linux/fs/dax.c
Linus Torvalds 088737f44b Writeback error handling fixes (pile #2)
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Merge tag 'for-linus-v4.13-2' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux

Pull Writeback error handling updates from Jeff Layton:
 "This pile represents the bulk of the writeback error handling fixes
  that I have for this cycle. Some of the earlier patches in this pile
  may look trivial but they are prerequisites for later patches in the
  series.

  The aim of this set is to improve how we track and report writeback
  errors to userland. Most applications that care about data integrity
  will periodically call fsync/fdatasync/msync to ensure that their
  writes have made it to the backing store.

  For a very long time, we have tracked writeback errors using two flags
  in the address_space: AS_EIO and AS_ENOSPC. Those flags are set when a
  writeback error occurs (via mapping_set_error) and are cleared as a
  side-effect of filemap_check_errors (as you noted yesterday). This
  model really sucks for userland.

  Only the first task to call fsync (or msync or fdatasync) will see the
  error. Any subsequent task calling fsync on a file will get back 0
  (unless another writeback error occurs in the interim). If I have
  several tasks writing to a file and calling fsync to ensure that their
  writes got stored, then I need to have them coordinate with one
  another. That's difficult enough, but in a world of containerized
  setups that coordination may even not be possible.

  But wait...it gets worse!

  The calls to filemap_check_errors can be buried pretty far down in the
  call stack, and there are internal callers of filemap_write_and_wait
  and the like that also end up clearing those errors. Many of those
  callers ignore the error return from that function or return it to
  userland at nonsensical times (e.g. truncate() or stat()). If I get
  back -EIO on a truncate, there is no reason to think that it was
  because some previous writeback failed, and a subsequent fsync() will
  (incorrectly) return 0.

  This pile aims to do three things:

   1) ensure that when a writeback error occurs that that error will be
      reported to userland on a subsequent fsync/fdatasync/msync call,
      regardless of what internal callers are doing

   2) report writeback errors on all file descriptions that were open at
      the time that the error occurred. This is a user-visible change,
      but I think most applications are written to assume this behavior
      anyway. Those that aren't are unlikely to be hurt by it.

   3) document what filesystems should do when there is a writeback
      error. Today, there is very little consistency between them, and a
      lot of cargo-cult copying. We need to make it very clear what
      filesystems should do in this situation.

  To achieve this, the set adds a new data type (errseq_t) and then
  builds new writeback error tracking infrastructure around that. Once
  all of that is in place, we change the filesystems to use the new
  infrastructure for reporting wb errors to userland.

  Note that this is just the initial foray into cleaning up this mess.
  There is a lot of work remaining here:

   1) convert the rest of the filesystems in a similar fashion. Once the
      initial set is in, then I think most other fs' will be fairly
      simple to convert. Hopefully most of those can in via individual
      filesystem trees.

   2) convert internal waiters on writeback to use errseq_t for
      detecting errors instead of relying on the AS_* flags. I have some
      draft patches for this for ext4, but they are not quite ready for
      prime time yet.

  This was a discussion topic this year at LSF/MM too. If you're
  interested in the gory details, LWN has some good articles about this:

      https://lwn.net/Articles/718734/
      https://lwn.net/Articles/724307/"

* tag 'for-linus-v4.13-2' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
  btrfs: minimal conversion to errseq_t writeback error reporting on fsync
  xfs: minimal conversion to errseq_t writeback error reporting
  ext4: use errseq_t based error handling for reporting data writeback errors
  fs: convert __generic_file_fsync to use errseq_t based reporting
  block: convert to errseq_t based writeback error tracking
  dax: set errors in mapping when writeback fails
  Documentation: flesh out the section in vfs.txt on storing and reporting writeback errors
  mm: set both AS_EIO/AS_ENOSPC and errseq_t in mapping_set_error
  fs: new infrastructure for writeback error handling and reporting
  lib: add errseq_t type and infrastructure for handling it
  mm: don't TestClearPageError in __filemap_fdatawait_range
  mm: clear AS_EIO/AS_ENOSPC when writeback initiation fails
  jbd2: don't clear and reset errors after waiting on writeback
  buffer: set errors in mapping at the time that the error occurs
  fs: check for writeback errors after syncing out buffers in generic_file_fsync
  buffer: use mapping_set_error instead of setting the flag
  mm: fix mapping_set_error call in me_pagecache_dirty
2017-07-07 19:38:17 -07:00

1512 lines
41 KiB
C

/*
* fs/dax.c - Direct Access filesystem code
* Copyright (c) 2013-2014 Intel Corporation
* Author: Matthew Wilcox <matthew.r.wilcox@intel.com>
* Author: Ross Zwisler <ross.zwisler@linux.intel.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*/
#include <linux/atomic.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h>
#include <linux/dax.h>
#include <linux/fs.h>
#include <linux/genhd.h>
#include <linux/highmem.h>
#include <linux/memcontrol.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/pagevec.h>
#include <linux/sched.h>
#include <linux/sched/signal.h>
#include <linux/uio.h>
#include <linux/vmstat.h>
#include <linux/pfn_t.h>
#include <linux/sizes.h>
#include <linux/mmu_notifier.h>
#include <linux/iomap.h>
#include "internal.h"
#define CREATE_TRACE_POINTS
#include <trace/events/fs_dax.h>
/* We choose 4096 entries - same as per-zone page wait tables */
#define DAX_WAIT_TABLE_BITS 12
#define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
static int __init init_dax_wait_table(void)
{
int i;
for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++)
init_waitqueue_head(wait_table + i);
return 0;
}
fs_initcall(init_dax_wait_table);
static int dax_is_pmd_entry(void *entry)
{
return (unsigned long)entry & RADIX_DAX_PMD;
}
static int dax_is_pte_entry(void *entry)
{
return !((unsigned long)entry & RADIX_DAX_PMD);
}
static int dax_is_zero_entry(void *entry)
{
return (unsigned long)entry & RADIX_DAX_HZP;
}
static int dax_is_empty_entry(void *entry)
{
return (unsigned long)entry & RADIX_DAX_EMPTY;
}
/*
* DAX radix tree locking
*/
struct exceptional_entry_key {
struct address_space *mapping;
pgoff_t entry_start;
};
struct wait_exceptional_entry_queue {
wait_queue_entry_t wait;
struct exceptional_entry_key key;
};
static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
pgoff_t index, void *entry, struct exceptional_entry_key *key)
{
unsigned long hash;
/*
* If 'entry' is a PMD, align the 'index' that we use for the wait
* queue to the start of that PMD. This ensures that all offsets in
* the range covered by the PMD map to the same bit lock.
*/
if (dax_is_pmd_entry(entry))
index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
key->mapping = mapping;
key->entry_start = index;
hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
return wait_table + hash;
}
static int wake_exceptional_entry_func(wait_queue_entry_t *wait, unsigned int mode,
int sync, void *keyp)
{
struct exceptional_entry_key *key = keyp;
struct wait_exceptional_entry_queue *ewait =
container_of(wait, struct wait_exceptional_entry_queue, wait);
if (key->mapping != ewait->key.mapping ||
key->entry_start != ewait->key.entry_start)
return 0;
return autoremove_wake_function(wait, mode, sync, NULL);
}
/*
* Check whether the given slot is locked. The function must be called with
* mapping->tree_lock held
*/
static inline int slot_locked(struct address_space *mapping, void **slot)
{
unsigned long entry = (unsigned long)
radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
return entry & RADIX_DAX_ENTRY_LOCK;
}
/*
* Mark the given slot is locked. The function must be called with
* mapping->tree_lock held
*/
static inline void *lock_slot(struct address_space *mapping, void **slot)
{
unsigned long entry = (unsigned long)
radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
entry |= RADIX_DAX_ENTRY_LOCK;
radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
return (void *)entry;
}
/*
* Mark the given slot is unlocked. The function must be called with
* mapping->tree_lock held
*/
static inline void *unlock_slot(struct address_space *mapping, void **slot)
{
unsigned long entry = (unsigned long)
radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK;
radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
return (void *)entry;
}
/*
* Lookup entry in radix tree, wait for it to become unlocked if it is
* exceptional entry and return it. The caller must call
* put_unlocked_mapping_entry() when he decided not to lock the entry or
* put_locked_mapping_entry() when he locked the entry and now wants to
* unlock it.
*
* The function must be called with mapping->tree_lock held.
*/
static void *get_unlocked_mapping_entry(struct address_space *mapping,
pgoff_t index, void ***slotp)
{
void *entry, **slot;
struct wait_exceptional_entry_queue ewait;
wait_queue_head_t *wq;
init_wait(&ewait.wait);
ewait.wait.func = wake_exceptional_entry_func;
for (;;) {
entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
&slot);
if (!entry || !radix_tree_exceptional_entry(entry) ||
!slot_locked(mapping, slot)) {
if (slotp)
*slotp = slot;
return entry;
}
wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
prepare_to_wait_exclusive(wq, &ewait.wait,
TASK_UNINTERRUPTIBLE);
spin_unlock_irq(&mapping->tree_lock);
schedule();
finish_wait(wq, &ewait.wait);
spin_lock_irq(&mapping->tree_lock);
}
}
static void dax_unlock_mapping_entry(struct address_space *mapping,
pgoff_t index)
{
void *entry, **slot;
spin_lock_irq(&mapping->tree_lock);
entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
!slot_locked(mapping, slot))) {
spin_unlock_irq(&mapping->tree_lock);
return;
}
unlock_slot(mapping, slot);
spin_unlock_irq(&mapping->tree_lock);
dax_wake_mapping_entry_waiter(mapping, index, entry, false);
}
static void put_locked_mapping_entry(struct address_space *mapping,
pgoff_t index, void *entry)
{
if (!radix_tree_exceptional_entry(entry)) {
unlock_page(entry);
put_page(entry);
} else {
dax_unlock_mapping_entry(mapping, index);
}
}
/*
* Called when we are done with radix tree entry we looked up via
* get_unlocked_mapping_entry() and which we didn't lock in the end.
*/
static void put_unlocked_mapping_entry(struct address_space *mapping,
pgoff_t index, void *entry)
{
if (!radix_tree_exceptional_entry(entry))
return;
/* We have to wake up next waiter for the radix tree entry lock */
dax_wake_mapping_entry_waiter(mapping, index, entry, false);
}
/*
* Find radix tree entry at given index. If it points to a page, return with
* the page locked. If it points to the exceptional entry, return with the
* radix tree entry locked. If the radix tree doesn't contain given index,
* create empty exceptional entry for the index and return with it locked.
*
* When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
* either return that locked entry or will return an error. This error will
* happen if there are any 4k entries (either zero pages or DAX entries)
* within the 2MiB range that we are requesting.
*
* We always favor 4k entries over 2MiB entries. There isn't a flow where we
* evict 4k entries in order to 'upgrade' them to a 2MiB entry. A 2MiB
* insertion will fail if it finds any 4k entries already in the tree, and a
* 4k insertion will cause an existing 2MiB entry to be unmapped and
* downgraded to 4k entries. This happens for both 2MiB huge zero pages as
* well as 2MiB empty entries.
*
* The exception to this downgrade path is for 2MiB DAX PMD entries that have
* real storage backing them. We will leave these real 2MiB DAX entries in
* the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
*
* Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
* persistent memory the benefit is doubtful. We can add that later if we can
* show it helps.
*/
static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
unsigned long size_flag)
{
bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
void *entry, **slot;
restart:
spin_lock_irq(&mapping->tree_lock);
entry = get_unlocked_mapping_entry(mapping, index, &slot);
if (entry) {
if (size_flag & RADIX_DAX_PMD) {
if (!radix_tree_exceptional_entry(entry) ||
dax_is_pte_entry(entry)) {
put_unlocked_mapping_entry(mapping, index,
entry);
entry = ERR_PTR(-EEXIST);
goto out_unlock;
}
} else { /* trying to grab a PTE entry */
if (radix_tree_exceptional_entry(entry) &&
dax_is_pmd_entry(entry) &&
(dax_is_zero_entry(entry) ||
dax_is_empty_entry(entry))) {
pmd_downgrade = true;
}
}
}
/* No entry for given index? Make sure radix tree is big enough. */
if (!entry || pmd_downgrade) {
int err;
if (pmd_downgrade) {
/*
* Make sure 'entry' remains valid while we drop
* mapping->tree_lock.
*/
entry = lock_slot(mapping, slot);
}
spin_unlock_irq(&mapping->tree_lock);
/*
* Besides huge zero pages the only other thing that gets
* downgraded are empty entries which don't need to be
* unmapped.
*/
if (pmd_downgrade && dax_is_zero_entry(entry))
unmap_mapping_range(mapping,
(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
err = radix_tree_preload(
mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
if (err) {
if (pmd_downgrade)
put_locked_mapping_entry(mapping, index, entry);
return ERR_PTR(err);
}
spin_lock_irq(&mapping->tree_lock);
if (!entry) {
/*
* We needed to drop the page_tree lock while calling
* radix_tree_preload() and we didn't have an entry to
* lock. See if another thread inserted an entry at
* our index during this time.
*/
entry = __radix_tree_lookup(&mapping->page_tree, index,
NULL, &slot);
if (entry) {
radix_tree_preload_end();
spin_unlock_irq(&mapping->tree_lock);
goto restart;
}
}
if (pmd_downgrade) {
radix_tree_delete(&mapping->page_tree, index);
mapping->nrexceptional--;
dax_wake_mapping_entry_waiter(mapping, index, entry,
true);
}
entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
err = __radix_tree_insert(&mapping->page_tree, index,
dax_radix_order(entry), entry);
radix_tree_preload_end();
if (err) {
spin_unlock_irq(&mapping->tree_lock);
/*
* Our insertion of a DAX entry failed, most likely
* because we were inserting a PMD entry and it
* collided with a PTE sized entry at a different
* index in the PMD range. We haven't inserted
* anything into the radix tree and have no waiters to
* wake.
*/
return ERR_PTR(err);
}
/* Good, we have inserted empty locked entry into the tree. */
mapping->nrexceptional++;
spin_unlock_irq(&mapping->tree_lock);
return entry;
}
/* Normal page in radix tree? */
if (!radix_tree_exceptional_entry(entry)) {
struct page *page = entry;
get_page(page);
spin_unlock_irq(&mapping->tree_lock);
lock_page(page);
/* Page got truncated? Retry... */
if (unlikely(page->mapping != mapping)) {
unlock_page(page);
put_page(page);
goto restart;
}
return page;
}
entry = lock_slot(mapping, slot);
out_unlock:
spin_unlock_irq(&mapping->tree_lock);
return entry;
}
/*
* We do not necessarily hold the mapping->tree_lock when we call this
* function so it is possible that 'entry' is no longer a valid item in the
* radix tree. This is okay because all we really need to do is to find the
* correct waitqueue where tasks might be waiting for that old 'entry' and
* wake them.
*/
void dax_wake_mapping_entry_waiter(struct address_space *mapping,
pgoff_t index, void *entry, bool wake_all)
{
struct exceptional_entry_key key;
wait_queue_head_t *wq;
wq = dax_entry_waitqueue(mapping, index, entry, &key);
/*
* Checking for locked entry and prepare_to_wait_exclusive() happens
* under mapping->tree_lock, ditto for entry handling in our callers.
* So at this point all tasks that could have seen our entry locked
* must be in the waitqueue and the following check will see them.
*/
if (waitqueue_active(wq))
__wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
}
static int __dax_invalidate_mapping_entry(struct address_space *mapping,
pgoff_t index, bool trunc)
{
int ret = 0;
void *entry;
struct radix_tree_root *page_tree = &mapping->page_tree;
spin_lock_irq(&mapping->tree_lock);
entry = get_unlocked_mapping_entry(mapping, index, NULL);
if (!entry || !radix_tree_exceptional_entry(entry))
goto out;
if (!trunc &&
(radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_DIRTY) ||
radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)))
goto out;
radix_tree_delete(page_tree, index);
mapping->nrexceptional--;
ret = 1;
out:
put_unlocked_mapping_entry(mapping, index, entry);
spin_unlock_irq(&mapping->tree_lock);
return ret;
}
/*
* Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
* entry to get unlocked before deleting it.
*/
int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
{
int ret = __dax_invalidate_mapping_entry(mapping, index, true);
/*
* This gets called from truncate / punch_hole path. As such, the caller
* must hold locks protecting against concurrent modifications of the
* radix tree (usually fs-private i_mmap_sem for writing). Since the
* caller has seen exceptional entry for this index, we better find it
* at that index as well...
*/
WARN_ON_ONCE(!ret);
return ret;
}
/*
* Invalidate exceptional DAX entry if it is clean.
*/
int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
pgoff_t index)
{
return __dax_invalidate_mapping_entry(mapping, index, false);
}
/*
* The user has performed a load from a hole in the file. Allocating
* a new page in the file would cause excessive storage usage for
* workloads with sparse files. We allocate a page cache page instead.
* We'll kick it out of the page cache if it's ever written to,
* otherwise it will simply fall out of the page cache under memory
* pressure without ever having been dirtied.
*/
static int dax_load_hole(struct address_space *mapping, void **entry,
struct vm_fault *vmf)
{
struct inode *inode = mapping->host;
struct page *page;
int ret;
/* Hole page already exists? Return it... */
if (!radix_tree_exceptional_entry(*entry)) {
page = *entry;
goto finish_fault;
}
/* This will replace locked radix tree entry with a hole page */
page = find_or_create_page(mapping, vmf->pgoff,
vmf->gfp_mask | __GFP_ZERO);
if (!page) {
ret = VM_FAULT_OOM;
goto out;
}
finish_fault:
vmf->page = page;
ret = finish_fault(vmf);
vmf->page = NULL;
*entry = page;
if (!ret) {
/* Grab reference for PTE that is now referencing the page */
get_page(page);
ret = VM_FAULT_NOPAGE;
}
out:
trace_dax_load_hole(inode, vmf, ret);
return ret;
}
static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev,
sector_t sector, size_t size, struct page *to,
unsigned long vaddr)
{
void *vto, *kaddr;
pgoff_t pgoff;
pfn_t pfn;
long rc;
int id;
rc = bdev_dax_pgoff(bdev, sector, size, &pgoff);
if (rc)
return rc;
id = dax_read_lock();
rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
if (rc < 0) {
dax_read_unlock(id);
return rc;
}
vto = kmap_atomic(to);
copy_user_page(vto, (void __force *)kaddr, vaddr, to);
kunmap_atomic(vto);
dax_read_unlock(id);
return 0;
}
/*
* By this point grab_mapping_entry() has ensured that we have a locked entry
* of the appropriate size so we don't have to worry about downgrading PMDs to
* PTEs. If we happen to be trying to insert a PTE and there is a PMD
* already in the tree, we will skip the insertion and just dirty the PMD as
* appropriate.
*/
static void *dax_insert_mapping_entry(struct address_space *mapping,
struct vm_fault *vmf,
void *entry, sector_t sector,
unsigned long flags)
{
struct radix_tree_root *page_tree = &mapping->page_tree;
int error = 0;
bool hole_fill = false;
void *new_entry;
pgoff_t index = vmf->pgoff;
if (vmf->flags & FAULT_FLAG_WRITE)
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
/* Replacing hole page with block mapping? */
if (!radix_tree_exceptional_entry(entry)) {
hole_fill = true;
/*
* Unmap the page now before we remove it from page cache below.
* The page is locked so it cannot be faulted in again.
*/
unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
PAGE_SIZE, 0);
error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
if (error)
return ERR_PTR(error);
} else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
/* replacing huge zero page with PMD block mapping */
unmap_mapping_range(mapping,
(vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
}
spin_lock_irq(&mapping->tree_lock);
new_entry = dax_radix_locked_entry(sector, flags);
if (hole_fill) {
__delete_from_page_cache(entry, NULL);
/* Drop pagecache reference */
put_page(entry);
error = __radix_tree_insert(page_tree, index,
dax_radix_order(new_entry), new_entry);
if (error) {
new_entry = ERR_PTR(error);
goto unlock;
}
mapping->nrexceptional++;
} else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
/*
* Only swap our new entry into the radix tree if the current
* entry is a zero page or an empty entry. If a normal PTE or
* PMD entry is already in the tree, we leave it alone. This
* means that if we are trying to insert a PTE and the
* existing entry is a PMD, we will just leave the PMD in the
* tree and dirty it if necessary.
*/
struct radix_tree_node *node;
void **slot;
void *ret;
ret = __radix_tree_lookup(page_tree, index, &node, &slot);
WARN_ON_ONCE(ret != entry);
__radix_tree_replace(page_tree, node, slot,
new_entry, NULL, NULL);
}
if (vmf->flags & FAULT_FLAG_WRITE)
radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
unlock:
spin_unlock_irq(&mapping->tree_lock);
if (hole_fill) {
radix_tree_preload_end();
/*
* We don't need hole page anymore, it has been replaced with
* locked radix tree entry now.
*/
if (mapping->a_ops->freepage)
mapping->a_ops->freepage(entry);
unlock_page(entry);
put_page(entry);
}
return new_entry;
}
static inline unsigned long
pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma)
{
unsigned long address;
address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
return address;
}
/* Walk all mappings of a given index of a file and writeprotect them */
static void dax_mapping_entry_mkclean(struct address_space *mapping,
pgoff_t index, unsigned long pfn)
{
struct vm_area_struct *vma;
pte_t pte, *ptep = NULL;
pmd_t *pmdp = NULL;
spinlock_t *ptl;
bool changed;
i_mmap_lock_read(mapping);
vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) {
unsigned long address;
cond_resched();
if (!(vma->vm_flags & VM_SHARED))
continue;
address = pgoff_address(index, vma);
changed = false;
if (follow_pte_pmd(vma->vm_mm, address, &ptep, &pmdp, &ptl))
continue;
if (pmdp) {
#ifdef CONFIG_FS_DAX_PMD
pmd_t pmd;
if (pfn != pmd_pfn(*pmdp))
goto unlock_pmd;
if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp))
goto unlock_pmd;
flush_cache_page(vma, address, pfn);
pmd = pmdp_huge_clear_flush(vma, address, pmdp);
pmd = pmd_wrprotect(pmd);
pmd = pmd_mkclean(pmd);
set_pmd_at(vma->vm_mm, address, pmdp, pmd);
changed = true;
unlock_pmd:
spin_unlock(ptl);
#endif
} else {
if (pfn != pte_pfn(*ptep))
goto unlock_pte;
if (!pte_dirty(*ptep) && !pte_write(*ptep))
goto unlock_pte;
flush_cache_page(vma, address, pfn);
pte = ptep_clear_flush(vma, address, ptep);
pte = pte_wrprotect(pte);
pte = pte_mkclean(pte);
set_pte_at(vma->vm_mm, address, ptep, pte);
changed = true;
unlock_pte:
pte_unmap_unlock(ptep, ptl);
}
if (changed)
mmu_notifier_invalidate_page(vma->vm_mm, address);
}
i_mmap_unlock_read(mapping);
}
static int dax_writeback_one(struct block_device *bdev,
struct dax_device *dax_dev, struct address_space *mapping,
pgoff_t index, void *entry)
{
struct radix_tree_root *page_tree = &mapping->page_tree;
void *entry2, **slot, *kaddr;
long ret = 0, id;
sector_t sector;
pgoff_t pgoff;
size_t size;
pfn_t pfn;
/*
* A page got tagged dirty in DAX mapping? Something is seriously
* wrong.
*/
if (WARN_ON(!radix_tree_exceptional_entry(entry)))
return -EIO;
spin_lock_irq(&mapping->tree_lock);
entry2 = get_unlocked_mapping_entry(mapping, index, &slot);
/* Entry got punched out / reallocated? */
if (!entry2 || !radix_tree_exceptional_entry(entry2))
goto put_unlocked;
/*
* Entry got reallocated elsewhere? No need to writeback. We have to
* compare sectors as we must not bail out due to difference in lockbit
* or entry type.
*/
if (dax_radix_sector(entry2) != dax_radix_sector(entry))
goto put_unlocked;
if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
dax_is_zero_entry(entry))) {
ret = -EIO;
goto put_unlocked;
}
/* Another fsync thread may have already written back this entry */
if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
goto put_unlocked;
/* Lock the entry to serialize with page faults */
entry = lock_slot(mapping, slot);
/*
* We can clear the tag now but we have to be careful so that concurrent
* dax_writeback_one() calls for the same index cannot finish before we
* actually flush the caches. This is achieved as the calls will look
* at the entry only under tree_lock and once they do that they will
* see the entry locked and wait for it to unlock.
*/
radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
spin_unlock_irq(&mapping->tree_lock);
/*
* Even if dax_writeback_mapping_range() was given a wbc->range_start
* in the middle of a PMD, the 'index' we are given will be aligned to
* the start index of the PMD, as will the sector we pull from
* 'entry'. This allows us to flush for PMD_SIZE and not have to
* worry about partial PMD writebacks.
*/
sector = dax_radix_sector(entry);
size = PAGE_SIZE << dax_radix_order(entry);
id = dax_read_lock();
ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
if (ret)
goto dax_unlock;
/*
* dax_direct_access() may sleep, so cannot hold tree_lock over
* its invocation.
*/
ret = dax_direct_access(dax_dev, pgoff, size / PAGE_SIZE, &kaddr, &pfn);
if (ret < 0)
goto dax_unlock;
if (WARN_ON_ONCE(ret < size / PAGE_SIZE)) {
ret = -EIO;
goto dax_unlock;
}
dax_mapping_entry_mkclean(mapping, index, pfn_t_to_pfn(pfn));
dax_flush(dax_dev, pgoff, kaddr, size);
/*
* After we have flushed the cache, we can clear the dirty tag. There
* cannot be new dirty data in the pfn after the flush has completed as
* the pfn mappings are writeprotected and fault waits for mapping
* entry lock.
*/
spin_lock_irq(&mapping->tree_lock);
radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_DIRTY);
spin_unlock_irq(&mapping->tree_lock);
trace_dax_writeback_one(mapping->host, index, size >> PAGE_SHIFT);
dax_unlock:
dax_read_unlock(id);
put_locked_mapping_entry(mapping, index, entry);
return ret;
put_unlocked:
put_unlocked_mapping_entry(mapping, index, entry2);
spin_unlock_irq(&mapping->tree_lock);
return ret;
}
/*
* Flush the mapping to the persistent domain within the byte range of [start,
* end]. This is required by data integrity operations to ensure file data is
* on persistent storage prior to completion of the operation.
*/
int dax_writeback_mapping_range(struct address_space *mapping,
struct block_device *bdev, struct writeback_control *wbc)
{
struct inode *inode = mapping->host;
pgoff_t start_index, end_index;
pgoff_t indices[PAGEVEC_SIZE];
struct dax_device *dax_dev;
struct pagevec pvec;
bool done = false;
int i, ret = 0;
if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
return -EIO;
if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
return 0;
dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
if (!dax_dev)
return -EIO;
start_index = wbc->range_start >> PAGE_SHIFT;
end_index = wbc->range_end >> PAGE_SHIFT;
trace_dax_writeback_range(inode, start_index, end_index);
tag_pages_for_writeback(mapping, start_index, end_index);
pagevec_init(&pvec, 0);
while (!done) {
pvec.nr = find_get_entries_tag(mapping, start_index,
PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
pvec.pages, indices);
if (pvec.nr == 0)
break;
for (i = 0; i < pvec.nr; i++) {
if (indices[i] > end_index) {
done = true;
break;
}
ret = dax_writeback_one(bdev, dax_dev, mapping,
indices[i], pvec.pages[i]);
if (ret < 0) {
mapping_set_error(mapping, ret);
goto out;
}
}
start_index = indices[pvec.nr - 1] + 1;
}
out:
put_dax(dax_dev);
trace_dax_writeback_range_done(inode, start_index, end_index);
return (ret < 0 ? ret : 0);
}
EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
static int dax_insert_mapping(struct address_space *mapping,
struct block_device *bdev, struct dax_device *dax_dev,
sector_t sector, size_t size, void **entryp,
struct vm_area_struct *vma, struct vm_fault *vmf)
{
unsigned long vaddr = vmf->address;
void *entry = *entryp;
void *ret, *kaddr;
pgoff_t pgoff;
int id, rc;
pfn_t pfn;
rc = bdev_dax_pgoff(bdev, sector, size, &pgoff);
if (rc)
return rc;
id = dax_read_lock();
rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
if (rc < 0) {
dax_read_unlock(id);
return rc;
}
dax_read_unlock(id);
ret = dax_insert_mapping_entry(mapping, vmf, entry, sector, 0);
if (IS_ERR(ret))
return PTR_ERR(ret);
*entryp = ret;
trace_dax_insert_mapping(mapping->host, vmf, ret);
return vm_insert_mixed(vma, vaddr, pfn);
}
/**
* dax_pfn_mkwrite - handle first write to DAX page
* @vmf: The description of the fault
*/
int dax_pfn_mkwrite(struct vm_fault *vmf)
{
struct file *file = vmf->vma->vm_file;
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
void *entry, **slot;
pgoff_t index = vmf->pgoff;
spin_lock_irq(&mapping->tree_lock);
entry = get_unlocked_mapping_entry(mapping, index, &slot);
if (!entry || !radix_tree_exceptional_entry(entry)) {
if (entry)
put_unlocked_mapping_entry(mapping, index, entry);
spin_unlock_irq(&mapping->tree_lock);
trace_dax_pfn_mkwrite_no_entry(inode, vmf, VM_FAULT_NOPAGE);
return VM_FAULT_NOPAGE;
}
radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);
entry = lock_slot(mapping, slot);
spin_unlock_irq(&mapping->tree_lock);
/*
* If we race with somebody updating the PTE and finish_mkwrite_fault()
* fails, we don't care. We need to return VM_FAULT_NOPAGE and retry
* the fault in either case.
*/
finish_mkwrite_fault(vmf);
put_locked_mapping_entry(mapping, index, entry);
trace_dax_pfn_mkwrite(inode, vmf, VM_FAULT_NOPAGE);
return VM_FAULT_NOPAGE;
}
EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
static bool dax_range_is_aligned(struct block_device *bdev,
unsigned int offset, unsigned int length)
{
unsigned short sector_size = bdev_logical_block_size(bdev);
if (!IS_ALIGNED(offset, sector_size))
return false;
if (!IS_ALIGNED(length, sector_size))
return false;
return true;
}
int __dax_zero_page_range(struct block_device *bdev,
struct dax_device *dax_dev, sector_t sector,
unsigned int offset, unsigned int size)
{
if (dax_range_is_aligned(bdev, offset, size)) {
sector_t start_sector = sector + (offset >> 9);
return blkdev_issue_zeroout(bdev, start_sector,
size >> 9, GFP_NOFS, 0);
} else {
pgoff_t pgoff;
long rc, id;
void *kaddr;
pfn_t pfn;
rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
if (rc)
return rc;
id = dax_read_lock();
rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr,
&pfn);
if (rc < 0) {
dax_read_unlock(id);
return rc;
}
memset(kaddr + offset, 0, size);
dax_flush(dax_dev, pgoff, kaddr + offset, size);
dax_read_unlock(id);
}
return 0;
}
EXPORT_SYMBOL_GPL(__dax_zero_page_range);
static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
{
return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9);
}
static loff_t
dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
struct iomap *iomap)
{
struct block_device *bdev = iomap->bdev;
struct dax_device *dax_dev = iomap->dax_dev;
struct iov_iter *iter = data;
loff_t end = pos + length, done = 0;
ssize_t ret = 0;
int id;
if (iov_iter_rw(iter) == READ) {
end = min(end, i_size_read(inode));
if (pos >= end)
return 0;
if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
return iov_iter_zero(min(length, end - pos), iter);
}
if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
return -EIO;
/*
* Write can allocate block for an area which has a hole page mapped
* into page tables. We have to tear down these mappings so that data
* written by write(2) is visible in mmap.
*/
if (iomap->flags & IOMAP_F_NEW) {
invalidate_inode_pages2_range(inode->i_mapping,
pos >> PAGE_SHIFT,
(end - 1) >> PAGE_SHIFT);
}
id = dax_read_lock();
while (pos < end) {
unsigned offset = pos & (PAGE_SIZE - 1);
const size_t size = ALIGN(length + offset, PAGE_SIZE);
const sector_t sector = dax_iomap_sector(iomap, pos);
ssize_t map_len;
pgoff_t pgoff;
void *kaddr;
pfn_t pfn;
if (fatal_signal_pending(current)) {
ret = -EINTR;
break;
}
ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
if (ret)
break;
map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size),
&kaddr, &pfn);
if (map_len < 0) {
ret = map_len;
break;
}
map_len = PFN_PHYS(map_len);
kaddr += offset;
map_len -= offset;
if (map_len > end - pos)
map_len = end - pos;
if (iov_iter_rw(iter) == WRITE)
map_len = dax_copy_from_iter(dax_dev, pgoff, kaddr,
map_len, iter);
else
map_len = copy_to_iter(kaddr, map_len, iter);
if (map_len <= 0) {
ret = map_len ? map_len : -EFAULT;
break;
}
pos += map_len;
length -= map_len;
done += map_len;
}
dax_read_unlock(id);
return done ? done : ret;
}
/**
* dax_iomap_rw - Perform I/O to a DAX file
* @iocb: The control block for this I/O
* @iter: The addresses to do I/O from or to
* @ops: iomap ops passed from the file system
*
* This function performs read and write operations to directly mapped
* persistent memory. The callers needs to take care of read/write exclusion
* and evicting any page cache pages in the region under I/O.
*/
ssize_t
dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
const struct iomap_ops *ops)
{
struct address_space *mapping = iocb->ki_filp->f_mapping;
struct inode *inode = mapping->host;
loff_t pos = iocb->ki_pos, ret = 0, done = 0;
unsigned flags = 0;
if (iov_iter_rw(iter) == WRITE) {
lockdep_assert_held_exclusive(&inode->i_rwsem);
flags |= IOMAP_WRITE;
} else {
lockdep_assert_held(&inode->i_rwsem);
}
while (iov_iter_count(iter)) {
ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
iter, dax_iomap_actor);
if (ret <= 0)
break;
pos += ret;
done += ret;
}
iocb->ki_pos += done;
return done ? done : ret;
}
EXPORT_SYMBOL_GPL(dax_iomap_rw);
static int dax_fault_return(int error)
{
if (error == 0)
return VM_FAULT_NOPAGE;
if (error == -ENOMEM)
return VM_FAULT_OOM;
return VM_FAULT_SIGBUS;
}
static int dax_iomap_pte_fault(struct vm_fault *vmf,
const struct iomap_ops *ops)
{
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
struct inode *inode = mapping->host;
unsigned long vaddr = vmf->address;
loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
sector_t sector;
struct iomap iomap = { 0 };
unsigned flags = IOMAP_FAULT;
int error, major = 0;
int vmf_ret = 0;
void *entry;
trace_dax_pte_fault(inode, vmf, vmf_ret);
/*
* Check whether offset isn't beyond end of file now. Caller is supposed
* to hold locks serializing us with truncate / punch hole so this is
* a reliable test.
*/
if (pos >= i_size_read(inode)) {
vmf_ret = VM_FAULT_SIGBUS;
goto out;
}
if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
flags |= IOMAP_WRITE;
entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
if (IS_ERR(entry)) {
vmf_ret = dax_fault_return(PTR_ERR(entry));
goto out;
}
/*
* It is possible, particularly with mixed reads & writes to private
* mappings, that we have raced with a PMD fault that overlaps with
* the PTE we need to set up. If so just return and the fault will be
* retried.
*/
if (pmd_trans_huge(*vmf->pmd) || pmd_devmap(*vmf->pmd)) {
vmf_ret = VM_FAULT_NOPAGE;
goto unlock_entry;
}
/*
* Note that we don't bother to use iomap_apply here: DAX required
* the file system block size to be equal the page size, which means
* that we never have to deal with more than a single extent here.
*/
error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
if (error) {
vmf_ret = dax_fault_return(error);
goto unlock_entry;
}
if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
error = -EIO; /* fs corruption? */
goto error_finish_iomap;
}
sector = dax_iomap_sector(&iomap, pos);
if (vmf->cow_page) {
switch (iomap.type) {
case IOMAP_HOLE:
case IOMAP_UNWRITTEN:
clear_user_highpage(vmf->cow_page, vaddr);
break;
case IOMAP_MAPPED:
error = copy_user_dax(iomap.bdev, iomap.dax_dev,
sector, PAGE_SIZE, vmf->cow_page, vaddr);
break;
default:
WARN_ON_ONCE(1);
error = -EIO;
break;
}
if (error)
goto error_finish_iomap;
__SetPageUptodate(vmf->cow_page);
vmf_ret = finish_fault(vmf);
if (!vmf_ret)
vmf_ret = VM_FAULT_DONE_COW;
goto finish_iomap;
}
switch (iomap.type) {
case IOMAP_MAPPED:
if (iomap.flags & IOMAP_F_NEW) {
count_vm_event(PGMAJFAULT);
count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
major = VM_FAULT_MAJOR;
}
error = dax_insert_mapping(mapping, iomap.bdev, iomap.dax_dev,
sector, PAGE_SIZE, &entry, vmf->vma, vmf);
/* -EBUSY is fine, somebody else faulted on the same PTE */
if (error == -EBUSY)
error = 0;
break;
case IOMAP_UNWRITTEN:
case IOMAP_HOLE:
if (!(vmf->flags & FAULT_FLAG_WRITE)) {
vmf_ret = dax_load_hole(mapping, &entry, vmf);
goto finish_iomap;
}
/*FALLTHRU*/
default:
WARN_ON_ONCE(1);
error = -EIO;
break;
}
error_finish_iomap:
vmf_ret = dax_fault_return(error) | major;
finish_iomap:
if (ops->iomap_end) {
int copied = PAGE_SIZE;
if (vmf_ret & VM_FAULT_ERROR)
copied = 0;
/*
* The fault is done by now and there's no way back (other
* thread may be already happily using PTE we have installed).
* Just ignore error from ->iomap_end since we cannot do much
* with it.
*/
ops->iomap_end(inode, pos, PAGE_SIZE, copied, flags, &iomap);
}
unlock_entry:
put_locked_mapping_entry(mapping, vmf->pgoff, entry);
out:
trace_dax_pte_fault_done(inode, vmf, vmf_ret);
return vmf_ret;
}
#ifdef CONFIG_FS_DAX_PMD
/*
* The 'colour' (ie low bits) within a PMD of a page offset. This comes up
* more often than one might expect in the below functions.
*/
#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
static int dax_pmd_insert_mapping(struct vm_fault *vmf, struct iomap *iomap,
loff_t pos, void **entryp)
{
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
const sector_t sector = dax_iomap_sector(iomap, pos);
struct dax_device *dax_dev = iomap->dax_dev;
struct block_device *bdev = iomap->bdev;
struct inode *inode = mapping->host;
const size_t size = PMD_SIZE;
void *ret = NULL, *kaddr;
long length = 0;
pgoff_t pgoff;
pfn_t pfn;
int id;
if (bdev_dax_pgoff(bdev, sector, size, &pgoff) != 0)
goto fallback;
id = dax_read_lock();
length = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
if (length < 0)
goto unlock_fallback;
length = PFN_PHYS(length);
if (length < size)
goto unlock_fallback;
if (pfn_t_to_pfn(pfn) & PG_PMD_COLOUR)
goto unlock_fallback;
if (!pfn_t_devmap(pfn))
goto unlock_fallback;
dax_read_unlock(id);
ret = dax_insert_mapping_entry(mapping, vmf, *entryp, sector,
RADIX_DAX_PMD);
if (IS_ERR(ret))
goto fallback;
*entryp = ret;
trace_dax_pmd_insert_mapping(inode, vmf, length, pfn, ret);
return vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd,
pfn, vmf->flags & FAULT_FLAG_WRITE);
unlock_fallback:
dax_read_unlock(id);
fallback:
trace_dax_pmd_insert_mapping_fallback(inode, vmf, length, pfn, ret);
return VM_FAULT_FALLBACK;
}
static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
void **entryp)
{
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
unsigned long pmd_addr = vmf->address & PMD_MASK;
struct inode *inode = mapping->host;
struct page *zero_page;
void *ret = NULL;
spinlock_t *ptl;
pmd_t pmd_entry;
zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);
if (unlikely(!zero_page))
goto fallback;
ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
RADIX_DAX_PMD | RADIX_DAX_HZP);
if (IS_ERR(ret))
goto fallback;
*entryp = ret;
ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
if (!pmd_none(*(vmf->pmd))) {
spin_unlock(ptl);
goto fallback;
}
pmd_entry = mk_pmd(zero_page, vmf->vma->vm_page_prot);
pmd_entry = pmd_mkhuge(pmd_entry);
set_pmd_at(vmf->vma->vm_mm, pmd_addr, vmf->pmd, pmd_entry);
spin_unlock(ptl);
trace_dax_pmd_load_hole(inode, vmf, zero_page, ret);
return VM_FAULT_NOPAGE;
fallback:
trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, ret);
return VM_FAULT_FALLBACK;
}
static int dax_iomap_pmd_fault(struct vm_fault *vmf,
const struct iomap_ops *ops)
{
struct vm_area_struct *vma = vmf->vma;
struct address_space *mapping = vma->vm_file->f_mapping;
unsigned long pmd_addr = vmf->address & PMD_MASK;
bool write = vmf->flags & FAULT_FLAG_WRITE;
unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
struct inode *inode = mapping->host;
int result = VM_FAULT_FALLBACK;
struct iomap iomap = { 0 };
pgoff_t max_pgoff, pgoff;
void *entry;
loff_t pos;
int error;
/*
* Check whether offset isn't beyond end of file now. Caller is
* supposed to hold locks serializing us with truncate / punch hole so
* this is a reliable test.
*/
pgoff = linear_page_index(vma, pmd_addr);
max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
trace_dax_pmd_fault(inode, vmf, max_pgoff, 0);
/* Fall back to PTEs if we're going to COW */
if (write && !(vma->vm_flags & VM_SHARED))
goto fallback;
/* If the PMD would extend outside the VMA */
if (pmd_addr < vma->vm_start)
goto fallback;
if ((pmd_addr + PMD_SIZE) > vma->vm_end)
goto fallback;
if (pgoff > max_pgoff) {
result = VM_FAULT_SIGBUS;
goto out;
}
/* If the PMD would extend beyond the file size */
if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
goto fallback;
/*
* grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
* PMD or a HZP entry. If it can't (because a 4k page is already in
* the tree, for instance), it will return -EEXIST and we just fall
* back to 4k entries.
*/
entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
if (IS_ERR(entry))
goto fallback;
/*
* It is possible, particularly with mixed reads & writes to private
* mappings, that we have raced with a PTE fault that overlaps with
* the PMD we need to set up. If so just return and the fault will be
* retried.
*/
if (!pmd_none(*vmf->pmd) && !pmd_trans_huge(*vmf->pmd) &&
!pmd_devmap(*vmf->pmd)) {
result = 0;
goto unlock_entry;
}
/*
* Note that we don't use iomap_apply here. We aren't doing I/O, only
* setting up a mapping, so really we're using iomap_begin() as a way
* to look up our filesystem block.
*/
pos = (loff_t)pgoff << PAGE_SHIFT;
error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
if (error)
goto unlock_entry;
if (iomap.offset + iomap.length < pos + PMD_SIZE)
goto finish_iomap;
switch (iomap.type) {
case IOMAP_MAPPED:
result = dax_pmd_insert_mapping(vmf, &iomap, pos, &entry);
break;
case IOMAP_UNWRITTEN:
case IOMAP_HOLE:
if (WARN_ON_ONCE(write))
break;
result = dax_pmd_load_hole(vmf, &iomap, &entry);
break;
default:
WARN_ON_ONCE(1);
break;
}
finish_iomap:
if (ops->iomap_end) {
int copied = PMD_SIZE;
if (result == VM_FAULT_FALLBACK)
copied = 0;
/*
* The fault is done by now and there's no way back (other
* thread may be already happily using PMD we have installed).
* Just ignore error from ->iomap_end since we cannot do much
* with it.
*/
ops->iomap_end(inode, pos, PMD_SIZE, copied, iomap_flags,
&iomap);
}
unlock_entry:
put_locked_mapping_entry(mapping, pgoff, entry);
fallback:
if (result == VM_FAULT_FALLBACK) {
split_huge_pmd(vma, vmf->pmd, vmf->address);
count_vm_event(THP_FAULT_FALLBACK);
}
out:
trace_dax_pmd_fault_done(inode, vmf, max_pgoff, result);
return result;
}
#else
static int dax_iomap_pmd_fault(struct vm_fault *vmf,
const struct iomap_ops *ops)
{
return VM_FAULT_FALLBACK;
}
#endif /* CONFIG_FS_DAX_PMD */
/**
* dax_iomap_fault - handle a page fault on a DAX file
* @vmf: The description of the fault
* @ops: iomap ops passed from the file system
*
* When a page fault occurs, filesystems may call this helper in
* their fault handler for DAX files. dax_iomap_fault() assumes the caller
* has done all the necessary locking for page fault to proceed
* successfully.
*/
int dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
const struct iomap_ops *ops)
{
switch (pe_size) {
case PE_SIZE_PTE:
return dax_iomap_pte_fault(vmf, ops);
case PE_SIZE_PMD:
return dax_iomap_pmd_fault(vmf, ops);
default:
return VM_FAULT_FALLBACK;
}
}
EXPORT_SYMBOL_GPL(dax_iomap_fault);