linux/mm/truncate.c
Hugh Dickins aa5b9178c0
mm: invalidation check mapping before folio_contains
Enabling tmpfs "direct IO" exposes it to invalidate_inode_pages2_range(),
which when swapping can hit the VM_BUG_ON_FOLIO(!folio_contains()): the
folio has been moved from page cache to swap cache (with folio->mapping
reset to NULL), but the folio_index() embedded in folio_contains() sees
swapcache, and so returns the swapcache_index() - whereas folio->index
would be the right one to check against the index from mapping's xarray.

There are different ways to fix this, but my preference is just to order
the checks in invalidate_inode_pages2_range() the same way that they are
in __filemap_get_folio() and find_lock_entries() and filemap_fault():
check folio->mapping before folio_contains().

Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <f0b31772-78d7-f198-6482-9f25aab8c13f@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-08-11 13:48:55 +02:00

860 lines
26 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* mm/truncate.c - code for taking down pages from address_spaces
*
* Copyright (C) 2002, Linus Torvalds
*
* 10Sep2002 Andrew Morton
* Initial version.
*/
#include <linux/kernel.h>
#include <linux/backing-dev.h>
#include <linux/dax.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/export.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/pagevec.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/buffer_head.h> /* grr. try_to_release_page */
#include <linux/shmem_fs.h>
#include <linux/rmap.h>
#include "internal.h"
/*
* Regular page slots are stabilized by the page lock even without the tree
* itself locked. These unlocked entries need verification under the tree
* lock.
*/
static inline void __clear_shadow_entry(struct address_space *mapping,
pgoff_t index, void *entry)
{
XA_STATE(xas, &mapping->i_pages, index);
xas_set_update(&xas, workingset_update_node);
if (xas_load(&xas) != entry)
return;
xas_store(&xas, NULL);
}
static void clear_shadow_entry(struct address_space *mapping, pgoff_t index,
void *entry)
{
spin_lock(&mapping->host->i_lock);
xa_lock_irq(&mapping->i_pages);
__clear_shadow_entry(mapping, index, entry);
xa_unlock_irq(&mapping->i_pages);
if (mapping_shrinkable(mapping))
inode_add_lru(mapping->host);
spin_unlock(&mapping->host->i_lock);
}
/*
* Unconditionally remove exceptional entries. Usually called from truncate
* path. Note that the folio_batch may be altered by this function by removing
* exceptional entries similar to what folio_batch_remove_exceptionals() does.
*/
static void truncate_folio_batch_exceptionals(struct address_space *mapping,
struct folio_batch *fbatch, pgoff_t *indices)
{
int i, j;
bool dax;
/* Handled by shmem itself */
if (shmem_mapping(mapping))
return;
for (j = 0; j < folio_batch_count(fbatch); j++)
if (xa_is_value(fbatch->folios[j]))
break;
if (j == folio_batch_count(fbatch))
return;
dax = dax_mapping(mapping);
if (!dax) {
spin_lock(&mapping->host->i_lock);
xa_lock_irq(&mapping->i_pages);
}
for (i = j; i < folio_batch_count(fbatch); i++) {
struct folio *folio = fbatch->folios[i];
pgoff_t index = indices[i];
if (!xa_is_value(folio)) {
fbatch->folios[j++] = folio;
continue;
}
if (unlikely(dax)) {
dax_delete_mapping_entry(mapping, index);
continue;
}
__clear_shadow_entry(mapping, index, folio);
}
if (!dax) {
xa_unlock_irq(&mapping->i_pages);
if (mapping_shrinkable(mapping))
inode_add_lru(mapping->host);
spin_unlock(&mapping->host->i_lock);
}
fbatch->nr = j;
}
/*
* Invalidate exceptional entry if easily possible. This handles exceptional
* entries for invalidate_inode_pages().
*/
static int invalidate_exceptional_entry(struct address_space *mapping,
pgoff_t index, void *entry)
{
/* Handled by shmem itself, or for DAX we do nothing. */
if (shmem_mapping(mapping) || dax_mapping(mapping))
return 1;
clear_shadow_entry(mapping, index, entry);
return 1;
}
/*
* Invalidate exceptional entry if clean. This handles exceptional entries for
* invalidate_inode_pages2() so for DAX it evicts only clean entries.
*/
static int invalidate_exceptional_entry2(struct address_space *mapping,
pgoff_t index, void *entry)
{
/* Handled by shmem itself */
if (shmem_mapping(mapping))
return 1;
if (dax_mapping(mapping))
return dax_invalidate_mapping_entry_sync(mapping, index);
clear_shadow_entry(mapping, index, entry);
return 1;
}
/**
* folio_invalidate - Invalidate part or all of a folio.
* @folio: The folio which is affected.
* @offset: start of the range to invalidate
* @length: length of the range to invalidate
*
* folio_invalidate() is called when all or part of the folio has become
* invalidated by a truncate operation.
*
* folio_invalidate() does not have to release all buffers, but it must
* ensure that no dirty buffer is left outside @offset and that no I/O
* is underway against any of the blocks which are outside the truncation
* point. Because the caller is about to free (and possibly reuse) those
* blocks on-disk.
*/
void folio_invalidate(struct folio *folio, size_t offset, size_t length)
{
const struct address_space_operations *aops = folio->mapping->a_ops;
if (aops->invalidate_folio)
aops->invalidate_folio(folio, offset, length);
}
EXPORT_SYMBOL_GPL(folio_invalidate);
/*
* If truncate cannot remove the fs-private metadata from the page, the page
* becomes orphaned. It will be left on the LRU and may even be mapped into
* user pagetables if we're racing with filemap_fault().
*
* We need to bail out if page->mapping is no longer equal to the original
* mapping. This happens a) when the VM reclaimed the page while we waited on
* its lock, b) when a concurrent invalidate_mapping_pages got there first and
* c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
*/
static void truncate_cleanup_folio(struct folio *folio)
{
if (folio_mapped(folio))
unmap_mapping_folio(folio);
if (folio_has_private(folio))
folio_invalidate(folio, 0, folio_size(folio));
/*
* Some filesystems seem to re-dirty the page even after
* the VM has canceled the dirty bit (eg ext3 journaling).
* Hence dirty accounting check is placed after invalidation.
*/
folio_cancel_dirty(folio);
folio_clear_mappedtodisk(folio);
}
int truncate_inode_folio(struct address_space *mapping, struct folio *folio)
{
if (folio->mapping != mapping)
return -EIO;
truncate_cleanup_folio(folio);
filemap_remove_folio(folio);
return 0;
}
/*
* Handle partial folios. The folio may be entirely within the
* range if a split has raced with us. If not, we zero the part of the
* folio that's within the [start, end] range, and then split the folio if
* it's large. split_page_range() will discard pages which now lie beyond
* i_size, and we rely on the caller to discard pages which lie within a
* newly created hole.
*
* Returns false if splitting failed so the caller can avoid
* discarding the entire folio which is stubbornly unsplit.
*/
bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end)
{
loff_t pos = folio_pos(folio);
unsigned int offset, length;
if (pos < start)
offset = start - pos;
else
offset = 0;
length = folio_size(folio);
if (pos + length <= (u64)end)
length = length - offset;
else
length = end + 1 - pos - offset;
folio_wait_writeback(folio);
if (length == folio_size(folio)) {
truncate_inode_folio(folio->mapping, folio);
return true;
}
/*
* We may be zeroing pages we're about to discard, but it avoids
* doing a complex calculation here, and then doing the zeroing
* anyway if the page split fails.
*/
folio_zero_range(folio, offset, length);
if (folio_has_private(folio))
folio_invalidate(folio, offset, length);
if (!folio_test_large(folio))
return true;
if (split_folio(folio) == 0)
return true;
if (folio_test_dirty(folio))
return false;
truncate_inode_folio(folio->mapping, folio);
return true;
}
/*
* Used to get rid of pages on hardware memory corruption.
*/
int generic_error_remove_page(struct address_space *mapping, struct page *page)
{
VM_BUG_ON_PAGE(PageTail(page), page);
if (!mapping)
return -EINVAL;
/*
* Only punch for normal data pages for now.
* Handling other types like directories would need more auditing.
*/
if (!S_ISREG(mapping->host->i_mode))
return -EIO;
return truncate_inode_folio(mapping, page_folio(page));
}
EXPORT_SYMBOL(generic_error_remove_page);
static long mapping_evict_folio(struct address_space *mapping,
struct folio *folio)
{
if (folio_test_dirty(folio) || folio_test_writeback(folio))
return 0;
/* The refcount will be elevated if any page in the folio is mapped */
if (folio_ref_count(folio) >
folio_nr_pages(folio) + folio_has_private(folio) + 1)
return 0;
if (folio_has_private(folio) && !filemap_release_folio(folio, 0))
return 0;
return remove_mapping(mapping, folio);
}
/**
* invalidate_inode_page() - Remove an unused page from the pagecache.
* @page: The page to remove.
*
* Safely invalidate one page from its pagecache mapping.
* It only drops clean, unused pages.
*
* Context: Page must be locked.
* Return: The number of pages successfully removed.
*/
long invalidate_inode_page(struct page *page)
{
struct folio *folio = page_folio(page);
struct address_space *mapping = folio_mapping(folio);
/* The page may have been truncated before it was locked */
if (!mapping)
return 0;
return mapping_evict_folio(mapping, folio);
}
/**
* truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
* @mapping: mapping to truncate
* @lstart: offset from which to truncate
* @lend: offset to which to truncate (inclusive)
*
* Truncate the page cache, removing the pages that are between
* specified offsets (and zeroing out partial pages
* if lstart or lend + 1 is not page aligned).
*
* Truncate takes two passes - the first pass is nonblocking. It will not
* block on page locks and it will not block on writeback. The second pass
* will wait. This is to prevent as much IO as possible in the affected region.
* The first pass will remove most pages, so the search cost of the second pass
* is low.
*
* We pass down the cache-hot hint to the page freeing code. Even if the
* mapping is large, it is probably the case that the final pages are the most
* recently touched, and freeing happens in ascending file offset order.
*
* Note that since ->invalidate_folio() accepts range to invalidate
* truncate_inode_pages_range is able to handle cases where lend + 1 is not
* page aligned properly.
*/
void truncate_inode_pages_range(struct address_space *mapping,
loff_t lstart, loff_t lend)
{
pgoff_t start; /* inclusive */
pgoff_t end; /* exclusive */
struct folio_batch fbatch;
pgoff_t indices[PAGEVEC_SIZE];
pgoff_t index;
int i;
struct folio *folio;
bool same_folio;
if (mapping_empty(mapping))
return;
/*
* 'start' and 'end' always covers the range of pages to be fully
* truncated. Partial pages are covered with 'partial_start' at the
* start of the range and 'partial_end' at the end of the range.
* Note that 'end' is exclusive while 'lend' is inclusive.
*/
start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (lend == -1)
/*
* lend == -1 indicates end-of-file so we have to set 'end'
* to the highest possible pgoff_t and since the type is
* unsigned we're using -1.
*/
end = -1;
else
end = (lend + 1) >> PAGE_SHIFT;
folio_batch_init(&fbatch);
index = start;
while (index < end && find_lock_entries(mapping, &index, end - 1,
&fbatch, indices)) {
truncate_folio_batch_exceptionals(mapping, &fbatch, indices);
for (i = 0; i < folio_batch_count(&fbatch); i++)
truncate_cleanup_folio(fbatch.folios[i]);
delete_from_page_cache_batch(mapping, &fbatch);
for (i = 0; i < folio_batch_count(&fbatch); i++)
folio_unlock(fbatch.folios[i]);
folio_batch_release(&fbatch);
cond_resched();
}
same_folio = (lstart >> PAGE_SHIFT) == (lend >> PAGE_SHIFT);
folio = __filemap_get_folio(mapping, lstart >> PAGE_SHIFT, FGP_LOCK, 0);
if (!IS_ERR(folio)) {
same_folio = lend < folio_pos(folio) + folio_size(folio);
if (!truncate_inode_partial_folio(folio, lstart, lend)) {
start = folio->index + folio_nr_pages(folio);
if (same_folio)
end = folio->index;
}
folio_unlock(folio);
folio_put(folio);
folio = NULL;
}
if (!same_folio) {
folio = __filemap_get_folio(mapping, lend >> PAGE_SHIFT,
FGP_LOCK, 0);
if (!IS_ERR(folio)) {
if (!truncate_inode_partial_folio(folio, lstart, lend))
end = folio->index;
folio_unlock(folio);
folio_put(folio);
}
}
index = start;
while (index < end) {
cond_resched();
if (!find_get_entries(mapping, &index, end - 1, &fbatch,
indices)) {
/* If all gone from start onwards, we're done */
if (index == start)
break;
/* Otherwise restart to make sure all gone */
index = start;
continue;
}
for (i = 0; i < folio_batch_count(&fbatch); i++) {
struct folio *folio = fbatch.folios[i];
/* We rely upon deletion not changing page->index */
if (xa_is_value(folio))
continue;
folio_lock(folio);
VM_BUG_ON_FOLIO(!folio_contains(folio, indices[i]), folio);
folio_wait_writeback(folio);
truncate_inode_folio(mapping, folio);
folio_unlock(folio);
}
truncate_folio_batch_exceptionals(mapping, &fbatch, indices);
folio_batch_release(&fbatch);
}
}
EXPORT_SYMBOL(truncate_inode_pages_range);
/**
* truncate_inode_pages - truncate *all* the pages from an offset
* @mapping: mapping to truncate
* @lstart: offset from which to truncate
*
* Called under (and serialised by) inode->i_rwsem and
* mapping->invalidate_lock.
*
* Note: When this function returns, there can be a page in the process of
* deletion (inside __filemap_remove_folio()) in the specified range. Thus
* mapping->nrpages can be non-zero when this function returns even after
* truncation of the whole mapping.
*/
void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
{
truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
}
EXPORT_SYMBOL(truncate_inode_pages);
/**
* truncate_inode_pages_final - truncate *all* pages before inode dies
* @mapping: mapping to truncate
*
* Called under (and serialized by) inode->i_rwsem.
*
* Filesystems have to use this in the .evict_inode path to inform the
* VM that this is the final truncate and the inode is going away.
*/
void truncate_inode_pages_final(struct address_space *mapping)
{
/*
* Page reclaim can not participate in regular inode lifetime
* management (can't call iput()) and thus can race with the
* inode teardown. Tell it when the address space is exiting,
* so that it does not install eviction information after the
* final truncate has begun.
*/
mapping_set_exiting(mapping);
if (!mapping_empty(mapping)) {
/*
* As truncation uses a lockless tree lookup, cycle
* the tree lock to make sure any ongoing tree
* modification that does not see AS_EXITING is
* completed before starting the final truncate.
*/
xa_lock_irq(&mapping->i_pages);
xa_unlock_irq(&mapping->i_pages);
}
truncate_inode_pages(mapping, 0);
}
EXPORT_SYMBOL(truncate_inode_pages_final);
/**
* mapping_try_invalidate - Invalidate all the evictable folios of one inode
* @mapping: the address_space which holds the folios to invalidate
* @start: the offset 'from' which to invalidate
* @end: the offset 'to' which to invalidate (inclusive)
* @nr_failed: How many folio invalidations failed
*
* This function is similar to invalidate_mapping_pages(), except that it
* returns the number of folios which could not be evicted in @nr_failed.
*/
unsigned long mapping_try_invalidate(struct address_space *mapping,
pgoff_t start, pgoff_t end, unsigned long *nr_failed)
{
pgoff_t indices[PAGEVEC_SIZE];
struct folio_batch fbatch;
pgoff_t index = start;
unsigned long ret;
unsigned long count = 0;
int i;
folio_batch_init(&fbatch);
while (find_lock_entries(mapping, &index, end, &fbatch, indices)) {
for (i = 0; i < folio_batch_count(&fbatch); i++) {
struct folio *folio = fbatch.folios[i];
/* We rely upon deletion not changing folio->index */
if (xa_is_value(folio)) {
count += invalidate_exceptional_entry(mapping,
indices[i], folio);
continue;
}
ret = mapping_evict_folio(mapping, folio);
folio_unlock(folio);
/*
* Invalidation is a hint that the folio is no longer
* of interest and try to speed up its reclaim.
*/
if (!ret) {
deactivate_file_folio(folio);
/* Likely in the lru cache of a remote CPU */
if (nr_failed)
(*nr_failed)++;
}
count += ret;
}
folio_batch_remove_exceptionals(&fbatch);
folio_batch_release(&fbatch);
cond_resched();
}
return count;
}
/**
* invalidate_mapping_pages - Invalidate all clean, unlocked cache of one inode
* @mapping: the address_space which holds the cache to invalidate
* @start: the offset 'from' which to invalidate
* @end: the offset 'to' which to invalidate (inclusive)
*
* This function removes pages that are clean, unmapped and unlocked,
* as well as shadow entries. It will not block on IO activity.
*
* If you want to remove all the pages of one inode, regardless of
* their use and writeback state, use truncate_inode_pages().
*
* Return: The number of indices that had their contents invalidated
*/
unsigned long invalidate_mapping_pages(struct address_space *mapping,
pgoff_t start, pgoff_t end)
{
return mapping_try_invalidate(mapping, start, end, NULL);
}
EXPORT_SYMBOL(invalidate_mapping_pages);
/*
* This is like invalidate_inode_page(), except it ignores the page's
* refcount. We do this because invalidate_inode_pages2() needs stronger
* invalidation guarantees, and cannot afford to leave pages behind because
* shrink_page_list() has a temp ref on them, or because they're transiently
* sitting in the folio_add_lru() caches.
*/
static int invalidate_complete_folio2(struct address_space *mapping,
struct folio *folio)
{
if (folio->mapping != mapping)
return 0;
if (folio_has_private(folio) &&
!filemap_release_folio(folio, GFP_KERNEL))
return 0;
spin_lock(&mapping->host->i_lock);
xa_lock_irq(&mapping->i_pages);
if (folio_test_dirty(folio))
goto failed;
BUG_ON(folio_has_private(folio));
__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);
return 1;
failed:
xa_unlock_irq(&mapping->i_pages);
spin_unlock(&mapping->host->i_lock);
return 0;
}
static int folio_launder(struct address_space *mapping, struct folio *folio)
{
if (!folio_test_dirty(folio))
return 0;
if (folio->mapping != mapping || mapping->a_ops->launder_folio == NULL)
return 0;
return mapping->a_ops->launder_folio(folio);
}
/**
* invalidate_inode_pages2_range - remove range of pages from an address_space
* @mapping: the address_space
* @start: the page offset 'from' which to invalidate
* @end: the page offset 'to' which to invalidate (inclusive)
*
* Any pages which are found to be mapped into pagetables are unmapped prior to
* invalidation.
*
* Return: -EBUSY if any pages could not be invalidated.
*/
int invalidate_inode_pages2_range(struct address_space *mapping,
pgoff_t start, pgoff_t end)
{
pgoff_t indices[PAGEVEC_SIZE];
struct folio_batch fbatch;
pgoff_t index;
int i;
int ret = 0;
int ret2 = 0;
int did_range_unmap = 0;
if (mapping_empty(mapping))
return 0;
folio_batch_init(&fbatch);
index = start;
while (find_get_entries(mapping, &index, end, &fbatch, indices)) {
for (i = 0; i < folio_batch_count(&fbatch); i++) {
struct folio *folio = fbatch.folios[i];
/* We rely upon deletion not changing folio->index */
if (xa_is_value(folio)) {
if (!invalidate_exceptional_entry2(mapping,
indices[i], folio))
ret = -EBUSY;
continue;
}
if (!did_range_unmap && folio_mapped(folio)) {
/*
* If folio is mapped, before taking its lock,
* zap the rest of the file in one hit.
*/
unmap_mapping_pages(mapping, indices[i],
(1 + end - indices[i]), false);
did_range_unmap = 1;
}
folio_lock(folio);
if (unlikely(folio->mapping != mapping)) {
folio_unlock(folio);
continue;
}
VM_BUG_ON_FOLIO(!folio_contains(folio, indices[i]), folio);
folio_wait_writeback(folio);
if (folio_mapped(folio))
unmap_mapping_folio(folio);
BUG_ON(folio_mapped(folio));
ret2 = folio_launder(mapping, folio);
if (ret2 == 0) {
if (!invalidate_complete_folio2(mapping, folio))
ret2 = -EBUSY;
}
if (ret2 < 0)
ret = ret2;
folio_unlock(folio);
}
folio_batch_remove_exceptionals(&fbatch);
folio_batch_release(&fbatch);
cond_resched();
}
/*
* For DAX we invalidate page tables after invalidating page cache. We
* could invalidate page tables while invalidating each entry however
* that would be expensive. And doing range unmapping before doesn't
* work as we have no cheap way to find whether page cache entry didn't
* get remapped later.
*/
if (dax_mapping(mapping)) {
unmap_mapping_pages(mapping, start, end - start + 1, false);
}
return ret;
}
EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
/**
* invalidate_inode_pages2 - remove all pages from an address_space
* @mapping: the address_space
*
* Any pages which are found to be mapped into pagetables are unmapped prior to
* invalidation.
*
* Return: -EBUSY if any pages could not be invalidated.
*/
int invalidate_inode_pages2(struct address_space *mapping)
{
return invalidate_inode_pages2_range(mapping, 0, -1);
}
EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
/**
* truncate_pagecache - unmap and remove pagecache that has been truncated
* @inode: inode
* @newsize: new file size
*
* inode's new i_size must already be written before truncate_pagecache
* is called.
*
* This function should typically be called before the filesystem
* releases resources associated with the freed range (eg. deallocates
* blocks). This way, pagecache will always stay logically coherent
* with on-disk format, and the filesystem would not have to deal with
* situations such as writepage being called for a page that has already
* had its underlying blocks deallocated.
*/
void truncate_pagecache(struct inode *inode, loff_t newsize)
{
struct address_space *mapping = inode->i_mapping;
loff_t holebegin = round_up(newsize, PAGE_SIZE);
/*
* unmap_mapping_range is called twice, first simply for
* efficiency so that truncate_inode_pages does fewer
* single-page unmaps. However after this first call, and
* before truncate_inode_pages finishes, it is possible for
* private pages to be COWed, which remain after
* truncate_inode_pages finishes, hence the second
* unmap_mapping_range call must be made for correctness.
*/
unmap_mapping_range(mapping, holebegin, 0, 1);
truncate_inode_pages(mapping, newsize);
unmap_mapping_range(mapping, holebegin, 0, 1);
}
EXPORT_SYMBOL(truncate_pagecache);
/**
* truncate_setsize - update inode and pagecache for a new file size
* @inode: inode
* @newsize: new file size
*
* truncate_setsize updates i_size and performs pagecache truncation (if
* necessary) to @newsize. It will be typically be called from the filesystem's
* setattr function when ATTR_SIZE is passed in.
*
* Must be called with a lock serializing truncates and writes (generally
* i_rwsem but e.g. xfs uses a different lock) and before all filesystem
* specific block truncation has been performed.
*/
void truncate_setsize(struct inode *inode, loff_t newsize)
{
loff_t oldsize = inode->i_size;
i_size_write(inode, newsize);
if (newsize > oldsize)
pagecache_isize_extended(inode, oldsize, newsize);
truncate_pagecache(inode, newsize);
}
EXPORT_SYMBOL(truncate_setsize);
/**
* pagecache_isize_extended - update pagecache after extension of i_size
* @inode: inode for which i_size was extended
* @from: original inode size
* @to: new inode size
*
* Handle extension of inode size either caused by extending truncate or by
* write starting after current i_size. We mark the page straddling current
* i_size RO so that page_mkwrite() is called on the nearest write access to
* the page. This way filesystem can be sure that page_mkwrite() is called on
* the page before user writes to the page via mmap after the i_size has been
* changed.
*
* The function must be called after i_size is updated so that page fault
* coming after we unlock the page will already see the new i_size.
* The function must be called while we still hold i_rwsem - this not only
* makes sure i_size is stable but also that userspace cannot observe new
* i_size value before we are prepared to store mmap writes at new inode size.
*/
void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to)
{
int bsize = i_blocksize(inode);
loff_t rounded_from;
struct page *page;
pgoff_t index;
WARN_ON(to > inode->i_size);
if (from >= to || bsize == PAGE_SIZE)
return;
/* Page straddling @from will not have any hole block created? */
rounded_from = round_up(from, bsize);
if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1)))
return;
index = from >> PAGE_SHIFT;
page = find_lock_page(inode->i_mapping, index);
/* Page not cached? Nothing to do */
if (!page)
return;
/*
* See clear_page_dirty_for_io() for details why set_page_dirty()
* is needed.
*/
if (page_mkclean(page))
set_page_dirty(page);
unlock_page(page);
put_page(page);
}
EXPORT_SYMBOL(pagecache_isize_extended);
/**
* truncate_pagecache_range - unmap and remove pagecache that is hole-punched
* @inode: inode
* @lstart: offset of beginning of hole
* @lend: offset of last byte of hole
*
* This function should typically be called before the filesystem
* releases resources associated with the freed range (eg. deallocates
* blocks). This way, pagecache will always stay logically coherent
* with on-disk format, and the filesystem would not have to deal with
* situations such as writepage being called for a page that has already
* had its underlying blocks deallocated.
*/
void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
{
struct address_space *mapping = inode->i_mapping;
loff_t unmap_start = round_up(lstart, PAGE_SIZE);
loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
/*
* This rounding is currently just for example: unmap_mapping_range
* expands its hole outwards, whereas we want it to contract the hole
* inwards. However, existing callers of truncate_pagecache_range are
* doing their own page rounding first. Note that unmap_mapping_range
* allows holelen 0 for all, and we allow lend -1 for end of file.
*/
/*
* Unlike in truncate_pagecache, unmap_mapping_range is called only
* once (before truncating pagecache), and without "even_cows" flag:
* hole-punching should not remove private COWed pages from the hole.
*/
if ((u64)unmap_end > (u64)unmap_start)
unmap_mapping_range(mapping, unmap_start,
1 + unmap_end - unmap_start, 0);
truncate_inode_pages_range(mapping, lstart, lend);
}
EXPORT_SYMBOL(truncate_pagecache_range);