v4.19.13 snapshot.
diff --git a/fs/dax.c b/fs/dax.c
new file mode 100644
index 0000000..3a2682a
--- /dev/null
+++ b/fs/dax.c
@@ -0,0 +1,1825 @@
+/*
+ * fs/dax.c - Direct Access filesystem code
+ * Copyright (c) 2013-2014 Intel Corporation
+ * Author: Matthew Wilcox <matthew.r.wilcox@intel.com>
+ * Author: Ross Zwisler <ross.zwisler@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ */
+
+#include <linux/atomic.h>
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h>
+#include <linux/dax.h>
+#include <linux/fs.h>
+#include <linux/genhd.h>
+#include <linux/highmem.h>
+#include <linux/memcontrol.h>
+#include <linux/mm.h>
+#include <linux/mutex.h>
+#include <linux/pagevec.h>
+#include <linux/sched.h>
+#include <linux/sched/signal.h>
+#include <linux/uio.h>
+#include <linux/vmstat.h>
+#include <linux/pfn_t.h>
+#include <linux/sizes.h>
+#include <linux/mmu_notifier.h>
+#include <linux/iomap.h>
+#include "internal.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/fs_dax.h>
+
+/* We choose 4096 entries - same as per-zone page wait tables */
+#define DAX_WAIT_TABLE_BITS 12
+#define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
+
+/* The 'colour' (ie low bits) within a PMD of a page offset. */
+#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
+#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);
+
+/*
+ * We use lowest available bit in exceptional entry for locking, one bit for
+ * the entry size (PMD) and two more to tell us if the entry is a zero page or
+ * an empty entry that is just used for locking. In total four special bits.
+ *
+ * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the ZERO_PAGE
+ * and EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
+ * block allocation.
+ */
+#define RADIX_DAX_SHIFT (RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
+#define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
+#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
+#define RADIX_DAX_ZERO_PAGE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
+#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
+
+static unsigned long dax_radix_pfn(void *entry)
+{
+ return (unsigned long)entry >> RADIX_DAX_SHIFT;
+}
+
+static void *dax_radix_locked_entry(unsigned long pfn, unsigned long flags)
+{
+ return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
+ (pfn << RADIX_DAX_SHIFT) | RADIX_DAX_ENTRY_LOCK);
+}
+
+static unsigned int dax_radix_order(void *entry)
+{
+ if ((unsigned long)entry & RADIX_DAX_PMD)
+ return PMD_SHIFT - PAGE_SHIFT;
+ return 0;
+}
+
+static int dax_is_pmd_entry(void *entry)
+{
+ return (unsigned long)entry & RADIX_DAX_PMD;
+}
+
+static int dax_is_pte_entry(void *entry)
+{
+ return !((unsigned long)entry & RADIX_DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+ return (unsigned long)entry & RADIX_DAX_ZERO_PAGE;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+ return (unsigned long)entry & RADIX_DAX_EMPTY;
+}
+
+/*
+ * DAX radix tree locking
+ */
+struct exceptional_entry_key {
+ struct address_space *mapping;
+ pgoff_t entry_start;
+};
+
+struct wait_exceptional_entry_queue {
+ wait_queue_entry_t wait;
+ struct exceptional_entry_key key;
+};
+
+static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
+ pgoff_t index, void *entry, struct exceptional_entry_key *key)
+{
+ unsigned long hash;
+
+ /*
+ * If 'entry' is a PMD, align the 'index' that we use for the wait
+ * queue to the start of that PMD. This ensures that all offsets in
+ * the range covered by the PMD map to the same bit lock.
+ */
+ if (dax_is_pmd_entry(entry))
+ index &= ~PG_PMD_COLOUR;
+
+ key->mapping = mapping;
+ key->entry_start = index;
+
+ hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
+ return wait_table + hash;
+}
+
+static int wake_exceptional_entry_func(wait_queue_entry_t *wait, unsigned int mode,
+ int sync, void *keyp)
+{
+ struct exceptional_entry_key *key = keyp;
+ struct wait_exceptional_entry_queue *ewait =
+ container_of(wait, struct wait_exceptional_entry_queue, wait);
+
+ if (key->mapping != ewait->key.mapping ||
+ key->entry_start != ewait->key.entry_start)
+ return 0;
+ return autoremove_wake_function(wait, mode, sync, NULL);
+}
+
+/*
+ * @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_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 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, wake_all ? 0 : 1, &key);
+}
+
+/*
+ * Check whether the given slot is locked. Must be called with the i_pages
+ * 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->i_pages.xa_lock);
+ return entry & RADIX_DAX_ENTRY_LOCK;
+}
+
+/*
+ * Mark the given slot as locked. Must be called with the i_pages 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->i_pages.xa_lock);
+
+ entry |= RADIX_DAX_ENTRY_LOCK;
+ radix_tree_replace_slot(&mapping->i_pages, slot, (void *)entry);
+ return (void *)entry;
+}
+
+/*
+ * Mark the given slot as unlocked. Must be called with the i_pages 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->i_pages.xa_lock);
+
+ entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK;
+ radix_tree_replace_slot(&mapping->i_pages, slot, (void *)entry);
+ return (void *)entry;
+}
+
+static void put_unlocked_mapping_entry(struct address_space *mapping,
+ pgoff_t index, 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.
+ *
+ * Must be called with the i_pages lock held.
+ */
+static void *__get_unlocked_mapping_entry(struct address_space *mapping,
+ pgoff_t index, void ***slotp, bool (*wait_fn)(void))
+{
+ 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 (;;) {
+ bool revalidate;
+
+ entry = __radix_tree_lookup(&mapping->i_pages, index, NULL,
+ &slot);
+ if (!entry ||
+ WARN_ON_ONCE(!radix_tree_exceptional_entry(entry)) ||
+ !slot_locked(mapping, slot)) {
+ if (slotp)
+ *slotp = slot;
+ return entry;
+ }
+
+ wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
+ prepare_to_wait_exclusive(wq, &ewait.wait,
+ TASK_UNINTERRUPTIBLE);
+ xa_unlock_irq(&mapping->i_pages);
+ revalidate = wait_fn();
+ finish_wait(wq, &ewait.wait);
+ xa_lock_irq(&mapping->i_pages);
+ if (revalidate) {
+ put_unlocked_mapping_entry(mapping, index, entry);
+ return ERR_PTR(-EAGAIN);
+ }
+ }
+}
+
+static bool entry_wait(void)
+{
+ schedule();
+ /*
+ * Never return an ERR_PTR() from
+ * __get_unlocked_mapping_entry(), just keep looping.
+ */
+ return false;
+}
+
+static void *get_unlocked_mapping_entry(struct address_space *mapping,
+ pgoff_t index, void ***slotp)
+{
+ return __get_unlocked_mapping_entry(mapping, index, slotp, entry_wait);
+}
+
+static void unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
+{
+ void *entry, **slot;
+
+ xa_lock_irq(&mapping->i_pages);
+ entry = __radix_tree_lookup(&mapping->i_pages, index, NULL, &slot);
+ if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
+ !slot_locked(mapping, slot))) {
+ xa_unlock_irq(&mapping->i_pages);
+ return;
+ }
+ unlock_slot(mapping, slot);
+ xa_unlock_irq(&mapping->i_pages);
+ dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+}
+
+static void put_locked_mapping_entry(struct address_space *mapping,
+ pgoff_t index)
+{
+ unlock_mapping_entry(mapping, index);
+}
+
+/*
+ * Called when we are done with radix tree entry we looked up via
+ * get_unlocked_mapping_entry() and which we didn't lock in the end.
+ */
+static void put_unlocked_mapping_entry(struct address_space *mapping,
+ pgoff_t index, void *entry)
+{
+ if (!entry)
+ return;
+
+ /* We have to wake up next waiter for the radix tree entry lock */
+ dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+}
+
+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_radix_end_pfn(void *entry)
+{
+ return dax_radix_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_radix_pfn(entry); \
+ pfn < dax_radix_end_pfn(entry); pfn++)
+
+/*
+ * TODO: for reflink+dax we need a way to associate a single page with
+ * multiple address_space instances at different linear_page_index()
+ * offsets.
+ */
+static void dax_associate_entry(void *entry, struct address_space *mapping,
+ struct vm_area_struct *vma, unsigned long address)
+{
+ 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);
+
+ 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);
+ 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;
+}
+
+static bool entry_wait_revalidate(void)
+{
+ rcu_read_unlock();
+ schedule();
+ rcu_read_lock();
+
+ /*
+ * Tell __get_unlocked_mapping_entry() to take a break, we need
+ * to revalidate page->mapping after dropping locks
+ */
+ return true;
+}
+
+bool dax_lock_mapping_entry(struct page *page)
+{
+ pgoff_t index;
+ struct inode *inode;
+ bool did_lock = false;
+ void *entry = NULL, **slot;
+ struct address_space *mapping;
+
+ rcu_read_lock();
+ for (;;) {
+ mapping = READ_ONCE(page->mapping);
+
+ 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.
+ */
+ inode = mapping->host;
+ if (S_ISCHR(inode->i_mode)) {
+ did_lock = true;
+ break;
+ }
+
+ xa_lock_irq(&mapping->i_pages);
+ if (mapping != page->mapping) {
+ xa_unlock_irq(&mapping->i_pages);
+ continue;
+ }
+ index = page->index;
+
+ entry = __get_unlocked_mapping_entry(mapping, index, &slot,
+ entry_wait_revalidate);
+ if (!entry) {
+ xa_unlock_irq(&mapping->i_pages);
+ break;
+ } else if (IS_ERR(entry)) {
+ xa_unlock_irq(&mapping->i_pages);
+ WARN_ON_ONCE(PTR_ERR(entry) != -EAGAIN);
+ continue;
+ }
+ lock_slot(mapping, slot);
+ did_lock = true;
+ xa_unlock_irq(&mapping->i_pages);
+ break;
+ }
+ rcu_read_unlock();
+
+ return did_lock;
+}
+
+void dax_unlock_mapping_entry(struct page *page)
+{
+ struct address_space *mapping = page->mapping;
+ struct inode *inode = mapping->host;
+
+ if (S_ISCHR(inode->i_mode))
+ return;
+
+ unlock_mapping_entry(mapping, page->index);
+}
+
+/*
+ * Find radix tree entry at given index. If it points to an exceptional entry,
+ * return it with the radix tree entry locked. If the radix tree doesn't
+ * contain given index, create an empty exceptional entry for the index and
+ * return with it locked.
+ *
+ * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return an error. This error will
+ * happen if there are any 4k entries within the 2MiB range that we are
+ * requesting.
+ *
+ * We always favor 4k entries over 2MiB entries. There isn't a flow where we
+ * evict 4k entries in order to 'upgrade' them to a 2MiB entry. A 2MiB
+ * insertion will fail if it finds any 4k entries already in the tree, and a
+ * 4k insertion will cause an existing 2MiB entry to be unmapped and
+ * downgraded to 4k entries. This happens for both 2MiB huge zero pages as
+ * well as 2MiB empty entries.
+ *
+ * The exception to this downgrade path is for 2MiB DAX PMD entries that have
+ * real storage backing them. We will leave these real 2MiB DAX entries in
+ * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
+ *
+ * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
+ * persistent memory the benefit is doubtful. We can add that later if we can
+ * show it helps.
+ */
+static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+ unsigned long size_flag)
+{
+ bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
+ void *entry, **slot;
+
+restart:
+ xa_lock_irq(&mapping->i_pages);
+ entry = get_unlocked_mapping_entry(mapping, index, &slot);
+
+ if (WARN_ON_ONCE(entry && !radix_tree_exceptional_entry(entry))) {
+ entry = ERR_PTR(-EIO);
+ goto out_unlock;
+ }
+
+ if (entry) {
+ if (size_flag & RADIX_DAX_PMD) {
+ if (dax_is_pte_entry(entry)) {
+ put_unlocked_mapping_entry(mapping, index,
+ entry);
+ entry = ERR_PTR(-EEXIST);
+ goto out_unlock;
+ }
+ } else { /* trying to grab a PTE entry */
+ if (dax_is_pmd_entry(entry) &&
+ (dax_is_zero_entry(entry) ||
+ dax_is_empty_entry(entry))) {
+ pmd_downgrade = true;
+ }
+ }
+ }
+
+ /* No entry for given index? Make sure radix tree is big enough. */
+ if (!entry || pmd_downgrade) {
+ int err;
+
+ if (pmd_downgrade) {
+ /*
+ * Make sure 'entry' remains valid while we drop
+ * the i_pages lock.
+ */
+ entry = lock_slot(mapping, slot);
+ }
+
+ xa_unlock_irq(&mapping->i_pages);
+ /*
+ * 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_pages(mapping, index & ~PG_PMD_COLOUR,
+ PG_PMD_NR, false);
+
+ err = radix_tree_preload(
+ mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
+ if (err) {
+ if (pmd_downgrade)
+ put_locked_mapping_entry(mapping, index);
+ return ERR_PTR(err);
+ }
+ xa_lock_irq(&mapping->i_pages);
+
+ if (!entry) {
+ /*
+ * We needed to drop the i_pages lock while calling
+ * radix_tree_preload() and we didn't have an entry to
+ * lock. See if another thread inserted an entry at
+ * our index during this time.
+ */
+ entry = __radix_tree_lookup(&mapping->i_pages, index,
+ NULL, &slot);
+ if (entry) {
+ radix_tree_preload_end();
+ xa_unlock_irq(&mapping->i_pages);
+ goto restart;
+ }
+ }
+
+ if (pmd_downgrade) {
+ dax_disassociate_entry(entry, mapping, false);
+ radix_tree_delete(&mapping->i_pages, 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->i_pages, index,
+ dax_radix_order(entry), entry);
+ radix_tree_preload_end();
+ if (err) {
+ xa_unlock_irq(&mapping->i_pages);
+ /*
+ * Our insertion of a DAX entry failed, most likely
+ * because we were inserting a PMD entry and it
+ * collided with a PTE sized entry at a different
+ * index in the PMD range. We haven't inserted
+ * anything into the radix tree and have no waiters to
+ * wake.
+ */
+ return ERR_PTR(err);
+ }
+ /* Good, we have inserted empty locked entry into the tree. */
+ mapping->nrexceptional++;
+ xa_unlock_irq(&mapping->i_pages);
+ return entry;
+ }
+ entry = lock_slot(mapping, slot);
+ out_unlock:
+ xa_unlock_irq(&mapping->i_pages);
+ return entry;
+}
+
+/**
+ * dax_layout_busy_page - find first pinned page in @mapping
+ * @mapping: address space to scan for a page with ref count > 1
+ *
+ * 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(struct address_space *mapping)
+{
+ pgoff_t indices[PAGEVEC_SIZE];
+ struct page *page = NULL;
+ struct pagevec pvec;
+ pgoff_t index, end;
+ unsigned i;
+
+ /*
+ * 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;
+
+ pagevec_init(&pvec);
+ index = 0;
+ end = -1;
+
+ /*
+ * If we race get_user_pages_fast() here either we'll see the
+ * elevated page count in the pagevec_lookup 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_range() 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_range(mapping, 0, 0, 1);
+
+ while (index < end && pagevec_lookup_entries(&pvec, mapping, index,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE),
+ indices)) {
+ pgoff_t nr_pages = 1;
+
+ for (i = 0; i < pagevec_count(&pvec); i++) {
+ struct page *pvec_ent = pvec.pages[i];
+ void *entry;
+
+ index = indices[i];
+ if (index >= end)
+ break;
+
+ if (WARN_ON_ONCE(
+ !radix_tree_exceptional_entry(pvec_ent)))
+ continue;
+
+ xa_lock_irq(&mapping->i_pages);
+ entry = get_unlocked_mapping_entry(mapping, index, NULL);
+ if (entry) {
+ page = dax_busy_page(entry);
+ /*
+ * Account for multi-order entries at
+ * the end of the pagevec.
+ */
+ if (i + 1 >= pagevec_count(&pvec))
+ nr_pages = 1UL << dax_radix_order(entry);
+ }
+ put_unlocked_mapping_entry(mapping, index, entry);
+ xa_unlock_irq(&mapping->i_pages);
+ if (page)
+ break;
+ }
+
+ /*
+ * We don't expect normal struct page entries to exist in our
+ * tree, but we keep these pagevec calls so that this code is
+ * consistent with the common pattern for handling pagevecs
+ * throughout the kernel.
+ */
+ pagevec_remove_exceptionals(&pvec);
+ pagevec_release(&pvec);
+ index += nr_pages;
+
+ if (page)
+ break;
+ }
+ return page;
+}
+EXPORT_SYMBOL_GPL(dax_layout_busy_page);
+
+static int __dax_invalidate_mapping_entry(struct address_space *mapping,
+ pgoff_t index, bool trunc)
+{
+ int ret = 0;
+ void *entry;
+ struct radix_tree_root *pages = &mapping->i_pages;
+
+ xa_lock_irq(pages);
+ entry = get_unlocked_mapping_entry(mapping, index, NULL);
+ if (!entry || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry)))
+ goto out;
+ if (!trunc &&
+ (radix_tree_tag_get(pages, index, PAGECACHE_TAG_DIRTY) ||
+ radix_tree_tag_get(pages, index, PAGECACHE_TAG_TOWRITE)))
+ goto out;
+ dax_disassociate_entry(entry, mapping, trunc);
+ radix_tree_delete(pages, index);
+ mapping->nrexceptional--;
+ ret = 1;
+out:
+ put_unlocked_mapping_entry(mapping, index, entry);
+ xa_unlock_irq(pages);
+ return ret;
+}
+/*
+ * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
+ * entry to get unlocked before deleting it.
+ */
+int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
+{
+ int ret = __dax_invalidate_mapping_entry(mapping, index, true);
+
+ /*
+ * This gets called from truncate / punch_hole path. As such, the caller
+ * must hold locks protecting against concurrent modifications of the
+ * radix tree (usually fs-private i_mmap_sem for writing). Since the
+ * caller has seen exceptional entry for this index, we better find it
+ * at that index as well...
+ */
+ WARN_ON_ONCE(!ret);
+ return ret;
+}
+
+/*
+ * Invalidate exceptional DAX entry if it is clean.
+ */
+int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
+ pgoff_t index)
+{
+ return __dax_invalidate_mapping_entry(mapping, index, false);
+}
+
+static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev,
+ sector_t sector, size_t size, struct page *to,
+ unsigned long vaddr)
+{
+ void *vto, *kaddr;
+ pgoff_t pgoff;
+ long rc;
+ int id;
+
+ rc = bdev_dax_pgoff(bdev, sector, size, &pgoff);
+ if (rc)
+ return rc;
+
+ id = dax_read_lock();
+ rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, NULL);
+ if (rc < 0) {
+ dax_read_unlock(id);
+ return rc;
+ }
+ vto = kmap_atomic(to);
+ copy_user_page(vto, (void __force *)kaddr, vaddr, to);
+ kunmap_atomic(vto);
+ dax_read_unlock(id);
+ return 0;
+}
+
+/*
+ * By this point grab_mapping_entry() has ensured that we have a locked entry
+ * of the appropriate size so we don't have to worry about downgrading PMDs to
+ * PTEs. If we happen to be trying to insert a PTE and there is a PMD
+ * already in the tree, we will skip the insertion and just dirty the PMD as
+ * appropriate.
+ */
+static void *dax_insert_mapping_entry(struct address_space *mapping,
+ struct vm_fault *vmf,
+ void *entry, pfn_t pfn_t,
+ unsigned long flags, bool dirty)
+{
+ struct radix_tree_root *pages = &mapping->i_pages;
+ unsigned long pfn = pfn_t_to_pfn(pfn_t);
+ pgoff_t index = vmf->pgoff;
+ void *new_entry;
+
+ if (dirty)
+ __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
+
+ if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_ZERO_PAGE)) {
+ /* we are replacing a zero page with block mapping */
+ if (dax_is_pmd_entry(entry))
+ unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
+ PG_PMD_NR, false);
+ else /* pte entry */
+ unmap_mapping_pages(mapping, vmf->pgoff, 1, false);
+ }
+
+ xa_lock_irq(pages);
+ new_entry = dax_radix_locked_entry(pfn, flags);
+ if (dax_entry_size(entry) != dax_entry_size(new_entry)) {
+ dax_disassociate_entry(entry, mapping, false);
+ dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address);
+ }
+
+ 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(pages, index, &node, &slot);
+ WARN_ON_ONCE(ret != entry);
+ __radix_tree_replace(pages, node, slot,
+ new_entry, NULL);
+ entry = new_entry;
+ }
+
+ if (dirty)
+ radix_tree_tag_set(pages, index, PAGECACHE_TAG_DIRTY);
+
+ xa_unlock_irq(pages);
+ return entry;
+}
+
+static inline unsigned long
+pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma)
+{
+ unsigned long address;
+
+ address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+ VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
+ return address;
+}
+
+/* Walk all mappings of a given index of a file and writeprotect them */
+static void dax_mapping_entry_mkclean(struct address_space *mapping,
+ pgoff_t index, unsigned long pfn)
+{
+ struct vm_area_struct *vma;
+ pte_t pte, *ptep = NULL;
+ pmd_t *pmdp = NULL;
+ spinlock_t *ptl;
+
+ i_mmap_lock_read(mapping);
+ vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) {
+ unsigned long address, start, end;
+
+ cond_resched();
+
+ if (!(vma->vm_flags & VM_SHARED))
+ continue;
+
+ address = pgoff_address(index, vma);
+
+ /*
+ * Note because we provide start/end to follow_pte_pmd it will
+ * call mmu_notifier_invalidate_range_start() on our behalf
+ * before taking any lock.
+ */
+ if (follow_pte_pmd(vma->vm_mm, address, &start, &end, &ptep, &pmdp, &ptl))
+ continue;
+
+ /*
+ * No need to call mmu_notifier_invalidate_range() as we are
+ * downgrading page table protection not changing it to point
+ * to a new page.
+ *
+ * See Documentation/vm/mmu_notifier.rst
+ */
+ if (pmdp) {
+#ifdef CONFIG_FS_DAX_PMD
+ pmd_t pmd;
+
+ if (pfn != pmd_pfn(*pmdp))
+ goto unlock_pmd;
+ if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp))
+ goto unlock_pmd;
+
+ flush_cache_page(vma, address, pfn);
+ pmd = pmdp_huge_clear_flush(vma, address, pmdp);
+ pmd = pmd_wrprotect(pmd);
+ pmd = pmd_mkclean(pmd);
+ set_pmd_at(vma->vm_mm, address, pmdp, pmd);
+unlock_pmd:
+#endif
+ spin_unlock(ptl);
+ } else {
+ if (pfn != pte_pfn(*ptep))
+ goto unlock_pte;
+ if (!pte_dirty(*ptep) && !pte_write(*ptep))
+ goto unlock_pte;
+
+ flush_cache_page(vma, address, pfn);
+ pte = ptep_clear_flush(vma, address, ptep);
+ pte = pte_wrprotect(pte);
+ pte = pte_mkclean(pte);
+ set_pte_at(vma->vm_mm, address, ptep, pte);
+unlock_pte:
+ pte_unmap_unlock(ptep, ptl);
+ }
+
+ mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
+ }
+ i_mmap_unlock_read(mapping);
+}
+
+static int dax_writeback_one(struct dax_device *dax_dev,
+ struct address_space *mapping, pgoff_t index, void *entry)
+{
+ struct radix_tree_root *pages = &mapping->i_pages;
+ void *entry2, **slot;
+ unsigned long pfn;
+ long ret = 0;
+ size_t size;
+
+ /*
+ * A page got tagged dirty in DAX mapping? Something is seriously
+ * wrong.
+ */
+ if (WARN_ON(!radix_tree_exceptional_entry(entry)))
+ return -EIO;
+
+ xa_lock_irq(pages);
+ entry2 = get_unlocked_mapping_entry(mapping, index, &slot);
+ /* Entry got punched out / reallocated? */
+ if (!entry2 || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry2)))
+ goto put_unlocked;
+ /*
+ * Entry got reallocated elsewhere? No need to writeback. We have to
+ * compare pfns as we must not bail out due to difference in lockbit
+ * or entry type.
+ */
+ if (dax_radix_pfn(entry2) != dax_radix_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 written back this entry */
+ if (!radix_tree_tag_get(pages, 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 the i_pages lock and once they do that
+ * they will see the entry locked and wait for it to unlock.
+ */
+ radix_tree_tag_clear(pages, index, PAGECACHE_TAG_TOWRITE);
+ xa_unlock_irq(pages);
+
+ /*
+ * 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 pfn we pull from 'entry'.
+ * This allows us to flush for PMD_SIZE and not have to worry about
+ * partial PMD writebacks.
+ */
+ pfn = dax_radix_pfn(entry);
+ size = PAGE_SIZE << dax_radix_order(entry);
+
+ dax_mapping_entry_mkclean(mapping, index, pfn);
+ dax_flush(dax_dev, page_address(pfn_to_page(pfn)), 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.
+ */
+ xa_lock_irq(pages);
+ radix_tree_tag_clear(pages, index, PAGECACHE_TAG_DIRTY);
+ xa_unlock_irq(pages);
+ trace_dax_writeback_one(mapping->host, index, size >> PAGE_SHIFT);
+ put_locked_mapping_entry(mapping, index);
+ return ret;
+
+ put_unlocked:
+ put_unlocked_mapping_entry(mapping, index, entry2);
+ xa_unlock_irq(pages);
+ return ret;
+}
+
+/*
+ * Flush the mapping to the persistent domain within the byte range of [start,
+ * end]. This is required by data integrity operations to ensure file data is
+ * on persistent storage prior to completion of the operation.
+ */
+int dax_writeback_mapping_range(struct address_space *mapping,
+ struct block_device *bdev, struct writeback_control *wbc)
+{
+ struct inode *inode = mapping->host;
+ pgoff_t start_index, end_index;
+ pgoff_t indices[PAGEVEC_SIZE];
+ struct dax_device *dax_dev;
+ struct pagevec pvec;
+ bool done = false;
+ int i, ret = 0;
+
+ if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
+ return -EIO;
+
+ if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
+ return 0;
+
+ dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
+ if (!dax_dev)
+ return -EIO;
+
+ start_index = wbc->range_start >> PAGE_SHIFT;
+ end_index = wbc->range_end >> PAGE_SHIFT;
+
+ trace_dax_writeback_range(inode, start_index, end_index);
+
+ tag_pages_for_writeback(mapping, start_index, end_index);
+
+ pagevec_init(&pvec);
+ while (!done) {
+ pvec.nr = find_get_entries_tag(mapping, start_index,
+ PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
+ pvec.pages, indices);
+
+ if (pvec.nr == 0)
+ break;
+
+ for (i = 0; i < pvec.nr; i++) {
+ if (indices[i] > end_index) {
+ done = true;
+ break;
+ }
+
+ ret = dax_writeback_one(dax_dev, mapping, indices[i],
+ pvec.pages[i]);
+ if (ret < 0) {
+ mapping_set_error(mapping, ret);
+ goto out;
+ }
+ }
+ start_index = indices[pvec.nr - 1] + 1;
+ }
+out:
+ put_dax(dax_dev);
+ trace_dax_writeback_range_done(inode, start_index, end_index);
+ return (ret < 0 ? ret : 0);
+}
+EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
+
+static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
+{
+ return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
+}
+
+static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
+ pfn_t *pfnp)
+{
+ const sector_t sector = dax_iomap_sector(iomap, pos);
+ pgoff_t pgoff;
+ int id, rc;
+ long length;
+
+ rc = bdev_dax_pgoff(iomap->bdev, sector, size, &pgoff);
+ if (rc)
+ return rc;
+ id = dax_read_lock();
+ length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
+ NULL, pfnp);
+ if (length < 0) {
+ rc = length;
+ goto out;
+ }
+ rc = -EINVAL;
+ if (PFN_PHYS(length) < size)
+ goto out;
+ if (pfn_t_to_pfn(*pfnp) & (PHYS_PFN(size)-1))
+ goto out;
+ /* For larger pages we need devmap */
+ if (length > 1 && !pfn_t_devmap(*pfnp))
+ goto out;
+ rc = 0;
+out:
+ dax_read_unlock(id);
+ return rc;
+}
+
+/*
+ * The user has performed a load from a hole in the file. Allocating a new
+ * page in the file would cause excessive storage usage for workloads with
+ * sparse files. Instead we insert a read-only mapping of the 4k zero page.
+ * If this page is ever written to we will re-fault and change the mapping to
+ * point to real DAX storage instead.
+ */
+static vm_fault_t dax_load_hole(struct address_space *mapping, void *entry,
+ struct vm_fault *vmf)
+{
+ struct inode *inode = mapping->host;
+ unsigned long vaddr = vmf->address;
+ pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr));
+ vm_fault_t ret;
+
+ dax_insert_mapping_entry(mapping, vmf, entry, pfn, RADIX_DAX_ZERO_PAGE,
+ false);
+ ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
+ trace_dax_load_hole(inode, vmf, ret);
+ return ret;
+}
+
+static bool dax_range_is_aligned(struct block_device *bdev,
+ unsigned int offset, unsigned int length)
+{
+ unsigned short sector_size = bdev_logical_block_size(bdev);
+
+ if (!IS_ALIGNED(offset, sector_size))
+ return false;
+ if (!IS_ALIGNED(length, sector_size))
+ return false;
+
+ return true;
+}
+
+int __dax_zero_page_range(struct block_device *bdev,
+ struct dax_device *dax_dev, sector_t sector,
+ unsigned int offset, unsigned int size)
+{
+ if (dax_range_is_aligned(bdev, offset, size)) {
+ sector_t start_sector = sector + (offset >> 9);
+
+ return blkdev_issue_zeroout(bdev, start_sector,
+ size >> 9, GFP_NOFS, 0);
+ } else {
+ pgoff_t pgoff;
+ long rc, id;
+ void *kaddr;
+
+ rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
+ if (rc)
+ return rc;
+
+ id = dax_read_lock();
+ rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr, NULL);
+ if (rc < 0) {
+ dax_read_unlock(id);
+ return rc;
+ }
+ memset(kaddr + offset, 0, size);
+ dax_flush(dax_dev, kaddr + offset, size);
+ dax_read_unlock(id);
+ }
+ return 0;
+}
+EXPORT_SYMBOL_GPL(__dax_zero_page_range);
+
+static loff_t
+dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
+ struct iomap *iomap)
+{
+ struct block_device *bdev = iomap->bdev;
+ struct dax_device *dax_dev = iomap->dax_dev;
+ struct iov_iter *iter = data;
+ loff_t end = pos + length, done = 0;
+ ssize_t ret = 0;
+ size_t xfer;
+ int id;
+
+ if (iov_iter_rw(iter) == READ) {
+ end = min(end, i_size_read(inode));
+ if (pos >= end)
+ return 0;
+
+ if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
+ return iov_iter_zero(min(length, end - pos), iter);
+ }
+
+ if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
+ return -EIO;
+
+ /*
+ * Write can allocate block for an area which has a hole page mapped
+ * into page tables. We have to tear down these mappings so that data
+ * written by write(2) is visible in mmap.
+ */
+ if (iomap->flags & IOMAP_F_NEW) {
+ invalidate_inode_pages2_range(inode->i_mapping,
+ pos >> PAGE_SHIFT,
+ (end - 1) >> PAGE_SHIFT);
+ }
+
+ id = dax_read_lock();
+ while (pos < end) {
+ unsigned offset = pos & (PAGE_SIZE - 1);
+ const size_t size = ALIGN(length + offset, PAGE_SIZE);
+ const sector_t sector = dax_iomap_sector(iomap, pos);
+ ssize_t map_len;
+ pgoff_t pgoff;
+ void *kaddr;
+
+ if (fatal_signal_pending(current)) {
+ ret = -EINTR;
+ break;
+ }
+
+ ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
+ if (ret)
+ break;
+
+ map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size),
+ &kaddr, NULL);
+ if (map_len < 0) {
+ ret = map_len;
+ break;
+ }
+
+ map_len = PFN_PHYS(map_len);
+ kaddr += offset;
+ map_len -= offset;
+ if (map_len > end - pos)
+ map_len = end - pos;
+
+ /*
+ * The userspace address for the memory copy has already been
+ * validated via access_ok() in either vfs_read() or
+ * vfs_write(), depending on which operation we are doing.
+ */
+ if (iov_iter_rw(iter) == WRITE)
+ 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 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 vm_fault_t dax_fault_return(int error)
+{
+ if (error == 0)
+ return VM_FAULT_NOPAGE;
+ if (error == -ENOMEM)
+ return VM_FAULT_OOM;
+ return VM_FAULT_SIGBUS;
+}
+
+/*
+ * MAP_SYNC on a dax mapping guarantees dirty metadata is
+ * flushed on write-faults (non-cow), but not read-faults.
+ */
+static bool dax_fault_is_synchronous(unsigned long flags,
+ struct vm_area_struct *vma, struct iomap *iomap)
+{
+ return (flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC)
+ && (iomap->flags & IOMAP_F_DIRTY);
+}
+
+static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
+ int *iomap_errp, const struct iomap_ops *ops)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct address_space *mapping = vma->vm_file->f_mapping;
+ struct inode *inode = mapping->host;
+ unsigned long vaddr = vmf->address;
+ loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
+ struct iomap iomap = { 0 };
+ unsigned flags = IOMAP_FAULT;
+ int error, major = 0;
+ bool write = vmf->flags & FAULT_FLAG_WRITE;
+ bool sync;
+ vm_fault_t ret = 0;
+ void *entry;
+ pfn_t pfn;
+
+ trace_dax_pte_fault(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 (pos >= i_size_read(inode)) {
+ ret = VM_FAULT_SIGBUS;
+ goto out;
+ }
+
+ if (write && !vmf->cow_page)
+ flags |= IOMAP_WRITE;
+
+ entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
+ if (IS_ERR(entry)) {
+ ret = dax_fault_return(PTR_ERR(entry));
+ goto out;
+ }
+
+ /*
+ * It is possible, particularly with mixed reads & writes to private
+ * mappings, that we have raced with a PMD fault that overlaps with
+ * the PTE we need to set up. If so just return and the fault will be
+ * retried.
+ */
+ if (pmd_trans_huge(*vmf->pmd) || pmd_devmap(*vmf->pmd)) {
+ ret = VM_FAULT_NOPAGE;
+ goto unlock_entry;
+ }
+
+ /*
+ * Note that we don't bother to use iomap_apply here: DAX required
+ * the file system block size to be equal the page size, which means
+ * that we never have to deal with more than a single extent here.
+ */
+ error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
+ if (iomap_errp)
+ *iomap_errp = error;
+ if (error) {
+ ret = dax_fault_return(error);
+ goto unlock_entry;
+ }
+ if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
+ error = -EIO; /* fs corruption? */
+ goto error_finish_iomap;
+ }
+
+ if (vmf->cow_page) {
+ sector_t sector = dax_iomap_sector(&iomap, pos);
+
+ switch (iomap.type) {
+ case IOMAP_HOLE:
+ case IOMAP_UNWRITTEN:
+ clear_user_highpage(vmf->cow_page, vaddr);
+ break;
+ case IOMAP_MAPPED:
+ error = copy_user_dax(iomap.bdev, iomap.dax_dev,
+ sector, PAGE_SIZE, vmf->cow_page, vaddr);
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ error = -EIO;
+ break;
+ }
+
+ if (error)
+ goto error_finish_iomap;
+
+ __SetPageUptodate(vmf->cow_page);
+ ret = finish_fault(vmf);
+ if (!ret)
+ ret = VM_FAULT_DONE_COW;
+ goto finish_iomap;
+ }
+
+ sync = dax_fault_is_synchronous(flags, vma, &iomap);
+
+ switch (iomap.type) {
+ case IOMAP_MAPPED:
+ if (iomap.flags & IOMAP_F_NEW) {
+ count_vm_event(PGMAJFAULT);
+ count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
+ major = VM_FAULT_MAJOR;
+ }
+ error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
+ if (error < 0)
+ goto error_finish_iomap;
+
+ entry = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
+ 0, write && !sync);
+
+ /*
+ * If we are doing synchronous page fault and inode needs fsync,
+ * we can insert PTE into page tables only after that happens.
+ * Skip insertion for now and return the pfn so that caller can
+ * insert it after fsync is done.
+ */
+ if (sync) {
+ if (WARN_ON_ONCE(!pfnp)) {
+ error = -EIO;
+ goto error_finish_iomap;
+ }
+ *pfnp = pfn;
+ ret = VM_FAULT_NEEDDSYNC | major;
+ goto finish_iomap;
+ }
+ trace_dax_insert_mapping(inode, vmf, entry);
+ if (write)
+ ret = vmf_insert_mixed_mkwrite(vma, vaddr, pfn);
+ else
+ ret = vmf_insert_mixed(vma, vaddr, pfn);
+
+ goto finish_iomap;
+ case IOMAP_UNWRITTEN:
+ case IOMAP_HOLE:
+ if (!write) {
+ ret = dax_load_hole(mapping, entry, vmf);
+ goto finish_iomap;
+ }
+ /*FALLTHRU*/
+ default:
+ WARN_ON_ONCE(1);
+ error = -EIO;
+ break;
+ }
+
+ error_finish_iomap:
+ ret = dax_fault_return(error);
+ finish_iomap:
+ if (ops->iomap_end) {
+ int copied = PAGE_SIZE;
+
+ if (ret & VM_FAULT_ERROR)
+ copied = 0;
+ /*
+ * The fault is done by now and there's no way back (other
+ * thread may be already happily using PTE we have installed).
+ * Just ignore error from ->iomap_end since we cannot do much
+ * with it.
+ */
+ ops->iomap_end(inode, pos, PAGE_SIZE, copied, flags, &iomap);
+ }
+ unlock_entry:
+ put_locked_mapping_entry(mapping, vmf->pgoff);
+ out:
+ trace_dax_pte_fault_done(inode, vmf, ret);
+ return ret | major;
+}
+
+#ifdef CONFIG_FS_DAX_PMD
+static vm_fault_t dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
+ void *entry)
+{
+ struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+ unsigned long pmd_addr = vmf->address & PMD_MASK;
+ struct inode *inode = mapping->host;
+ struct page *zero_page;
+ void *ret = NULL;
+ spinlock_t *ptl;
+ pmd_t pmd_entry;
+ 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);
+ ret = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
+ RADIX_DAX_PMD | RADIX_DAX_ZERO_PAGE, false);
+
+ 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 vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
+ const struct iomap_ops *ops)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct address_space *mapping = vma->vm_file->f_mapping;
+ unsigned long pmd_addr = vmf->address & PMD_MASK;
+ bool write = vmf->flags & FAULT_FLAG_WRITE;
+ bool sync;
+ unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
+ struct inode *inode = mapping->host;
+ vm_fault_t result = VM_FAULT_FALLBACK;
+ struct iomap iomap = { 0 };
+ pgoff_t max_pgoff, pgoff;
+ void *entry;
+ loff_t pos;
+ int error;
+ pfn_t pfn;
+
+ /*
+ * Check whether offset isn't beyond end of file now. Caller is
+ * supposed to hold locks serializing us with truncate / punch hole so
+ * this is a reliable test.
+ */
+ pgoff = linear_page_index(vma, pmd_addr);
+ max_pgoff = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+
+ trace_dax_pmd_fault(inode, vmf, max_pgoff, 0);
+
+ /*
+ * Make sure that the faulting address's PMD offset (color) matches
+ * the PMD offset from the start of the file. This is necessary so
+ * that a PMD range in the page table overlaps exactly with a PMD
+ * range in the radix tree.
+ */
+ if ((vmf->pgoff & PG_PMD_COLOUR) !=
+ ((vmf->address >> PAGE_SHIFT) & PG_PMD_COLOUR))
+ goto fallback;
+
+ /* Fall back to PTEs if we're going to COW */
+ if (write && !(vma->vm_flags & VM_SHARED))
+ goto fallback;
+
+ /* If the PMD would extend outside the VMA */
+ if (pmd_addr < vma->vm_start)
+ goto fallback;
+ if ((pmd_addr + PMD_SIZE) > vma->vm_end)
+ goto fallback;
+
+ if (pgoff >= max_pgoff) {
+ result = VM_FAULT_SIGBUS;
+ goto out;
+ }
+
+ /* If the PMD would extend beyond the file size */
+ if ((pgoff | PG_PMD_COLOUR) >= max_pgoff)
+ goto fallback;
+
+ /*
+ * grab_mapping_entry() will make sure we get a 2MiB empty entry, a
+ * 2MiB zero page entry or a DAX PMD. If it can't (because a 4k page
+ * is already in the tree, for instance), it will return -EEXIST and
+ * we just fall back to 4k entries.
+ */
+ entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
+ if (IS_ERR(entry))
+ goto fallback;
+
+ /*
+ * It is possible, particularly with mixed reads & writes to private
+ * mappings, that we have raced with a PTE fault that overlaps with
+ * the PMD we need to set up. If so just return and the fault will be
+ * retried.
+ */
+ if (!pmd_none(*vmf->pmd) && !pmd_trans_huge(*vmf->pmd) &&
+ !pmd_devmap(*vmf->pmd)) {
+ result = 0;
+ goto unlock_entry;
+ }
+
+ /*
+ * Note that we don't use iomap_apply here. We aren't doing I/O, only
+ * setting up a mapping, so really we're using iomap_begin() as a way
+ * to look up our filesystem block.
+ */
+ pos = (loff_t)pgoff << PAGE_SHIFT;
+ error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+ if (error)
+ goto unlock_entry;
+
+ if (iomap.offset + iomap.length < pos + PMD_SIZE)
+ goto finish_iomap;
+
+ sync = dax_fault_is_synchronous(iomap_flags, vma, &iomap);
+
+ switch (iomap.type) {
+ case IOMAP_MAPPED:
+ error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
+ if (error < 0)
+ goto finish_iomap;
+
+ entry = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
+ RADIX_DAX_PMD, write && !sync);
+
+ /*
+ * If we are doing synchronous page fault and inode needs fsync,
+ * we can insert PMD into page tables only after that happens.
+ * Skip insertion for now and return the pfn so that caller can
+ * insert it after fsync is done.
+ */
+ if (sync) {
+ if (WARN_ON_ONCE(!pfnp))
+ goto finish_iomap;
+ *pfnp = pfn;
+ result = VM_FAULT_NEEDDSYNC;
+ goto finish_iomap;
+ }
+
+ trace_dax_pmd_insert_mapping(inode, vmf, PMD_SIZE, pfn, entry);
+ result = vmf_insert_pfn_pmd(vma, vmf->address, vmf->pmd, pfn,
+ write);
+ break;
+ case IOMAP_UNWRITTEN:
+ case IOMAP_HOLE:
+ if (WARN_ON_ONCE(write))
+ break;
+ result = dax_pmd_load_hole(vmf, &iomap, entry);
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ break;
+ }
+
+ finish_iomap:
+ if (ops->iomap_end) {
+ int copied = PMD_SIZE;
+
+ if (result == VM_FAULT_FALLBACK)
+ copied = 0;
+ /*
+ * The fault is done by now and there's no way back (other
+ * thread may be already happily using PMD we have installed).
+ * Just ignore error from ->iomap_end since we cannot do much
+ * with it.
+ */
+ ops->iomap_end(inode, pos, PMD_SIZE, copied, iomap_flags,
+ &iomap);
+ }
+ unlock_entry:
+ put_locked_mapping_entry(mapping, pgoff);
+ fallback:
+ if (result == VM_FAULT_FALLBACK) {
+ split_huge_pmd(vma, vmf->pmd, vmf->address);
+ count_vm_event(THP_FAULT_FALLBACK);
+ }
+out:
+ trace_dax_pmd_fault_done(inode, vmf, max_pgoff, result);
+ return result;
+}
+#else
+static 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
+ * @pe_size: Size 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, enum page_entry_size pe_size,
+ pfn_t *pfnp, int *iomap_errp, const struct iomap_ops *ops)
+{
+ switch (pe_size) {
+ case PE_SIZE_PTE:
+ return dax_iomap_pte_fault(vmf, pfnp, iomap_errp, ops);
+ case PE_SIZE_PMD:
+ return dax_iomap_pmd_fault(vmf, pfnp, ops);
+ default:
+ return VM_FAULT_FALLBACK;
+ }
+}
+EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+/**
+ * dax_insert_pfn_mkwrite - insert PTE or PMD entry into page tables
+ * @vmf: The description of the fault
+ * @pe_size: Size of entry to be inserted
+ * @pfn: PFN to insert
+ *
+ * This function inserts writeable PTE or PMD entry into page tables for mmaped
+ * DAX file. It takes care of marking corresponding radix tree entry as dirty
+ * as well.
+ */
+static vm_fault_t dax_insert_pfn_mkwrite(struct vm_fault *vmf,
+ enum page_entry_size pe_size,
+ pfn_t pfn)
+{
+ struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+ void *entry, **slot;
+ pgoff_t index = vmf->pgoff;
+ vm_fault_t ret;
+
+ xa_lock_irq(&mapping->i_pages);
+ entry = get_unlocked_mapping_entry(mapping, index, &slot);
+ /* Did we race with someone splitting entry or so? */
+ if (!entry ||
+ (pe_size == PE_SIZE_PTE && !dax_is_pte_entry(entry)) ||
+ (pe_size == PE_SIZE_PMD && !dax_is_pmd_entry(entry))) {
+ put_unlocked_mapping_entry(mapping, index, entry);
+ xa_unlock_irq(&mapping->i_pages);
+ trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
+ VM_FAULT_NOPAGE);
+ return VM_FAULT_NOPAGE;
+ }
+ radix_tree_tag_set(&mapping->i_pages, index, PAGECACHE_TAG_DIRTY);
+ entry = lock_slot(mapping, slot);
+ xa_unlock_irq(&mapping->i_pages);
+ switch (pe_size) {
+ case PE_SIZE_PTE:
+ ret = vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
+ break;
+#ifdef CONFIG_FS_DAX_PMD
+ case PE_SIZE_PMD:
+ ret = vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd,
+ pfn, true);
+ break;
+#endif
+ default:
+ ret = VM_FAULT_FALLBACK;
+ }
+ put_locked_mapping_entry(mapping, index);
+ 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
+ * @pe_size: Size of entry to be inserted
+ * @pfn: PFN to insert
+ *
+ * This function ensures that the file range touched by the page fault is
+ * stored persistently on the media and handles inserting of appropriate page
+ * table entry.
+ */
+vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf,
+ enum page_entry_size pe_size, pfn_t pfn)
+{
+ int err;
+ loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT;
+ size_t len = 0;
+
+ if (pe_size == PE_SIZE_PTE)
+ len = PAGE_SIZE;
+ else if (pe_size == PE_SIZE_PMD)
+ len = PMD_SIZE;
+ else
+ WARN_ON_ONCE(1);
+ err = vfs_fsync_range(vmf->vma->vm_file, start, start + len - 1, 1);
+ if (err)
+ return VM_FAULT_SIGBUS;
+ return dax_insert_pfn_mkwrite(vmf, pe_size, pfn);
+}
+EXPORT_SYMBOL_GPL(dax_finish_sync_fault);