btrfs-progs: Return earlier for previous item

Follow kernel code to return earlier for btrfs_previous_item() function.

Before this patch, btrfs_previous_item() doesn't use its min_objectid to
exit, this makes caller to check key to exit, and if caller doesn't
check, it will iterate all previous item.

This patch will check min_objectid and type, to early return and save
some time.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/ctree.c b/ctree.c
index 933833b..6875bb4 100644 (file)
--- a/ctree.c
+++ b/ctree.c
@@ -2880,6 +2880,7 @@ int btrfs_previous_item(struct btrfs_root *root,
 {
        struct btrfs_key found_key;
        struct extent_buffer *leaf;
+       u32 nritems;
        int ret;
 
        while(1) {
@@ -2891,9 +2892,20 @@ int btrfs_previous_item(struct btrfs_root *root,
                        path->slots[0]--;
                }
                leaf = path->nodes[0];
+               nritems = btrfs_header_nritems(leaf);
+               if (nritems == 0)
+                       return 1;
+               if (path->slots[0] == nritems)
+                       path->slots[0]--;
+
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+               if (found_key.objectid < min_objectid)
+                       break;
                if (found_key.type == type)
                        return 0;
+               if (found_key.objectid == min_objectid &&
+                   found_key.type < type)
+                       break;
        }
        return 1;
 }