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btrfs: use cached state when looking for delalloc ranges with fiemap

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During fiemap, whenever we find a hole or prealloc extent, we will look
for delalloc in that range, and one of the things we do for that is to
find out ranges in the inode's io_tree marked with EXTENT_DELALLOC, using
calls to count_range_bits().

Since we process file extents from left to right, if we have a file with
several holes or prealloc extents, we benefit from keeping a cached extent
state record for calls to count_range_bits(). Most of the time the last
extent state record we visited in one call to count_range_bits() matches
the first extent state record we will use in the next call to
count_range_bits(), so there's a benefit here. So use an extent state
record to cache results from count_range_bits() calls during fiemap.

This change is part of a patchset that has the goal to make performance
better for applications that use lseek's SEEK_HOLE and SEEK_DATA modes to
iterate over the extents of a file. Two examples are the cp program from
coreutils 9.0+ and the tar program (when using its --sparse / -S option).
A sample test and results are listed in the changelog of the last patch
in the series:

  1/9 btrfs: remove leftover setting of EXTENT_UPTODATE state in an inode's io_tree
  2/9 btrfs: add an early exit when searching for delalloc range for lseek/fiemap
  3/9 btrfs: skip unnecessary delalloc searches during lseek/fiemap
  4/9 btrfs: search for delalloc more efficiently during lseek/fiemap
  5/9 btrfs: remove no longer used btrfs_next_extent_map()
  6/9 btrfs: allow passing a cached state record to count_range_bits()
  7/9 btrfs: update stale comment for count_range_bits()
  8/9 btrfs: use cached state when looking for delalloc ranges with fiemap
  9/9 btrfs: use cached state when looking for delalloc ranges with lseek

Reported-by: Wang Yugui <wangyugui@e16-tech.com>
Link: https://lore.kernel.org/linux-btrfs/20221106073028.71F9.409509F4@e16-tech.com/
Link: https://lore.kernel.org/linux-btrfs/CAL3q7H5NSVicm7nYBJ7x8fFkDpno8z3PYt5aPU43Bajc1H0h1Q@mail.gmail.com/
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana 2022-11-11 11:50:34 +00:00 committed by David Sterba
parent 1ee51a0625
commit b3e744fe6d
3 changed files with 18 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
fs/btrfs/extent_io.c
View File

@ -3698,6 +3698,7 @@ static int fiemap_search_slot(struct btrfs_inode *inode, struct btrfs_path *path
static int fiemap_process_hole(struct btrfs_inode *inode,
struct fiemap_extent_info *fieinfo,
struct fiemap_cache *cache,
struct extent_state **delalloc_cached_state,
struct btrfs_backref_share_check_ctx *backref_ctx,
u64 disk_bytenr, u64 extent_offset,
u64 extent_gen,
@ -3722,6 +3723,7 @@ static int fiemap_process_hole(struct btrfs_inode *inode,
bool delalloc;
delalloc = btrfs_find_delalloc_in_range(inode, cur_offset, end,
delalloc_cached_state,
&delalloc_start,
&delalloc_end);
if (!delalloc)
@ -3892,6 +3894,7 @@ int extent_fiemap(struct btrfs_inode *inode, struct fiemap_extent_info *fieinfo,
{
const u64 ino = btrfs_ino(inode);
struct extent_state *cached_state = NULL;
struct extent_state *delalloc_cached_state = NULL;
struct btrfs_path *path;
struct fiemap_cache cache = { 0 };
struct btrfs_backref_share_check_ctx *backref_ctx;
@ -3966,6 +3969,7 @@ int extent_fiemap(struct btrfs_inode *inode, struct fiemap_extent_info *fieinfo,
const u64 range_end = min(key.offset, lockend) - 1;
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx, 0, 0, 0,
prev_extent_end, range_end);
if (ret < 0) {
@ -4006,6 +4010,7 @@ int extent_fiemap(struct btrfs_inode *inode, struct fiemap_extent_info *fieinfo,
extent_len, flags);
} else if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx,
disk_bytenr, extent_offset,
extent_gen, key.offset,
@ -4013,6 +4018,7 @@ int extent_fiemap(struct btrfs_inode *inode, struct fiemap_extent_info *fieinfo,
} else if (disk_bytenr == 0) {
/* We have an explicit hole. */
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state,
backref_ctx, 0, 0, 0,
key.offset, extent_end - 1);
} else {
@ -4070,7 +4076,8 @@ check_eof_delalloc:
path = NULL;
if (!stopped && prev_extent_end < lockend) {
ret = fiemap_process_hole(inode, fieinfo, &cache, backref_ctx,
ret = fiemap_process_hole(inode, fieinfo, &cache,
&delalloc_cached_state, backref_ctx,
0, 0, 0, prev_extent_end, lockend - 1);
if (ret < 0)
goto out_unlock;
@ -4088,6 +4095,7 @@ check_eof_delalloc:
delalloc = btrfs_find_delalloc_in_range(inode,
prev_extent_end,
i_size - 1,
&delalloc_cached_state,
&delalloc_start,
&delalloc_end);
if (!delalloc)
@ -4102,6 +4110,7 @@ check_eof_delalloc:
out_unlock:
unlock_extent(&inode->io_tree, lockstart, lockend, &cached_state);
out:
free_extent_state(delalloc_cached_state);
btrfs_free_backref_share_ctx(backref_ctx);
btrfs_free_path(path);
return ret;

10
fs/btrfs/file.c
View File

@ -3214,6 +3214,7 @@ out:
* looping while it gets adjacent subranges, and merging them together.
*/
static bool find_delalloc_subrange(struct btrfs_inode *inode, u64 start, u64 end,
struct extent_state **cached_state,
bool *search_io_tree,
u64 *delalloc_start_ret, u64 *delalloc_end_ret)
{
@ -3236,7 +3237,7 @@ static bool find_delalloc_subrange(struct btrfs_inode *inode, u64 start, u64 end
delalloc_len = count_range_bits(&inode->io_tree,
delalloc_start_ret, end,
len, EXTENT_DELALLOC, 1,
NULL);
cached_state);
} else {
spin_unlock(&inode->lock);
}
@ -3324,6 +3325,8 @@ static bool find_delalloc_subrange(struct btrfs_inode *inode, u64 start, u64 end
* sector size aligned.
* @end: The end offset (inclusive value) of the search range.
* It does not need to be sector size aligned.
* @cached_state: Extent state record used for speeding up delalloc
* searches in the inode's io_tree. Can be NULL.
* @delalloc_start_ret: Output argument, set to the start offset of the
* subrange found with delalloc (may not be sector size
* aligned).
@ -3335,6 +3338,7 @@ static bool find_delalloc_subrange(struct btrfs_inode *inode, u64 start, u64 end
* end offsets of the subrange.
*/
bool btrfs_find_delalloc_in_range(struct btrfs_inode *inode, u64 start, u64 end,
struct extent_state **cached_state,
u64 *delalloc_start_ret, u64 *delalloc_end_ret)
{
u64 cur_offset = round_down(start, inode->root->fs_info->sectorsize);
@ -3348,7 +3352,7 @@ bool btrfs_find_delalloc_in_range(struct btrfs_inode *inode, u64 start, u64 end,
bool delalloc;
delalloc = find_delalloc_subrange(inode, cur_offset, end,
&search_io_tree,
cached_state, &search_io_tree,
&delalloc_start,
&delalloc_end);
if (!delalloc)
@ -3400,7 +3404,7 @@ static bool find_desired_extent_in_hole(struct btrfs_inode *inode, int whence,
u64 delalloc_end;
bool delalloc;
delalloc = btrfs_find_delalloc_in_range(inode, start, end,
delalloc = btrfs_find_delalloc_in_range(inode, start, end, NULL,
&delalloc_start, &delalloc_end);
if (delalloc && whence == SEEK_DATA) {
*start_ret = delalloc_start;

1
fs/btrfs/file.h
View File

@ -27,6 +27,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos,
size_t *write_bytes, bool nowait);
void btrfs_check_nocow_unlock(struct btrfs_inode *inode);
bool btrfs_find_delalloc_in_range(struct btrfs_inode *inode, u64 start, u64 end,
struct extent_state **cached_state,
u64 *delalloc_start_ret, u64 *delalloc_end_ret);
#endif