Btrfs: fix to search one more bitmap for cluster setup

Suppose there are two bitmaps [0, 256], [256, 512] and one extent
[100, 120] in the free space cache, and we want to setup a cluster
with offset=100, bytes=50.

In this case, there will be only one bitmap [256, 512] in the temporary
bitmaps list, and then setup_cluster_bitmap() won't search bitmap [0, 256].

The cause is, the list is constructed in setup_cluster_no_bitmap(),
and only bitmaps with bitmap_entry->offset >= offset will be added
into the list, and the very bitmap that convers offset has
bitmap_entry->offset <= offset.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.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 181760f9d2abb7aa0902a65cc93effb3f3d1b41d..8f792f41feabd3419c865c918cf7c24b5557945c 100644 (file)
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2453,10 +2453,22 @@ setup_cluster_bitmap(struct btrfs_block_group_cache *block_group,
        struct btrfs_free_space *entry;
        struct rb_node *node;
        int ret = -ENOSPC;
+       u64 bitmap_offset = offset_to_bitmap(ctl, offset);
 
        if (ctl->total_bitmaps == 0)
                return -ENOSPC;
 
+       /*
+        * The bitmap that covers offset won't be in the list unless offset
+        * is just its start offset.
+        */
+       entry = list_first_entry(bitmaps, struct btrfs_free_space, list);
+       if (entry->offset != bitmap_offset) {
+               entry = tree_search_offset(ctl, bitmap_offset, 1, 0);
+               if (entry && list_empty(&entry->list))
+                       list_add(&entry->list, bitmaps);
+       }
+
        /*
         * First check our cached list of bitmaps and see if there is an entry
         * here that will work.