linux/fs/dax.c

1470 lines
40 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/pmem.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 long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
{
struct request_queue *q = bdev->bd_queue;
long rc = -EIO;
dax->addr = ERR_PTR(-EIO);
if (blk_queue_enter(q, true) != 0)
return rc;
rc = bdev_direct_access(bdev, dax);
if (rc < 0) {
dax->addr = ERR_PTR(rc);
blk_queue_exit(q);
return rc;
}
return rc;
}
static void dax_unmap_atomic(struct block_device *bdev,
const struct blk_dax_ctl *dax)
{
if (IS_ERR(dax->addr))
return;
blk_queue_exit(bdev->bd_queue);
}
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;
}
struct page *read_dax_sector(struct block_device *bdev, sector_t n)
{
struct page *page = alloc_pages(GFP_KERNEL, 0);
struct blk_dax_ctl dax = {
.size = PAGE_SIZE,
.sector = n & ~((((int) PAGE_SIZE) / 512) - 1),
};
long rc;
if (!page)
return ERR_PTR(-ENOMEM);
rc = dax_map_atomic(bdev, &dax);
if (rc < 0)
return ERR_PTR(rc);
memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE);
dax_unmap_atomic(bdev, &dax);
return page;
}
/*
* DAX radix tree locking
*/
struct exceptional_entry_key {
struct address_space *mapping;
pgoff_t entry_start;
};
struct wait_exceptional_entry_queue {
wait_queue_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_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 (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);
/*
* Someone already created the entry? This is a
* normal failure when inserting PMDs in a range
* that already contains PTEs. In that case we want
* to return -EEXIST immediately.
*/
if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
goto restart;
/*
* Our insertion of a DAX PMD entry failed, most
* likely because 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 easily possible. This handles DAX
* entries for invalidate_inode_pages() so we evict the entry only if we can
* do so without blocking.
*/
int dax_invalidate_mapping_entry(struct address_space *mapping, pgoff_t index)
{
int ret = 0;
void *entry, **slot;
struct radix_tree_root *page_tree = &mapping->page_tree;
spin_lock_irq(&mapping->tree_lock);
entry = __radix_tree_lookup(page_tree, index, NULL, &slot);
if (!entry || !radix_tree_exceptional_entry(entry) ||
slot_locked(mapping, slot))
goto out;
if (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:
spin_unlock_irq(&mapping->tree_lock);
if (ret)
dax_wake_mapping_entry_waiter(mapping, index, entry, true);
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 page *page;
int ret;
/* Hole page already exists? Return it... */
if (!radix_tree_exceptional_entry(*entry)) {
page = *entry;
goto out;
}
/* 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)
return VM_FAULT_OOM;
out:
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);
return VM_FAULT_NOPAGE;
}
return ret;
}
static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size,
struct page *to, unsigned long vaddr)
{
struct blk_dax_ctl dax = {
.sector = sector,
.size = size,
};
void *vto;
if (dax_map_atomic(bdev, &dax) < 0)
return PTR_ERR(dax.addr);
vto = kmap_atomic(to);
copy_user_page(vto, (void __force *)dax.addr, vaddr, to);
kunmap_atomic(vto);
dax_unmap_atomic(bdev, &dax);
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 address_space *mapping, pgoff_t index, void *entry)
{
struct radix_tree_root *page_tree = &mapping->page_tree;
struct blk_dax_ctl dax;
void *entry2, **slot;
int ret = 0;
/*
* 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.
*/
dax.sector = dax_radix_sector(entry);
dax.size = PAGE_SIZE << dax_radix_order(entry);
/*
* We cannot hold tree_lock while calling dax_map_atomic() because it
* eventually calls cond_resched().
*/
ret = dax_map_atomic(bdev, &dax);
if (ret < 0) {
put_locked_mapping_entry(mapping, index, entry);
return ret;
}
if (WARN_ON_ONCE(ret < dax.size)) {
ret = -EIO;
goto unmap;
}
dax_mapping_entry_mkclean(mapping, index, pfn_t_to_pfn(dax.pfn));
wb_cache_pmem(dax.addr, dax.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);
unmap:
dax_unmap_atomic(bdev, &dax);
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 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;
start_index = wbc->range_start >> PAGE_SHIFT;
end_index = wbc->range_end >> PAGE_SHIFT;
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, mapping, indices[i],
pvec.pages[i]);
if (ret < 0)
return ret;
}
}
return 0;
}
EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
static int dax_insert_mapping(struct address_space *mapping,
struct block_device *bdev, sector_t sector, size_t size,
void **entryp, struct vm_area_struct *vma, struct vm_fault *vmf)
{
unsigned long vaddr = vmf->address;
struct blk_dax_ctl dax = {
.sector = sector,
.size = size,
};
void *ret;
void *entry = *entryp;
if (dax_map_atomic(bdev, &dax) < 0)
return PTR_ERR(dax.addr);
dax_unmap_atomic(bdev, &dax);
ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
if (IS_ERR(ret))
return PTR_ERR(ret);
*entryp = ret;
return vm_insert_mixed(vma, vaddr, dax.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;
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);
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);
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, sector_t sector,
unsigned int offset, unsigned int length)
{
struct blk_dax_ctl dax = {
.sector = sector,
.size = PAGE_SIZE,
};
if (dax_range_is_aligned(bdev, offset, length)) {
sector_t start_sector = dax.sector + (offset >> 9);
return blkdev_issue_zeroout(bdev, start_sector,
length >> 9, GFP_NOFS, true);
} else {
if (dax_map_atomic(bdev, &dax) < 0)
return PTR_ERR(dax.addr);
clear_pmem(dax.addr + offset, length);
dax_unmap_atomic(bdev, &dax);
}
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 iov_iter *iter = data;
loff_t end = pos + length, done = 0;
ssize_t ret = 0;
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) && inode->i_mapping->nrpages) {
invalidate_inode_pages2_range(inode->i_mapping,
pos >> PAGE_SHIFT,
(end - 1) >> PAGE_SHIFT);
}
while (pos < end) {
unsigned offset = pos & (PAGE_SIZE - 1);
struct blk_dax_ctl dax = { 0 };
ssize_t map_len;
if (fatal_signal_pending(current)) {
ret = -EINTR;
break;
}
dax.sector = dax_iomap_sector(iomap, pos);
dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
map_len = dax_map_atomic(iomap->bdev, &dax);
if (map_len < 0) {
ret = map_len;
break;
}
dax.addr += offset;
map_len -= offset;
if (map_len > end - pos)
map_len = end - pos;
if (iov_iter_rw(iter) == WRITE)
map_len = copy_from_iter_pmem(dax.addr, map_len, iter);
else
map_len = copy_to_iter(dax.addr, map_len, iter);
dax_unmap_atomic(iomap->bdev, &dax);
if (map_len <= 0) {
ret = map_len ? map_len : -EFAULT;
break;
}
pos += map_len;
length -= map_len;
done += map_len;
}
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;
/*
* 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))
return VM_FAULT_SIGBUS;
if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
flags |= IOMAP_WRITE;
/*
* 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)
return dax_fault_return(error);
if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
vmf_ret = dax_fault_return(-EIO); /* fs corruption? */
goto finish_iomap;
}
entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
if (IS_ERR(entry)) {
vmf_ret = dax_fault_return(PTR_ERR(entry));
goto 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, sector, PAGE_SIZE,
vmf->cow_page, vaddr);
break;
default:
WARN_ON_ONCE(1);
error = -EIO;
break;
}
if (error)
goto error_unlock_entry;
__SetPageUptodate(vmf->cow_page);
vmf_ret = finish_fault(vmf);
if (!vmf_ret)
vmf_ret = VM_FAULT_DONE_COW;
goto unlock_entry;
}
switch (iomap.type) {
case IOMAP_MAPPED:
if (iomap.flags & IOMAP_F_NEW) {
count_vm_event(PGMAJFAULT);
mem_cgroup_count_vm_event(vmf->vma->vm_mm, PGMAJFAULT);
major = VM_FAULT_MAJOR;
}
error = dax_insert_mapping(mapping, iomap.bdev, 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 unlock_entry;
}
/*FALLTHRU*/
default:
WARN_ON_ONCE(1);
error = -EIO;
break;
}
error_unlock_entry:
vmf_ret = dax_fault_return(error) | major;
unlock_entry:
put_locked_mapping_entry(mapping, vmf->pgoff, entry);
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);
}
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;
struct block_device *bdev = iomap->bdev;
struct inode *inode = mapping->host;
struct blk_dax_ctl dax = {
.sector = dax_iomap_sector(iomap, pos),
.size = PMD_SIZE,
};
long length = dax_map_atomic(bdev, &dax);
void *ret = NULL;
if (length < 0) /* dax_map_atomic() failed */
goto fallback;
if (length < PMD_SIZE)
goto unmap_fallback;
if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
goto unmap_fallback;
if (!pfn_t_devmap(dax.pfn))
goto unmap_fallback;
dax_unmap_atomic(bdev, &dax);
ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
RADIX_DAX_PMD);
if (IS_ERR(ret))
goto fallback;
*entryp = ret;
trace_dax_pmd_insert_mapping(inode, vmf, length, dax.pfn, ret);
return vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd,
dax.pfn, vmf->flags & FAULT_FLAG_WRITE);
unmap_fallback:
dax_unmap_atomic(bdev, &dax);
fallback:
trace_dax_pmd_insert_mapping_fallback(inode, vmf, length,
dax.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;
/*
* 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 fallback;
if (iomap.offset + iomap.length < pos + PMD_SIZE)
goto finish_iomap;
/*
* 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 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))
goto unlock_entry;
result = dax_pmd_load_hole(vmf, &iomap, &entry);
break;
default:
WARN_ON_ONCE(1);
break;
}
unlock_entry:
put_locked_mapping_entry(mapping, pgoff, entry);
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);
}
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);