio, bit_nr, TASK_UNINTERRUPTIBLE, SHARED);
}
EXPORT_SYMBOL(folio_wait_bit);
int folio_wait_bit_killable(struct folio *folio, int bit_nr)
{
return folio_wait_bit_common(folio, bit_nr, TASK_KILLABLE, SHARED);
}
EXPORT_SYMBOL(folio_wait_bit_killable);
/**
* folio_put_wait_locked - Drop a reference and wait for it to be unlocked
* @folio: The folio to wait for.
* @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc).
*
* The caller should hold a reference on @folio. They expect the page to
* become unlocked relatively soon, but do not wish to hold up migration
* (for example) by holding the reference while waiting for the folio to
* come unlocked. After this function returns, the caller should not
* dereference @folio.
*
* Return: 0 if the folio was unlocked or -EINTR if interrupted by a signal.
*/
static int folio_put_wait_locked(struct folio *folio, int state)
{
return folio_wait_bit_common(folio, PG_locked, state, DROP);
}
/**
* folio_add_wait_queue - Add an arbitrary waiter to a folio's wait queue
* @folio: Folio defining the wait queue of interest
* @waiter: Waiter to add to the queue
*
* Add an arbitrary @waiter to the wait queue for the nominated @folio.
*/
void folio_add_wait_queue(struct folio *folio, wait_queue_entry_t *waiter)
{
wait_queue_head_t *q = folio_waitqueue(folio);
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
__add_wait_queue_entry_tail(q, waiter);
folio_set_waiters(folio);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(folio_add_wait_queue);
#ifndef clear_bit_unlock_is_negative_byte
/*
* PG_waiters is the high bit in the same byte as PG_lock.
*
* On x86 (and on many other architectures), we can clear PG_lock and
* test the sign bit at the same time. But if the architecture does
* not support that special operation, we just do this all by hand
* instead.
*
* The read of PG_waiters has to be after (or concurrently with) PG_locked
* being cleared, but a memory barrier should be unnecessary since it is
* in the same byte as PG_locked.
*/
static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
{
clear_bit_unlock(nr, mem);
/* smp_mb__after_atomic(); */
return test_bit(PG_waiters, mem);
}
#endif
/**
* folio_unlock - Unlock a locked folio.
* @folio: The folio.
*
* Unlocks the folio and wakes up any thread sleeping on the page lock.
*
* Context: May be called from interrupt or process context. May not be
* called from NMI context.
*/
void folio_unlock(struct folio *folio)
{
/* Bit 7 allows x86 to check the byte's sign bit */
BUILD_BUG_ON(PG_waiters != 7);
BUILD_BUG_ON(PG_locked > 7);
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
if (clear_bit_unlock_is_negative_byte(PG_locked, folio_flags(folio, 0)))
folio_wake_bit(folio, PG_locked);
}
EXPORT_SYMBOL(folio_unlock);
/**
* folio_end_private_2 - Clear PG_private_2 and wake any waiters.
* @folio: The folio.
*
* Clear the PG_private_2 bit on a folio and wake up any sleepers waiting for
* it. The folio reference held for PG_private_2 being set is released.
*
* This is, for example, used when a netfs folio is being written to a local
* disk cache, thereby allowing writes to the cache for the same folio to be
* serialised.
*/
void folio_end_private_2(struct folio *folio)
{
VM_BUG_ON_FOLIO(!folio_test_private_2(folio), folio);
clear_bit_unlock(PG_private_2, folio_flags(folio, 0));
folio_wake_bit(folio, PG_private_2);
folio_put(folio);
}
EXPORT_SYMBOL(folio_end_private_2);
/**
* folio_wait_private_2 - Wait for PG_private_2 to be cleared on a folio.
* @folio: The folio to wait on.
*
* Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio.
*/
void folio_wait_private_2(struct folio *folio)
{
while (folio_test_private_2(folio))
folio_wait_bit(folio, PG_private_2);
}
EXPORT_SYMBOL(folio_wait_private_2);
/**
* folio_wait_private_2_killable - Wait for PG_private_2 to be cleared on a folio.
* @folio: The folio to wait on.
*
* Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio or until a
* fatal signal is received by the calling task.
*
* Return:
* - 0 if successful.
* - -EINTR if a fatal signal was encountered.
*/
int folio_wait_private_2_killable(struct folio *folio)
{
int ret = 0;
while (folio_test_private_2(folio)) {
ret = folio_wait_bit_killable(folio, PG_private_2);
if (ret < 0)
break;
}
return ret;
}
EXPORT_SYMBOL(folio_wait_private_2_killable);
/**
* folio_end_writeback - End writeback against a folio.
* @folio: The folio.
*/
void folio_end_writeback(struct folio *folio)
{
/*
* folio_test_clear_reclaim() could be used here but it is an
* atomic operation and overkill in this particular case. Failing
* to shuffle a folio marked for immediate reclaim is too mild
* a gain to justify taking an atomic operation penalty at the
* end of every folio writeback.
*/
if (folio_test_reclaim(folio)) {
folio_clear_reclaim(folio);
folio_rotate_reclaimable(folio);
}
/*
* Writeback does not hold a folio reference of its own, relying
* on truncation to wait for the clearing of PG_writeback.
* But here we must make sure that the folio is not freed and
* reused before the folio_wake().
*/
folio_get(folio);
if (!__folio_end_writeback(folio))
BUG();
smp_mb__after_atomic();
folio_wake(folio, PG_writeback);
acct_reclaim_writeback(folio);
folio_put(folio);
}
EXPORT_SYMBOL(folio_end_writeback);
/**
* __folio_lock - Get a lock on the folio, assuming we need to sleep to get it.
* @folio: The folio to lock
*/
void __folio_lock(struct folio *folio)
{
folio_wait_bit_common(folio, PG_locked, TASK_UNINTERRUPTIBLE,
EXCLUSIVE);
}
EXPORT_SYMBOL(__folio_lock);
int __folio_lock_killable(struct folio *folio)
{
return folio_wait_bit_common(folio, PG_locked, TASK_KILLABLE,
EXCLUSIVE);
}
EXPORT_SYMBOL_GPL(__folio_lock_killable);
static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait)
{
struct wait_queue_head *q = folio_waitqueue(folio);
int ret = 0;
wait->folio = folio;
wait->bit_nr = PG_locked;
spin_lock_irq(&q->lock);
__add_wait_queue_entry_tail(q, &wait->wait);
folio_set_waiters(folio);
ret = !folio_trylock(folio);
/*
* If we were successful now, we know we're still on the
* waitqueue as we're still under the lock. This means it's
* safe to remove and return success, we know the callback
* isn't going to trigger.
*/
if (!ret)
__remove_wait_queue(q, &wait->wait);
else
ret = -EIOCBQUEUED;
spin_unlock_irq(&q->lock);
return ret;
}
/*
* Return values:
* 0 - folio is locked.
* non-zero - folio is not locked.
* mmap_lock or per-VMA lock has been released (mmap_read_unlock() or
* vma_end_read()), unless flags had both FAULT_FLAG_ALLOW_RETRY and
* FAULT_FLAG_RETRY_NOWAIT set, in which case the lock is still held.
*
* If neither ALLOW_RETRY nor KILLABLE are set, will always return 0
* with the folio locked and the mmap_lock/per-VMA lock is left unperturbed.
*/
vm_fault_t __folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf)
{
unsigned int flags = vmf->flags;
if (fault_flag_allow_retry_first(flags)) {
/*
* CAUTION! In this case, mmap_lock/per-VMA lock is not
* released even though returning VM_FAULT_RETRY.
*/
if (flags & FAULT_FLAG_RETRY_NOWAIT)
return VM_FAULT_RETRY;
release_fault_lock(vmf);
if (flags & FAULT_FLAG_KILLABLE)
folio_wait_locked_killable(folio);
else
folio_wait_locked(folio);
return VM_FAULT_RETRY;
}
if (flags & FAULT_FLAG_KILLABLE) {
bool ret;
ret = __folio_lock_killable(folio);
if (ret) {
release_fault_lock(vmf);
return VM_FAULT_RETRY;
}
} else {
__folio_lock(folio);
}
return 0;
}
/**
* page_cache_next_miss() - Find the next gap in the page cache.
* @mapping: Mapping.
* @index: Index.
* @max_scan: Maximum range to search.
*
* Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the
* gap with the lowest index.
*
* This function may be called under the rcu_read_lock. However, this will
* not atomically search a snapshot of the cache at a single point in time.
* For example, if a gap is created at index 5, then subsequently a gap is
* created at index 10, page_cache_next_miss covering both indices may
* return 10 if called under the rcu_read_lock.
*
* Return: The index of the gap if found, otherwise an index outside the
* range specified (in which case 'return - index >= max_scan' will be true).
* In the rare case of index wrap-around, 0 will be returned.
*/
pgoff_t page_cache_next_miss(struct address_space *mapping,
pgoff_t index, unsigned long max_scan)
{
XA_STATE(xas, &mapping->i_pages, index);
while (max_scan--) {
void *entry = xas_next(&xas);
if (!entry || xa_is_value(entry))
break;
if (xas.xa_index == 0)
break;
}
return xas.xa_index;
}
EXPORT_SYMBOL(page_cache_next_miss);
/**
* page_cache_prev_miss() - Find the previous gap in the page cache.
* @mapping: Mapping.
* @index: Index.
* @max_scan: Maximum range to search.
*
* Search the range [max(index - max_scan + 1, 0), index] for the
* gap with the highest index.
*
* This function may be called under the rcu_read_lock. However, this will
* not atomically search a snapshot of the cache at a single point in time.
* For example, if a gap is created at index 10, then subsequently a gap is
* created at index 5, page_cache_prev_miss() covering both indices may
* return 5 if called under the rcu_read_lock.
*
* Return: The index of the gap if found, otherwise an index outside the
* range specified (in which case 'index - return >= max_scan' will be true).
* In the rare case of wrap-around, ULONG_MAX will be returned.
*/
pgoff_t page_cache_prev_miss(struct address_space *mapping,
pgoff_t index, unsigned long max_scan)
{
XA_STATE(xas, &mapping->i_pages, index);
while (max_scan--) {
void *entry = xas_prev(&xas);
if (!entry || xa_is_value(entry))
break;
if (xas.xa_index == ULONG_MAX)
break;
}
return xas.xa_index;
}
EXPORT_SYMBOL(page_cache_prev_miss);
/*
* Lockless page cache protocol:
* On the lookup side:
* 1. Load the folio from i_pages
* 2. Increment the refcount if it's not zero
* 3. If the folio is not found by xas_reload(), put the refcount and retry
*
* On the removal side:
* A. Freeze the page (by zeroing the refcount if nobody else has a reference)
* B. Remove the page from i_pages
* C. Return the page to the page allocator
*
* This means that any page may have its reference count temporarily
* increased by a speculative page cache (or fast GUP) lookup as it can
* be allocated by another user before the RCU grace period expires.
* Because the refcount temporarily acquired here may end up being the
* last refcount on the page, any page allocation must be freeable by
* folio_put().
*/
/*
* filemap_get_entry - Get a page cache entry.
* @mapping: the address_space to search
* @index: The page cache index.
*
* Looks up the page cache entry at @mapping & @index. If it is a folio,
* it is returned with an increased refcount. If it is a shadow entry
* of a previously evicted folio, or a swap entry from shmem/tmpfs,
* it is returned without further action.
*
* Return: The folio, swap or shadow entry, %NULL if nothing is found.
*/
void *filemap_get_entry(struct address_space *mapping, pgoff_t index)
{
XA_STATE(xas, &mapping->i_pages, index);
struct folio *folio;
rcu_read_lock();
repeat:
xas_reset(&xas);
folio = xas_load(&xas);
if (xas_retry(&xas, folio))
goto repeat;
/*
* A shadow entry of a recently evicted page, or a swap entry from
* shmem/tmpfs. Return it without attempting to raise page count.
*/
if (!folio || xa_is_value(folio))
goto out;
if (!folio_try_get_rcu(folio))
goto repeat;
if (unlikely(folio != xas_reload(&xas))) {
folio_put(folio);
goto repeat;
}
out:
rcu_read_unlock();
return folio;
}
/**
* __filemap_get_folio - Find and get a reference to a folio.
* @mapping: The address_space to search.
* @index: The page index.
* @fgp_flags: %FGP flags modify how the folio is returned.
* @gfp: Memory allocation flags to use if %FGP_CREAT is specified.
*
* Looks up the page cache entry at @mapping & @index.
*
* If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
* if the %GFP flags specified for %FGP_CREAT are atomic.
*
* If this function returns a folio, it is returned with an increased refcount.
*
* Return: The found folio or an ERR_PTR() otherwise.
*/
struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
fgf_t fgp_flags, gfp_t gfp)
{
struct folio *folio;
repeat:
folio = filemap_get_entry(mapping, index);
if (xa_is_value(folio))
folio = NULL;
if (!folio)
goto no_page;
if (fgp_flags & FGP_LOCK) {
if (fgp_flags & FGP_NOWAIT) {
if (!folio_trylock(folio)) {
folio_put(folio);
return ERR_PTR(-EAGAIN);
}
} else {
folio_lock(folio);
}
/* Has the page been truncated? */
if (unlikely(folio->mapping != mapping)) {
folio_unlock(folio);
folio_put(folio);
goto repeat;
}
VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
}
if (fgp_flags & FGP_ACCESSED)
folio_mark_accessed(folio);
else if (fgp_flags & FGP_WRITE) {
/* Clear idle flag for buffer write */
if (folio_test_idle(folio))
folio_clear_idle(folio);
}
if (fgp_flags & FGP_STABLE)
folio_wait_stable(folio);
no_page:
if (!folio && (fgp_flags & FGP_CREAT)) {
unsigned order = FGF_GET_ORDER(fgp_flags);
int err;
if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
gfp |= __GFP_WRITE;
if (fgp_flags & FGP_NOFS)
gfp &= ~__GFP_FS;
if (fgp_flags & FGP_NOWAIT) {
gfp &= ~GFP_KERNEL;
gfp |= GFP_NOWAIT | __GFP_NOWARN;
}
if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
fgp_flags |= FGP_LOCK;
if (!mapping_large_folio_support(mapping))
order = 0;
if (order > MAX_PAGECACHE_ORDER)
order = MAX_PAGECACHE_ORDER;
/* If we're not aligned, allocate a smaller folio */
if (index & ((1UL << order) - 1))
order = __ffs(index);
do {
gfp_t alloc_gfp = gfp;
err = -ENOMEM;
if (order == 1)
order = 0;
if (order > 0)
alloc_gfp |= __GFP_NORETRY | __GFP_NOWARN;
folio = filemap_alloc_folio(alloc_gfp, order);
if (!folio)
continue;
/* Init accessed so avoid atomic mark_page_accessed later */
if (fgp_flags & FGP_ACCESSED)
__folio_set_referenced(folio);
err = filemap_add_folio(mapping, folio, index, gfp);
if (!err)
break;
folio_put(folio);
folio = NULL;
} while (order-- > 0);
if (err == -EEXIST)
goto repeat;
if (err)
return ERR_PTR(err);
/*
* filemap_add_folio locks the page, and for mmap
* we expect an unlocked page.
*/
if (folio && (fgp_flags & FGP_FOR_MMAP))
folio_unlock(folio);
}
if (!folio)
return ERR_PTR(-ENOENT);
return folio;
}
EXPORT_SYMBOL(__filemap_get_folio);
static inline struct folio *find_get_entry(struct xa_state *xas, pgoff_t max,
xa_mark_t mark)
{
struct folio *folio;
retry:
if (mark == XA_PRESENT)
folio = xas_find(xas, max);
else
folio = xas_find_marked(xas, max, mark);
if (xas_retry(xas, folio))
goto retry;
/*
* A shadow entry of a recently evicted page, a swap
* entry from shmem/tmpfs or a DAX entry. Return it
* without attempting to raise page count.
*/
if (!folio || xa_is_value(folio))
return folio;
if (!folio_try_get_rcu(folio))
goto reset;
if (unlikely(folio != xas_reload(xas))) {
folio_put(folio);
goto reset;
}
return folio;
reset:
xas_reset(xas);
goto retry;
}
/**
* find_get_entries - gang pagecache lookup
* @mapping: The address_space to search
* @start: The starting page cache index
* @end: The final page index (inclusive).
* @fbatch: Where the resulting entries are placed.
* @indices: The cache indices corresponding to the entries in @entries
*
* find_get_entries() will search for and return a batch of entries in
* the mapping. The entries are placed in @fbatch. find_get_entries()
* takes a reference on any actual folios it returns.
*
* The entries have ascending indexes. The indices may not be consecutive
* due to not-present entries or large folios.
*
* Any shadow entries of evicted folios, or swap entries from
* shmem/tmpfs, are included in the returned array.
*
* Return: The number of entries which were found.
*/
unsigned find_get_entries(struct address_space *mapping, pgoff_t *start,
pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
{
XA_STATE(xas, &mapping->i_pages, *start);
struct folio *folio;
rcu_read_lock();
while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) {
indices[fbatch->nr] = xas.xa_index;
if (!folio_batch_add(fbatch, folio))
break;
}
rcu_read_unlock();
if (folio_batch_count(fbatch)) {
unsigned long nr = 1;
int idx = folio_batch_count(fbatch) - 1;
folio = fbatch->folios[idx];
if (!xa_is_value(folio))
nr = folio_nr_pages(folio);
*start = indices[idx] + nr;
}
return folio_batch_count(fbatch);
}
/**
* find_lock_entries - Find a batch of pagecache entries.
* @mapping: The address_space to search.
* @start: The starting page cache index.
* @end: The final page index (inclusive).
* @fbatch: Where the resulting entries are placed.
* @indices: The cache indices of the entries in @fbatch.
*
* find_lock_entries() will return a batch of entries from @mapping.
* Swap, shadow and DAX entries are included. Folios are returned
* locked and with an incremented refcount. Folios which are locked
* by somebody else or under writeback are skipped. Folios which are
* partially outside the range are not returned.
*
* The entries have ascending indexes. The indices may not be consecutive
* due to not-present entries, large folios, folios which could not be
* locked or folios under writeback.
*
* Return: The number of entries which were found.
*/
unsigned find_lock_entries(struct address_space *mapping, pgoff_t *start,
pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
{
XA_STATE(xas, &mapping->i_pages, *start);
struct folio *folio;
rcu_read_lock();
while ((folio = find_get_entry(&xas, end, XA_PRESENT))) {
if (!xa_is_value(folio)) {
if (folio->index < *start)
goto put;
if (folio_next_index(folio) - 1 > end)
goto put;
if (!folio_trylock(folio))
goto put;
if (folio->mapping != mapping ||
folio_test_writeback(folio))
goto unlock;
VM_BUG_ON_FOLIO(!folio_contains(folio, xas.xa_index),
folio);
}
indices[fbatch->nr] = xas.xa_index;
if (!folio_batch_add(fbatch, folio))
break;
continue;
unlock:
folio_unlock(folio);
put:
folio_put(folio);
}
rcu_read_unlock();
if (folio_batch_count(fbatch)) {
unsigned long nr = 1;
int idx = folio_batch_count(fbatch) - 1;
folio = fbatch->folios[idx];
if (!xa_is_value(folio))
nr = folio_nr_pages(folio);
*start = indices[idx] + nr;
}
return folio_batch_count(fbatch);
}
/**
* filemap_get_folios - Get a batch of folios
* @mapping: The address_space to search
* @start: The starting page index
* @end: The final page index (inclusive)
* @fbatch: The batch to fill.
*
* Search for and return a batch of folios in the mapping starting at
* index @start and up to index @end (inclusive). The folios are returned
* in @fbatch with an elevated reference count.
*
* The first folio may start before @start; if it does, it will contain
* @start. The final folio may extend beyond @end; if it does, it will
* contain @end. The folios have ascending indices. There may be gaps
* between the folios if there are indices which have no folio in the
* page cache. If folios are added to or removed from the page cache
* while this is running, they may or may not be found by this call.
*
* Return: The number of folios which were found.
* We also update @start to index the next folio for the traversal.
*/
unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
pgoff_t end, struct folio_batch *fbatch)
{
XA_STATE(xas, &mapping->i_pages, *start);
struct folio *folio;
rcu_read_lock();
while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) {
/* Skip over shadow, swap and DAX entries */
if (xa_is_value(folio))
continue;
if (!folio_batch_add(fbatch, folio)) {
unsigned long nr = folio_nr_pages(folio);
*start = folio->index + nr;
goto out;
}
}
/*
* We come here when there is no page beyond @end. We take care to not
* overflow the index @start as it confuses some of the callers. This
* breaks the iteration when there is a page at index -1 but that is
* already broken anyway.
*/
if (end == (pgoff_t)-1)
*start = (pgoff_t)-1;
else
*start = end + 1;
out:
rcu_read_unlock();
return folio_batch_count(fbatch);
}
EXPORT_SYMBOL(filemap_get_folios);
/**
* filemap_get_folios_contig - Get a batch of contiguous folios
* @mapping: The address_space to search
* @start: The starting page index
* @end: The final page index (inclusive)
* @fbatch: The batch to fill
*
* filemap_get_folios_contig() works exactly like filemap_get_folios(),
* except the returned folios are guaranteed to be contiguous. This may
* not return all contiguous folios if the batch gets filled up.
*
* Return: The number of folios found.
* Also update @start to be positioned for traversal of the next folio.
*/
unsigned filemap_get_folios_contig(struct address_space *mapping,
pgoff_t *start, pgoff_t end, struct folio_batch *fbatch)
{
XA_STATE(xas, &mapping->i_pages, *start);
unsigned long nr;
struct folio *folio;
rcu_read_lock();
for (folio = xas_load(&xas); folio && xas.xa_index <= end;
folio = xas_next(&xas)) {
if (xas_retry(&xas, folio))
continue;
/*
* If the entry has been swapped out, we can stop looking.
* No current caller is looking for DAX entries.
*/
if (xa_is_value(folio))
goto update_start;
if (!folio_try_get_rcu(folio))
goto retry;
if (unlikely(folio != xas_reload(&xas)))
goto put_folio;
if (!folio_batch_add(fbatch, folio)) {
nr = folio_nr_pages(folio);
*start = folio->index + nr;
goto out;
}
continue;
put_folio:
folio_put(folio);
retry:
xas_reset(&xas);
}
update_start:
nr = folio_batch_count(fbatch);
if (nr) {
folio = fbatch->folios[nr - 1];
*start = folio->index + folio_nr_pages(folio);
}
out:
rcu_read_unlock();
return folio_batch_count(fbatch);
}
EXPORT_SYMBOL(filemap_get_folios_contig);
/**
* filemap_get_folios_tag - Get a batch of folios matching @tag
* @mapping: The address_space to search
* @start: The starting page index
* @end: The final page index (inclusive)
* @tag: The tag index
* @fbatch: The batch to fill
*
* Same as filemap_get_folios(), but only returning folios tagged with @tag.
*
* Return: The number of folios found.
* Also update @start to index the next folio for traversal.
*/
unsigned filemap_get_folios_tag(struct address_space *mapping, pgoff_t *start,
pgoff_t end, xa_mark_t tag, struct folio_batch *fbatch)
{
XA_STATE(xas, &mapping->i_pages, *start);
struct folio *folio;
rcu_read_lock();
while ((folio = find_get_entry(&xas, end, tag)) != NULL) {
/*
* Shadow entries should never be tagged, but this iteration
* is lockless so there is a window for page reclaim to evict
* a page we saw tagged. Skip over it.
*/
if (xa_is_value(folio))
continue;
if (!folio_batch_add(fbatch, folio)) {
unsigned long nr = folio_nr_pages(folio);
*start = folio->index + nr;
goto out;
}
}
/*
* We come here when there is no page beyond @end. We take care to not
* overflow the index @start as it confuses some of the callers. This
* breaks the iteration when there is a page at index -1 but that is
* already broke anyway.
*/
if (end == (pgoff_t)-1)
*start = (pgoff_t)-1;
else
*start = end + 1;
out:
rcu_read_unlock();
return folio_batch_count(fbatch);
}
EXPORT_SYMBOL(filemap_get_folios_tag);
/*
* CD/DVDs are error prone. When a medium error occurs, the driver may fail
* a _large_ part of the i/o request. Imagine the worst scenario:
*
* ---R__________________________________________B__________
* ^ reading here ^ bad block(assume 4k)
*
* read(R) => miss => readahead(R...B) => media error => frustrating retries
* => failing the whole request => read(R) => read(R+1) =>
* readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
* readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
* readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
*
* It is going insane. Fix it by quickly scaling down the readahead size.
*/
static void shrink_readahead_size_eio(struct file_ra_state *ra)
{
ra->ra_pages /= 4;
}
/*
* filemap_get_read_batch - Get a batch of folios for read
*
* Get a batch of folios which represent a contiguous range of bytes in
* the file. No exceptional entries will be returned. If @index is in
* the middle of a folio, the entire folio will be returned. The last
* folio in the batch may have the readahead flag set or the uptodate flag
* clear so that the caller can take the appropriate action.
*/
static void filemap_get_read_batch(struct address_space *mapping,
pgoff_t index, pgoff_t max, struct folio_batch *fbatch)
{
XA_STATE(xas, &mapping->i_pages, index);
struct folio *folio;
rcu_read_lock();
for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) {
if (xas_retry(&xas, folio))
continue;
if (xas.xa_index > max || xa_is_value(folio))
break;
if (xa_is_sibling(folio))
break;
if (!folio_try_get_rcu(folio))
goto retry;
if (unlikely(folio != xas_reload(&xas)))
goto put_folio;
if (!folio_batch_add(fbatch, folio))
break;
if (!folio_test_uptodate(folio))
break;
if (folio_test_readahead(folio))
break;
xas_advance(&xas, folio_next_index(folio) - 1);
continue;
put_folio:
folio_put(folio);
retry:
xas_reset(&xas);
}
rcu_read_unlock();
}
static int filemap_read_folio(struct file *file, filler_t filler,
struct folio *folio)
{
bool workingset = folio_test_workingset(folio);
unsigned long pflags;
int error;
/*
* A previous I/O error may have been due to temporary failures,
* eg. multipath errors. PG_error will be set again if read_folio
* fails.
*/
folio_clear_error(folio);
/* Start the actual read. The read will unlock the page. */
if (unlikely(workingset))
psi_memstall_enter(&pflags);
error = filler(file, folio);
if (unlikely(workingset))
psi_memstall_leave(&pflags);
if (error)
return error;
error = folio_wait_locked_killable(folio);
if (error)
return error;
if (folio_test_uptodate(folio))
return 0;
if (file)
shrink_readahead_size_eio(&file->f_ra);
return -EIO;
}
static bool filemap_range_uptodate(struct address_space *mapping,
loff_t pos, size_t count, struct folio *folio,
bool need_uptodate)
{
if (folio_test_uptodate(folio))
return true;
/* pipes can't handle partially uptodate pages */
if (need_uptodate)
return false;
if (!mapping->a_ops->is_partially_uptodate)
return false;
if (mapping->host->i_blkbits >= folio_shift(folio))
return false;
if (folio_pos(folio) > pos) {
count -= folio_pos(folio) - pos;
pos = 0;
} else {
pos -= folio_pos(folio);
}
return mapping->a_ops->is_partially_uptodate(folio, pos, count);
}
static int filemap_update_page(struct kiocb *iocb,
struct address_space *mapping, size_t count,
struct folio *folio, bool need_uptodate)
{
int error;
if (iocb->ki_flags & IOCB_NOWAIT) {
if (!filemap_invalidate_trylock_shared(mapping))
return -EAGAIN;
} else {
filemap_invalidate_lock_shared(mapping);
}
if (!folio_trylock(folio)) {
error = -EAGAIN;
if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
goto unlock_mapping;
if (!(iocb->ki_flags & IOCB_WAITQ)) {
filemap_invalidate_unlock_shared(mapping);
/*
* This is where we usually end up waiting for a
* previously submitted readahead to finish.
*/
folio_put_wait_locked(folio, TASK_KILLABLE);
return AOP_TRUNCATED_PAGE;
}
error = __folio_lock_async(folio, iocb->ki_waitq);
if (error)
goto unlock_mapping;
}
error = AOP_TRUNCATED_PAGE;
if (!folio->mapping)
goto unlock;
error = 0;
if (filemap_range_uptodate(mapping, iocb->ki_pos, count, folio,
need_uptodate))
goto unlock;
error = -EAGAIN;
if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
goto unlock;
error = filemap_read_folio(iocb->ki_filp, mapping->a_ops->read_folio,
folio);
goto unlock_mapping;
unlock:
folio_unlock(folio);
unlock_mapping:
filemap_invalidate_unlock_shared(mapping);
if (error == AOP_TRUNCATED_PAGE)
folio_put(folio);
return error;
}
static int filemap_create_folio(struct file *file,
struct address_space *mapping, pgoff_t index,
struct folio_batch *fbatch)
{
struct folio *folio;
int error;
folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0);
if (!folio)
return -ENOMEM;
/*
* Protect against truncate / hole punch. Grabbing invalidate_lock
* here assures we cannot instantiate and bring uptodate new
* pagecache folios after evicting page cache during truncate
* and before actually freeing blocks. Note that we could
* release invalidate_lock after inserting the folio into
* the page cache as the locked folio would then be enough to
* synchronize with hole punching. But there are code paths
* such as filemap_update_page() filling in partially uptodate
* pages or ->readahead() that need to hold invalidate_lock
* while mapping blocks for IO so let's hold the lock here as
* well to keep locking rules simple.
*/
filemap_invalidate_lock_shared(mapping);
error = filemap_add_folio(mapping, folio, index,
mapping_gfp_constraint(mapping, GFP_KERNEL));
if (error == -EEXIST)
error = AOP_TRUNCATED_PAGE;
if (error)
goto error;
error = filemap_read_folio(file, mapping->a_ops->read_folio, folio);
if (error)
goto error;
filemap_invalidate_unlock_shared(mapping);
folio_batch_add(fbatch, folio);
return 0;
error:
filemap_invalidate_unlock_shared(mapping);
folio_put(folio);
return error;
}
static int filemap_readahead(struct kiocb *iocb, struct file *file,
struct address_space *mapping, struct folio *folio,
pgoff_t last_index)
{
DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, folio->index);
if (iocb->ki_flags & IOCB_NOIO)
return -EAGAIN;
page_cache_async_ra(&ractl, folio, last_index - folio->index);
return 0;
}
static int filemap_get_pages(struct kiocb *iocb, size_t count,
struct folio_batch *fbatch, bool need_uptodate)
{
struct file *filp = iocb->ki_filp;
struct address_space *mapping = filp->f_mapping;
struct file_ra_state *ra = &filp->f_ra;
pgoff_t index = iocb->ki_pos >> PAGE_SHIFT;
pgoff_t last_index;
struct folio *folio;
int err = 0;
/* "last_index" is the index of the page beyond the end of the read */
last_index = DIV_ROUND_UP(iocb->ki_pos + count, PAGE_SIZE);
retry:
if (fatal_signal_pending(current))
return -EINTR;
filemap_get_read_batch(mapping, index, last_index - 1, fbatch);
if (!folio_batch_count(fbatch)) {
if (iocb->ki_flags & IOCB_NOIO)
return -EAGAIN;
page_cache_sync_readahead(mapping, ra, filp, index,
last_index - index);
filemap_get_read_batch(mapping, index, last_index - 1, fbatch);
}
if (!folio_batch_count(fbatch)) {
if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
return -EAGAIN;
err = filemap_create_folio(filp, mapping,
iocb->ki_pos >> PAGE_SHIFT, fbatch);
if (err == AOP_TRUNCATED_PAGE)
goto retry;
return err;
}
folio = fbatch->folios[folio_batch_count(fbatch) - 1];
if (folio_test_readahead(folio)) {
err = filemap_readahead(iocb, filp, mapping, folio, last_index);
if (err)
goto err;
}
if (!folio_test_uptodate(folio)) {
if ((iocb->ki_flags & IOCB_WAITQ) &&
folio_batch_count(fbatch) > 1)
iocb->ki_flags |= IOCB_NOWAIT;
err = filemap_update_page(iocb, mapping, count, folio,
need_uptodate);
if (err)
goto err;
}
return 0;
err:
if (err < 0)
folio_put(folio);
if (likely(--fbatch->nr))
return 0;
if (err == AOP_TRUNCATED_PAGE)
goto retry;
return err;
}
static inline bool pos_same_folio(loff_t pos1, loff_t pos2, struct folio *folio)
{
unsigned int shift = folio_shift(folio);
return (pos1 >> shift == pos2 >> shift);
}
/**
* filemap_read - Read data from the page cache.
* @iocb: The iocb to read.
* @iter: Destination for the data.
* @already_read: Number of bytes already read by the caller.
*
* Copies data from the page cache. If the data is not currently present,
* uses the readahead and read_folio address_space operations to fetch it.
*
* Return: Total number of bytes copied, including those already read by
* the caller. If an error happens before any bytes are copied, returns
* a negative error number.
*/
ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
ssize_t already_read)
{
struct file *filp = iocb->ki_filp;
struct file_ra_state *ra = &filp->f_ra;
struct address_space *mapping = filp->f_mapping;
struct inode *inode = mapping->host;
struct folio_batch fbatch;
int i, error = 0;
bool writably_mapped;
loff_t isize, end_offset;
loff_t last_pos = ra->prev_pos;
if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes))
return 0;
if (unlikely(!iov_iter_count(iter)))
return 0;
iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
folio_batch_init(&fbatch);
do {
cond_resched();
/*
* If we've already successfully copied some data, then we
* can no longer safely return -EIOCBQUEUED. Hence mark
* an async read NOWAIT at that point.
*/
if ((iocb->ki_flags & IOCB_WAITQ) && already_read)
iocb->ki_flags |= IOCB_NOWAIT;
if (unlikely(iocb->ki_pos >= i_size_read(inode)))
break;
error = filemap_get_pages(iocb, iter->count, &fbatch, false);
if (error < 0)
break;
/*
* i_size must be checked after we know the pages are Uptodate.
*
* Checking i_size after the check allows us to calculate
* the correct value for "nr", which means the zero-filled
* part of the page is not copied back to userspace (unless
* another truncate extends the file - this is desired though).
*/
isize = i_size_read(inode);
if (unlikely(iocb->ki_pos >= isize))
goto put_folios;
end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count);
/*
* Once we start copying data, we don't want to be touching any
* cachelines that might be contended:
*/
writably_mapped = mapping_writably_mapped(mapping);
/*
* When a read accesses the same folio several times, only
* mark it as accessed the first time.
*/
if (!pos_same_folio(iocb->ki_pos, last_pos - 1,
fbatch.folios[0]))
folio_mark_accessed(fbatch.folios[0]);
for (i = 0; i < folio_batch_count(&fbatch); i++) {
struct folio *folio = fbatch.folios[i];
size_t fsize = folio_size(folio);
size_t offset = iocb->ki_pos & (fsize - 1);
size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos,
fsize - offset);
size_t copied;
if (end_offset < folio_pos(folio))
break;
if (i > 0)
folio_mark_accessed(folio);
/*
* If users can be writing to this folio using arbitrary
* virtual addresses, take care of potential aliasing
* before reading the folio on the kernel side.
*/
if (writably_mapped)
flush_dcache_folio(folio);
copied = copy_folio_to_iter(folio, offset, bytes, iter);
already_read += copied;
iocb->ki_pos += copied;
last_pos = iocb->ki_pos;
if (copied < bytes) {
error = -EFAULT;
break;
}
}
put_folios:
for (i = 0; i < folio_batch_count(&fbatch); i++)
folio_put(fbatch.folios[i]);
folio_batch_init(&fbatch);
} while (iov_iter_count(iter) && iocb->ki_pos < isize && !error);
file_accessed(filp);
ra->prev_pos = last_pos;
return already_read ? already_read : error;
}
EXPORT_SYMBOL_GPL(filemap_read);
int kiocb_write_and_wait(struct kiocb *iocb, size_t count)
{
struct address_space *mapping = iocb->ki_filp->f_mapping;
loff_t pos = iocb->ki_pos;
loff_t end = pos + count - 1;
if (iocb->ki_flags & IOCB_NOWAIT) {
if (filemap_range_needs_writeback(mapping, pos, end))
return -EAGAIN;
return 0;
}
return filemap_write_and_wait_range(mapping, pos, end);
}
int kiocb_invalidate_pages(struct kiocb *iocb, size_t count)
{
struct address_space *mapping = iocb->ki_filp->f_mapping;
loff_t pos = iocb->ki_pos;
loff_t end = pos + count - 1;
int ret;
if (iocb->ki_flags & IOCB_NOWAIT) {
/* we could block if there are any pages in the range */
if (filemap_range_has_page(mapping, pos, end))
return -EAGAIN;
} else {
ret = filemap_write_and_wait_range(mapping, pos, end);
if (ret)
return ret;
}
/*
* After a write we want buffered reads to be sure to go to disk to get
* the new data. We invalidate clean cached page from the region we're
* about to write. We do this *before* the write so that we can return
* without clobbering -EIOCBQUEUED from ->direct_IO().
*/
return invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
end >> PAGE_SHIFT);
}
/**
* generic_file_read_iter - generic filesystem read routine
* @iocb: kernel I/O control block
* @iter: destination for the data read
*
* This is the "read_iter()" routine for all filesystems
* that can use the page cache directly.
*
* The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall
* be returned when no data can be read without waiting for I/O requests
* to complete; it doesn't prevent readahead.
*
* The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O
* requests shall be made for the read or for readahead. When no data
* can be read, -EAGAIN shall be returned. When readahead would be
* triggered, a partial, possibly empty read shall be returned.
*
* Return:
* * number of bytes copied, even for partial reads
* * negative error code (or 0 if IOCB_NOIO) if nothing was read
*/
ssize_t
generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
size_t count = iov_iter_count(iter);
ssize_t retval = 0;
if (!count)
return 0; /* skip atime */
if (iocb->ki_flags & IOCB_DIRECT) {
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
retval = kiocb_write_and_wait(iocb, count);
if (retval < 0)
return retval;
file_accessed(file);
retval = mapping->a_ops->direct_IO(iocb, iter);
if (retval >= 0) {
iocb->ki_pos += retval;
count -= retval;
}
if (retval != -EIOCBQUEUED)
iov_iter_revert(iter, count - iov_iter_count(iter));
/*
* Btrfs can have a short DIO read if we encounter
* compressed extents, so if there was an error, or if
* we've already read everything we wanted to, or if
* there was a short read because we hit EOF, go ahead
* and return. Otherwise fallthrough to buffered io for
* the rest of the read. Buffered reads will not work for
* DAX files, so don't bother trying.
*/
if (retval < 0 || !count || IS_DAX(inode))
return retval;
if (iocb->ki_pos >= i_size_read(inode))
return retval;
}
return filemap_read(iocb, iter, retval);
}
EXPORT_SYMBOL(generic_file_read_iter);
/*
* Splice subpages from a folio into a pipe.
*/
size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
struct folio *folio, loff_t fpos, size_t size)
{
struct page *page;
size_t spliced = 0, offset = offset_in_folio(folio, fpos);
page = folio_page(folio, offset / PAGE_SIZE);
size = min(size, folio_size(folio) - offset);
offset %= PAGE_SIZE;
while (spliced < size &&
!pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
struct pipe_buffer *buf = pipe_head_buf(pipe);
size_t part = min_t(size_t, PAGE_SIZE - offset, size - spliced);
*buf = (struct pipe_buffer) {
.ops = &page_cache_pipe_buf_ops,
.page = page,
.offset = offset,
.len = part,
};
folio_get(folio);
pipe->head++;
page++;
spliced += part;
offset = 0;
}
return spliced;
}
/**
* filemap_splice_read - Splice data from a file's pagecache into a pipe
* @in: The file to read from
* @ppos: Pointer to the file position to read from
* @pipe: The pipe to splice into
* @len: The amount to splice
* @flags: The SPLICE_F_* flags
*
* This function gets folios from a file's pagecache and splices them into the
* pipe. Readahead will be called as necessary to fill more folios. This may
* be used for blockdevs also.
*
* Return: On success, the number of bytes read will be returned and *@ppos
* will be updated if appropriate; 0 will be returned if there is no more data
* to be read; -EAGAIN will be returned if the pipe had no space, and some
* other negative error code will be returned on error. A short read may occur
* if the pipe has insufficient space, we reach the end of the data or we hit a
* hole.
*/
ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe,
size_t len, unsigned int flags)
{
struct folio_batch fbatch;
struct kiocb iocb;
size_t total_spliced = 0, used, npages;
loff_t isize, end_offset;
bool writably_mapped;
int i, error = 0;
if (unlikely(*ppos >= in->f_mapping->host->i_sb->s_maxbytes))
return 0;
init_sync_kiocb(&iocb, in);
iocb.ki_pos = *ppos;
/* Work out how much data we can actually add into the pipe */
used = pipe_occupancy(pipe->head, pipe->tail);
npages = max_t(ssize_t, pipe->max_usage - used, 0);
len = min_t(size_t, len, npages * PAGE_SIZE);
folio_batch_init(&fbatch);
do {
cond_resched();
if (*ppos >= i_size_read(in->f_mapping->host))
break;
iocb.ki_pos = *ppos;
error = filemap_get_pages(&iocb, len, &fbatch, true);
if (error < 0)
break;
/*
* i_size must be checked after we know the pages are Uptodate.
*
* Checking i_size after the check allows us to calculate
* the correct value for "nr", which means the zero-filled
* part of the page is not copied back to userspace (unless
* another truncate extends the file - this is desired though).
*/
isize = i_size_read(in->f_mapping->host);
if (unlikely(*ppos >= isize))
break;
end_offset = min_t(loff_t, isize, *ppos + len);
/*
* Once we start copying data, we don't want to be touching any
* cachelines that might be contended:
*/
writably_mapped = mapping_writably_mapped(in->f_mapping);
for (i = 0; i < folio_batch_count(&fbatch); i++) {
struct folio *folio = fbatch.folios[i];
size_t n;
if (folio_pos(folio) >= end_offset)
goto out;
folio_mark_accessed(folio);
/*
* If users can be writing to this folio using arbitrary
* virtual addresses, take care of potential aliasing
* before reading the folio on the kernel side.
*/
if (writably_mapped)
flush_dcache_folio(folio);
n = min_t(loff_t, len, isize - *ppos);
n = splice_folio_into_pipe(pipe, folio, *ppos, n);
if (!n)
goto out;
len -= n;
total_spliced += n;
*ppos += n;
in->f_ra.prev_pos = *ppos;
if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
goto out;
}
folio_batch_release(&fbatch);
} while (len);
out:
folio_batch_release(&fbatch);
file_accessed(in);
return total_spliced ? total_spliced : error;
}
EXPORT_SYMBOL(filemap_splice_read);
static inline loff_t folio_seek_hole_data(struct xa_state *xas,
struct address_space *mapping, struct folio *folio,
loff_t start, loff_t end, bool seek_data)
{
const struct address_space_operations *ops = mapping->a_ops;
size_t offset, bsz = i_blocksize(mapping->host);
if (xa_is_value(folio) || folio_test_uptodate(folio))
return seek_data ? start : end;
if (!ops->is_partially_uptodate)
return seek_data ? end : start;
xas_pause(xas);
rcu_read_unlock();
folio_lock(folio);
if (unlikely(folio->mapping != mapping))
goto unlock;
offset = offset_in_folio(folio, start) & ~(bsz - 1);
do {
if (ops->is_partially_uptodate(folio, offset, bsz) ==
seek_data)
break;
start = (start + bsz) & ~(bsz - 1);
offset += bsz;
} while (offset < folio_size(folio));
unlock:
folio_unlock(folio);
rcu_read_lock();
return start;
}
static inline size_t seek_folio_size(struct xa_state *xas, struct folio *folio)
{
if (xa_is_value(folio))
return PAGE_SIZE << xa_get_order(xas->xa, xas->xa_index);
return folio_size(folio);
}
/**
* mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache.
* @mapping: Address space to search.
* @start: First byte to consider.
* @end: Limit of search (exclusive).
* @whence: Either SEEK_HOLE or SEEK_DATA.
*
* If the page cache knows which blocks contain holes and which blocks
* contain data, your filesystem can use this function to implement
* SEEK_HOLE and SEEK_DATA. This is useful for filesystems which are
* entirely memory-based such as tmpfs, and filesystems which support
* unwritten extents.
*
* Return: The requested offset on success, or -ENXIO if @whence specifies
* SEEK_DATA and there is no data after @start. There is an implicit hole
* after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start
* and @end contain data.
*/
loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start,
loff_t end, int whence)
{
XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT);
pgoff_t max = (end - 1) >> PAGE_SHIFT;
bool seek_data = (whence == SEEK_DATA);
struct folio *folio;
if (end <= start)
return -ENXIO;
rcu_read_lock();
while ((folio = find_get_entry(&xas, max, XA_PRESENT))) {
loff_t pos = (u64)xas.xa_index << PAGE_SHIFT;
size_t seek_size;
if (start < pos) {
if (!seek_data)
goto unlock;
start = pos;
}
seek_size = seek_folio_size(&xas, folio);
pos = round_up((u64)pos + 1, seek_size);
start = folio_seek_hole_data(&xas, mapping, folio, start, pos,
seek_data);
if (start < pos)
goto unlock;
if (start >= end)
break;
if (seek_size > PAGE_SIZE)
xas_set(&xas, pos >> PAGE_SHIFT);
if (!xa_is_value(folio))
folio_put(folio);
}
if (seek_data)
start = -ENXIO;
unlock:
rcu_read_unlock();
if (folio && !xa_is_value(folio))
folio_put(folio);
if (start > end)
return end;
return start;
}
#ifdef CONFIG_MMU
#define MMAP_LOTSAMISS (100)
/*
* lock_folio_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock
* @vmf - the vm_fault for this fault.
* @folio - the folio to lock.
* @fpin - the pointer to the file we may pin (or is already pinned).
*
* This works similar to lock_folio_or_retry in that it can drop the
* mmap_lock. It differs in that it actually returns the folio locked
* if it returns 1 and 0 if it couldn't lock the folio. If we did have
* to drop the mmap_lock then fpin will point to the pinned file and
* needs to be fput()'ed at a later point.
*/
static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio,
struct file **fpin)
{
if (folio_trylock(folio))
return 1;
/*
* NOTE! This will make us return with VM_FAULT_RETRY, but with
* the fault lock still held. That's how FAULT_FLAG_RETRY_NOWAIT
* is supposed to work. We have way too many special cases..
*/
if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
return 0;
*fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
if (vmf->flags & FAULT_FLAG_KILLABLE) {
if (__folio_lock_killable(folio)) {
/*
* We didn't have the right flags to drop the
* fault lock, but all fault_handlers only check
* for fatal signals if we return VM_FAULT_RETRY,
* so we need to drop the fault lock here and
* return 0 if we don't have a fpin.
*/
if (*fpin == NULL)
release_fault_lock(vmf);
return 0;
}
} else
__folio_lock(folio);
return 1;
}
/*
* Synchronous readahead happens when we don't even find a page in the page
* cache at all. We don't want to perform IO under the mmap sem, so if we have
* to drop the mmap sem we return the file that was pinned in order for us to do
* that. If we didn't pin a file then we return NULL. The file that is
* returned needs to be fput()'ed when we're done with it.
*/
static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
{
struct file *file = vmf->vma->vm_file;
struct file_ra_state *ra = &file->f_ra;
struct address_space *mapping = file->f_mapping;
DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff);
struct file *fpin = NULL;
unsigned long vm_flags = vmf->vma->vm_flags;
unsigned int mmap_miss;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
/* Use the readahead code, even if readahead is disabled */
if (vm_flags & VM_HUGEPAGE) {
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
ractl._index &= ~((unsigned long)HPAGE_PMD_NR - 1);
ra->size = HPAGE_PMD_NR;
/*
* Fetch two PMD folios, so we get the chance to actually
* readahead, unless we've been told not to.
*/
if (!(vm_flags & VM_RAND_READ))
ra->size *= 2;
ra->async_size = HPAGE_PMD_NR;
page_cache_ra_order(&ractl, ra, HPAGE_PMD_ORDER);
return fpin;
}
#endif
/* If we don't want any read-ahead, don't bother */
if (vm_flags & VM_RAND_READ)
return fpin;
if (!ra->ra_pages)
return fpin;
if (vm_flags & VM_SEQ_READ) {
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
page_cache_sync_ra(&ractl, ra->ra_pages);
return fpin;
}
/* Avoid banging the cache line if not needed */
mmap_miss = READ_ONCE(ra->mmap_miss);
if (mmap_miss < MMAP_LOTSAMISS * 10)
WRITE_ONCE(ra->mmap_miss, ++mmap_miss);
/*
* Do we miss much more than hit in this file? If so,
* stop bothering with read-ahead. It will only hurt.
*/
if (mmap_miss > MMAP_LOTSAMISS)
return fpin;
/*
* mmap read-around
*/
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2);
ra->size = ra->ra_pages;
ra->async_size = ra->ra_pages / 4;
ractl._index = ra->start;
page_cache_ra_order(&ractl, ra, 0);
return fpin;
}
/*
* Asynchronous readahead happens when we find the page and PG_readahead,
* so we want to possibly extend the readahead further. We return the file that
* was pinned if we have to drop the mmap_lock in order to do IO.
*/
static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
struct folio *folio)
{
struct file *file = vmf->vma->vm_file;
struct file_ra_state *ra = &file->f_ra;
DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, vmf->pgoff);
struct file *fpin = NULL;
unsigned int mmap_miss;
/* If we don't want any read-ahead, don't bother */
if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages)
return fpin;
mmap_miss = READ_ONCE(ra->mmap_miss);
if (mmap_miss)
WRITE_ONCE(ra->mmap_miss, --mmap_miss);
if (folio_test_readahead(folio)) {
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
page_cache_async_ra(&ractl, folio, ra->ra_pages);
}
return fpin;
}
/**
* filemap_fault - read in file data for page fault handling
* @vmf: struct vm_fault containing details of the fault
*
* filemap_fault() is invoked via the vma operations vector for a
* mapped memory region to read in file data during a page fault.
*
* The goto's are kind of ugly, but this streamlines the normal case of having
* it in the page cache, and handles the special cases reasonably without
* having a lot of duplicated code.
*
* vma->vm_mm->mmap_lock must be held on entry.
*
* If our return value has VM_FAULT_RETRY set, it's because the mmap_lock
* may be dropped before doing I/O or by lock_folio_maybe_drop_mmap().
*
* If our return value does not have VM_FAULT_RETRY set, the mmap_lock
* has not been released.
*
* We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
*
* Return: bitwise-OR of %VM_FAULT_ codes.
*/
vm_fault_t filemap_fault(struct vm_fault *vmf)
{
int error;
struct file *file = vmf->vma->vm_file;
struct file *fpin = NULL;
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
pgoff_t max_idx, index = vmf->pgoff;
struct folio *folio;
vm_fault_t ret = 0;
bool mapping_locked = false;
max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
if (unlikely(index >= max_idx))
return VM_FAULT_SIGBUS;
/*
* Do we have something in the page cache already?
*/
folio = filemap_get_folio(mapping, index);
if (likely(!IS_ERR(folio))) {
/*
* We found the page, so try async readahead before waiting for
* the lock.
*/
if (!(vmf->flags & FAULT_FLAG_TRIED))
fpin = do_async_mmap_readahead(vmf, folio);
if (unlikely(!folio_test_uptodate(folio))) {
filemap_invalidate_lock_shared(mapping);
mapping_locked = true;
}
} else {
/* No page in the page cache at all */
count_vm_event(PGMAJFAULT);
count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
ret = VM_FAULT_MAJOR;
fpin = do_sync_mmap_readahead(vmf);
retry_find:
/*
* See comment in filemap_create_folio() why we need
* invalidate_lock
*/
if (!mapping_locked) {
filemap_invalidate_lock_shared(mapping);
mapping_locked = true;
}
folio = __filemap_get_folio(mapping, index,
FGP_CREAT|FGP_FOR_MMAP,
vmf->gfp_mask);
if (IS_ERR(folio)) {
if (fpin)
goto out_retry;
filemap_invalidate_unlock_shared(mapping);
return VM_FAULT_OOM;
}
}
if (!lock_folio_maybe_drop_mmap(vmf, folio, &fpin))
goto out_retry;
/* Did it get truncated? */
if (unlikely(folio->mapping != mapping)) {
folio_unlock(folio);
folio_put(folio);
goto retry_find;
}
VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
/*
* We have a locked folio in the page cache, now we need to check
* that it's up-to-date. If not, it is going to be due to an error,
* or because readahead was otherwise unable to retrieve it.
*/
if (unlikely(!folio_test_uptodate(folio))) {
/*
* If the invalidate lock is not held, the folio was in cache
* and uptodate and now it is not. Strange but possible since we
* didn't hold the page lock all the time. Let's drop
* everything, get the invalidate lock and try again.
*/
if (!mapping_locked) {
folio_unlock(folio);
folio_put(folio);
goto retry_find;
}
/*
* OK, the folio is really not uptodate. This can be because the
* VMA has the VM_RAND_READ flag set, or because an error
* arose. Let's read it in directly.
*/
goto page_not_uptodate;
}
/*
* We've made it this far and we had to drop our mmap_lock, now is the
* time to return to the upper layer and have it re-find the vma and
* redo the fault.
*/
if (fpin) {
folio_unlock(folio);
goto out_retry;
}
if (mapping_locked)
filemap_invalidate_unlock_shared(mapping);
/*
* Found the page and have a reference on it.
* We must recheck i_size under page lock.
*/
max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
if (unlikely(index >= max_idx)) {
folio_unlock(folio);
folio_put(folio);
return VM_FAULT_SIGBUS;
}
vmf->page = folio_file_page(folio, index);
return ret | VM_FAULT_LOCKED;
page_not_uptodate:
/*
* Umm, take care of errors if the page isn't up-to-date.
* Try to re-read it _once_. We do this synchronously,
* because there really aren't any performance issues here
* and we need to check for errors.
*/
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
error = filemap_read_folio(file, mapping->a_ops->read_folio, folio);
if (fpin)
goto out_retry;
folio_put(folio);
if (!error || error == AOP_TRUNCATED_PAGE)
goto retry_find;
filemap_invalidate_unlock_shared(mapping);
return VM_FAULT_SIGBUS;
out_retry:
/*
* We dropped the mmap_lock, we need to return to the fault handler to
* re-find the vma and come back and find our hopefully still populated
* page.
*/
if (!IS_ERR(folio))
folio_put(folio);
if (mapping_locked)
filemap_invalidate_unlock_shared(mapping);
if (fpin)
fput(fpin);
return ret | VM_FAULT_RETRY;
}
EXPORT_SYMBOL(filemap_fault);
static bool filemap_map_pmd(struct vm_fault *vmf, struct folio *folio,
pgoff_t start)
{
struct mm_struct *mm = vmf->vma->vm_mm;
/* Huge page is mapped? No need to proceed. */
if (pmd_trans_huge(*vmf->pmd)) {
folio_unlock(folio);
folio_put(folio);
return true;
}
if (pmd_none(*vmf->pmd) && folio_test_pmd_mappable(folio)) {
struct page *page = folio_file_page(folio, start);
vm_fault_t ret = do_set_pmd(vmf, page);
if (!ret) {
/* The page is mapped successfully, reference consumed. */
folio_unlock(folio);
return true;
}
}
if (pmd_none(*vmf->pmd))
pmd_install(mm, vmf->pmd, &vmf->prealloc_pte);
return false;
}
static struct folio *next_uptodate_folio(struct xa_state *xas,
struct address_space *mapping, pgoff_t end_pgoff)
{
struct folio *folio = xas_next_entry(xas, end_pgoff);
unsigned long max_idx;
do {
if (!folio)
return NULL;
if (xas_retry(xas, folio))
continue;
if (xa_is_value(folio))
continue;
if (folio_test_locked(folio))
continue;
if (!folio_try_get_rcu(folio))
continue;
/* Has the page moved or been split? */
if (unlikely(folio != xas_reload(xas)))
goto skip;
if (!folio_test_uptodate(folio) || folio_test_readahead(folio))
goto skip;
if (!folio_trylock(folio))
goto skip;
if (folio->mapping != mapping)
goto unlock;
if (!folio_test_uptodate(folio))
goto unlock;
max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
if (xas->xa_index >= max_idx)
goto unlock;
return folio;
unlock:
folio_unlock(folio);
skip:
folio_put(folio);
} while ((folio = xas_next_entry(xas, end_pgoff)) != NULL);
return NULL;
}
/*
* Map page range [start_page, start_page + nr_pages) of folio.
* start_page is gotten from start by folio_page(folio, start)
*/
static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
struct folio *folio, unsigned long start,
unsigned long addr, unsigned int nr_pages,
unsigned int *mmap_miss)
{
vm_fault_t ret = 0;
struct page *page = folio_page(folio, start);
unsigned int count = 0;
pte_t *old_ptep = vmf->pte;
do {
if (PageHWPoison(page + count))
goto skip;
(*mmap_miss)++;
/*
* NOTE: If there're PTE markers, we'll leave them to be
* handled in the specific fault path, and it'll prohibit the
* fault-around logic.
*/
if (!pte_none(vmf->pte[count]))
goto skip;
count++;
continue;
skip:
if (count) {
set_pte_range(vmf, folio, page, count, addr);
folio_ref_add(folio, count);
if (in_range(vmf->address, addr, count * PAGE_SIZE))
ret = VM_FAULT_NOPAGE;
}
count++;
page += count;
vmf->pte += count;
addr += count * PAGE_SIZE;
count = 0;
} while (--nr_pages > 0);
if (count) {
set_pte_range(vmf, folio, page, count, addr);
folio_ref_add(folio, count);
if (in_range(vmf->address, addr, count * PAGE_SIZE))
ret = VM_FAULT_NOPAGE;
}
vmf->pte = old_ptep;
return ret;
}
static vm_fault_t filemap_map_order0_folio(struct vm_fault *vmf,
struct folio *folio, unsigned long addr,
unsigned int *mmap_miss)
{
vm_fault_t ret = 0;
struct page *page = &folio->page;
if (PageHWPoison(page))
return ret;
(*mmap_miss)++;
/*
* NOTE: If there're PTE markers, we'll leave them to be
* handled in the specific fault path, and it'll prohibit
* the fault-around logic.
*/
if (!pte_none(ptep_get(vmf->pte)))
return ret;
if (vmf->address == addr)
ret = VM_FAULT_NOPAGE;
set_pte_range(vmf, folio, page, 1, addr);
folio_ref_inc(folio);
return ret;
}
vm_fault_t filemap_map_pages(struct vm_fault *vmf,
pgoff_t start_pgoff, pgoff_t end_pgoff)
{
struct vm_area_struct *vma = vmf->vma;
struct file *file = vma->vm_file;
struct address_space *mapping = file->f_mapping;
pgoff_t last_pgoff = start_pgoff;
unsigned long addr;
XA_STATE(xas, &mapping->i_pages, start_pgoff);
struct folio *folio;
vm_fault_t ret = 0;
unsigned int nr_pages = 0, mmap_miss = 0, mmap_miss_saved;
rcu_read_lock();
folio = next_uptodate_folio(&xas, mapping, end_pgoff);
if (!folio)
goto out;
if (filemap_map_pmd(vmf, folio, start_pgoff)) {
ret = VM_FAULT_NOPAGE;
goto out;
}
addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
if (!vmf->pte) {
folio_unlock(folio);
folio_put(folio);
goto out;
}
do {
unsigned long end;
addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
vmf->pte += xas.xa_index - last_pgoff;
last_pgoff = xas.xa_index;
end = folio_next_index(folio) - 1;
nr_pages = min(end, end_pgoff) - xas.xa_index + 1;
if (!folio_test_large(folio))
ret |= filemap_map_order0_folio(vmf,
folio, addr, &mmap_miss);
else
ret |= filemap_map_folio_range(vmf, folio,
xas.xa_index - folio->index, addr,
nr_pages, &mmap_miss);
folio_unlock(folio);
folio_put(folio);
} while ((folio = next_uptodate_folio(&xas, mapping, end_pgoff)) != NULL);
pte_unmap_unlock(vmf->pte, vmf->ptl);
out:
rcu_read_unlock();
mmap_miss_saved = READ_ONCE(file->f_ra.mmap_miss);
if (mmap_miss >= mmap_miss_saved)
WRITE_ONCE(file->f_ra.mmap_miss, 0);
else
WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss_saved - mmap_miss);
return ret;
}
EXPORT_SYMBOL(filemap_map_pages);
vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
{
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
struct folio *folio = page_folio(vmf->page);
vm_fault_t ret = VM_FAULT_LOCKED;
sb_start_pagefault(mapping->host->i_sb);
file_update_time(vmf->vma->vm_file);
folio_lock(folio);
if (folio->mapping != mapping) {
folio_unlock(folio);
ret = VM_FAULT_NOPAGE;
goto out;
}
/*
* We mark the folio dirty already here so that when freeze is in
* progress, we are guaranteed that writeback during freezing will
* see the dirty folio and writeprotect it again.
*/
folio_mark_dirty(folio);
folio_wait_stable(folio);
out:
sb_end_pagefault(mapping->host->i_sb);
return ret;
}
const struct vm_operations_struct generic_file_vm_ops = {
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = filemap_page_mkwrite,
};
/* This is used for a general mmap of a disk file */
int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
{
struct address_space *mapping = file->f_mapping;
if (!mapping->a_ops->read_folio)
return -ENOEXEC;
file_accessed(file);
vma->vm_ops = &generic_file_vm_ops;
return 0;
}
/*
* This is for filesystems which do not implement ->writepage.
*/
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
{
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
return -EINVAL;
return generic_file_mmap(file, vma);
}
#else
vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
{
return VM_FAULT_SIGBUS;
}
int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
{
return -ENOSYS;
}
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
{
return -ENOSYS;
}
#endif /* CONFIG_MMU */
EXPORT_SYMBOL(filemap_page_mkwrite);
EXPORT_SYMBOL(generic_file_mmap);
EXPORT_SYMBOL(generic_file_readonly_mmap);
static struct folio *do_read_cache_folio(struct address_space *mapping,
pgoff_t index, filler_t filler, struct file *file, gfp_t gfp)
{
struct folio *folio;
int err;
if (!filler)
filler = mapping->a_ops->read_folio;
repeat:
folio = filemap_get_folio(mapping, index);
if (IS_ERR(folio)) {
folio = filemap_alloc_folio(gfp, 0);
if (!folio)
return ERR_PTR(-ENOMEM);
err = filemap_add_folio(mapping, folio, index, gfp);
if (unlikely(err)) {
folio_put(folio);
if (err == -EEXIST)
goto repeat;
/* Presumably ENOMEM for xarray node */
return ERR_PTR(err);
}
goto filler;
}
if (folio_test_uptodate(folio))
goto out;
if (!folio_trylock(folio)) {
folio_put_wait_locked(folio, TASK_UNINTERRUPTIBLE);
goto repeat;
}
/* Folio was truncated from mapping */
if (!folio->mapping) {
folio_unlock(folio);
folio_put(folio);
goto repeat;
}
/* Someone else locked and filled the page in a very small window */
if (folio_test_uptodate(folio)) {
folio_unlock(folio);
goto out;
}
filler:
err = filemap_read_folio(file, filler, folio);
if (err) {
folio_put(folio);
if (err == AOP_TRUNCATED_PAGE)
goto repeat;
return ERR_PTR(err);
}
out:
folio_mark_accessed(folio);
return folio;
}
/**
* read_cache_folio - Read into page cache, fill it if needed.
* @mapping: The address_space to read from.
* @index: The index to read.
* @filler: Function to perform the read, or NULL to use aops->read_folio().
* @file: Passed to filler function, may be NULL if not required.
*
* Read one page into the page cache. If it succeeds, the folio returned
* will contain @index, but it may not be the first page of the folio.
*
* If the filler function returns an error, it will be returned to the
* caller.
*
* Context: May sleep. Expects mapping->invalidate_lock to be held.
* Return: An uptodate folio on success, ERR_PTR() on failure.
*/
struct folio *read_cache_folio(struct address_space *mapping, pgoff_t index,
filler_t filler, struct file *file)
{
return do_read_cache_folio(mapping, index, filler, file,
mapping_gfp_mask(mapping));
}
EXPORT_SYMBOL(read_cache_folio);
/**
* mapping_read_folio_gfp - Read into page cache, using specified allocation flags.
* @mapping: The address_space for the folio.
* @index: The index that the allocated folio will contain.
* @gfp: The page allocator flags to use if allocating.
*
* This is the same as "read_cache_folio(mapping, index, NULL, NULL)", but with
* any new memory allocations done using the specified allocation flags.
*
* The most likely error from this function is EIO, but ENOMEM is
* possible and so is EINTR. If ->read_folio returns another error,
* that will be returned to the caller.
*
* The function expects mapping->invalidate_lock to be already held.
*
* Return: Uptodate folio on success, ERR_PTR() on failure.
*/
struct folio *mapping_read_folio_gfp(struct address_space *mapping,
pgoff_t index, gfp_t gfp)
{
return do_read_cache_folio(mapping, index, NULL, NULL, gfp);
}
EXPORT_SYMBOL(mapping_read_folio_gfp);
static struct page *do_read_cache_page(struct address_space *mapping,
pgoff_t index, filler_t *filler, struct file *file, gfp_t gfp)
{
struct folio *folio;
folio = do_read_cache_folio(mapping, index, filler, file, gfp);
if (IS_ERR(folio))
return &folio->page;
return folio_file_page(folio, index);
}
struct page *read_cache_page(struct address_space *mapping,
pgoff_t index, filler_t *filler, struct file *file)
{
return do_read_cache_page(mapping, index, filler, file,
mapping_gfp_mask(mapping));
}
EXPORT_SYMBOL(read_cache_page);
/**
* read_cache_page_gfp - read into page cache, using specified page allocation flags.
* @mapping: the page's address_space
* @index: the page index
* @gfp: the page allocator flags to use if allocating
*
* This is the same as "read_mapping_page(mapping, index, NULL)", but with
* any new page allocations done using the specified allocation flags.
*
* If the page does not get brought uptodate, return -EIO.
*
* The function expects mapping->invalidate_lock to be already held.
*
* Return: up to date page on success, ERR_PTR() on failure.
*/
struct page *read_cache_page_gfp(struct address_space *mapping,
pgoff_t index,
gfp_t gfp)
{
return do_read_cache_page(mapping, index, NULL, NULL, gfp);
}
EXPORT_SYMBOL(read_cache_page_gfp);
/*
* Warn about a page cache invalidation failure during a direct I/O write.
*/
static void dio_warn_stale_pagecache(struct file *filp)
{
static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST);
char pathname[128];
char *path;
errseq_set(&filp->f_mapping->wb_err, -EIO);
if (__ratelimit(&_rs)) {
path = file_path(filp, pathname, sizeof(pathname));
if (IS_ERR(path))
path = "(unknown)";
pr_crit("Page cache invalidation failure on direct I/O. Possible data corruption due to collision with buffered I/O!\n");
pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid,
current->comm);
}
}
void kiocb_invalidate_post_direct_write(struct kiocb *iocb, size_t count)
{
struct address_space *mapping = iocb->ki_filp->f_mapping;
if (mapping->nrpages &&
invalidate_inode_pages2_range(mapping,
iocb->ki_pos >> PAGE_SHIFT,
(iocb->ki_pos + count - 1) >> PAGE_SHIFT))
dio_warn_stale_pagecache(iocb->ki_filp);
}
ssize_t
generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
{
struct address_space *mapping = iocb->ki_filp->f_mapping;
size_t write_len = iov_iter_count(from);
ssize_t written;
/*
* If a page can not be invalidated, return 0 to fall back
* to buffered write.
*/
written = kiocb_invalidate_pages(iocb, write_len);
if (written) {
if (written == -EBUSY)
return 0;
return written;
}
written = mapping->a_ops->direct_IO(iocb, from);
/*
* Finally, try again to invalidate clean pages which might have been
* cached by non-direct readahead, or faulted in by get_user_pages()
* if the source of the write was an mmap'ed region of the file
* we're writing. Either one is a pretty crazy thing to do,
* so we don't support it 100%. If this invalidation
* fails, tough, the write still worked...
*
* Most of the time we do not need this since dio_complete() will do
* the invalidation for us. However there are some file systems that
* do not end up with dio_complete() being called, so let's not break
* them by removing it completely.
*
* Noticeable example is a blkdev_direct_IO().
*
* Skip invalidation for async writes or if mapping has no pages.
*/
if (written > 0) {
struct inode *inode = mapping->host;
loff_t pos = iocb->ki_pos;
kiocb_invalidate_post_direct_write(iocb, written);
pos += written;
write_len -= written;
if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
i_size_write(inode, pos);
mark_inode_dirty(inode);
}
iocb->ki_pos = pos;
}
if (written != -EIOCBQUEUED)
iov_iter_revert(from, write_len - iov_iter_count(from));
return written;
}
EXPORT_SYMBOL(generic_file_direct_write);
ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
{
struct file *file = iocb->ki_filp;
loff_t pos = iocb->ki_pos;
struct address_space *mapping = file->f_mapping;
const struct address_space_operations *a_ops = mapping->a_ops;
long status = 0;
ssize_t written = 0;
do {
struct page *page;
unsigned long offset; /* Offset into pagecache page */
unsigned long bytes; /* Bytes to write to page */
size_t copied; /* Bytes copied from user */
void *fsdata = NULL;
offset = (pos & (PAGE_SIZE - 1));
bytes = min_t(unsigned long, PAGE_SIZE - offset,
iov_iter_count(i));
again:
/*
* Bring in the user page that we will copy from _first_.
* Otherwise there's a nasty deadlock on copying from the
* same page as we're writing to, without it being marked
* up-to-date.
*/
if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) {
status = -EFAULT;
break;
}
if (fatal_signal_pending(current)) {
status = -EINTR;
break;
}
status = a_ops->write_begin(file, mapping, pos, bytes,
&page, &fsdata);
if (unlikely(status < 0))
break;
if (mapping_writably_mapped(mapping))
flush_dcache_page(page);
copied = copy_page_from_iter_atomic(page, offset, bytes, i);
flush_dcache_page(page);
status = a_ops->write_end(file, mapping, pos, bytes, copied,
page, fsdata);
if (unlikely(status != copied)) {
iov_iter_revert(i, copied - max(status, 0L));
if (unlikely(status < 0))
break;
}
cond_resched();
if (unlikely(status == 0)) {
/*
* A short copy made ->write_end() reject the
* thing entirely. Might be memory poisoning
* halfway through, might be a race with munmap,
* might be severe memory pressure.
*/
if (copied)
bytes = copied;
goto again;
}
pos += status;
written += status;
balance_dirty_pages_ratelimited(mapping);
} while (iov_iter_count(i));
if (!written)
return status;
iocb->ki_pos += written;
return written;
}
EXPORT_SYMBOL(generic_perform_write);
/**
* __generic_file_write_iter - write data to a file
* @iocb: IO state structure (file, offset, etc.)
* @from: iov_iter with data to write
*
* This function does all the work needed for actually writing data to a
* file. It does all basic checks, removes SUID from the file, updates
* modification times and calls proper subroutines depending on whether we
* do direct IO or a standard buffered write.
*
* It expects i_rwsem to be grabbed unless we work on a block device or similar
* object which does not need locking at all.
*
* This function does *not* take care of syncing data in case of O_SYNC write.
* A caller has to handle it. This is mainly due to the fact that we want to
* avoid syncing under i_rwsem.
*
* Return:
* * number of bytes written, even for truncated writes
* * negative error code if no data has been written at all
*/
ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
ssize_t ret;
ret = file_remove_privs(file);
if (ret)
return ret;
ret = file_update_time(file);
if (ret)
return ret;
if (iocb->ki_flags & IOCB_DIRECT) {
ret = generic_file_direct_write(iocb, from);
/*
* If the write stopped short of completing, fall back to
* buffered writes. Some filesystems do this for writes to
* holes, for example. For DAX files, a buffered write will
* not succeed (even if it did, DAX does not handle dirty
* page-cache pages correctly).
*/
if (ret < 0 || !iov_iter_count(from) || IS_DAX(inode))
return ret;
return direct_write_fallback(iocb, from, ret,
generic_perform_write(iocb, from));
}
return generic_perform_write(iocb, from);
}
EXPORT_SYMBOL(__generic_file_write_iter);
/**
* generic_file_write_iter - write data to a file
* @iocb: IO state structure
* @from: iov_iter with data to write
*
* This is a wrapper around __generic_file_write_iter() to be used by most
* filesystems. It takes care of syncing the file in case of O_SYNC file
* and acquires i_rwsem as needed.
* Return:
* * negative error code if no data has been written at all of
* vfs_fsync_range() failed for a synchronous write
* * number of bytes written, even for truncated writes
*/
ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
ssize_t ret;
inode_lock(inode);
ret = generic_write_checks(iocb, from);
if (ret > 0)
ret = __generic_file_write_iter(iocb, from);
inode_unlock(inode);
if (ret > 0)
ret = generic_write_sync(iocb, ret);
return ret;
}
EXPORT_SYMBOL(generic_file_write_iter);
/**
* filemap_release_folio() - Release fs-specific metadata on a folio.
* @folio: The folio which the kernel is trying to free.
* @gfp: Memory allocation flags (and I/O mode).
*
* The address_space is trying to release any data attached to a folio
* (presumably at folio->private).
*
* This will also be called if the private_2 flag is set on a page,
* indicating that the folio has other metadata associated with it.
*
* The @gfp argument specifies whether I/O may be performed to release
* this page (__GFP_IO), and whether the call may block
* (__GFP_RECLAIM & __GFP_FS).
*
* Return: %true if the release was successful, otherwise %false.
*/
bool filemap_release_folio(struct folio *folio, gfp_t gfp)
{
struct address_space * const mapping = folio->mapping;
BUG_ON(!folio_test_locked(folio));
if (!folio_needs_release(folio))
return true;
if (folio_test_writeback(folio))
return false;
if (mapping && mapping->a_ops->release_folio)
return mapping->a_ops->release_folio(folio, gfp);
return try_to_free_buffers(folio);
}
EXPORT_SYMBOL(filemap_release_folio);
#ifdef CONFIG_CACHESTAT_SYSCALL
/**
* filemap_cachestat() - compute the page cache statistics of a mapping
* @mapping: The mapping to compute the statistics for.
* @first_index: The starting page cache index.
* @last_index: The final page index (inclusive).
* @cs: the cachestat struct to write the result to.
*
* This will query the page cache statistics of a mapping in the
* page range of [first_index, last_index] (inclusive). The statistics
* queried include: number of dirty pages, number of pages marked for
* writeback, and the number of (recently) evicted pages.
*/
static void filemap_cachestat(struct address_space *mapping,
pgoff_t first_index, pgoff_t last_index, struct cachestat *cs)
{
XA_STATE(xas, &mapping->i_pages, first_index);
struct folio *folio;
rcu_read_lock();
xas_for_each(&xas, folio, last_index) {
unsigned long nr_pages;
pgoff_t folio_first_index, folio_last_index;
if (xas_retry(&xas, folio))
continue;
if (xa_is_value(folio)) {
/* page is evicted */
void *shadow = (void *)folio;
bool workingset; /* not used */
int order = xa_get_order(xas.xa, xas.xa_index);
nr_pages = 1 << order;
folio_first_index = round_down(xas.xa_index, 1 << order);
folio_last_index = folio_first_index + nr_pages - 1;
/* Folios might straddle the range boundaries, only count covered pages */
if (folio_first_index < first_index)
nr_pages -= first_index - folio_first_index;
if (folio_last_index > last_index)
nr_pages -= folio_last_index - last_index;
cs->nr_evicted += nr_pages;
#ifdef CONFIG_SWAP /* implies CONFIG_MMU */
if (shmem_mapping(mapping)) {
/* shmem file - in swap cache */
swp_entry_t swp = radix_to_swp_entry(folio);
shadow = get_shadow_from_swap_cache(swp);
}
#endif
if (workingset_test_recent(shadow, true, &workingset))
cs->nr_recently_evicted += nr_pages;
goto resched;
}
nr_pages = folio_nr_pages(folio);
folio_first_index = folio_pgoff(folio);
folio_last_index = folio_first_index + nr_pages - 1;
/* Folios might straddle the range boundaries, only count covered pages */
if (folio_first_index < first_index)
nr_pages -= first_index - folio_first_index;
if (folio_last_index > last_index)
nr_pages -= folio_last_index - last_index;
/* page is in cache */
cs->nr_cache += nr_pages;
if (folio_test_dirty(folio))
cs->nr_dirty += nr_pages;
if (folio_test_writeback(folio))
cs->nr_writeback += nr_pages;
resched:
if (need_resched()) {
xas_pause(&xas);
cond_resched_rcu();
}
}
rcu_read_unlock();
}
/*
* The cachestat(2) system call.
*
* cachestat() returns the page cache statistics of a file in the
* bytes range specified by `off` and `len`: number of cached pages,
* number of dirty pages, number of pages marked for writeback,
* number of evicted pages, and number of recently evicted pages.
*
* An evicted page is a page that is previously in the page cache
* but has been evicted since. A page is recently evicted if its last
* eviction was recent enough that its reentry to the cache would
* indicate that it is actively being used by the system, and that
* there is memory pressure on the system.
*
* `off` and `len` must be non-negative integers. If `len` > 0,
* the queried range is [`off`, `off` + `len`]. If `len` == 0,
* we will query in the range from `off` to the end of the file.
*
* The `flags` argument is unused for now, but is included for future
* extensibility. User should pass 0 (i.e no flag specified).
*
* Currently, hugetlbfs is not supported.
*
* Because the status of a page can change after cachestat() checks it
* but before it returns to the application, the returned values may
* contain stale information.
*
* return values:
* zero - success
* -EFAULT - cstat or cstat_range points to an illegal address
* -EINVAL - invalid flags
* -EBADF - invalid file descriptor
* -EOPNOTSUPP - file descriptor is of a hugetlbfs file
*/
SYSCALL_DEFINE4(cachestat, unsigned int, fd,
struct cachestat_range __user *, cstat_range,
struct cachestat __user *, cstat, unsigned int, flags)
{
struct fd f = fdget(fd);
struct address_space *mapping;
struct cachestat_range csr;
struct cachestat cs;
pgoff_t first_index, last_index;
if (!f.file)
return -EBADF;
if (copy_from_user(&csr, cstat_range,
sizeof(struct cachestat_range))) {
fdput(f);
return -EFAULT;
}
/* hugetlbfs is not supported */
if (is_file_hugepages(f.file)) {
fdput(f);
return -EOPNOTSUPP;
}
if (flags != 0) {
fdput(f);
return -EINVAL;
}
first_index = csr.off >> PAGE_SHIFT;
last_index =
csr.len == 0 ? ULONG_MAX : (csr.off + csr.len - 1) >> PAGE_SHIFT;
memset(&cs, 0, sizeof(struct cachestat));
mapping = f.file->f_mapping;
filemap_cachestat(mapping, first_index, last_index, &cs);
fdput(f);
if (copy_to_user(cstat, &cs, sizeof(struct cachestat)))
return -EFAULT;
return 0;
}
#endif /* CONFIG_CACHESTAT_SYSCALL */
Reference in a new issue View git blame Copy permalink