summaryrefslogtreecommitdiffstats
path: root/fs/dax.c
diff options
context:
space:
mode:
authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /fs/dax.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/dax.c')
-rw-r--r--fs/dax.c2067
1 files changed, 2067 insertions, 0 deletions
diff --git a/fs/dax.c b/fs/dax.c
new file mode 100644
index 0000000000..3380b43cb6
--- /dev/null
+++ b/fs/dax.c
@@ -0,0 +1,2067 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 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>
+ */
+
+#include <linux/atomic.h>
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h>
+#include <linux/dax.h>
+#include <linux/fs.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 <linux/rmap.h>
+#include <asm/pgalloc.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)
+#define PG_PMD_NR (PMD_SIZE >> PAGE_SHIFT)
+
+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);
+
+/*
+ * DAX pagecache entries use XArray value entries so they can't be mistaken
+ * for pages. We use one bit 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 DAX_SHIFT (4)
+#define DAX_LOCKED (1UL << 0)
+#define DAX_PMD (1UL << 1)
+#define DAX_ZERO_PAGE (1UL << 2)
+#define DAX_EMPTY (1UL << 3)
+
+static unsigned long dax_to_pfn(void *entry)
+{
+ return xa_to_value(entry) >> DAX_SHIFT;
+}
+
+static void *dax_make_entry(pfn_t pfn, unsigned long flags)
+{
+ return xa_mk_value(flags | (pfn_t_to_pfn(pfn) << DAX_SHIFT));
+}
+
+static bool dax_is_locked(void *entry)
+{
+ return xa_to_value(entry) & DAX_LOCKED;
+}
+
+static unsigned int dax_entry_order(void *entry)
+{
+ if (xa_to_value(entry) & DAX_PMD)
+ return PMD_ORDER;
+ return 0;
+}
+
+static unsigned long dax_is_pmd_entry(void *entry)
+{
+ return xa_to_value(entry) & DAX_PMD;
+}
+
+static bool dax_is_pte_entry(void *entry)
+{
+ return !(xa_to_value(entry) & DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+ return xa_to_value(entry) & DAX_ZERO_PAGE;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+ return xa_to_value(entry) & DAX_EMPTY;
+}
+
+/*
+ * true if the entry that was found is of a smaller order than the entry
+ * we were looking for
+ */
+static bool dax_is_conflict(void *entry)
+{
+ return entry == XA_RETRY_ENTRY;
+}
+
+/*
+ * DAX page cache entry locking
+ */
+struct exceptional_entry_key {
+ struct xarray *xa;
+ pgoff_t entry_start;
+};
+
+struct wait_exceptional_entry_queue {
+ wait_queue_entry_t wait;
+ struct exceptional_entry_key key;
+};
+
+/**
+ * enum dax_wake_mode: waitqueue wakeup behaviour
+ * @WAKE_ALL: wake all waiters in the waitqueue
+ * @WAKE_NEXT: wake only the first waiter in the waitqueue
+ */
+enum dax_wake_mode {
+ WAKE_ALL,
+ WAKE_NEXT,
+};
+
+static wait_queue_head_t *dax_entry_waitqueue(struct xa_state *xas,
+ void *entry, struct exceptional_entry_key *key)
+{
+ unsigned long hash;
+ unsigned long index = xas->xa_index;
+
+ /*
+ * 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->xa = xas->xa;
+ key->entry_start = index;
+
+ hash = hash_long((unsigned long)xas->xa ^ 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->xa != ewait->key.xa ||
+ key->entry_start != ewait->key.entry_start)
+ return 0;
+ return autoremove_wake_function(wait, mode, sync, NULL);
+}
+
+/*
+ * @entry may no longer be the entry at the index in the mapping.
+ * The important information it's conveying is whether the entry at
+ * this index used to be a PMD entry.
+ */
+static void dax_wake_entry(struct xa_state *xas, void *entry,
+ enum dax_wake_mode mode)
+{
+ struct exceptional_entry_key key;
+ wait_queue_head_t *wq;
+
+ wq = dax_entry_waitqueue(xas, entry, &key);
+
+ /*
+ * Checking for locked entry and prepare_to_wait_exclusive() happens
+ * under the i_pages 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, mode == WAKE_ALL ? 0 : 1, &key);
+}
+
+/*
+ * Look up entry in page cache, wait for it to become unlocked if it
+ * is a DAX entry and return it. The caller must subsequently call
+ * put_unlocked_entry() if it did not lock the entry or dax_unlock_entry()
+ * if it did. The entry returned may have a larger order than @order.
+ * If @order is larger than the order of the entry found in i_pages, this
+ * function returns a dax_is_conflict entry.
+ *
+ * Must be called with the i_pages lock held.
+ */
+static void *get_unlocked_entry(struct xa_state *xas, unsigned int order)
+{
+ void *entry;
+ struct wait_exceptional_entry_queue ewait;
+ wait_queue_head_t *wq;
+
+ init_wait(&ewait.wait);
+ ewait.wait.func = wake_exceptional_entry_func;
+
+ for (;;) {
+ entry = xas_find_conflict(xas);
+ if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
+ return entry;
+ if (dax_entry_order(entry) < order)
+ return XA_RETRY_ENTRY;
+ if (!dax_is_locked(entry))
+ return entry;
+
+ wq = dax_entry_waitqueue(xas, entry, &ewait.key);
+ prepare_to_wait_exclusive(wq, &ewait.wait,
+ TASK_UNINTERRUPTIBLE);
+ xas_unlock_irq(xas);
+ xas_reset(xas);
+ schedule();
+ finish_wait(wq, &ewait.wait);
+ xas_lock_irq(xas);
+ }
+}
+
+/*
+ * The only thing keeping the address space around is the i_pages lock
+ * (it's cycled in clear_inode() after removing the entries from i_pages)
+ * After we call xas_unlock_irq(), we cannot touch xas->xa.
+ */
+static void wait_entry_unlocked(struct xa_state *xas, void *entry)
+{
+ struct wait_exceptional_entry_queue ewait;
+ wait_queue_head_t *wq;
+
+ init_wait(&ewait.wait);
+ ewait.wait.func = wake_exceptional_entry_func;
+
+ wq = dax_entry_waitqueue(xas, entry, &ewait.key);
+ /*
+ * Unlike get_unlocked_entry() there is no guarantee that this
+ * path ever successfully retrieves an unlocked entry before an
+ * inode dies. Perform a non-exclusive wait in case this path
+ * never successfully performs its own wake up.
+ */
+ prepare_to_wait(wq, &ewait.wait, TASK_UNINTERRUPTIBLE);
+ xas_unlock_irq(xas);
+ schedule();
+ finish_wait(wq, &ewait.wait);
+}
+
+static void put_unlocked_entry(struct xa_state *xas, void *entry,
+ enum dax_wake_mode mode)
+{
+ if (entry && !dax_is_conflict(entry))
+ dax_wake_entry(xas, entry, mode);
+}
+
+/*
+ * We used the xa_state to get the entry, but then we locked the entry and
+ * dropped the xa_lock, so we know the xa_state is stale and must be reset
+ * before use.
+ */
+static void dax_unlock_entry(struct xa_state *xas, void *entry)
+{
+ void *old;
+
+ BUG_ON(dax_is_locked(entry));
+ xas_reset(xas);
+ xas_lock_irq(xas);
+ old = xas_store(xas, entry);
+ xas_unlock_irq(xas);
+ BUG_ON(!dax_is_locked(old));
+ dax_wake_entry(xas, entry, WAKE_NEXT);
+}
+
+/*
+ * Return: The entry stored at this location before it was locked.
+ */
+static void *dax_lock_entry(struct xa_state *xas, void *entry)
+{
+ unsigned long v = xa_to_value(entry);
+ return xas_store(xas, xa_mk_value(v | DAX_LOCKED));
+}
+
+static unsigned long dax_entry_size(void *entry)
+{
+ if (dax_is_zero_entry(entry))
+ return 0;
+ else if (dax_is_empty_entry(entry))
+ return 0;
+ else if (dax_is_pmd_entry(entry))
+ return PMD_SIZE;
+ else
+ return PAGE_SIZE;
+}
+
+static unsigned long dax_end_pfn(void *entry)
+{
+ return dax_to_pfn(entry) + dax_entry_size(entry) / PAGE_SIZE;
+}
+
+/*
+ * Iterate through all mapped pfns represented by an entry, i.e. skip
+ * 'empty' and 'zero' entries.
+ */
+#define for_each_mapped_pfn(entry, pfn) \
+ for (pfn = dax_to_pfn(entry); \
+ pfn < dax_end_pfn(entry); pfn++)
+
+static inline bool dax_page_is_shared(struct page *page)
+{
+ return page->mapping == PAGE_MAPPING_DAX_SHARED;
+}
+
+/*
+ * Set the page->mapping with PAGE_MAPPING_DAX_SHARED flag, increase the
+ * refcount.
+ */
+static inline void dax_page_share_get(struct page *page)
+{
+ if (page->mapping != PAGE_MAPPING_DAX_SHARED) {
+ /*
+ * Reset the index if the page was already mapped
+ * regularly before.
+ */
+ if (page->mapping)
+ page->share = 1;
+ page->mapping = PAGE_MAPPING_DAX_SHARED;
+ }
+ page->share++;
+}
+
+static inline unsigned long dax_page_share_put(struct page *page)
+{
+ return --page->share;
+}
+
+/*
+ * When it is called in dax_insert_entry(), the shared flag will indicate that
+ * whether this entry is shared by multiple files. If so, set the page->mapping
+ * PAGE_MAPPING_DAX_SHARED, and use page->share as refcount.
+ */
+static void dax_associate_entry(void *entry, struct address_space *mapping,
+ struct vm_area_struct *vma, unsigned long address, bool shared)
+{
+ unsigned long size = dax_entry_size(entry), pfn, index;
+ int i = 0;
+
+ if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
+ return;
+
+ index = linear_page_index(vma, address & ~(size - 1));
+ for_each_mapped_pfn(entry, pfn) {
+ struct page *page = pfn_to_page(pfn);
+
+ if (shared) {
+ dax_page_share_get(page);
+ } else {
+ WARN_ON_ONCE(page->mapping);
+ page->mapping = mapping;
+ page->index = index + i++;
+ }
+ }
+}
+
+static void dax_disassociate_entry(void *entry, struct address_space *mapping,
+ bool trunc)
+{
+ unsigned long pfn;
+
+ if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
+ return;
+
+ for_each_mapped_pfn(entry, pfn) {
+ struct page *page = pfn_to_page(pfn);
+
+ WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
+ if (dax_page_is_shared(page)) {
+ /* keep the shared flag if this page is still shared */
+ if (dax_page_share_put(page) > 0)
+ continue;
+ } else
+ WARN_ON_ONCE(page->mapping && page->mapping != mapping);
+ page->mapping = NULL;
+ page->index = 0;
+ }
+}
+
+static struct page *dax_busy_page(void *entry)
+{
+ unsigned long pfn;
+
+ for_each_mapped_pfn(entry, pfn) {
+ struct page *page = pfn_to_page(pfn);
+
+ if (page_ref_count(page) > 1)
+ return page;
+ }
+ return NULL;
+}
+
+/**
+ * dax_lock_folio - Lock the DAX entry corresponding to a folio
+ * @folio: The folio whose entry we want to lock
+ *
+ * Context: Process context.
+ * Return: A cookie to pass to dax_unlock_folio() or 0 if the entry could
+ * not be locked.
+ */
+dax_entry_t dax_lock_folio(struct folio *folio)
+{
+ XA_STATE(xas, NULL, 0);
+ void *entry;
+
+ /* Ensure folio->mapping isn't freed while we look at it */
+ rcu_read_lock();
+ for (;;) {
+ struct address_space *mapping = READ_ONCE(folio->mapping);
+
+ entry = NULL;
+ if (!mapping || !dax_mapping(mapping))
+ break;
+
+ /*
+ * In the device-dax case there's no need to lock, a
+ * struct dev_pagemap pin is sufficient to keep the
+ * inode alive, and we assume we have dev_pagemap pin
+ * otherwise we would not have a valid pfn_to_page()
+ * translation.
+ */
+ entry = (void *)~0UL;
+ if (S_ISCHR(mapping->host->i_mode))
+ break;
+
+ xas.xa = &mapping->i_pages;
+ xas_lock_irq(&xas);
+ if (mapping != folio->mapping) {
+ xas_unlock_irq(&xas);
+ continue;
+ }
+ xas_set(&xas, folio->index);
+ entry = xas_load(&xas);
+ if (dax_is_locked(entry)) {
+ rcu_read_unlock();
+ wait_entry_unlocked(&xas, entry);
+ rcu_read_lock();
+ continue;
+ }
+ dax_lock_entry(&xas, entry);
+ xas_unlock_irq(&xas);
+ break;
+ }
+ rcu_read_unlock();
+ return (dax_entry_t)entry;
+}
+
+void dax_unlock_folio(struct folio *folio, dax_entry_t cookie)
+{
+ struct address_space *mapping = folio->mapping;
+ XA_STATE(xas, &mapping->i_pages, folio->index);
+
+ if (S_ISCHR(mapping->host->i_mode))
+ return;
+
+ dax_unlock_entry(&xas, (void *)cookie);
+}
+
+/*
+ * dax_lock_mapping_entry - Lock the DAX entry corresponding to a mapping
+ * @mapping: the file's mapping whose entry we want to lock
+ * @index: the offset within this file
+ * @page: output the dax page corresponding to this dax entry
+ *
+ * Return: A cookie to pass to dax_unlock_mapping_entry() or 0 if the entry
+ * could not be locked.
+ */
+dax_entry_t dax_lock_mapping_entry(struct address_space *mapping, pgoff_t index,
+ struct page **page)
+{
+ XA_STATE(xas, NULL, 0);
+ void *entry;
+
+ rcu_read_lock();
+ for (;;) {
+ entry = NULL;
+ if (!dax_mapping(mapping))
+ break;
+
+ xas.xa = &mapping->i_pages;
+ xas_lock_irq(&xas);
+ xas_set(&xas, index);
+ entry = xas_load(&xas);
+ if (dax_is_locked(entry)) {
+ rcu_read_unlock();
+ wait_entry_unlocked(&xas, entry);
+ rcu_read_lock();
+ continue;
+ }
+ if (!entry ||
+ dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+ /*
+ * Because we are looking for entry from file's mapping
+ * and index, so the entry may not be inserted for now,
+ * or even a zero/empty entry. We don't think this is
+ * an error case. So, return a special value and do
+ * not output @page.
+ */
+ entry = (void *)~0UL;
+ } else {
+ *page = pfn_to_page(dax_to_pfn(entry));
+ dax_lock_entry(&xas, entry);
+ }
+ xas_unlock_irq(&xas);
+ break;
+ }
+ rcu_read_unlock();
+ return (dax_entry_t)entry;
+}
+
+void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index,
+ dax_entry_t cookie)
+{
+ XA_STATE(xas, &mapping->i_pages, index);
+
+ if (cookie == ~0UL)
+ return;
+
+ dax_unlock_entry(&xas, (void *)cookie);
+}
+
+/*
+ * Find page cache entry at given index. If it is a DAX entry, return it
+ * with the entry locked. If the page cache doesn't contain an entry at
+ * that index, add a locked empty entry.
+ *
+ * When requesting an entry with size DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return VM_FAULT_FALLBACK.
+ * This will happen if there are any PTE entries within the PMD range
+ * that we are requesting.
+ *
+ * We always favor PTE entries over PMD entries. There isn't a flow where we
+ * evict PTE entries in order to 'upgrade' them to a PMD entry. A PMD
+ * insertion will fail if it finds any PTE entries already in the tree, and a
+ * PTE insertion will cause an existing PMD entry to be unmapped and
+ * downgraded to PTE entries. This happens for both PMD zero pages as
+ * well as PMD empty entries.
+ *
+ * The exception to this downgrade path is for PMD entries that have
+ * real storage backing them. We will leave these real PMD entries in
+ * the tree, and PTE writes will simply dirty the entire PMD 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.
+ *
+ * On error, this function does not return an ERR_PTR. Instead it returns
+ * a VM_FAULT code, encoded as an xarray internal entry. The ERR_PTR values
+ * overlap with xarray value entries.
+ */
+static void *grab_mapping_entry(struct xa_state *xas,
+ struct address_space *mapping, unsigned int order)
+{
+ unsigned long index = xas->xa_index;
+ bool pmd_downgrade; /* splitting PMD entry into PTE entries? */
+ void *entry;
+
+retry:
+ pmd_downgrade = false;
+ xas_lock_irq(xas);
+ entry = get_unlocked_entry(xas, order);
+
+ if (entry) {
+ if (dax_is_conflict(entry))
+ goto fallback;
+ if (!xa_is_value(entry)) {
+ xas_set_err(xas, -EIO);
+ goto out_unlock;
+ }
+
+ if (order == 0) {
+ if (dax_is_pmd_entry(entry) &&
+ (dax_is_zero_entry(entry) ||
+ dax_is_empty_entry(entry))) {
+ pmd_downgrade = true;
+ }
+ }
+ }
+
+ if (pmd_downgrade) {
+ /*
+ * Make sure 'entry' remains valid while we drop
+ * the i_pages lock.
+ */
+ dax_lock_entry(xas, entry);
+
+ /*
+ * Besides huge zero pages the only other thing that gets
+ * downgraded are empty entries which don't need to be
+ * unmapped.
+ */
+ if (dax_is_zero_entry(entry)) {
+ xas_unlock_irq(xas);
+ unmap_mapping_pages(mapping,
+ xas->xa_index & ~PG_PMD_COLOUR,
+ PG_PMD_NR, false);
+ xas_reset(xas);
+ xas_lock_irq(xas);
+ }
+
+ dax_disassociate_entry(entry, mapping, false);
+ xas_store(xas, NULL); /* undo the PMD join */
+ dax_wake_entry(xas, entry, WAKE_ALL);
+ mapping->nrpages -= PG_PMD_NR;
+ entry = NULL;
+ xas_set(xas, index);
+ }
+
+ if (entry) {
+ dax_lock_entry(xas, entry);
+ } else {
+ unsigned long flags = DAX_EMPTY;
+
+ if (order > 0)
+ flags |= DAX_PMD;
+ entry = dax_make_entry(pfn_to_pfn_t(0), flags);
+ dax_lock_entry(xas, entry);
+ if (xas_error(xas))
+ goto out_unlock;
+ mapping->nrpages += 1UL << order;
+ }
+
+out_unlock:
+ xas_unlock_irq(xas);
+ if (xas_nomem(xas, mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM))
+ goto retry;
+ if (xas->xa_node == XA_ERROR(-ENOMEM))
+ return xa_mk_internal(VM_FAULT_OOM);
+ if (xas_error(xas))
+ return xa_mk_internal(VM_FAULT_SIGBUS);
+ return entry;
+fallback:
+ xas_unlock_irq(xas);
+ return xa_mk_internal(VM_FAULT_FALLBACK);
+}
+
+/**
+ * dax_layout_busy_page_range - find first pinned page in @mapping
+ * @mapping: address space to scan for a page with ref count > 1
+ * @start: Starting offset. Page containing 'start' is included.
+ * @end: End offset. Page containing 'end' is included. If 'end' is LLONG_MAX,
+ * pages from 'start' till the end of file are included.
+ *
+ * DAX requires ZONE_DEVICE mapped pages. These pages are never
+ * 'onlined' to the page allocator so they are considered idle when
+ * page->count == 1. A filesystem uses this interface to determine if
+ * any page in the mapping is busy, i.e. for DMA, or other
+ * get_user_pages() usages.
+ *
+ * It is expected that the filesystem is holding locks to block the
+ * establishment of new mappings in this address_space. I.e. it expects
+ * to be able to run unmap_mapping_range() and subsequently not race
+ * mapping_mapped() becoming true.
+ */
+struct page *dax_layout_busy_page_range(struct address_space *mapping,
+ loff_t start, loff_t end)
+{
+ void *entry;
+ unsigned int scanned = 0;
+ struct page *page = NULL;
+ pgoff_t start_idx = start >> PAGE_SHIFT;
+ pgoff_t end_idx;
+ XA_STATE(xas, &mapping->i_pages, start_idx);
+
+ /*
+ * In the 'limited' case get_user_pages() for dax is disabled.
+ */
+ if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
+ return NULL;
+
+ if (!dax_mapping(mapping) || !mapping_mapped(mapping))
+ return NULL;
+
+ /* If end == LLONG_MAX, all pages from start to till end of file */
+ if (end == LLONG_MAX)
+ end_idx = ULONG_MAX;
+ else
+ end_idx = end >> PAGE_SHIFT;
+ /*
+ * If we race get_user_pages_fast() here either we'll see the
+ * elevated page count in the iteration and wait, or
+ * get_user_pages_fast() will see that the page it took a reference
+ * against is no longer mapped in the page tables and bail to the
+ * get_user_pages() slow path. The slow path is protected by
+ * pte_lock() and pmd_lock(). New references are not taken without
+ * holding those locks, and unmap_mapping_pages() will not zero the
+ * pte or pmd without holding the respective lock, so we are
+ * guaranteed to either see new references or prevent new
+ * references from being established.
+ */
+ unmap_mapping_pages(mapping, start_idx, end_idx - start_idx + 1, 0);
+
+ xas_lock_irq(&xas);
+ xas_for_each(&xas, entry, end_idx) {
+ if (WARN_ON_ONCE(!xa_is_value(entry)))
+ continue;
+ if (unlikely(dax_is_locked(entry)))
+ entry = get_unlocked_entry(&xas, 0);
+ if (entry)
+ page = dax_busy_page(entry);
+ put_unlocked_entry(&xas, entry, WAKE_NEXT);
+ if (page)
+ break;
+ if (++scanned % XA_CHECK_SCHED)
+ continue;
+
+ xas_pause(&xas);
+ xas_unlock_irq(&xas);
+ cond_resched();
+ xas_lock_irq(&xas);
+ }
+ xas_unlock_irq(&xas);
+ return page;
+}
+EXPORT_SYMBOL_GPL(dax_layout_busy_page_range);
+
+struct page *dax_layout_busy_page(struct address_space *mapping)
+{
+ return dax_layout_busy_page_range(mapping, 0, LLONG_MAX);
+}
+EXPORT_SYMBOL_GPL(dax_layout_busy_page);
+
+static int __dax_invalidate_entry(struct address_space *mapping,
+ pgoff_t index, bool trunc)
+{
+ XA_STATE(xas, &mapping->i_pages, index);
+ int ret = 0;
+ void *entry;
+
+ xas_lock_irq(&xas);
+ entry = get_unlocked_entry(&xas, 0);
+ if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
+ goto out;
+ if (!trunc &&
+ (xas_get_mark(&xas, PAGECACHE_TAG_DIRTY) ||
+ xas_get_mark(&xas, PAGECACHE_TAG_TOWRITE)))
+ goto out;
+ dax_disassociate_entry(entry, mapping, trunc);
+ xas_store(&xas, NULL);
+ mapping->nrpages -= 1UL << dax_entry_order(entry);
+ ret = 1;
+out:
+ put_unlocked_entry(&xas, entry, WAKE_ALL);
+ xas_unlock_irq(&xas);
+ return ret;
+}
+
+static int __dax_clear_dirty_range(struct address_space *mapping,
+ pgoff_t start, pgoff_t end)
+{
+ XA_STATE(xas, &mapping->i_pages, start);
+ unsigned int scanned = 0;
+ void *entry;
+
+ xas_lock_irq(&xas);
+ xas_for_each(&xas, entry, end) {
+ entry = get_unlocked_entry(&xas, 0);
+ xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY);
+ xas_clear_mark(&xas, PAGECACHE_TAG_TOWRITE);
+ put_unlocked_entry(&xas, entry, WAKE_NEXT);
+
+ if (++scanned % XA_CHECK_SCHED)
+ continue;
+
+ xas_pause(&xas);
+ xas_unlock_irq(&xas);
+ cond_resched();
+ xas_lock_irq(&xas);
+ }
+ xas_unlock_irq(&xas);
+
+ return 0;
+}
+
+/*
+ * Delete DAX entry at @index from @mapping. Wait for it
+ * to be unlocked before deleting it.
+ */
+int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
+{
+ int ret = __dax_invalidate_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
+ * page cache (usually fs-private i_mmap_sem for writing). Since the
+ * caller has seen a DAX entry for this index, we better find it
+ * at that index as well...
+ */
+ WARN_ON_ONCE(!ret);
+ return ret;
+}
+
+/*
+ * Invalidate DAX entry if it is clean.
+ */
+int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
+ pgoff_t index)
+{
+ return __dax_invalidate_entry(mapping, index, false);
+}
+
+static pgoff_t dax_iomap_pgoff(const struct iomap *iomap, loff_t pos)
+{
+ return PHYS_PFN(iomap->addr + (pos & PAGE_MASK) - iomap->offset);
+}
+
+static int copy_cow_page_dax(struct vm_fault *vmf, const struct iomap_iter *iter)
+{
+ pgoff_t pgoff = dax_iomap_pgoff(&iter->iomap, iter->pos);
+ void *vto, *kaddr;
+ long rc;
+ int id;
+
+ id = dax_read_lock();
+ rc = dax_direct_access(iter->iomap.dax_dev, pgoff, 1, DAX_ACCESS,
+ &kaddr, NULL);
+ if (rc < 0) {
+ dax_read_unlock(id);
+ return rc;
+ }
+ vto = kmap_atomic(vmf->cow_page);
+ copy_user_page(vto, kaddr, vmf->address, vmf->cow_page);
+ kunmap_atomic(vto);
+ dax_read_unlock(id);
+ return 0;
+}
+
+/*
+ * 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(const struct iomap_iter *iter,
+ struct vm_area_struct *vma)
+{
+ return (iter->flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC) &&
+ (iter->iomap.flags & IOMAP_F_DIRTY);
+}
+
+/*
+ * 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_entry(struct xa_state *xas, struct vm_fault *vmf,
+ const struct iomap_iter *iter, void *entry, pfn_t pfn,
+ unsigned long flags)
+{
+ struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+ void *new_entry = dax_make_entry(pfn, flags);
+ bool write = iter->flags & IOMAP_WRITE;
+ bool dirty = write && !dax_fault_is_synchronous(iter, vmf->vma);
+ bool shared = iter->iomap.flags & IOMAP_F_SHARED;
+
+ if (dirty)
+ __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
+
+ if (shared || (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE))) {
+ unsigned long index = xas->xa_index;
+ /* we are replacing a zero page with block mapping */
+ if (dax_is_pmd_entry(entry))
+ unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
+ PG_PMD_NR, false);
+ else /* pte entry */
+ unmap_mapping_pages(mapping, index, 1, false);
+ }
+
+ xas_reset(xas);
+ xas_lock_irq(xas);
+ if (shared || dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+ void *old;
+
+ dax_disassociate_entry(entry, mapping, false);
+ dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address,
+ shared);
+ /*
+ * Only swap our new entry into the page cache if the current
+ * entry is a zero page or an empty entry. If a normal PTE or
+ * PMD entry is already in the cache, 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.
+ */
+ old = dax_lock_entry(xas, new_entry);
+ WARN_ON_ONCE(old != xa_mk_value(xa_to_value(entry) |
+ DAX_LOCKED));
+ entry = new_entry;
+ } else {
+ xas_load(xas); /* Walk the xa_state */
+ }
+
+ if (dirty)
+ xas_set_mark(xas, PAGECACHE_TAG_DIRTY);
+
+ if (write && shared)
+ xas_set_mark(xas, PAGECACHE_TAG_TOWRITE);
+
+ xas_unlock_irq(xas);
+ return entry;
+}
+
+static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
+ struct address_space *mapping, void *entry)
+{
+ unsigned long pfn, index, count, end;
+ long ret = 0;
+ struct vm_area_struct *vma;
+
+ /*
+ * A page got tagged dirty in DAX mapping? Something is seriously
+ * wrong.
+ */
+ if (WARN_ON(!xa_is_value(entry)))
+ return -EIO;
+
+ if (unlikely(dax_is_locked(entry))) {
+ void *old_entry = entry;
+
+ entry = get_unlocked_entry(xas, 0);
+
+ /* Entry got punched out / reallocated? */
+ if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
+ goto put_unlocked;
+ /*
+ * Entry got reallocated elsewhere? No need to writeback.
+ * We have to compare pfns as we must not bail out due to
+ * difference in lockbit or entry type.
+ */
+ if (dax_to_pfn(old_entry) != dax_to_pfn(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 done this entry */
+ if (!xas_get_mark(xas, PAGECACHE_TAG_TOWRITE))
+ goto put_unlocked;
+ }
+
+ /* Lock the entry to serialize with page faults */
+ dax_lock_entry(xas, entry);
+
+ /*
+ * 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 the i_pages lock and once they do that
+ * they will see the entry locked and wait for it to unlock.
+ */
+ xas_clear_mark(xas, PAGECACHE_TAG_TOWRITE);
+ xas_unlock_irq(xas);
+
+ /*
+ * If dax_writeback_mapping_range() was given a wbc->range_start
+ * in the middle of a PMD, the 'index' we use needs to be
+ * aligned to the start of the PMD.
+ * This allows us to flush for PMD_SIZE and not have to worry about
+ * partial PMD writebacks.
+ */
+ pfn = dax_to_pfn(entry);
+ count = 1UL << dax_entry_order(entry);
+ index = xas->xa_index & ~(count - 1);
+ end = index + count - 1;
+
+ /* Walk all mappings of a given index of a file and writeprotect them */
+ i_mmap_lock_read(mapping);
+ vma_interval_tree_foreach(vma, &mapping->i_mmap, index, end) {
+ pfn_mkclean_range(pfn, count, index, vma);
+ cond_resched();
+ }
+ i_mmap_unlock_read(mapping);
+
+ dax_flush(dax_dev, page_address(pfn_to_page(pfn)), count * PAGE_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.
+ */
+ xas_reset(xas);
+ xas_lock_irq(xas);
+ xas_store(xas, entry);
+ xas_clear_mark(xas, PAGECACHE_TAG_DIRTY);
+ dax_wake_entry(xas, entry, WAKE_NEXT);
+
+ trace_dax_writeback_one(mapping->host, index, count);
+ return ret;
+
+ put_unlocked:
+ put_unlocked_entry(xas, entry, WAKE_NEXT);
+ 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 dax_device *dax_dev, struct writeback_control *wbc)
+{
+ XA_STATE(xas, &mapping->i_pages, wbc->range_start >> PAGE_SHIFT);
+ struct inode *inode = mapping->host;
+ pgoff_t end_index = wbc->range_end >> PAGE_SHIFT;
+ void *entry;
+ int ret = 0;
+ unsigned int scanned = 0;
+
+ if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
+ return -EIO;
+
+ if (mapping_empty(mapping) || wbc->sync_mode != WB_SYNC_ALL)
+ return 0;
+
+ trace_dax_writeback_range(inode, xas.xa_index, end_index);
+
+ tag_pages_for_writeback(mapping, xas.xa_index, end_index);
+
+ xas_lock_irq(&xas);
+ xas_for_each_marked(&xas, entry, end_index, PAGECACHE_TAG_TOWRITE) {
+ ret = dax_writeback_one(&xas, dax_dev, mapping, entry);
+ if (ret < 0) {
+ mapping_set_error(mapping, ret);
+ break;
+ }
+ if (++scanned % XA_CHECK_SCHED)
+ continue;
+
+ xas_pause(&xas);
+ xas_unlock_irq(&xas);
+ cond_resched();
+ xas_lock_irq(&xas);
+ }
+ xas_unlock_irq(&xas);
+ trace_dax_writeback_range_done(inode, xas.xa_index, end_index);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
+
+static int dax_iomap_direct_access(const struct iomap *iomap, loff_t pos,
+ size_t size, void **kaddr, pfn_t *pfnp)
+{
+ pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
+ int id, rc = 0;
+ long length;
+
+ id = dax_read_lock();
+ length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
+ DAX_ACCESS, kaddr, pfnp);
+ if (length < 0) {
+ rc = length;
+ goto out;
+ }
+ if (!pfnp)
+ goto out_check_addr;
+ 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_check_addr:
+ if (!kaddr)
+ goto out;
+ if (!*kaddr)
+ rc = -EFAULT;
+out:
+ dax_read_unlock(id);
+ return rc;
+}
+
+/**
+ * dax_iomap_copy_around - Prepare for an unaligned write to a shared/cow page
+ * by copying the data before and after the range to be written.
+ * @pos: address to do copy from.
+ * @length: size of copy operation.
+ * @align_size: aligned w.r.t align_size (either PMD_SIZE or PAGE_SIZE)
+ * @srcmap: iomap srcmap
+ * @daddr: destination address to copy to.
+ *
+ * This can be called from two places. Either during DAX write fault (page
+ * aligned), to copy the length size data to daddr. Or, while doing normal DAX
+ * write operation, dax_iomap_iter() might call this to do the copy of either
+ * start or end unaligned address. In the latter case the rest of the copy of
+ * aligned ranges is taken care by dax_iomap_iter() itself.
+ * If the srcmap contains invalid data, such as HOLE and UNWRITTEN, zero the
+ * area to make sure no old data remains.
+ */
+static int dax_iomap_copy_around(loff_t pos, uint64_t length, size_t align_size,
+ const struct iomap *srcmap, void *daddr)
+{
+ loff_t head_off = pos & (align_size - 1);
+ size_t size = ALIGN(head_off + length, align_size);
+ loff_t end = pos + length;
+ loff_t pg_end = round_up(end, align_size);
+ /* copy_all is usually in page fault case */
+ bool copy_all = head_off == 0 && end == pg_end;
+ /* zero the edges if srcmap is a HOLE or IOMAP_UNWRITTEN */
+ bool zero_edge = srcmap->flags & IOMAP_F_SHARED ||
+ srcmap->type == IOMAP_UNWRITTEN;
+ void *saddr = 0;
+ int ret = 0;
+
+ if (!zero_edge) {
+ ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL);
+ if (ret)
+ return dax_mem2blk_err(ret);
+ }
+
+ if (copy_all) {
+ if (zero_edge)
+ memset(daddr, 0, size);
+ else
+ ret = copy_mc_to_kernel(daddr, saddr, length);
+ goto out;
+ }
+
+ /* Copy the head part of the range */
+ if (head_off) {
+ if (zero_edge)
+ memset(daddr, 0, head_off);
+ else {
+ ret = copy_mc_to_kernel(daddr, saddr, head_off);
+ if (ret)
+ return -EIO;
+ }
+ }
+
+ /* Copy the tail part of the range */
+ if (end < pg_end) {
+ loff_t tail_off = head_off + length;
+ loff_t tail_len = pg_end - end;
+
+ if (zero_edge)
+ memset(daddr + tail_off, 0, tail_len);
+ else {
+ ret = copy_mc_to_kernel(daddr + tail_off,
+ saddr + tail_off, tail_len);
+ if (ret)
+ return -EIO;
+ }
+ }
+out:
+ if (zero_edge)
+ dax_flush(srcmap->dax_dev, daddr, size);
+ return ret ? -EIO : 0;
+}
+
+/*
+ * 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 vm_fault_t dax_load_hole(struct xa_state *xas, struct vm_fault *vmf,
+ const struct iomap_iter *iter, void **entry)
+{
+ struct inode *inode = iter->inode;
+ unsigned long vaddr = vmf->address;
+ pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr));
+ vm_fault_t ret;
+
+ *entry = dax_insert_entry(xas, vmf, iter, *entry, pfn, DAX_ZERO_PAGE);
+
+ ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
+ trace_dax_load_hole(inode, vmf, ret);
+ return ret;
+}
+
+#ifdef CONFIG_FS_DAX_PMD
+static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
+ const struct iomap_iter *iter, void **entry)
+{
+ struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+ unsigned long pmd_addr = vmf->address & PMD_MASK;
+ struct vm_area_struct *vma = vmf->vma;
+ struct inode *inode = mapping->host;
+ pgtable_t pgtable = NULL;
+ struct page *zero_page;
+ spinlock_t *ptl;
+ pmd_t pmd_entry;
+ pfn_t pfn;
+
+ zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);
+
+ if (unlikely(!zero_page))
+ goto fallback;
+
+ pfn = page_to_pfn_t(zero_page);
+ *entry = dax_insert_entry(xas, vmf, iter, *entry, pfn,
+ DAX_PMD | DAX_ZERO_PAGE);
+
+ if (arch_needs_pgtable_deposit()) {
+ pgtable = pte_alloc_one(vma->vm_mm);
+ if (!pgtable)
+ return VM_FAULT_OOM;
+ }
+
+ ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
+ if (!pmd_none(*(vmf->pmd))) {
+ spin_unlock(ptl);
+ goto fallback;
+ }
+
+ if (pgtable) {
+ pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
+ mm_inc_nr_ptes(vma->vm_mm);
+ }
+ 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, *entry);
+ return VM_FAULT_NOPAGE;
+
+fallback:
+ if (pgtable)
+ pte_free(vma->vm_mm, pgtable);
+ trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, *entry);
+ return VM_FAULT_FALLBACK;
+}
+#else
+static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
+ const struct iomap_iter *iter, void **entry)
+{
+ return VM_FAULT_FALLBACK;
+}
+#endif /* CONFIG_FS_DAX_PMD */
+
+static s64 dax_unshare_iter(struct iomap_iter *iter)
+{
+ struct iomap *iomap = &iter->iomap;
+ const struct iomap *srcmap = iomap_iter_srcmap(iter);
+ loff_t pos = iter->pos;
+ loff_t length = iomap_length(iter);
+ int id = 0;
+ s64 ret = 0;
+ void *daddr = NULL, *saddr = NULL;
+
+ /* don't bother with blocks that are not shared to start with */
+ if (!(iomap->flags & IOMAP_F_SHARED))
+ return length;
+
+ id = dax_read_lock();
+ ret = dax_iomap_direct_access(iomap, pos, length, &daddr, NULL);
+ if (ret < 0)
+ goto out_unlock;
+
+ /* zero the distance if srcmap is HOLE or UNWRITTEN */
+ if (srcmap->flags & IOMAP_F_SHARED || srcmap->type == IOMAP_UNWRITTEN) {
+ memset(daddr, 0, length);
+ dax_flush(iomap->dax_dev, daddr, length);
+ ret = length;
+ goto out_unlock;
+ }
+
+ ret = dax_iomap_direct_access(srcmap, pos, length, &saddr, NULL);
+ if (ret < 0)
+ goto out_unlock;
+
+ if (copy_mc_to_kernel(daddr, saddr, length) == 0)
+ ret = length;
+ else
+ ret = -EIO;
+
+out_unlock:
+ dax_read_unlock(id);
+ return dax_mem2blk_err(ret);
+}
+
+int dax_file_unshare(struct inode *inode, loff_t pos, loff_t len,
+ const struct iomap_ops *ops)
+{
+ struct iomap_iter iter = {
+ .inode = inode,
+ .pos = pos,
+ .len = len,
+ .flags = IOMAP_WRITE | IOMAP_UNSHARE | IOMAP_DAX,
+ };
+ int ret;
+
+ while ((ret = iomap_iter(&iter, ops)) > 0)
+ iter.processed = dax_unshare_iter(&iter);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dax_file_unshare);
+
+static int dax_memzero(struct iomap_iter *iter, loff_t pos, size_t size)
+{
+ const struct iomap *iomap = &iter->iomap;
+ const struct iomap *srcmap = iomap_iter_srcmap(iter);
+ unsigned offset = offset_in_page(pos);
+ pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
+ void *kaddr;
+ long ret;
+
+ ret = dax_direct_access(iomap->dax_dev, pgoff, 1, DAX_ACCESS, &kaddr,
+ NULL);
+ if (ret < 0)
+ return dax_mem2blk_err(ret);
+
+ memset(kaddr + offset, 0, size);
+ if (iomap->flags & IOMAP_F_SHARED)
+ ret = dax_iomap_copy_around(pos, size, PAGE_SIZE, srcmap,
+ kaddr);
+ else
+ dax_flush(iomap->dax_dev, kaddr + offset, size);
+ return ret;
+}
+
+static s64 dax_zero_iter(struct iomap_iter *iter, bool *did_zero)
+{
+ const struct iomap *iomap = &iter->iomap;
+ const struct iomap *srcmap = iomap_iter_srcmap(iter);
+ loff_t pos = iter->pos;
+ u64 length = iomap_length(iter);
+ s64 written = 0;
+
+ /* already zeroed? we're done. */
+ if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
+ return length;
+
+ /*
+ * invalidate the pages whose sharing state is to be changed
+ * because of CoW.
+ */
+ if (iomap->flags & IOMAP_F_SHARED)
+ invalidate_inode_pages2_range(iter->inode->i_mapping,
+ pos >> PAGE_SHIFT,
+ (pos + length - 1) >> PAGE_SHIFT);
+
+ do {
+ unsigned offset = offset_in_page(pos);
+ unsigned size = min_t(u64, PAGE_SIZE - offset, length);
+ pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
+ long rc;
+ int id;
+
+ id = dax_read_lock();
+ if (IS_ALIGNED(pos, PAGE_SIZE) && size == PAGE_SIZE)
+ rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
+ else
+ rc = dax_memzero(iter, pos, size);
+ dax_read_unlock(id);
+
+ if (rc < 0)
+ return rc;
+ pos += size;
+ length -= size;
+ written += size;
+ } while (length > 0);
+
+ if (did_zero)
+ *did_zero = true;
+ return written;
+}
+
+int dax_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
+ const struct iomap_ops *ops)
+{
+ struct iomap_iter iter = {
+ .inode = inode,
+ .pos = pos,
+ .len = len,
+ .flags = IOMAP_DAX | IOMAP_ZERO,
+ };
+ int ret;
+
+ while ((ret = iomap_iter(&iter, ops)) > 0)
+ iter.processed = dax_zero_iter(&iter, did_zero);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dax_zero_range);
+
+int dax_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
+ const struct iomap_ops *ops)
+{
+ unsigned int blocksize = i_blocksize(inode);
+ unsigned int off = pos & (blocksize - 1);
+
+ /* Block boundary? Nothing to do */
+ if (!off)
+ return 0;
+ return dax_zero_range(inode, pos, blocksize - off, did_zero, ops);
+}
+EXPORT_SYMBOL_GPL(dax_truncate_page);
+
+static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
+ struct iov_iter *iter)
+{
+ const struct iomap *iomap = &iomi->iomap;
+ const struct iomap *srcmap = iomap_iter_srcmap(iomi);
+ loff_t length = iomap_length(iomi);
+ loff_t pos = iomi->pos;
+ struct dax_device *dax_dev = iomap->dax_dev;
+ loff_t end = pos + length, done = 0;
+ bool write = iov_iter_rw(iter) == WRITE;
+ bool cow = write && iomap->flags & IOMAP_F_SHARED;
+ ssize_t ret = 0;
+ size_t xfer;
+ int id;
+
+ if (!write) {
+ end = min(end, i_size_read(iomi->inode));
+ if (pos >= end)
+ return 0;
+
+ if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
+ return iov_iter_zero(min(length, end - pos), iter);
+ }
+
+ /*
+ * In DAX mode, enforce either pure overwrites of written extents, or
+ * writes to unwritten extents as part of a copy-on-write operation.
+ */
+ if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED &&
+ !(iomap->flags & IOMAP_F_SHARED)))
+ 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 || cow) {
+ /*
+ * Filesystem allows CoW on non-shared extents. The src extents
+ * may have been mmapped with dirty mark before. To be able to
+ * invalidate its dax entries, we need to clear the dirty mark
+ * in advance.
+ */
+ if (cow)
+ __dax_clear_dirty_range(iomi->inode->i_mapping,
+ pos >> PAGE_SHIFT,
+ (end - 1) >> PAGE_SHIFT);
+ invalidate_inode_pages2_range(iomi->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);
+ pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
+ ssize_t map_len;
+ bool recovery = false;
+ void *kaddr;
+
+ if (fatal_signal_pending(current)) {
+ ret = -EINTR;
+ break;
+ }
+
+ map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size),
+ DAX_ACCESS, &kaddr, NULL);
+ if (map_len == -EHWPOISON && iov_iter_rw(iter) == WRITE) {
+ map_len = dax_direct_access(dax_dev, pgoff,
+ PHYS_PFN(size), DAX_RECOVERY_WRITE,
+ &kaddr, NULL);
+ if (map_len > 0)
+ recovery = true;
+ }
+ if (map_len < 0) {
+ ret = dax_mem2blk_err(map_len);
+ break;
+ }
+
+ if (cow) {
+ ret = dax_iomap_copy_around(pos, length, PAGE_SIZE,
+ srcmap, kaddr);
+ if (ret)
+ break;
+ }
+
+ map_len = PFN_PHYS(map_len);
+ kaddr += offset;
+ map_len -= offset;
+ if (map_len > end - pos)
+ map_len = end - pos;
+
+ if (recovery)
+ xfer = dax_recovery_write(dax_dev, pgoff, kaddr,
+ map_len, iter);
+ else if (write)
+ xfer = dax_copy_from_iter(dax_dev, pgoff, kaddr,
+ map_len, iter);
+ else
+ xfer = dax_copy_to_iter(dax_dev, pgoff, kaddr,
+ map_len, iter);
+
+ pos += xfer;
+ length -= xfer;
+ done += xfer;
+
+ if (xfer == 0)
+ ret = -EFAULT;
+ if (xfer < map_len)
+ break;
+ }
+ 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 iomap_iter iomi = {
+ .inode = iocb->ki_filp->f_mapping->host,
+ .pos = iocb->ki_pos,
+ .len = iov_iter_count(iter),
+ .flags = IOMAP_DAX,
+ };
+ loff_t done = 0;
+ int ret;
+
+ if (!iomi.len)
+ return 0;
+
+ if (iov_iter_rw(iter) == WRITE) {
+ lockdep_assert_held_write(&iomi.inode->i_rwsem);
+ iomi.flags |= IOMAP_WRITE;
+ } else {
+ lockdep_assert_held(&iomi.inode->i_rwsem);
+ }
+
+ if (iocb->ki_flags & IOCB_NOWAIT)
+ iomi.flags |= IOMAP_NOWAIT;
+
+ while ((ret = iomap_iter(&iomi, ops)) > 0)
+ iomi.processed = dax_iomap_iter(&iomi, iter);
+
+ done = iomi.pos - iocb->ki_pos;
+ iocb->ki_pos = iomi.pos;
+ return done ? done : ret;
+}
+EXPORT_SYMBOL_GPL(dax_iomap_rw);
+
+static vm_fault_t dax_fault_return(int error)
+{
+ if (error == 0)
+ return VM_FAULT_NOPAGE;
+ return vmf_error(error);
+}
+
+/*
+ * When handling a synchronous page fault and the inode need a fsync, we can
+ * insert the PTE/PMD into page tables only after that fsync happened. Skip
+ * insertion for now and return the pfn so that caller can insert it after the
+ * fsync is done.
+ */
+static vm_fault_t dax_fault_synchronous_pfnp(pfn_t *pfnp, pfn_t pfn)
+{
+ if (WARN_ON_ONCE(!pfnp))
+ return VM_FAULT_SIGBUS;
+ *pfnp = pfn;
+ return VM_FAULT_NEEDDSYNC;
+}
+
+static vm_fault_t dax_fault_cow_page(struct vm_fault *vmf,
+ const struct iomap_iter *iter)
+{
+ vm_fault_t ret;
+ int error = 0;
+
+ switch (iter->iomap.type) {
+ case IOMAP_HOLE:
+ case IOMAP_UNWRITTEN:
+ clear_user_highpage(vmf->cow_page, vmf->address);
+ break;
+ case IOMAP_MAPPED:
+ error = copy_cow_page_dax(vmf, iter);
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ error = -EIO;
+ break;
+ }
+
+ if (error)
+ return dax_fault_return(error);
+
+ __SetPageUptodate(vmf->cow_page);
+ ret = finish_fault(vmf);
+ if (!ret)
+ return VM_FAULT_DONE_COW;
+ return ret;
+}
+
+/**
+ * dax_fault_iter - Common actor to handle pfn insertion in PTE/PMD fault.
+ * @vmf: vm fault instance
+ * @iter: iomap iter
+ * @pfnp: pfn to be returned
+ * @xas: the dax mapping tree of a file
+ * @entry: an unlocked dax entry to be inserted
+ * @pmd: distinguish whether it is a pmd fault
+ */
+static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
+ const struct iomap_iter *iter, pfn_t *pfnp,
+ struct xa_state *xas, void **entry, bool pmd)
+{
+ const struct iomap *iomap = &iter->iomap;
+ const struct iomap *srcmap = iomap_iter_srcmap(iter);
+ size_t size = pmd ? PMD_SIZE : PAGE_SIZE;
+ loff_t pos = (loff_t)xas->xa_index << PAGE_SHIFT;
+ bool write = iter->flags & IOMAP_WRITE;
+ unsigned long entry_flags = pmd ? DAX_PMD : 0;
+ int err = 0;
+ pfn_t pfn;
+ void *kaddr;
+
+ if (!pmd && vmf->cow_page)
+ return dax_fault_cow_page(vmf, iter);
+
+ /* if we are reading UNWRITTEN and HOLE, return a hole. */
+ if (!write &&
+ (iomap->type == IOMAP_UNWRITTEN || iomap->type == IOMAP_HOLE)) {
+ if (!pmd)
+ return dax_load_hole(xas, vmf, iter, entry);
+ return dax_pmd_load_hole(xas, vmf, iter, entry);
+ }
+
+ if (iomap->type != IOMAP_MAPPED && !(iomap->flags & IOMAP_F_SHARED)) {
+ WARN_ON_ONCE(1);
+ return pmd ? VM_FAULT_FALLBACK : VM_FAULT_SIGBUS;
+ }
+
+ err = dax_iomap_direct_access(iomap, pos, size, &kaddr, &pfn);
+ if (err)
+ return pmd ? VM_FAULT_FALLBACK : dax_fault_return(err);
+
+ *entry = dax_insert_entry(xas, vmf, iter, *entry, pfn, entry_flags);
+
+ if (write && iomap->flags & IOMAP_F_SHARED) {
+ err = dax_iomap_copy_around(pos, size, size, srcmap, kaddr);
+ if (err)
+ return dax_fault_return(err);
+ }
+
+ if (dax_fault_is_synchronous(iter, vmf->vma))
+ return dax_fault_synchronous_pfnp(pfnp, pfn);
+
+ /* insert PMD pfn */
+ if (pmd)
+ return vmf_insert_pfn_pmd(vmf, pfn, write);
+
+ /* insert PTE pfn */
+ if (write)
+ return vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
+ return vmf_insert_mixed(vmf->vma, vmf->address, pfn);
+}
+
+static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
+ int *iomap_errp, const struct iomap_ops *ops)
+{
+ struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+ XA_STATE(xas, &mapping->i_pages, vmf->pgoff);
+ struct iomap_iter iter = {
+ .inode = mapping->host,
+ .pos = (loff_t)vmf->pgoff << PAGE_SHIFT,
+ .len = PAGE_SIZE,
+ .flags = IOMAP_DAX | IOMAP_FAULT,
+ };
+ vm_fault_t ret = 0;
+ void *entry;
+ int error;
+
+ trace_dax_pte_fault(iter.inode, 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 (iter.pos >= i_size_read(iter.inode)) {
+ ret = VM_FAULT_SIGBUS;
+ goto out;
+ }
+
+ if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
+ iter.flags |= IOMAP_WRITE;
+
+ entry = grab_mapping_entry(&xas, mapping, 0);
+ if (xa_is_internal(entry)) {
+ ret = xa_to_internal(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)) {
+ ret = VM_FAULT_NOPAGE;
+ goto unlock_entry;
+ }
+
+ while ((error = iomap_iter(&iter, ops)) > 0) {
+ if (WARN_ON_ONCE(iomap_length(&iter) < PAGE_SIZE)) {
+ iter.processed = -EIO; /* fs corruption? */
+ continue;
+ }
+
+ ret = dax_fault_iter(vmf, &iter, pfnp, &xas, &entry, false);
+ if (ret != VM_FAULT_SIGBUS &&
+ (iter.iomap.flags & IOMAP_F_NEW)) {
+ count_vm_event(PGMAJFAULT);
+ count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
+ ret |= VM_FAULT_MAJOR;
+ }
+
+ if (!(ret & VM_FAULT_ERROR))
+ iter.processed = PAGE_SIZE;
+ }
+
+ if (iomap_errp)
+ *iomap_errp = error;
+ if (!ret && error)
+ ret = dax_fault_return(error);
+
+unlock_entry:
+ dax_unlock_entry(&xas, entry);
+out:
+ trace_dax_pte_fault_done(iter.inode, vmf, ret);
+ return ret;
+}
+
+#ifdef CONFIG_FS_DAX_PMD
+static bool dax_fault_check_fallback(struct vm_fault *vmf, struct xa_state *xas,
+ pgoff_t max_pgoff)
+{
+ unsigned long pmd_addr = vmf->address & PMD_MASK;
+ bool write = vmf->flags & FAULT_FLAG_WRITE;
+
+ /*
+ * 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 page cache.
+ */
+ if ((vmf->pgoff & PG_PMD_COLOUR) !=
+ ((vmf->address >> PAGE_SHIFT) & PG_PMD_COLOUR))
+ return true;
+
+ /* Fall back to PTEs if we're going to COW */
+ if (write && !(vmf->vma->vm_flags & VM_SHARED))
+ return true;
+
+ /* If the PMD would extend outside the VMA */
+ if (pmd_addr < vmf->vma->vm_start)
+ return true;
+ if ((pmd_addr + PMD_SIZE) > vmf->vma->vm_end)
+ return true;
+
+ /* If the PMD would extend beyond the file size */
+ if ((xas->xa_index | PG_PMD_COLOUR) >= max_pgoff)
+ return true;
+
+ return false;
+}
+
+static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
+ const struct iomap_ops *ops)
+{
+ struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+ XA_STATE_ORDER(xas, &mapping->i_pages, vmf->pgoff, PMD_ORDER);
+ struct iomap_iter iter = {
+ .inode = mapping->host,
+ .len = PMD_SIZE,
+ .flags = IOMAP_DAX | IOMAP_FAULT,
+ };
+ vm_fault_t ret = VM_FAULT_FALLBACK;
+ pgoff_t max_pgoff;
+ void *entry;
+
+ if (vmf->flags & FAULT_FLAG_WRITE)
+ iter.flags |= IOMAP_WRITE;
+
+ /*
+ * 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.
+ */
+ max_pgoff = DIV_ROUND_UP(i_size_read(iter.inode), PAGE_SIZE);
+
+ trace_dax_pmd_fault(iter.inode, vmf, max_pgoff, 0);
+
+ if (xas.xa_index >= max_pgoff) {
+ ret = VM_FAULT_SIGBUS;
+ goto out;
+ }
+
+ if (dax_fault_check_fallback(vmf, &xas, max_pgoff))
+ goto fallback;
+
+ /*
+ * grab_mapping_entry() will make sure we get an empty PMD entry,
+ * a zero PMD entry or a DAX PMD. If it can't (because a PTE
+ * entry is already in the array, for instance), it will return
+ * VM_FAULT_FALLBACK.
+ */
+ entry = grab_mapping_entry(&xas, mapping, PMD_ORDER);
+ if (xa_is_internal(entry)) {
+ ret = xa_to_internal(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)) {
+ ret = 0;
+ goto unlock_entry;
+ }
+
+ iter.pos = (loff_t)xas.xa_index << PAGE_SHIFT;
+ while (iomap_iter(&iter, ops) > 0) {
+ if (iomap_length(&iter) < PMD_SIZE)
+ continue; /* actually breaks out of the loop */
+
+ ret = dax_fault_iter(vmf, &iter, pfnp, &xas, &entry, true);
+ if (ret != VM_FAULT_FALLBACK)
+ iter.processed = PMD_SIZE;
+ }
+
+unlock_entry:
+ dax_unlock_entry(&xas, entry);
+fallback:
+ if (ret == VM_FAULT_FALLBACK) {
+ split_huge_pmd(vmf->vma, vmf->pmd, vmf->address);
+ count_vm_event(THP_FAULT_FALLBACK);
+ }
+out:
+ trace_dax_pmd_fault_done(iter.inode, vmf, max_pgoff, ret);
+ return ret;
+}
+#else
+static vm_fault_t 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
+ * @order: Order of the page to fault in
+ * @pfnp: PFN to insert for synchronous faults if fsync is required
+ * @iomap_errp: Storage for detailed error code in case of error
+ * @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.
+ */
+vm_fault_t dax_iomap_fault(struct vm_fault *vmf, unsigned int order,
+ pfn_t *pfnp, int *iomap_errp, const struct iomap_ops *ops)
+{
+ if (order == 0)
+ return dax_iomap_pte_fault(vmf, pfnp, iomap_errp, ops);
+ else if (order == PMD_ORDER)
+ return dax_iomap_pmd_fault(vmf, pfnp, ops);
+ else
+ 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
+ * @pfn: PFN to insert
+ * @order: Order of entry to insert.
+ *
+ * This function inserts a writeable PTE or PMD entry into the page tables
+ * for an mmaped DAX file. It also marks the page cache entry as dirty.
+ */
+static vm_fault_t
+dax_insert_pfn_mkwrite(struct vm_fault *vmf, pfn_t pfn, unsigned int order)
+{
+ struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+ XA_STATE_ORDER(xas, &mapping->i_pages, vmf->pgoff, order);
+ void *entry;
+ vm_fault_t ret;
+
+ xas_lock_irq(&xas);
+ entry = get_unlocked_entry(&xas, order);
+ /* Did we race with someone splitting entry or so? */
+ if (!entry || dax_is_conflict(entry) ||
+ (order == 0 && !dax_is_pte_entry(entry))) {
+ put_unlocked_entry(&xas, entry, WAKE_NEXT);
+ xas_unlock_irq(&xas);
+ trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
+ VM_FAULT_NOPAGE);
+ return VM_FAULT_NOPAGE;
+ }
+ xas_set_mark(&xas, PAGECACHE_TAG_DIRTY);
+ dax_lock_entry(&xas, entry);
+ xas_unlock_irq(&xas);
+ if (order == 0)
+ ret = vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
+#ifdef CONFIG_FS_DAX_PMD
+ else if (order == PMD_ORDER)
+ ret = vmf_insert_pfn_pmd(vmf, pfn, FAULT_FLAG_WRITE);
+#endif
+ else
+ ret = VM_FAULT_FALLBACK;
+ dax_unlock_entry(&xas, entry);
+ trace_dax_insert_pfn_mkwrite(mapping->host, vmf, ret);
+ return ret;
+}
+
+/**
+ * dax_finish_sync_fault - finish synchronous page fault
+ * @vmf: The description of the fault
+ * @order: Order 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.
+ */
+vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf, unsigned int order,
+ pfn_t pfn)
+{
+ int err;
+ loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT;
+ size_t len = PAGE_SIZE << order;
+
+ 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, pfn, order);
+}
+EXPORT_SYMBOL_GPL(dax_finish_sync_fault);
+
+static loff_t dax_range_compare_iter(struct iomap_iter *it_src,
+ struct iomap_iter *it_dest, u64 len, bool *same)
+{
+ const struct iomap *smap = &it_src->iomap;
+ const struct iomap *dmap = &it_dest->iomap;
+ loff_t pos1 = it_src->pos, pos2 = it_dest->pos;
+ void *saddr, *daddr;
+ int id, ret;
+
+ len = min(len, min(smap->length, dmap->length));
+
+ if (smap->type == IOMAP_HOLE && dmap->type == IOMAP_HOLE) {
+ *same = true;
+ return len;
+ }
+
+ if (smap->type == IOMAP_HOLE || dmap->type == IOMAP_HOLE) {
+ *same = false;
+ return 0;
+ }
+
+ id = dax_read_lock();
+ ret = dax_iomap_direct_access(smap, pos1, ALIGN(pos1 + len, PAGE_SIZE),
+ &saddr, NULL);
+ if (ret < 0)
+ goto out_unlock;
+
+ ret = dax_iomap_direct_access(dmap, pos2, ALIGN(pos2 + len, PAGE_SIZE),
+ &daddr, NULL);
+ if (ret < 0)
+ goto out_unlock;
+
+ *same = !memcmp(saddr, daddr, len);
+ if (!*same)
+ len = 0;
+ dax_read_unlock(id);
+ return len;
+
+out_unlock:
+ dax_read_unlock(id);
+ return -EIO;
+}
+
+int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
+ struct inode *dst, loff_t dstoff, loff_t len, bool *same,
+ const struct iomap_ops *ops)
+{
+ struct iomap_iter src_iter = {
+ .inode = src,
+ .pos = srcoff,
+ .len = len,
+ .flags = IOMAP_DAX,
+ };
+ struct iomap_iter dst_iter = {
+ .inode = dst,
+ .pos = dstoff,
+ .len = len,
+ .flags = IOMAP_DAX,
+ };
+ int ret, compared = 0;
+
+ while ((ret = iomap_iter(&src_iter, ops)) > 0 &&
+ (ret = iomap_iter(&dst_iter, ops)) > 0) {
+ compared = dax_range_compare_iter(&src_iter, &dst_iter,
+ min(src_iter.len, dst_iter.len), same);
+ if (compared < 0)
+ return ret;
+ src_iter.processed = dst_iter.processed = compared;
+ }
+ return ret;
+}
+
+int dax_remap_file_range_prep(struct file *file_in, loff_t pos_in,
+ struct file *file_out, loff_t pos_out,
+ loff_t *len, unsigned int remap_flags,
+ const struct iomap_ops *ops)
+{
+ return __generic_remap_file_range_prep(file_in, pos_in, file_out,
+ pos_out, len, remap_flags, ops);
+}
+EXPORT_SYMBOL_GPL(dax_remap_file_range_prep);