Btrfs: make sure a bitmap has enough bytes

We have only been checking for min_bytes available in bitmap entries, but we
won't successfully setup a bitmap cluster unless it has at least bytes in the
bitmap, so in the common case min_bytes is 4k and we want something like 2MB, so
if there are a bunch of bitmap entries with less than 2mb's in them, we'll
search all them anyway, which is suboptimal.  Fix this check.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index efe20032e4a1385f3c8ada815eab5c82c93fce9b..6e7406932341b93dd0204526260b435cc5cb1d9b 100644 (file)
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2475,7 +2475,7 @@ setup_cluster_bitmap(struct btrfs_block_group_cache *block_group,
        }
 
        list_for_each_entry(entry, bitmaps, list) {
-               if (entry->bytes < min_bytes)
+               if (entry->bytes < bytes)
                        continue;
                ret = btrfs_bitmap_cluster(block_group, entry, cluster, offset,
                                           bytes, cont1_bytes, min_bytes);