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authorQu Wenruo <wqu@suse.com>2020-02-13 14:11:04 +0800
committerDavid Sterba <dsterba@suse.com>2020-05-25 11:25:16 +0200
commita37f232b7b65789cadc9834d389f6390de11b583 (patch)
tree4b36e9c656727c9a4f6511074400e85632047ff6 /fs/btrfs/backref.h
parent78d933c79cb649906577715af15400c7724ca633 (diff)
downloadlinux-a37f232b7b65789cadc9834d389f6390de11b583.tar.bz2
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.h38
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