From a37f232b7b65789cadc9834d389f6390de11b583 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Thu, 13 Feb 2020 14:11:04 +0800 Subject: 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 Reviewed-by: Josef Bacik Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/backref.h | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) (limited to 'fs/btrfs/backref.h') 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 -- cgit v1.2.3-73-gaa49b