linux/fs/dax.c
Linus Torvalds f6f3732162 Revert "mm: replace p??_write with pte_access_permitted in fault + gup paths"
This reverts commits 5c9d2d5c26, c7da82b894, and e7fe7b5cae.

We'll probably need to revisit this, but basically we should not
complicate the get_user_pages_fast() case, and checking the actual page
table protection key bits will require more care anyway, since the
protection keys depend on the exact state of the VM in question.

Particularly when doing a "remote" page lookup (ie in somebody elses VM,
not your own), you need to be much more careful than this was.  Dave
Hansen says:

 "So, the underlying bug here is that we now a get_user_pages_remote()
  and then go ahead and do the p*_access_permitted() checks against the
  current PKRU. This was introduced recently with the addition of the
  new p??_access_permitted() calls.

  We have checks in the VMA path for the "remote" gups and we avoid
  consulting PKRU for them. This got missed in the pkeys selftests
  because I did a ptrace read, but not a *write*. I also didn't
  explicitly test it against something where a COW needed to be done"

It's also not entirely clear that it makes sense to check the protection
key bits at this level at all.  But one possible eventual solution is to
make the get_user_pages_fast() case just abort if it sees protection key
bits set, which makes us fall back to the regular get_user_pages() case,
which then has a vma and can do the check there if we want to.

We'll see.

Somewhat related to this all: what we _do_ want to do some day is to
check the PAGE_USER bit - it should obviously always be set for user
pages, but it would be a good check to have back.  Because we have no
generic way to test for it, we lost it as part of moving over from the
architecture-specific x86 GUP implementation to the generic one in
commit e585513b76 ("x86/mm/gup: Switch GUP to the generic
get_user_page_fast() implementation").

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-12-15 18:53:22 -08:00

1594 lines
44 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)
/* The 'colour' (ie low bits) within a PMD of a page offset. */
#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
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);
/*
* We use lowest available bit in exceptional entry for locking, one bit for
* the entry size (PMD) and two more to tell us if the entry is a zero page or
* an empty entry that is just used for locking. In total four special bits.
*
* If the PMD bit isn't set the entry has size PAGE_SIZE, and if the ZERO_PAGE
* and EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
* block allocation.
*/
#define RADIX_DAX_SHIFT (RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
#define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
#define RADIX_DAX_ZERO_PAGE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
static unsigned long dax_radix_sector(void *entry)
{
return (unsigned long)entry >> RADIX_DAX_SHIFT;
}
static void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
{
return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
((unsigned long)sector << RADIX_DAX_SHIFT) |
RADIX_DAX_ENTRY_LOCK);
}
static unsigned int dax_radix_order(void *entry)
{
if ((unsigned long)entry & RADIX_DAX_PMD)
return PMD_SHIFT - PAGE_SHIFT;
return 0;
}
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_ZERO_PAGE;
}
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 &= ~PG_PMD_COLOUR;
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);
}
/*
* 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.
*/
static 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);
}
/*
* 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 ||
WARN_ON_ONCE(!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)
{
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 (!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 an exceptional entry,
* return it with the radix tree entry locked. If the radix tree doesn't
* contain given index, create an 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 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 (WARN_ON_ONCE(entry && !radix_tree_exceptional_entry(entry))) {
entry = ERR_PTR(-EIO);
goto out_unlock;
}
if (entry) {
if (size_flag & RADIX_DAX_PMD) {
if (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 (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);
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;
}
entry = lock_slot(mapping, slot);
out_unlock:
spin_unlock_irq(&mapping->tree_lock);
return entry;
}
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 || WARN_ON_ONCE(!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);
}
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, bool dirty)
{
struct radix_tree_root *page_tree = &mapping->page_tree;
void *new_entry;
pgoff_t index = vmf->pgoff;
if (dirty)
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_ZERO_PAGE)) {
/* we are replacing a zero page with block mapping */
if (dax_is_pmd_entry(entry))
unmap_mapping_range(mapping,
(vmf->pgoff << PAGE_SHIFT) & PMD_MASK,
PMD_SIZE, 0);
else /* pte entry */
unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
PAGE_SIZE, 0);
}
spin_lock_irq(&mapping->tree_lock);
new_entry = dax_radix_locked_entry(sector, flags);
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);
entry = new_entry;
}
if (dirty)
radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
spin_unlock_irq(&mapping->tree_lock);
return 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;
i_mmap_lock_read(mapping);
vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) {
unsigned long address, start, end;
cond_resched();
if (!(vma->vm_flags & VM_SHARED))
continue;
address = pgoff_address(index, vma);
/*
* Note because we provide start/end to follow_pte_pmd it will
* call mmu_notifier_invalidate_range_start() on our behalf
* before taking any lock.
*/
if (follow_pte_pmd(vma->vm_mm, address, &start, &end, &ptep, &pmdp, &ptl))
continue;
/*
* No need to call mmu_notifier_invalidate_range() as we are
* downgrading page table protection not changing it to point
* to a new page.
*
* See Documentation/vm/mmu_notifier.txt
*/
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);
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);
unlock_pte:
pte_unmap_unlock(ptep, ptl);
}
mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
}
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 || WARN_ON_ONCE(!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, 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);
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);
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 sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
{
return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
}
static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
pfn_t *pfnp)
{
const sector_t sector = dax_iomap_sector(iomap, pos);
pgoff_t pgoff;
void *kaddr;
int id, rc;
long length;
rc = bdev_dax_pgoff(iomap->bdev, sector, size, &pgoff);
if (rc)
return rc;
id = dax_read_lock();
length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
&kaddr, pfnp);
if (length < 0) {
rc = length;
goto out;
}
rc = -EINVAL;
if (PFN_PHYS(length) < size)
goto out;
if (pfn_t_to_pfn(*pfnp) & (PHYS_PFN(size)-1))
goto out;
/* For larger pages we need devmap */
if (length > 1 && !pfn_t_devmap(*pfnp))
goto out;
rc = 0;
out:
dax_read_unlock(id);
return rc;
}
/*
* 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. Instead we insert a read-only mapping of the 4k zero page.
* If this page is ever written to we will re-fault and change the mapping to
* point to real DAX storage instead.
*/
static int dax_load_hole(struct address_space *mapping, void *entry,
struct vm_fault *vmf)
{
struct inode *inode = mapping->host;
unsigned long vaddr = vmf->address;
int ret = VM_FAULT_NOPAGE;
struct page *zero_page;
void *entry2;
zero_page = ZERO_PAGE(0);
if (unlikely(!zero_page)) {
ret = VM_FAULT_OOM;
goto out;
}
entry2 = dax_insert_mapping_entry(mapping, vmf, entry, 0,
RADIX_DAX_ZERO_PAGE, false);
if (IS_ERR(entry2)) {
ret = VM_FAULT_SIGBUS;
goto out;
}
vm_insert_mixed(vmf->vma, vaddr, page_to_pfn_t(zero_page));
out:
trace_dax_load_hole(inode, vmf, ret);
return ret;
}
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, kaddr + offset, size);
dax_read_unlock(id);
}
return 0;
}
EXPORT_SYMBOL_GPL(__dax_zero_page_range);
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;
/*
* The userspace address for the memory copy has already been
* validated via access_ok() in either vfs_read() or
* vfs_write(), depending on which operation we are doing.
*/
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;
}
/*
* MAP_SYNC on a dax mapping guarantees dirty metadata is
* flushed on write-faults (non-cow), but not read-faults.
*/
static bool dax_fault_is_synchronous(unsigned long flags,
struct vm_area_struct *vma, struct iomap *iomap)
{
return (flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC)
&& (iomap->flags & IOMAP_F_DIRTY);
}
static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
const struct iomap_ops *ops)
{
struct vm_area_struct *vma = vmf->vma;
struct address_space *mapping = vma->vm_file->f_mapping;
struct inode *inode = mapping->host;
unsigned long vaddr = vmf->address;
loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
struct iomap iomap = { 0 };
unsigned flags = IOMAP_FAULT;
int error, major = 0;
bool write = vmf->flags & FAULT_FLAG_WRITE;
bool sync;
int vmf_ret = 0;
void *entry;
pfn_t pfn;
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 (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;
}
if (vmf->cow_page) {
sector_t sector = dax_iomap_sector(&iomap, pos);
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;
}
sync = dax_fault_is_synchronous(flags, vma, &iomap);
switch (iomap.type) {
case IOMAP_MAPPED:
if (iomap.flags & IOMAP_F_NEW) {
count_vm_event(PGMAJFAULT);
count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
major = VM_FAULT_MAJOR;
}
error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
if (error < 0)
goto error_finish_iomap;
entry = dax_insert_mapping_entry(mapping, vmf, entry,
dax_iomap_sector(&iomap, pos),
0, write && !sync);
if (IS_ERR(entry)) {
error = PTR_ERR(entry);
goto error_finish_iomap;
}
/*
* If we are doing synchronous page fault and inode needs fsync,
* we can insert PTE into page tables only after that happens.
* Skip insertion for now and return the pfn so that caller can
* insert it after fsync is done.
*/
if (sync) {
if (WARN_ON_ONCE(!pfnp)) {
error = -EIO;
goto error_finish_iomap;
}
*pfnp = pfn;
vmf_ret = VM_FAULT_NEEDDSYNC | major;
goto finish_iomap;
}
trace_dax_insert_mapping(inode, vmf, entry);
if (write)
error = vm_insert_mixed_mkwrite(vma, vaddr, pfn);
else
error = vm_insert_mixed(vma, vaddr, pfn);
/* -EBUSY is fine, somebody else faulted on the same PTE */
if (error == -EBUSY)
error = 0;
break;
case IOMAP_UNWRITTEN:
case IOMAP_HOLE:
if (!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);
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_load_hole(struct vm_fault *vmf, struct iomap *iomap,
void *entry)
{
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, entry, 0,
RADIX_DAX_PMD | RADIX_DAX_ZERO_PAGE, false);
if (IS_ERR(ret))
goto fallback;
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, pfn_t *pfnp,
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;
bool sync;
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;
pfn_t pfn;
/*
* 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 = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
trace_dax_pmd_fault(inode, vmf, max_pgoff, 0);
/*
* Make sure that the faulting address's PMD offset (color) matches
* the PMD offset from the start of the file. This is necessary so
* that a PMD range in the page table overlaps exactly with a PMD
* range in the radix tree.
*/
if ((vmf->pgoff & PG_PMD_COLOUR) !=
((vmf->address >> PAGE_SHIFT) & PG_PMD_COLOUR))
goto fallback;
/* 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 2MiB empty entry, a
* 2MiB zero page entry or a DAX PMD. 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;
sync = dax_fault_is_synchronous(iomap_flags, vma, &iomap);
switch (iomap.type) {
case IOMAP_MAPPED:
error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
if (error < 0)
goto finish_iomap;
entry = dax_insert_mapping_entry(mapping, vmf, entry,
dax_iomap_sector(&iomap, pos),
RADIX_DAX_PMD, write && !sync);
if (IS_ERR(entry))
goto finish_iomap;
/*
* If we are doing synchronous page fault and inode needs fsync,
* we can insert PMD into page tables only after that happens.
* Skip insertion for now and return the pfn so that caller can
* insert it after fsync is done.
*/
if (sync) {
if (WARN_ON_ONCE(!pfnp))
goto finish_iomap;
*pfnp = pfn;
result = VM_FAULT_NEEDDSYNC;
goto finish_iomap;
}
trace_dax_pmd_insert_mapping(inode, vmf, PMD_SIZE, pfn, entry);
result = vmf_insert_pfn_pmd(vma, vmf->address, vmf->pmd, pfn,
write);
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);
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, pfn_t *pfnp,
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
* @pe_size: Size of the page to fault in
* @pfnp: PFN to insert for synchronous faults if fsync is required
* @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,
pfn_t *pfnp, const struct iomap_ops *ops)
{
switch (pe_size) {
case PE_SIZE_PTE:
return dax_iomap_pte_fault(vmf, pfnp, ops);
case PE_SIZE_PMD:
return dax_iomap_pmd_fault(vmf, pfnp, ops);
default:
return VM_FAULT_FALLBACK;
}
}
EXPORT_SYMBOL_GPL(dax_iomap_fault);
/**
* dax_insert_pfn_mkwrite - insert PTE or PMD entry into page tables
* @vmf: The description of the fault
* @pe_size: Size of entry to be inserted
* @pfn: PFN to insert
*
* This function inserts writeable PTE or PMD entry into page tables for mmaped
* DAX file. It takes care of marking corresponding radix tree entry as dirty
* as well.
*/
static int dax_insert_pfn_mkwrite(struct vm_fault *vmf,
enum page_entry_size pe_size,
pfn_t pfn)
{
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
void *entry, **slot;
pgoff_t index = vmf->pgoff;
int vmf_ret, error;
spin_lock_irq(&mapping->tree_lock);
entry = get_unlocked_mapping_entry(mapping, index, &slot);
/* Did we race with someone splitting entry or so? */
if (!entry ||
(pe_size == PE_SIZE_PTE && !dax_is_pte_entry(entry)) ||
(pe_size == PE_SIZE_PMD && !dax_is_pmd_entry(entry))) {
put_unlocked_mapping_entry(mapping, index, entry);
spin_unlock_irq(&mapping->tree_lock);
trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, 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);
switch (pe_size) {
case PE_SIZE_PTE:
error = vm_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
vmf_ret = dax_fault_return(error);
break;
#ifdef CONFIG_FS_DAX_PMD
case PE_SIZE_PMD:
vmf_ret = vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd,
pfn, true);
break;
#endif
default:
vmf_ret = VM_FAULT_FALLBACK;
}
put_locked_mapping_entry(mapping, index);
trace_dax_insert_pfn_mkwrite(mapping->host, vmf, vmf_ret);
return vmf_ret;
}
/**
* dax_finish_sync_fault - finish synchronous page fault
* @vmf: The description of the fault
* @pe_size: Size of entry to be inserted
* @pfn: PFN to insert
*
* This function ensures that the file range touched by the page fault is
* stored persistently on the media and handles inserting of appropriate page
* table entry.
*/
int dax_finish_sync_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
pfn_t pfn)
{
int err;
loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT;
size_t len = 0;
if (pe_size == PE_SIZE_PTE)
len = PAGE_SIZE;
else if (pe_size == PE_SIZE_PMD)
len = PMD_SIZE;
else
WARN_ON_ONCE(1);
err = vfs_fsync_range(vmf->vma->vm_file, start, start + len - 1, 1);
if (err)
return VM_FAULT_SIGBUS;
return dax_insert_pfn_mkwrite(vmf, pe_size, pfn);
}
EXPORT_SYMBOL_GPL(dax_finish_sync_fault);