blob: b4c9a6aa118cd22f11246fcd45fc032fbccb79b2 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include "messages.h"
#include "ctree.h"
#include "extent_map.h"
#include "compression.h"
#include "btrfs_inode.h"
#include "disk-io.h"
static struct kmem_cache *extent_map_cache;
int __init extent_map_init(void)
{
extent_map_cache = kmem_cache_create("btrfs_extent_map",
sizeof(struct extent_map), 0, 0, NULL);
if (!extent_map_cache)
return -ENOMEM;
return 0;
}
void __cold extent_map_exit(void)
{
kmem_cache_destroy(extent_map_cache);
}
/*
* Initialize the extent tree @tree. Should be called for each new inode or
* other user of the extent_map interface.
*/
void extent_map_tree_init(struct extent_map_tree *tree)
{
tree->map = RB_ROOT_CACHED;
INIT_LIST_HEAD(&tree->modified_extents);
rwlock_init(&tree->lock);
}
/*
* Allocate a new extent_map structure. The new structure is returned with a
* reference count of one and needs to be freed using free_extent_map()
*/
struct extent_map *alloc_extent_map(void)
{
struct extent_map *em;
em = kmem_cache_zalloc(extent_map_cache, GFP_NOFS);
if (!em)
return NULL;
RB_CLEAR_NODE(&em->rb_node);
refcount_set(&em->refs, 1);
INIT_LIST_HEAD(&em->list);
return em;
}
/*
* Drop the reference out on @em by one and free the structure if the reference
* count hits zero.
*/
void free_extent_map(struct extent_map *em)
{
if (!em)
return;
if (refcount_dec_and_test(&em->refs)) {
WARN_ON(extent_map_in_tree(em));
WARN_ON(!list_empty(&em->list));
kmem_cache_free(extent_map_cache, em);
}
}
/* Do the math around the end of an extent, handling wrapping. */
static u64 range_end(u64 start, u64 len)
{
if (start + len < start)
return (u64)-1;
return start + len;
}
static void dec_evictable_extent_maps(struct btrfs_inode *inode)
{
struct btrfs_fs_info *fs_info = inode->root->fs_info;
if (!btrfs_is_testing(fs_info) && is_fstree(btrfs_root_id(inode->root)))
percpu_counter_dec(&fs_info->evictable_extent_maps);
}
static int tree_insert(struct rb_root_cached *root, struct extent_map *em)
{
struct rb_node **p = &root->rb_root.rb_node;
struct rb_node *parent = NULL;
struct extent_map *entry = NULL;
struct rb_node *orig_parent = NULL;
u64 end = range_end(em->start, em->len);
bool leftmost = true;
while (*p) {
parent = *p;
entry = rb_entry(parent, struct extent_map, rb_node);
if (em->start < entry->start) {
p = &(*p)->rb_left;
} else if (em->start >= extent_map_end(entry)) {
p = &(*p)->rb_right;
leftmost = false;
} else {
return -EEXIST;
}
}
orig_parent = parent;
while (parent && em->start >= extent_map_end(entry)) {
parent = rb_next(parent);
entry = rb_entry(parent, struct extent_map, rb_node);
}
if (parent)
if (end > entry->start && em->start < extent_map_end(entry))
return -EEXIST;
parent = orig_parent;
entry = rb_entry(parent, struct extent_map, rb_node);
while (parent && em->start < entry->start) {
parent = rb_prev(parent);
entry = rb_entry(parent, struct extent_map, rb_node);
}
if (parent)
if (end > entry->start && em->start < extent_map_end(entry))
return -EEXIST;
rb_link_node(&em->rb_node, orig_parent, p);
rb_insert_color_cached(&em->rb_node, root, leftmost);
return 0;
}
/*
* Search through the tree for an extent_map with a given offset. If it can't
* be found, try to find some neighboring extents
*/
static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
struct rb_node **prev_or_next_ret)
{
struct rb_node *n = root->rb_node;
struct rb_node *prev = NULL;
struct rb_node *orig_prev = NULL;
struct extent_map *entry;
struct extent_map *prev_entry = NULL;
ASSERT(prev_or_next_ret);
while (n) {
entry = rb_entry(n, struct extent_map, rb_node);
prev = n;
prev_entry = entry;
if (offset < entry->start)
n = n->rb_left;
else if (offset >= extent_map_end(entry))
n = n->rb_right;
else
return n;
}
orig_prev = prev;
while (prev && offset >= extent_map_end(prev_entry)) {
prev = rb_next(prev);
prev_entry = rb_entry(prev, struct extent_map, rb_node);
}
/*
* Previous extent map found, return as in this case the caller does not
* care about the next one.
*/
if (prev) {
*prev_or_next_ret = prev;
return NULL;
}
prev = orig_prev;
prev_entry = rb_entry(prev, struct extent_map, rb_node);
while (prev && offset < prev_entry->start) {
prev = rb_prev(prev);
prev_entry = rb_entry(prev, struct extent_map, rb_node);
}
*prev_or_next_ret = prev;
return NULL;
}
static inline u64 extent_map_block_end(const struct extent_map *em)
{
if (em->block_start + em->block_len < em->block_start)
return (u64)-1;
return em->block_start + em->block_len;
}
static bool can_merge_extent_map(const struct extent_map *em)
{
if (em->flags & EXTENT_FLAG_PINNED)
return false;
/* Don't merge compressed extents, we need to know their actual size. */
if (extent_map_is_compressed(em))
return false;
if (em->flags & EXTENT_FLAG_LOGGING)
return false;
/*
* We don't want to merge stuff that hasn't been written to the log yet
* since it may not reflect exactly what is on disk, and that would be
* bad.
*/
if (!list_empty(&em->list))
return false;
return true;
}
/* Check to see if two extent_map structs are adjacent and safe to merge. */
static bool mergeable_maps(const struct extent_map *prev, const struct extent_map *next)
{
if (extent_map_end(prev) != next->start)
return false;
if (prev->flags != next->flags)
return false;
if (next->block_start < EXTENT_MAP_LAST_BYTE - 1)
return next->block_start == extent_map_block_end(prev);
/* HOLES and INLINE extents. */
return next->block_start == prev->block_start;
}
static void try_merge_map(struct btrfs_inode *inode, struct extent_map *em)
{
struct extent_map_tree *tree = &inode->extent_tree;
struct extent_map *merge = NULL;
struct rb_node *rb;
/*
* We can't modify an extent map that is in the tree and that is being
* used by another task, as it can cause that other task to see it in
* inconsistent state during the merging. We always have 1 reference for
* the tree and 1 for this task (which is unpinning the extent map or
* clearing the logging flag), so anything > 2 means it's being used by
* other tasks too.
*/
if (refcount_read(&em->refs) > 2)
return;
if (!can_merge_extent_map(em))
return;
if (em->start != 0) {
rb = rb_prev(&em->rb_node);
if (rb)
merge = rb_entry(rb, struct extent_map, rb_node);
if (rb && can_merge_extent_map(merge) && mergeable_maps(merge, em)) {
em->start = merge->start;
em->orig_start = merge->orig_start;
em->len += merge->len;
em->block_len += merge->block_len;
em->block_start = merge->block_start;
em->generation = max(em->generation, merge->generation);
em->flags |= EXTENT_FLAG_MERGED;
rb_erase_cached(&merge->rb_node, &tree->map);
RB_CLEAR_NODE(&merge->rb_node);
free_extent_map(merge);
dec_evictable_extent_maps(inode);
}
}
rb = rb_next(&em->rb_node);
if (rb)
merge = rb_entry(rb, struct extent_map, rb_node);
if (rb && can_merge_extent_map(merge) && mergeable_maps(em, merge)) {
em->len += merge->len;
em->block_len += merge->block_len;
rb_erase_cached(&merge->rb_node, &tree->map);
RB_CLEAR_NODE(&merge->rb_node);
em->generation = max(em->generation, merge->generation);
em->flags |= EXTENT_FLAG_MERGED;
free_extent_map(merge);
dec_evictable_extent_maps(inode);
}
}
/*
* Unpin an extent from the cache.
*
* @inode: the inode from which we are unpinning an extent range
* @start: logical offset in the file
* @len: length of the extent
* @gen: generation that this extent has been modified in
*
* Called after an extent has been written to disk properly. Set the generation
* to the generation that actually added the file item to the inode so we know
* we need to sync this extent when we call fsync().
*
* Returns: 0 on success
* -ENOENT when the extent is not found in the tree
* -EUCLEAN if the found extent does not match the expected start
*/
int unpin_extent_cache(struct btrfs_inode *inode, u64 start, u64 len, u64 gen)
{
struct btrfs_fs_info *fs_info = inode->root->fs_info;
struct extent_map_tree *tree = &inode->extent_tree;
int ret = 0;
struct extent_map *em;
write_lock(&tree->lock);
em = lookup_extent_mapping(tree, start, len);
if (WARN_ON(!em)) {
btrfs_warn(fs_info,
"no extent map found for inode %llu (root %lld) when unpinning extent range [%llu, %llu), generation %llu",
btrfs_ino(inode), btrfs_root_id(inode->root),
start, start + len, gen);
ret = -ENOENT;
goto out;
}
if (WARN_ON(em->start != start)) {
btrfs_warn(fs_info,
"found extent map for inode %llu (root %lld) with unexpected start offset %llu when unpinning extent range [%llu, %llu), generation %llu",
btrfs_ino(inode), btrfs_root_id(inode->root),
em->start, start, start + len, gen);
ret = -EUCLEAN;
goto out;
}
em->generation = gen;
em->flags &= ~EXTENT_FLAG_PINNED;
try_merge_map(inode, em);
out:
write_unlock(&tree->lock);
free_extent_map(em);
return ret;
}
void clear_em_logging(struct btrfs_inode *inode, struct extent_map *em)
{
lockdep_assert_held_write(&inode->extent_tree.lock);
em->flags &= ~EXTENT_FLAG_LOGGING;
if (extent_map_in_tree(em))
try_merge_map(inode, em);
}
static inline void setup_extent_mapping(struct btrfs_inode *inode,
struct extent_map *em,
int modified)
{
refcount_inc(&em->refs);
ASSERT(list_empty(&em->list));
if (modified)
list_add(&em->list, &inode->extent_tree.modified_extents);
else
try_merge_map(inode, em);
}
/*
* Add a new extent map to an inode's extent map tree.
*
* @inode: the target inode
* @em: map to insert
* @modified: indicate whether the given @em should be added to the
* modified list, which indicates the extent needs to be logged
*
* Insert @em into the @inode's extent map tree or perform a simple
* forward/backward merge with existing mappings. The extent_map struct passed
* in will be inserted into the tree directly, with an additional reference
* taken, or a reference dropped if the merge attempt was successful.
*/
static int add_extent_mapping(struct btrfs_inode *inode,
struct extent_map *em, int modified)
{
struct extent_map_tree *tree = &inode->extent_tree;
struct btrfs_root *root = inode->root;
struct btrfs_fs_info *fs_info = root->fs_info;
int ret;
lockdep_assert_held_write(&tree->lock);
ret = tree_insert(&tree->map, em);
if (ret)
return ret;
setup_extent_mapping(inode, em, modified);
if (!btrfs_is_testing(fs_info) && is_fstree(btrfs_root_id(root)))
percpu_counter_inc(&fs_info->evictable_extent_maps);
return 0;
}
static struct extent_map *
__lookup_extent_mapping(struct extent_map_tree *tree,
u64 start, u64 len, int strict)
{
struct extent_map *em;
struct rb_node *rb_node;
struct rb_node *prev_or_next = NULL;
u64 end = range_end(start, len);
rb_node = __tree_search(&tree->map.rb_root, start, &prev_or_next);
if (!rb_node) {
if (prev_or_next)
rb_node = prev_or_next;
else
return NULL;
}
em = rb_entry(rb_node, struct extent_map, rb_node);
if (strict && !(end > em->start && start < extent_map_end(em)))
return NULL;
refcount_inc(&em->refs);
return em;
}
/*
* Lookup extent_map that intersects @start + @len range.
*
* @tree: tree to lookup in
* @start: byte offset to start the search
* @len: length of the lookup range
*
* Find and return the first extent_map struct in @tree that intersects the
* [start, len] range. There may be additional objects in the tree that
* intersect, so check the object returned carefully to make sure that no
* additional lookups are needed.
*/
struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
u64 start, u64 len)
{
return __lookup_extent_mapping(tree, start, len, 1);
}
/*
* Find a nearby extent map intersecting @start + @len (not an exact search).
*
* @tree: tree to lookup in
* @start: byte offset to start the search
* @len: length of the lookup range
*
* Find and return the first extent_map struct in @tree that intersects the
* [start, len] range.
*
* If one can't be found, any nearby extent may be returned
*/
struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
u64 start, u64 len)
{
return __lookup_extent_mapping(tree, start, len, 0);
}
/*
* Remove an extent_map from its inode's extent tree.
*
* @inode: the inode the extent map belongs to
* @em: extent map being removed
*
* Remove @em from the extent tree of @inode. No reference counts are dropped,
* and no checks are done to see if the range is in use.
*/
void remove_extent_mapping(struct btrfs_inode *inode, struct extent_map *em)
{
struct extent_map_tree *tree = &inode->extent_tree;
lockdep_assert_held_write(&tree->lock);
WARN_ON(em->flags & EXTENT_FLAG_PINNED);
rb_erase_cached(&em->rb_node, &tree->map);
if (!(em->flags & EXTENT_FLAG_LOGGING))
list_del_init(&em->list);
RB_CLEAR_NODE(&em->rb_node);
dec_evictable_extent_maps(inode);
}
static void replace_extent_mapping(struct btrfs_inode *inode,
struct extent_map *cur,
struct extent_map *new,
int modified)
{
struct extent_map_tree *tree = &inode->extent_tree;
lockdep_assert_held_write(&tree->lock);
WARN_ON(cur->flags & EXTENT_FLAG_PINNED);
ASSERT(extent_map_in_tree(cur));
if (!(cur->flags & EXTENT_FLAG_LOGGING))
list_del_init(&cur->list);
rb_replace_node_cached(&cur->rb_node, &new->rb_node, &tree->map);
RB_CLEAR_NODE(&cur->rb_node);
setup_extent_mapping(inode, new, modified);
}
static struct extent_map *next_extent_map(const struct extent_map *em)
{
struct rb_node *next;
next = rb_next(&em->rb_node);
if (!next)
return NULL;
return container_of(next, struct extent_map, rb_node);
}
static struct extent_map *prev_extent_map(struct extent_map *em)
{
struct rb_node *prev;
prev = rb_prev(&em->rb_node);
if (!prev)
return NULL;
return container_of(prev, struct extent_map, rb_node);
}
/*
* Helper for btrfs_get_extent. Given an existing extent in the tree,
* the existing extent is the nearest extent to map_start,
* and an extent that you want to insert, deal with overlap and insert
* the best fitted new extent into the tree.
*/
static noinline int merge_extent_mapping(struct btrfs_inode *inode,
struct extent_map *existing,
struct extent_map *em,
u64 map_start)
{
struct extent_map *prev;
struct extent_map *next;
u64 start;
u64 end;
u64 start_diff;
if (map_start < em->start || map_start >= extent_map_end(em))
return -EINVAL;
if (existing->start > map_start) {
next = existing;
prev = prev_extent_map(next);
} else {
prev = existing;
next = next_extent_map(prev);
}
start = prev ? extent_map_end(prev) : em->start;
start = max_t(u64, start, em->start);
end = next ? next->start : extent_map_end(em);
end = min_t(u64, end, extent_map_end(em));
start_diff = start - em->start;
em->start = start;
em->len = end - start;
if (em->block_start < EXTENT_MAP_LAST_BYTE &&
!extent_map_is_compressed(em)) {
em->block_start += start_diff;
em->block_len = em->len;
}
return add_extent_mapping(inode, em, 0);
}
/*
* Add extent mapping into an inode's extent map tree.
*
* @inode: target inode
* @em_in: extent we are inserting
* @start: start of the logical range btrfs_get_extent() is requesting
* @len: length of the logical range btrfs_get_extent() is requesting
*
* Note that @em_in's range may be different from [start, start+len),
* but they must be overlapped.
*
* Insert @em_in into the inode's extent map tree. In case there is an
* overlapping range, handle the -EEXIST by either:
* a) Returning the existing extent in @em_in if @start is within the
* existing em.
* b) Merge the existing extent with @em_in passed in.
*
* Return 0 on success, otherwise -EEXIST.
*
*/
int btrfs_add_extent_mapping(struct btrfs_inode *inode,
struct extent_map **em_in, u64 start, u64 len)
{
int ret;
struct extent_map *em = *em_in;
struct btrfs_fs_info *fs_info = inode->root->fs_info;
/*
* Tree-checker should have rejected any inline extent with non-zero
* file offset. Here just do a sanity check.
*/
if (em->block_start == EXTENT_MAP_INLINE)
ASSERT(em->start == 0);
ret = add_extent_mapping(inode, em, 0);
/* it is possible that someone inserted the extent into the tree
* while we had the lock dropped. It is also possible that
* an overlapping map exists in the tree
*/
if (ret == -EEXIST) {
struct extent_map *existing;
existing = search_extent_mapping(&inode->extent_tree, start, len);
trace_btrfs_handle_em_exist(fs_info, existing, em, start, len);
/*
* existing will always be non-NULL, since there must be
* extent causing the -EEXIST.
*/
if (start >= existing->start &&
start < extent_map_end(existing)) {
free_extent_map(em);
*em_in = existing;
ret = 0;
} else {
u64 orig_start = em->start;
u64 orig_len = em->len;
/*
* The existing extent map is the one nearest to
* the [start, start + len) range which overlaps
*/
ret = merge_extent_mapping(inode, existing, em, start);
if (WARN_ON(ret)) {
free_extent_map(em);
*em_in = NULL;
btrfs_warn(fs_info,
"extent map merge error existing [%llu, %llu) with em [%llu, %llu) start %llu",
existing->start, extent_map_end(existing),
orig_start, orig_start + orig_len, start);
}
free_extent_map(existing);
}
}
ASSERT(ret == 0 || ret == -EEXIST);
return ret;
}
/*
* Drop all extent maps from a tree in the fastest possible way, rescheduling
* if needed. This avoids searching the tree, from the root down to the first
* extent map, before each deletion.
*/
static void drop_all_extent_maps_fast(struct btrfs_inode *inode)
{
struct extent_map_tree *tree = &inode->extent_tree;
write_lock(&tree->lock);
while (!RB_EMPTY_ROOT(&tree->map.rb_root)) {
struct extent_map *em;
struct rb_node *node;
node = rb_first_cached(&tree->map);
em = rb_entry(node, struct extent_map, rb_node);
em->flags &= ~(EXTENT_FLAG_PINNED | EXTENT_FLAG_LOGGING);
remove_extent_mapping(inode, em);
free_extent_map(em);
cond_resched_rwlock_write(&tree->lock);
}
write_unlock(&tree->lock);
}
/*
* Drop all extent maps in a given range.
*
* @inode: The target inode.
* @start: Start offset of the range.
* @end: End offset of the range (inclusive value).
* @skip_pinned: Indicate if pinned extent maps should be ignored or not.
*
* This drops all the extent maps that intersect the given range [@start, @end].
* Extent maps that partially overlap the range and extend behind or beyond it,
* are split.
* The caller should have locked an appropriate file range in the inode's io
* tree before calling this function.
*/
void btrfs_drop_extent_map_range(struct btrfs_inode *inode, u64 start, u64 end,
bool skip_pinned)
{
struct extent_map *split;
struct extent_map *split2;
struct extent_map *em;
struct extent_map_tree *em_tree = &inode->extent_tree;
u64 len = end - start + 1;
WARN_ON(end < start);
if (end == (u64)-1) {
if (start == 0 && !skip_pinned) {
drop_all_extent_maps_fast(inode);
return;
}
len = (u64)-1;
} else {
/* Make end offset exclusive for use in the loop below. */
end++;
}
/*
* It's ok if we fail to allocate the extent maps, see the comment near
* the bottom of the loop below. We only need two spare extent maps in
* the worst case, where the first extent map that intersects our range
* starts before the range and the last extent map that intersects our
* range ends after our range (and they might be the same extent map),
* because we need to split those two extent maps at the boundaries.
*/
split = alloc_extent_map();
split2 = alloc_extent_map();
write_lock(&em_tree->lock);
em = lookup_extent_mapping(em_tree, start, len);
while (em) {
/* extent_map_end() returns exclusive value (last byte + 1). */
const u64 em_end = extent_map_end(em);
struct extent_map *next_em = NULL;
u64 gen;
unsigned long flags;
bool modified;
bool compressed;
if (em_end < end) {
next_em = next_extent_map(em);
if (next_em) {
if (next_em->start < end)
refcount_inc(&next_em->refs);
else
next_em = NULL;
}
}
if (skip_pinned && (em->flags & EXTENT_FLAG_PINNED)) {
start = em_end;
goto next;
}
flags = em->flags;
/*
* In case we split the extent map, we want to preserve the
* EXTENT_FLAG_LOGGING flag on our extent map, but we don't want
* it on the new extent maps.
*/
em->flags &= ~(EXTENT_FLAG_PINNED | EXTENT_FLAG_LOGGING);
modified = !list_empty(&em->list);
/*
* The extent map does not cross our target range, so no need to
* split it, we can remove it directly.
*/
if (em->start >= start && em_end <= end)
goto remove_em;
gen = em->generation;
compressed = extent_map_is_compressed(em);
if (em->start < start) {
if (!split) {
split = split2;
split2 = NULL;
if (!split)
goto remove_em;
}
split->start = em->start;
split->len = start - em->start;
if (em->block_start < EXTENT_MAP_LAST_BYTE) {
split->orig_start = em->orig_start;
split->block_start = em->block_start;
if (compressed)
split->block_len = em->block_len;
else
split->block_len = split->len;
split->orig_block_len = max(split->block_len,
em->orig_block_len);
split->ram_bytes = em->ram_bytes;
} else {
split->orig_start = split->start;
split->block_len = 0;
split->block_start = em->block_start;
split->orig_block_len = 0;
split->ram_bytes = split->len;
}
split->generation = gen;
split->flags = flags;
replace_extent_mapping(inode, em, split, modified);
free_extent_map(split);
split = split2;
split2 = NULL;
}
if (em_end > end) {
if (!split) {
split = split2;
split2 = NULL;
if (!split)
goto remove_em;
}
split->start = end;
split->len = em_end - end;
split->block_start = em->block_start;
split->flags = flags;
split->generation = gen;
if (em->block_start < EXTENT_MAP_LAST_BYTE) {
split->orig_block_len = max(em->block_len,
em->orig_block_len);
split->ram_bytes = em->ram_bytes;
if (compressed) {
split->block_len = em->block_len;
split->orig_start = em->orig_start;
} else {
const u64 diff = end - em->start;
split->block_len = split->len;
split->block_start += diff;
split->orig_start = em->orig_start;
}
} else {
split->ram_bytes = split->len;
split->orig_start = split->start;
split->block_len = 0;
split->orig_block_len = 0;
}
if (extent_map_in_tree(em)) {
replace_extent_mapping(inode, em, split, modified);
} else {
int ret;
ret = add_extent_mapping(inode, split, modified);
/* Logic error, shouldn't happen. */
ASSERT(ret == 0);
if (WARN_ON(ret != 0) && modified)
btrfs_set_inode_full_sync(inode);
}
free_extent_map(split);
split = NULL;
}
remove_em:
if (extent_map_in_tree(em)) {
/*
* If the extent map is still in the tree it means that
* either of the following is true:
*
* 1) It fits entirely in our range (doesn't end beyond
* it or starts before it);
*
* 2) It starts before our range and/or ends after our
* range, and we were not able to allocate the extent
* maps for split operations, @split and @split2.
*
* If we are at case 2) then we just remove the entire
* extent map - this is fine since if anyone needs it to
* access the subranges outside our range, will just
* load it again from the subvolume tree's file extent
* item. However if the extent map was in the list of
* modified extents, then we must mark the inode for a
* full fsync, otherwise a fast fsync will miss this
* extent if it's new and needs to be logged.
*/
if ((em->start < start || em_end > end) && modified) {
ASSERT(!split);
btrfs_set_inode_full_sync(inode);
}
remove_extent_mapping(inode, em);
}
/*
* Once for the tree reference (we replaced or removed the
* extent map from the tree).
*/
free_extent_map(em);
next:
/* Once for us (for our lookup reference). */
free_extent_map(em);
em = next_em;
}
write_unlock(&em_tree->lock);
free_extent_map(split);
free_extent_map(split2);
}
/*
* Replace a range in the inode's extent map tree with a new extent map.
*
* @inode: The target inode.
* @new_em: The new extent map to add to the inode's extent map tree.
* @modified: Indicate if the new extent map should be added to the list of
* modified extents (for fast fsync tracking).
*
* Drops all the extent maps in the inode's extent map tree that intersect the
* range of the new extent map and adds the new extent map to the tree.
* The caller should have locked an appropriate file range in the inode's io
* tree before calling this function.
*/
int btrfs_replace_extent_map_range(struct btrfs_inode *inode,
struct extent_map *new_em,
bool modified)
{
const u64 end = new_em->start + new_em->len - 1;
struct extent_map_tree *tree = &inode->extent_tree;
int ret;
ASSERT(!extent_map_in_tree(new_em));
/*
* The caller has locked an appropriate file range in the inode's io
* tree, but getting -EEXIST when adding the new extent map can still
* happen in case there are extents that partially cover the range, and
* this is due to two tasks operating on different parts of the extent.
* See commit 18e83ac75bfe67 ("Btrfs: fix unexpected EEXIST from
* btrfs_get_extent") for an example and details.
*/
do {
btrfs_drop_extent_map_range(inode, new_em->start, end, false);
write_lock(&tree->lock);
ret = add_extent_mapping(inode, new_em, modified);
write_unlock(&tree->lock);
} while (ret == -EEXIST);
return ret;
}
/*
* Split off the first pre bytes from the extent_map at [start, start + len],
* and set the block_start for it to new_logical.
*
* This function is used when an ordered_extent needs to be split.
*/
int split_extent_map(struct btrfs_inode *inode, u64 start, u64 len, u64 pre,
u64 new_logical)
{
struct extent_map_tree *em_tree = &inode->extent_tree;
struct extent_map *em;
struct extent_map *split_pre = NULL;
struct extent_map *split_mid = NULL;
int ret = 0;
unsigned long flags;
ASSERT(pre != 0);
ASSERT(pre < len);
split_pre = alloc_extent_map();
if (!split_pre)
return -ENOMEM;
split_mid = alloc_extent_map();
if (!split_mid) {
ret = -ENOMEM;
goto out_free_pre;
}
lock_extent(&inode->io_tree, start, start + len - 1, NULL);
write_lock(&em_tree->lock);
em = lookup_extent_mapping(em_tree, start, len);
if (!em) {
ret = -EIO;
goto out_unlock;
}
ASSERT(em->len == len);
ASSERT(!extent_map_is_compressed(em));
ASSERT(em->block_start < EXTENT_MAP_LAST_BYTE);
ASSERT(em->flags & EXTENT_FLAG_PINNED);
ASSERT(!(em->flags & EXTENT_FLAG_LOGGING));
ASSERT(!list_empty(&em->list));
flags = em->flags;
em->flags &= ~EXTENT_FLAG_PINNED;
/* First, replace the em with a new extent_map starting from * em->start */
split_pre->start = em->start;
split_pre->len = pre;
split_pre->orig_start = split_pre->start;
split_pre->block_start = new_logical;
split_pre->block_len = split_pre->len;
split_pre->orig_block_len = split_pre->block_len;
split_pre->ram_bytes = split_pre->len;
split_pre->flags = flags;
split_pre->generation = em->generation;
replace_extent_mapping(inode, em, split_pre, 1);
/*
* Now we only have an extent_map at:
* [em->start, em->start + pre]
*/
/* Insert the middle extent_map. */
split_mid->start = em->start + pre;
split_mid->len = em->len - pre;
split_mid->orig_start = split_mid->start;
split_mid->block_start = em->block_start + pre;
split_mid->block_len = split_mid->len;
split_mid->orig_block_len = split_mid->block_len;
split_mid->ram_bytes = split_mid->len;
split_mid->flags = flags;
split_mid->generation = em->generation;
add_extent_mapping(inode, split_mid, 1);
/* Once for us */
free_extent_map(em);
/* Once for the tree */
free_extent_map(em);
out_unlock:
write_unlock(&em_tree->lock);
unlock_extent(&inode->io_tree, start, start + len - 1, NULL);
free_extent_map(split_mid);
out_free_pre:
free_extent_map(split_pre);
return ret;
}
struct btrfs_em_shrink_ctx {
long nr_to_scan;
long scanned;
u64 last_ino;
u64 last_root;
};
static long btrfs_scan_inode(struct btrfs_inode *inode, struct btrfs_em_shrink_ctx *ctx)
{
const u64 cur_fs_gen = btrfs_get_fs_generation(inode->root->fs_info);
struct extent_map_tree *tree = &inode->extent_tree;
long nr_dropped = 0;
struct rb_node *node;
/*
* Take the mmap lock so that we serialize with the inode logging phase
* of fsync because we may need to set the full sync flag on the inode,
* in case we have to remove extent maps in the tree's list of modified
* extents. If we set the full sync flag in the inode while an fsync is
* in progress, we may risk missing new extents because before the flag
* is set, fsync decides to only wait for writeback to complete and then
* during inode logging it sees the flag set and uses the subvolume tree
* to find new extents, which may not be there yet because ordered
* extents haven't completed yet.
*
* We also do a try lock because otherwise we could deadlock. This is
* because the shrinker for this filesystem may be invoked while we are
* in a path that is holding the mmap lock in write mode. For example in
* a reflink operation while COWing an extent buffer, when allocating
* pages for a new extent buffer and under memory pressure, the shrinker
* may be invoked, and therefore we would deadlock by attempting to read
* lock the mmap lock while we are holding already a write lock on it.
*/
if (!down_read_trylock(&inode->i_mmap_lock))
return 0;
/*
* We want to be fast because we can be called from any path trying to
* allocate memory, so if the lock is busy we don't want to spend time
* waiting for it - either some task is about to do IO for the inode or
* we may have another task shrinking extent maps, here in this code, so
* skip this inode.
*/
if (!write_trylock(&tree->lock)) {
up_read(&inode->i_mmap_lock);
return 0;
}
node = rb_first_cached(&tree->map);
while (node) {
struct extent_map *em;
em = rb_entry(node, struct extent_map, rb_node);
node = rb_next(node);
ctx->scanned++;
if (em->flags & EXTENT_FLAG_PINNED)
goto next;
/*
* If the inode is in the list of modified extents (new) and its
* generation is the same (or is greater than) the current fs
* generation, it means it was not yet persisted so we have to
* set the full sync flag so that the next fsync will not miss
* it.
*/
if (!list_empty(&em->list) && em->generation >= cur_fs_gen)
btrfs_set_inode_full_sync(inode);
remove_extent_mapping(inode, em);
trace_btrfs_extent_map_shrinker_remove_em(inode, em);
/* Drop the reference for the tree. */
free_extent_map(em);
nr_dropped++;
next:
if (ctx->scanned >= ctx->nr_to_scan)
break;
/*
* Stop if we need to reschedule or there's contention on the
* lock. This is to avoid slowing other tasks trying to take the
* lock and because the shrinker might be called during a memory
* allocation path and we want to avoid taking a very long time
* and slowing down all sorts of tasks.
*/
if (need_resched() || rwlock_needbreak(&tree->lock))
break;
}
write_unlock(&tree->lock);
up_read(&inode->i_mmap_lock);
return nr_dropped;
}
static long btrfs_scan_root(struct btrfs_root *root, struct btrfs_em_shrink_ctx *ctx)
{
struct btrfs_inode *inode;
long nr_dropped = 0;
u64 min_ino = ctx->last_ino + 1;
inode = btrfs_find_first_inode(root, min_ino);
while (inode) {
nr_dropped += btrfs_scan_inode(inode, ctx);
min_ino = btrfs_ino(inode) + 1;
ctx->last_ino = btrfs_ino(inode);
btrfs_add_delayed_iput(inode);
if (ctx->scanned >= ctx->nr_to_scan)
break;
/*
* We may be called from memory allocation paths, so we don't
* want to take too much time and slowdown tasks.
*/
if (need_resched())
break;
inode = btrfs_find_first_inode(root, min_ino);
}
if (inode) {
/*
* There are still inodes in this root or we happened to process
* the last one and reached the scan limit. In either case set
* the current root to this one, so we'll resume from the next
* inode if there is one or we will find out this was the last
* one and move to the next root.
*/
ctx->last_root = btrfs_root_id(root);
} else {
/*
* No more inodes in this root, set extent_map_shrinker_last_ino to 0 so
* that when processing the next root we start from its first inode.
*/
ctx->last_ino = 0;
ctx->last_root = btrfs_root_id(root) + 1;
}
return nr_dropped;
}
long btrfs_free_extent_maps(struct btrfs_fs_info *fs_info, long nr_to_scan)
{
struct btrfs_em_shrink_ctx ctx;
u64 start_root_id;
u64 next_root_id;
bool cycled = false;
long nr_dropped = 0;
ctx.scanned = 0;
ctx.nr_to_scan = nr_to_scan;
/*
* In case we have multiple tasks running this shrinker, make the next
* one start from the next inode in case it starts before we finish.
*/
spin_lock(&fs_info->extent_map_shrinker_lock);
ctx.last_ino = fs_info->extent_map_shrinker_last_ino;
fs_info->extent_map_shrinker_last_ino++;
ctx.last_root = fs_info->extent_map_shrinker_last_root;
spin_unlock(&fs_info->extent_map_shrinker_lock);
start_root_id = ctx.last_root;
next_root_id = ctx.last_root;
if (trace_btrfs_extent_map_shrinker_scan_enter_enabled()) {
s64 nr = percpu_counter_sum_positive(&fs_info->evictable_extent_maps);
trace_btrfs_extent_map_shrinker_scan_enter(fs_info, nr_to_scan,
nr, ctx.last_root,
ctx.last_ino);
}
/*
* We may be called from memory allocation paths, so we don't want to
* take too much time and slowdown tasks, so stop if we need reschedule.
*/
while (ctx.scanned < ctx.nr_to_scan && !need_resched()) {
struct btrfs_root *root;
unsigned long count;
spin_lock(&fs_info->fs_roots_radix_lock);
count = radix_tree_gang_lookup(&fs_info->fs_roots_radix,
(void **)&root,
(unsigned long)next_root_id, 1);
if (count == 0) {
spin_unlock(&fs_info->fs_roots_radix_lock);
if (start_root_id > 0 && !cycled) {
next_root_id = 0;
ctx.last_root = 0;
ctx.last_ino = 0;
cycled = true;
continue;
}
break;
}
next_root_id = btrfs_root_id(root) + 1;
root = btrfs_grab_root(root);
spin_unlock(&fs_info->fs_roots_radix_lock);
if (!root)
continue;
if (is_fstree(btrfs_root_id(root)))
nr_dropped += btrfs_scan_root(root, &ctx);
btrfs_put_root(root);
}
/*
* In case of multiple tasks running this extent map shrinking code this
* isn't perfect but it's simple and silences things like KCSAN. It's
* not possible to know which task made more progress because we can
* cycle back to the first root and first inode if it's not the first
* time the shrinker ran, see the above logic. Also a task that started
* later may finish ealier than another task and made less progress. So
* make this simple and update to the progress of the last task that
* finished, with the occasional possiblity of having two consecutive
* runs of the shrinker process the same inodes.
*/
spin_lock(&fs_info->extent_map_shrinker_lock);
fs_info->extent_map_shrinker_last_ino = ctx.last_ino;
fs_info->extent_map_shrinker_last_root = ctx.last_root;
spin_unlock(&fs_info->extent_map_shrinker_lock);
if (trace_btrfs_extent_map_shrinker_scan_exit_enabled()) {
s64 nr = percpu_counter_sum_positive(&fs_info->evictable_extent_maps);
trace_btrfs_extent_map_shrinker_scan_exit(fs_info, nr_dropped,
nr, ctx.last_root,
ctx.last_ino);
}
return nr_dropped;
}