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

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>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 33cc3a9..704ae7c 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -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;

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index dc83996..da390f8 100644 (file)
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -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;

diff --git a/fs/btrfs/file.h b/fs/btrfs/file.h
index f3d794e..82b34fb 100644 (file)
--- a/fs/btrfs/file.h
+++ b/fs/btrfs/file.h
@@ -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