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author | Qu Wenruo <wqu@suse.com> | 2020-02-13 14:11:04 +0800 |
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committer | David Sterba <dsterba@suse.com> | 2020-05-25 11:25:16 +0200 |
commit | a37f232b7b65789cadc9834d389f6390de11b583 (patch) | |
tree | 4b36e9c656727c9a4f6511074400e85632047ff6 /fs/btrfs/backref.h | |
parent | 78d933c79cb649906577715af15400c7724ca633 (diff) | |
download | linux-a37f232b7b65789cadc9834d389f6390de11b583.tar.gz linux-a37f232b7b65789cadc9834d389f6390de11b583.tar.bz2 linux-a37f232b7b65789cadc9834d389f6390de11b583.zip |
btrfs: backref: introduce the skeleton of btrfs_backref_iter
Due to the complex nature of btrfs extent tree, when we want to iterate
all backrefs of one extent, this involves quite a lot of work, like
searching the EXTENT_ITEM/METADATA_ITEM, iteration through inline and keyed
backrefs.
Normally this would result in a complex code, something like:
btrfs_search_slot()
/* Ensure we are at EXTENT_ITEM/METADATA_ITEM */
while (1) { /* Loop for extent tree items */
while (ptr < end) { /* Loop for inlined items */
/* Real work here */
}
next:
ret = btrfs_next_item()
/* Ensure we're still at keyed item for specified bytenr */
}
The idea of btrfs_backref_iter is to avoid such complex and hard to
read code structure, but something like the following:
iter = btrfs_backref_iter_alloc();
ret = btrfs_backref_iter_start(iter, bytenr);
if (ret < 0)
goto out;
for (; ; ret = btrfs_backref_iter_next(iter)) {
/* Real work here */
}
out:
btrfs_backref_iter_free(iter);
This patch is just the skeleton + btrfs_backref_iter_start() code.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/backref.h')
-rw-r--r-- | fs/btrfs/backref.h | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h index 723d6da99114..4ae37fad819a 100644 --- a/fs/btrfs/backref.h +++ b/fs/btrfs/backref.h @@ -78,4 +78,42 @@ struct prelim_ref { u64 wanted_disk_byte; }; +/* + * Iterate backrefs of one extent. + * + * Now it only supports iteration of tree block in commit root. + */ +struct btrfs_backref_iter { + u64 bytenr; + struct btrfs_path *path; + struct btrfs_fs_info *fs_info; + struct btrfs_key cur_key; + u32 item_ptr; + u32 cur_ptr; + u32 end_ptr; +}; + +struct btrfs_backref_iter *btrfs_backref_iter_alloc( + struct btrfs_fs_info *fs_info, gfp_t gfp_flag); + +static inline void btrfs_backref_iter_free(struct btrfs_backref_iter *iter) +{ + if (!iter) + return; + btrfs_free_path(iter->path); + kfree(iter); +} + +int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr); + +static inline void btrfs_backref_iter_release(struct btrfs_backref_iter *iter) +{ + iter->bytenr = 0; + iter->item_ptr = 0; + iter->cur_ptr = 0; + iter->end_ptr = 0; + btrfs_release_path(iter->path); + memset(&iter->cur_key, 0, sizeof(iter->cur_key)); +} + #endif |