diff options
author | Arne Jansen <sensille@gmx.net> | 2011-09-13 09:18:10 (GMT) |
---|---|---|
committer | Jan Schmidt <list.btrfs@jan-o-sch.net> | 2012-07-10 13:14:42 (GMT) |
commit | 2f38b3e1900634e64a186873b3388b1bf85dabc0 (patch) | |
tree | 21017a51174be9ba31696e4e4c8daa18ce2d59f8 | |
parent | 630dc772ea51bca3ec6fac609f450cbe0cafd1d6 (diff) | |
download | linux-fsl-qoriq-2f38b3e1900634e64a186873b3388b1bf85dabc0.tar.xz |
Btrfs: add helper for tree enumeration
Often no exact match is wanted but just the next lower or
higher item. There's a lot of duplicated code throughout
btrfs to deal with the corner cases. This patch adds a
helper function that can facilitate searching.
Signed-off-by: Arne Jansen <sensille@gmx.net>
-rw-r--r-- | fs/btrfs/ctree.c | 72 | ||||
-rw-r--r-- | fs/btrfs/ctree.h | 3 |
2 files changed, 75 insertions, 0 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index bef68ab..fb21431 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -2789,6 +2789,78 @@ done: } /* + * helper to use instead of search slot if no exact match is needed but + * instead the next or previous item should be returned. + * When find_higher is true, the next higher item is returned, the next lower + * otherwise. + * When return_any and find_higher are both true, and no higher item is found, + * return the next lower instead. + * When return_any is true and find_higher is false, and no lower item is found, + * return the next higher instead. + * It returns 0 if any item is found, 1 if none is found (tree empty), and + * < 0 on error + */ +int btrfs_search_slot_for_read(struct btrfs_root *root, + struct btrfs_key *key, struct btrfs_path *p, + int find_higher, int return_any) +{ + int ret; + struct extent_buffer *leaf; + +again: + ret = btrfs_search_slot(NULL, root, key, p, 0, 0); + if (ret <= 0) + return ret; + /* + * a return value of 1 means the path is at the position where the + * item should be inserted. Normally this is the next bigger item, + * but in case the previous item is the last in a leaf, path points + * to the first free slot in the previous leaf, i.e. at an invalid + * item. + */ + leaf = p->nodes[0]; + + if (find_higher) { + if (p->slots[0] >= btrfs_header_nritems(leaf)) { + ret = btrfs_next_leaf(root, p); + if (ret <= 0) + return ret; + if (!return_any) + return 1; + /* + * no higher item found, return the next + * lower instead + */ + return_any = 0; + find_higher = 0; + btrfs_release_path(p); + goto again; + } + } else { + if (p->slots[0] >= btrfs_header_nritems(leaf)) { + /* we're sitting on an invalid slot */ + if (p->slots[0] == 0) { + ret = btrfs_prev_leaf(root, p); + if (ret <= 0) + return ret; + if (!return_any) + return 1; + /* + * no lower item found, return the next + * higher instead + */ + return_any = 0; + find_higher = 1; + btrfs_release_path(p); + goto again; + } + --p->slots[0]; + } + } + return 0; +} + +/* * adjust the pointers going up the tree, starting at level * making sure the right key of each node is points to 'key'. * This is used after shifting pointers to the left, so it stops diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 33088b0..27cf995 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -2856,6 +2856,9 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root ins_len, int cow); int btrfs_search_old_slot(struct btrfs_root *root, struct btrfs_key *key, struct btrfs_path *p, u64 time_seq); +int btrfs_search_slot_for_read(struct btrfs_root *root, + struct btrfs_key *key, struct btrfs_path *p, + int find_higher, int return_any); int btrfs_realloc_node(struct btrfs_trans_handle *trans, struct btrfs_root *root, struct extent_buffer *parent, int start_slot, int cache_only, u64 *last_ret, |