dax.c 43.7 KB
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/*
 * 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>
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#include <linux/dax.h>
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#include <linux/fs.h>
#include <linux/genhd.h>
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#include <linux/highmem.h>
#include <linux/memcontrol.h>
#include <linux/mm.h>
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#include <linux/mutex.h>
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#include <linux/pagevec.h>
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#include <linux/sched.h>
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#include <linux/sched/signal.h>
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#include <linux/uio.h>
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#include <linux/vmstat.h>
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#include <linux/pfn_t.h>
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#include <linux/sizes.h>
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#include <linux/mmu_notifier.h>
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#include <linux/iomap.h>
#include "internal.h"
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#define CREATE_TRACE_POINTS
#include <trace/events/fs_dax.h>

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/* 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)

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/* The 'colour' (ie low bits) within a PMD of a page offset.  */
#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
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#define PG_PMD_NR	(PMD_SIZE >> PAGE_SHIFT)
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static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
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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);

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/*
 * We use lowest available bit in exceptional entry for locking, one bit for
 * the entry size (PMD) and two more to tell us if the entry is a zero page or
 * an empty entry that is just used for locking.  In total four special bits.
 *
 * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the ZERO_PAGE
 * and EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
 * block allocation.
 */
#define RADIX_DAX_SHIFT		(RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
#define RADIX_DAX_ENTRY_LOCK	(1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
#define RADIX_DAX_PMD		(1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
#define RADIX_DAX_ZERO_PAGE	(1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
#define RADIX_DAX_EMPTY		(1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))

static unsigned long dax_radix_sector(void *entry)
{
	return (unsigned long)entry >> RADIX_DAX_SHIFT;
}

static void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
{
	return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
			((unsigned long)sector << RADIX_DAX_SHIFT) |
			RADIX_DAX_ENTRY_LOCK);
}

static unsigned int dax_radix_order(void *entry)
{
	if ((unsigned long)entry & RADIX_DAX_PMD)
		return PMD_SHIFT - PAGE_SHIFT;
	return 0;
}

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static int dax_is_pmd_entry(void *entry)
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{
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	return (unsigned long)entry & RADIX_DAX_PMD;
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}

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static int dax_is_pte_entry(void *entry)
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{
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	return !((unsigned long)entry & RADIX_DAX_PMD);
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}

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static int dax_is_zero_entry(void *entry)
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{
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	return (unsigned long)entry & RADIX_DAX_ZERO_PAGE;
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}

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static int dax_is_empty_entry(void *entry)
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{
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	return (unsigned long)entry & RADIX_DAX_EMPTY;
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}

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/*
 * DAX radix tree locking
 */
struct exceptional_entry_key {
	struct address_space *mapping;
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	pgoff_t entry_start;
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};

struct wait_exceptional_entry_queue {
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	wait_queue_entry_t wait;
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	struct exceptional_entry_key key;
};

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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.
	 */
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	if (dax_is_pmd_entry(entry))
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		index &= ~PG_PMD_COLOUR;
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	key->mapping = mapping;
	key->entry_start = index;

	hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
	return wait_table + hash;
}

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static int wake_exceptional_entry_func(wait_queue_entry_t *wait, unsigned int mode,
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				       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 ||
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	    key->entry_start != ewait->key.entry_start)
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		return 0;
	return autoremove_wake_function(wait, mode, sync, NULL);
}

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/*
 * We do not necessarily hold the mapping->tree_lock when we call this
 * function so it is possible that 'entry' is no longer a valid item in the
 * radix tree.  This is okay because all we really need to do is to find the
 * correct waitqueue where tasks might be waiting for that old 'entry' and
 * wake them.
 */
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static void dax_wake_mapping_entry_waiter(struct address_space *mapping,
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		pgoff_t index, void *entry, bool wake_all)
{
	struct exceptional_entry_key key;
	wait_queue_head_t *wq;

	wq = dax_entry_waitqueue(mapping, index, entry, &key);

	/*
	 * Checking for locked entry and prepare_to_wait_exclusive() happens
	 * under mapping->tree_lock, ditto for entry handling in our callers.
	 * So at this point all tasks that could have seen our entry locked
	 * must be in the waitqueue and the following check will see them.
	 */
	if (waitqueue_active(wq))
		__wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
}

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/*
 * Check whether the given slot is locked. The function must be called with
 * mapping->tree_lock held
 */
static inline int slot_locked(struct address_space *mapping, void **slot)
{
	unsigned long entry = (unsigned long)
		radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
	return entry & RADIX_DAX_ENTRY_LOCK;
}

/*
 * Mark the given slot is locked. The function must be called with
 * mapping->tree_lock held
 */
static inline void *lock_slot(struct address_space *mapping, void **slot)
{
	unsigned long entry = (unsigned long)
		radix_tree_deref_slot_protected(slot, &mapping->tree_lock);

	entry |= RADIX_DAX_ENTRY_LOCK;
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	radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
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	return (void *)entry;
}

/*
 * Mark the given slot is unlocked. The function must be called with
 * mapping->tree_lock held
 */
static inline void *unlock_slot(struct address_space *mapping, void **slot)
{
	unsigned long entry = (unsigned long)
		radix_tree_deref_slot_protected(slot, &mapping->tree_lock);

	entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK;
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	radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
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	return (void *)entry;
}

/*
 * Lookup entry in radix tree, wait for it to become unlocked if it is
 * exceptional entry and return it. The caller must call
 * put_unlocked_mapping_entry() when he decided not to lock the entry or
 * put_locked_mapping_entry() when he locked the entry and now wants to
 * unlock it.
 *
 * The function must be called with mapping->tree_lock held.
 */
static void *get_unlocked_mapping_entry(struct address_space *mapping,
					pgoff_t index, void ***slotp)
{
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	void *entry, **slot;
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	struct wait_exceptional_entry_queue ewait;
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	wait_queue_head_t *wq;
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	init_wait(&ewait.wait);
	ewait.wait.func = wake_exceptional_entry_func;

	for (;;) {
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		entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
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					  &slot);
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		if (!entry ||
		    WARN_ON_ONCE(!radix_tree_exceptional_entry(entry)) ||
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		    !slot_locked(mapping, slot)) {
			if (slotp)
				*slotp = slot;
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			return entry;
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		}
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		wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
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		prepare_to_wait_exclusive(wq, &ewait.wait,
					  TASK_UNINTERRUPTIBLE);
		spin_unlock_irq(&mapping->tree_lock);
		schedule();
		finish_wait(wq, &ewait.wait);
		spin_lock_irq(&mapping->tree_lock);
	}
}

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static void dax_unlock_mapping_entry(struct address_space *mapping,
				     pgoff_t index)
{
	void *entry, **slot;

	spin_lock_irq(&mapping->tree_lock);
	entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
	if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
			 !slot_locked(mapping, slot))) {
		spin_unlock_irq(&mapping->tree_lock);
		return;
	}
	unlock_slot(mapping, slot);
	spin_unlock_irq(&mapping->tree_lock);
	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
}

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static void put_locked_mapping_entry(struct address_space *mapping,
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		pgoff_t index)
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{
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	dax_unlock_mapping_entry(mapping, index);
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}

/*
 * 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)
{
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	if (!entry)
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		return;

	/* We have to wake up next waiter for the radix tree entry lock */
	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
}

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/*
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 * 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.
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 *
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 * 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
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 * happen if there are any 4k entries within the 2MiB range that we are
 * requesting.
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 *
 * 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.
 *
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 * 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.
 */
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static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
		unsigned long size_flag)
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{
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	bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
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	void *entry, **slot;
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restart:
	spin_lock_irq(&mapping->tree_lock);
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	entry = get_unlocked_mapping_entry(mapping, index, &slot);
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	if (WARN_ON_ONCE(entry && !radix_tree_exceptional_entry(entry))) {
		entry = ERR_PTR(-EIO);
		goto out_unlock;
	}

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	if (entry) {
		if (size_flag & RADIX_DAX_PMD) {
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			if (dax_is_pte_entry(entry)) {
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				put_unlocked_mapping_entry(mapping, index,
						entry);
				entry = ERR_PTR(-EEXIST);
				goto out_unlock;
			}
		} else { /* trying to grab a PTE entry */
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			if (dax_is_pmd_entry(entry) &&
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			    (dax_is_zero_entry(entry) ||
			     dax_is_empty_entry(entry))) {
				pmd_downgrade = true;
			}
		}
	}

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	/* No entry for given index? Make sure radix tree is big enough. */
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	if (!entry || pmd_downgrade) {
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		int err;

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		if (pmd_downgrade) {
			/*
			 * Make sure 'entry' remains valid while we drop
			 * mapping->tree_lock.
			 */
			entry = lock_slot(mapping, slot);
		}

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		spin_unlock_irq(&mapping->tree_lock);
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		/*
		 * 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))
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			unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
							PG_PMD_NR, false);
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		err = radix_tree_preload(
				mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
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		if (err) {
			if (pmd_downgrade)
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				put_locked_mapping_entry(mapping, index);
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			return ERR_PTR(err);
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		}
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		spin_lock_irq(&mapping->tree_lock);
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		if (!entry) {
			/*
			 * We needed to drop the page_tree lock while calling
			 * radix_tree_preload() and we didn't have an entry to
			 * lock.  See if another thread inserted an entry at
			 * our index during this time.
			 */
			entry = __radix_tree_lookup(&mapping->page_tree, index,
					NULL, &slot);
			if (entry) {
				radix_tree_preload_end();
				spin_unlock_irq(&mapping->tree_lock);
				goto restart;
			}
		}

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		if (pmd_downgrade) {
			radix_tree_delete(&mapping->page_tree, index);
			mapping->nrexceptional--;
			dax_wake_mapping_entry_waiter(mapping, index, entry,
					true);
		}

		entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);

		err = __radix_tree_insert(&mapping->page_tree, index,
				dax_radix_order(entry), entry);
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		radix_tree_preload_end();
		if (err) {
			spin_unlock_irq(&mapping->tree_lock);
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			/*
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			 * 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.
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			 */
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			return ERR_PTR(err);
		}
		/* Good, we have inserted empty locked entry into the tree. */
		mapping->nrexceptional++;
		spin_unlock_irq(&mapping->tree_lock);
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		return entry;
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	}
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	entry = lock_slot(mapping, slot);
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 out_unlock:
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	spin_unlock_irq(&mapping->tree_lock);
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	return entry;
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}

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static int __dax_invalidate_mapping_entry(struct address_space *mapping,
					  pgoff_t index, bool trunc)
{
	int ret = 0;
	void *entry;
	struct radix_tree_root *page_tree = &mapping->page_tree;

	spin_lock_irq(&mapping->tree_lock);
	entry = get_unlocked_mapping_entry(mapping, index, NULL);
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	if (!entry || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry)))
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		goto out;
	if (!trunc &&
	    (radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_DIRTY) ||
	     radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)))
		goto out;
	radix_tree_delete(page_tree, index);
	mapping->nrexceptional--;
	ret = 1;
out:
	put_unlocked_mapping_entry(mapping, index, entry);
	spin_unlock_irq(&mapping->tree_lock);
	return ret;
}
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/*
 * 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)
{
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	int ret = __dax_invalidate_mapping_entry(mapping, index, true);
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	/*
	 * 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...
	 */
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	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);
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}

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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)
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{
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	void *vto, *kaddr;
	pgoff_t pgoff;
	pfn_t pfn;
	long rc;
	int id;

	rc = bdev_dax_pgoff(bdev, sector, size, &pgoff);
	if (rc)
		return rc;

	id = dax_read_lock();
	rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
	if (rc < 0) {
		dax_read_unlock(id);
		return rc;
	}
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	vto = kmap_atomic(to);
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	copy_user_page(vto, (void __force *)kaddr, vaddr, to);
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	kunmap_atomic(vto);
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	dax_read_unlock(id);
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	return 0;
}

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/*
 * 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.
 */
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static void *dax_insert_mapping_entry(struct address_space *mapping,
				      struct vm_fault *vmf,
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				      void *entry, sector_t sector,
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				      unsigned long flags, bool dirty)
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{
	struct radix_tree_root *page_tree = &mapping->page_tree;
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	void *new_entry;
	pgoff_t index = vmf->pgoff;
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	if (dirty)
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		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
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	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))
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			unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
							PG_PMD_NR, false);
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		else /* pte entry */
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			unmap_mapping_pages(mapping, vmf->pgoff, 1, false);
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	}

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	spin_lock_irq(&mapping->tree_lock);
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	new_entry = dax_radix_locked_entry(sector, flags);

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	if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
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		/*
		 * 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.
		 */
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		struct radix_tree_node *node;
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		void **slot;
		void *ret;
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		ret = __radix_tree_lookup(page_tree, index, &node, &slot);
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		WARN_ON_ONCE(ret != entry);
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		__radix_tree_replace(page_tree, node, slot,
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				     new_entry, NULL);
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		entry = new_entry;
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	}
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	if (dirty)
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		radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
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	spin_unlock_irq(&mapping->tree_lock);
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	return entry;
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}

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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;
593 594
	pte_t pte, *ptep = NULL;
	pmd_t *pmdp = NULL;
595 596 597 598
	spinlock_t *ptl;

	i_mmap_lock_read(mapping);
	vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) {
599
		unsigned long address, start, end;
600 601 602 603 604 605 606

		cond_resched();

		if (!(vma->vm_flags & VM_SHARED))
			continue;

		address = pgoff_address(index, vma);
607 608 609 610 611 612 613

		/*
		 * 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))
614 615
			continue;

616 617 618 619 620 621 622
		/*
		 * No need to call mmu_notifier_invalidate_range() as we are
		 * downgrading page table protection not changing it to point
		 * to a new page.
		 *
		 * See Documentation/vm/mmu_notifier.txt
		 */
623 624 625 626 627 628
		if (pmdp) {
#ifdef CONFIG_FS_DAX_PMD
			pmd_t pmd;

			if (pfn != pmd_pfn(*pmdp))
				goto unlock_pmd;
629
			if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp))
630 631 632 633 634 635 636 637 638
				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
639
			spin_unlock(ptl);
640 641 642 643 644 645 646 647 648 649 650 651 652 653
		} 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);
		}
654

655
		mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
656 657 658 659
	}
	i_mmap_unlock_read(mapping);
}

660
static int dax_writeback_one(struct block_device *bdev,
661 662
		struct dax_device *dax_dev, struct address_space *mapping,
		pgoff_t index, void *entry)
663 664
{
	struct radix_tree_root *page_tree = &mapping->page_tree;
665 666 667 668 669 670
	void *entry2, **slot, *kaddr;
	long ret = 0, id;
	sector_t sector;
	pgoff_t pgoff;
	size_t size;
	pfn_t pfn;
671 672

	/*
673 674
	 * A page got tagged dirty in DAX mapping? Something is seriously
	 * wrong.
675
	 */
676 677
	if (WARN_ON(!radix_tree_exceptional_entry(entry)))
		return -EIO;
678

679 680 681
	spin_lock_irq(&mapping->tree_lock);
	entry2 = get_unlocked_mapping_entry(mapping, index, &slot);
	/* Entry got punched out / reallocated? */
682
	if (!entry2 || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry2)))
683 684 685 686 687 688 689 690
		goto put_unlocked;
	/*
	 * Entry got reallocated elsewhere? No need to writeback. We have to
	 * compare sectors as we must not bail out due to difference in lockbit
	 * or entry type.
	 */
	if (dax_radix_sector(entry2) != dax_radix_sector(entry))
		goto put_unlocked;
691 692
	if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
				dax_is_zero_entry(entry))) {
693
		ret = -EIO;
694
		goto put_unlocked;
695 696
	}

697 698 699 700 701 702 703 704 705 706 707 708 709 710 711
	/* Another fsync thread may have already written back this entry */
	if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
		goto put_unlocked;
	/* Lock the entry to serialize with page faults */
	entry = lock_slot(mapping, slot);
	/*
	 * We can clear the tag now but we have to be careful so that concurrent
	 * dax_writeback_one() calls for the same index cannot finish before we
	 * actually flush the caches. This is achieved as the calls will look
	 * at the entry only under tree_lock and once they do that they will
	 * see the entry locked and wait for it to unlock.
	 */
	radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
	spin_unlock_irq(&mapping->tree_lock);

712 713 714 715 716 717 718
	/*
	 * Even if dax_writeback_mapping_range() was given a wbc->range_start
	 * in the middle of a PMD, the 'index' we are given will be aligned to
	 * the start index of the PMD, as will the sector we pull from
	 * 'entry'.  This allows us to flush for PMD_SIZE and not have to
	 * worry about partial PMD writebacks.
	 */
719 720 721 722 723 724 725
	sector = dax_radix_sector(entry);
	size = PAGE_SIZE << dax_radix_order(entry);

	id = dax_read_lock();
	ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
	if (ret)
		goto dax_unlock;
726 727

	/*
728 729
	 * dax_direct_access() may sleep, so cannot hold tree_lock over
	 * its invocation.
730
	 */
731 732 733
	ret = dax_direct_access(dax_dev, pgoff, size / PAGE_SIZE, &kaddr, &pfn);
	if (ret < 0)
		goto dax_unlock;
734

735
	if (WARN_ON_ONCE(ret < size / PAGE_SIZE)) {
736
		ret = -EIO;
737
		goto dax_unlock;
738 739
	}

740
	dax_mapping_entry_mkclean(mapping, index, pfn_t_to_pfn(pfn));
741
	dax_flush(dax_dev, kaddr, size);
742 743 744 745 746 747 748 749 750
	/*
	 * After we have flushed the cache, we can clear the dirty tag. There
	 * cannot be new dirty data in the pfn after the flush has completed as
	 * the pfn mappings are writeprotected and fault waits for mapping
	 * entry lock.
	 */
	spin_lock_irq(&mapping->tree_lock);
	radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_DIRTY);
	spin_unlock_irq(&mapping->tree_lock);
751
	trace_dax_writeback_one(mapping->host, index, size >> PAGE_SHIFT);
752 753
 dax_unlock:
	dax_read_unlock(id);
754
	put_locked_mapping_entry(mapping, index);
755 756
	return ret;

757 758
 put_unlocked:
	put_unlocked_mapping_entry(mapping, index, entry2);
759 760 761 762 763 764 765 766 767
	spin_unlock_irq(&mapping->tree_lock);
	return ret;
}

/*
 * Flush the mapping to the persistent domain within the byte range of [start,
 * end]. This is required by data integrity operations to ensure file data is
 * on persistent storage prior to completion of the operation.
 */
768 769
int dax_writeback_mapping_range(struct address_space *mapping,
		struct block_device *bdev, struct writeback_control *wbc)
770 771
{
	struct inode *inode = mapping->host;
772
	pgoff_t start_index, end_index;
773
	pgoff_t indices[PAGEVEC_SIZE];
774
	struct dax_device *dax_dev;
775 776 777 778 779 780 781
	struct pagevec pvec;
	bool done = false;
	int i, ret = 0;

	if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
		return -EIO;

782 783 784
	if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
		return 0;

785 786 787 788
	dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
	if (!dax_dev)
		return -EIO;

789 790
	start_index = wbc->range_start >> PAGE_SHIFT;
	end_index = wbc->range_end >> PAGE_SHIFT;
791

792 793
	trace_dax_writeback_range(inode, start_index, end_index);

794 795
	tag_pages_for_writeback(mapping, start_index, end_index);

796
	pagevec_init(&pvec);
797 798 799 800 801 802 803 804 805 806 807 808 809 810
	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;
			}

811 812
			ret = dax_writeback_one(bdev, dax_dev, mapping,
					indices[i], pvec.pages[i]);
813 814
			if (ret < 0) {
				mapping_set_error(mapping, ret);
815
				goto out;
816
			}
817
		}
818
		start_index = indices[pvec.nr - 1] + 1;
819
	}
820
out:
821
	put_dax(dax_dev);
822 823
	trace_dax_writeback_range_done(inode, start_index, end_index);
	return (ret < 0 ? ret : 0);
824 825 826
}
EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);

827
static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
828
{
829
	return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
830 831
}

832 833
static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
			 pfn_t *pfnp)
834
{
835
	const sector_t sector = dax_iomap_sector(iomap, pos);
836
	pgoff_t pgoff;
837
	void *kaddr;
838
	int id, rc;
839
	long length;
840

841
	rc = bdev_dax_pgoff(iomap->bdev, sector, size, &pgoff);
842 843 844
	if (rc)
		return rc;
	id = dax_read_lock();
845 846 847 848 849
	length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
				   &kaddr, pfnp);
	if (length < 0) {
		rc = length;
		goto out;
850
	}
851 852 853 854 855 856 857 858 859 860
	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:
861
	dax_read_unlock(id);
862
	return rc;
863 864
}

865
/*
866 867 868 869 870
 * 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.
871
 */
872
static int dax_load_hole(struct address_space *mapping, void *entry,
873 874 875
			 struct vm_fault *vmf)
{
	struct inode *inode = mapping->host;
876 877 878 879
	unsigned long vaddr = vmf->address;
	int ret = VM_FAULT_NOPAGE;
	struct page *zero_page;
	void *entry2;
880

881 882
	zero_page = ZERO_PAGE(0);
	if (unlikely(!zero_page)) {
883 884 885 886
		ret = VM_FAULT_OOM;
		goto out;
	}

887
	entry2 = dax_insert_mapping_entry(mapping, vmf, entry, 0,
888
			RADIX_DAX_ZERO_PAGE, false);
889 890 891
	if (IS_ERR(entry2)) {
		ret = VM_FAULT_SIGBUS;
		goto out;
892
	}
893 894

	vm_insert_mixed(vmf->vma, vaddr, page_to_pfn_t(zero_page));
895 896 897 898 899
out:
	trace_dax_load_hole(inode, vmf, ret);
	return ret;
}

900 901 902 903 904 905 906 907 908 909 910 911 912
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;
}

913 914 915
int __dax_zero_page_range(struct block_device *bdev,
		struct dax_device *dax_dev, sector_t sector,
		unsigned int offset, unsigned int size)
916
{
917 918
	if (dax_range_is_aligned(bdev, offset, size)) {
		sector_t start_sector = sector + (offset >> 9);
919 920

		return blkdev_issue_zeroout(bdev, start_sector,
921
				size >> 9, GFP_NOFS, 0);
922
	} else {
923 924 925 926 927
		pgoff_t pgoff;
		long rc, id;
		void *kaddr;
		pfn_t pfn;

928
		rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
929 930 931 932
		if (rc)
			return rc;

		id = dax_read_lock();
933
		rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr,
934 935 936 937 938
				&pfn);
		if (rc < 0) {
			dax_read_unlock(id);
			return rc;
		}
939
		memset(kaddr + offset, 0, size);
940
		dax_flush(dax_dev, kaddr + offset, size);
941
		dax_read_unlock(id);
942
	}
943 944 945 946
	return 0;
}
EXPORT_SYMBOL_GPL(__dax_zero_page_range);

947
static loff_t
948
dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
949 950
		struct iomap *iomap)
{
951 952
	struct block_device *bdev = iomap->bdev;
	struct dax_device *dax_dev = iomap->dax_dev;
953 954 955
	struct iov_iter *iter = data;
	loff_t end = pos + length, done = 0;
	ssize_t ret = 0;
956
	int id;
957 958 959 960 961 962 963 964 965 966 967 968 969

	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;

970 971 972 973 974
	/*
	 * 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.
	 */
975
	if (iomap->flags & IOMAP_F_NEW) {
976 977 978 979 980
		invalidate_inode_pages2_range(inode->i_mapping,
					      pos >> PAGE_SHIFT,
					      (end - 1) >> PAGE_SHIFT);
	}

981
	id = dax_read_lock();
982 983
	while (pos < end) {
		unsigned offset = pos & (PAGE_SIZE - 1);
984 985
		const size_t size = ALIGN(length + offset, PAGE_SIZE);
		const sector_t sector = dax_iomap_sector(iomap, pos);
986
		ssize_t map_len;
987 988 989
		pgoff_t pgoff;
		void *kaddr;
		pfn_t pfn;
990

991 992 993 994 995
		if (fatal_signal_pending(current)) {
			ret = -EINTR;
			break;
		}

996 997 998 999 1000 1001
		ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
		if (ret)
			break;

		map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size),
				&kaddr, &pfn);
1002 1003 1004 1005 1006
		if (map_len < 0) {
			ret = map_len;
			break;
		}

1007 1008
		map_len = PFN_PHYS(map_len);
		kaddr += offset;
1009 1010 1011 1012
		map_len -= offset;
		if (map_len > end - pos)
			map_len = end - pos;

1013 1014 1015 1016 1017
		/*
		 * 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.
		 */
1018
		if (iov_iter_rw(iter) == WRITE)
1019 1020
			map_len = dax_copy_from_iter(dax_dev, pgoff, kaddr,
					map_len, iter);
1021
		else
1022
			map_len = copy_to_iter(kaddr, map_len, iter);
1023 1024 1025 1026 1027 1028 1029 1030 1031
		if (map_len <= 0) {
			ret = map_len ? map_len : -EFAULT;
			break;
		}

		pos += map_len;
		length -= map_len;
		done += map_len;
	}
1032
	dax_read_unlock(id);
1033 1034 1035 1036 1037

	return done ? done : ret;
}

/**
1038
 * dax_iomap_rw - Perform I/O to a DAX file
1039 1040 1041 1042 1043 1044 1045 1046 1047
 * @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
1048
dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
1049
		const struct iomap_ops *ops)
1050 1051 1052 1053 1054 1055
{
	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;

1056 1057
	if (iov_iter_rw(iter) == WRITE) {
		lockdep_assert_held_exclusive(&inode->i_rwsem);
1058
		flags |= IOMAP_WRITE;
1059 1060 1061
	} else {
		lockdep_assert_held(&inode->i_rwsem);
	}
1062 1063 1064

	while (iov_iter_count(iter)) {
		ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
1065
				iter, dax_iomap_actor);
1066 1067 1068 1069 1070 1071 1072 1073 1074
		if (ret <= 0)
			break;
		pos += ret;
		done += ret;
	}

	iocb->ki_pos += done;
	return done ? done : ret;
}
1075
EXPORT_SYMBOL_GPL(dax_iomap_rw);
1076

1077 1078 1079 1080 1081 1082 1083 1084 1085
static int dax_fault_return(int error)
{
	if (error == 0)
		return VM_FAULT_NOPAGE;
	if (error == -ENOMEM)
		return VM_FAULT_OOM;
	return VM_FAULT_SIGBUS;
}

1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096
/*
 * 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);
}

1097
static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
1098
			       const struct iomap_ops *ops)
1099
{
1100 1101
	struct vm_area_struct *vma = vmf->vma;
	struct address_space *mapping = vma->vm_file->f_mapping;
1102
	struct inode *inode = mapping->host;
1103
	unsigned long vaddr = vmf->address;
1104 1105
	loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
	struct iomap iomap = { 0 };
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Jan Kara committed
1106
	unsigned flags = IOMAP_FAULT;
1107
	int error, major = 0;
1108
	bool write = vmf->flags & FAULT_FLAG_WRITE;
1109
	bool sync;
1110
	int vmf_ret = 0;
1111
	void *entry;
1112
	pfn_t pfn;
1113

1114
	trace_dax_pte_fault(inode, vmf, vmf_ret);
1115 1116 1117 1118 1119
	/*
	 * 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.
	 */
1120 1121 1122 1123
	if (pos >= i_size_read(inode)) {
		vmf_ret = VM_FAULT_SIGBUS;
		goto out;
	}
1124

1125
	if (write && !vmf->cow_page)
1126 1127
		flags |= IOMAP_WRITE;

1128 1129 1130 1131 1132 1133
	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
	if (IS_ERR(entry)) {
		vmf_ret = dax_fault_return(PTR_ERR(entry));
		goto out;
	}

1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144
	/*
	 * It is possible, particularly with mixed reads & writes to private
	 * mappings, that we have raced with a PMD fault that overlaps with
	 * the PTE we need to set up.  If so just return and the fault will be
	 * retried.
	 */
	if (pmd_trans_huge(*vmf->pmd) || pmd_devmap(*vmf->pmd)) {
		vmf_ret = VM_FAULT_NOPAGE;
		goto unlock_entry;
	}

1145 1146 1147 1148 1149 1150
	/*
	 * 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);
1151 1152
	if (error) {
		vmf_ret = dax_fault_return(error);
1153
		goto unlock_entry;
1154
	}
1155
	if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
1156 1157
		error = -EIO;	/* fs corruption? */
		goto error_finish_iomap;
1158 1159 1160
	}

	if (vmf->cow_page) {
1161 1162
		sector_t sector = dax_iomap_sector(&iomap, pos);

1163 1164 1165 1166 1167 1168
		switch (iomap.type) {
		case IOMAP_HOLE:
		case IOMAP_UNWRITTEN:
			clear_user_highpage(vmf->cow_page, vaddr);
			break;
		case IOMAP_MAPPED:
1169 1170
			error = copy_user_dax(iomap.bdev, iomap.dax_dev,
					sector, PAGE_SIZE, vmf->cow_page, vaddr);
1171 1172 1173 1174 1175 1176 1177 1178
			break;
		default:
			WARN_ON_ONCE(1);
			error = -EIO;
			break;
		}

		if (error)
1179
			goto error_finish_iomap;
1180 1181 1182 1183 1184

		__SetPageUptodate(vmf->cow_page);
		vmf_ret = finish_fault(vmf);
		if (!vmf_ret)
			vmf_ret = VM_FAULT_DONE_COW;
1185
		goto finish_iomap;
1186 1187
	}

1188
	sync = dax_fault_is_synchronous(flags, vma, &iomap);
1189

1190 1191 1192 1193
	switch (iomap.type) {
	case IOMAP_MAPPED:
		if (iomap.flags & IOMAP_F_NEW) {
			count_vm_event(PGMAJFAULT);
1194
			count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
1195 1196
			major = VM_FAULT_MAJOR;
		}
1197 1198 1199 1200 1201 1202
		error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
		if (error < 0)
			goto error_finish_iomap;

		entry = dax_insert_mapping_entry(mapping, vmf, entry,
						 dax_iomap_sector(&iomap, pos),
1203
						 0, write && !sync);
1204 1205 1206 1207 1208
		if (IS_ERR(entry)) {
			error = PTR_ERR(entry);
			goto error_finish_iomap;
		}

1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223
		/*
		 * If we are doing synchronous page fault and inode needs fsync,
		 * we can insert PTE into page tables only after that happens.
		 * Skip insertion for now and return the pfn so that caller can
		 * insert it after fsync is done.
		 */
		if (sync) {
			if (WARN_ON_ONCE(!pfnp)) {
				error = -EIO;
				goto error_finish_iomap;
			}
			*pfnp = pfn;
			vmf_ret = VM_FAULT_NEEDDSYNC | major;
			goto finish_iomap;
		}
1224 1225 1226 1227 1228 1229
		trace_dax_insert_mapping(inode, vmf, entry);
		if (write)
			error = vm_insert_mixed_mkwrite(vma, vaddr, pfn);
		else
			error = vm_insert_mixed(vma, vaddr, pfn);

1230 1231 1232
		/* -EBUSY is fine, somebody else faulted on the same PTE */
		if (error == -EBUSY)
			error = 0;
1233 1234 1235
		break;
	case IOMAP_UNWRITTEN:
	case IOMAP_HOLE:
1236
		if (!write) {
1237
			vmf_ret = dax_load_hole(mapping, entry, vmf);
1238
			goto finish_iomap;
1239
		}
1240 1241 1242 1243 1244 1245 1246
		/*FALLTHRU*/
	default:
		WARN_ON_ONCE(1);
		error = -EIO;
		break;
	}

1247
 error_finish_iomap:
1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261
	vmf_ret = dax_fault_return(error) | major;
 finish_iomap:
	if (ops->iomap_end) {
		int copied = PAGE_SIZE;

		if (vmf_ret & VM_FAULT_ERROR)
			copied = 0;
		/*
		 * The fault is done by now and there's no way back (other
		 * thread may be already happily using PTE we have installed).
		 * Just ignore error from ->iomap_end since we cannot do much
		 * with it.
		 */
		ops->iomap_end(inode, pos, PAGE_SIZE, copied, flags, &iomap);
1262
	}
1263
 unlock_entry:
1264
	put_locked_mapping_entry(mapping, vmf->pgoff);
1265
 out:
1266
	trace_dax_pte_fault_done(inode, vmf, vmf_ret);
1267
	return vmf_ret;
1268
}
1269 1270

#ifdef CONFIG_FS_DAX_PMD
1271
static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
1272
		void *entry)
1273
{
1274 1275
	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
	unsigned long pmd_addr = vmf->address & PMD_MASK;
1276
	struct inode *inode = mapping->host;