Btrfs: Protect the readonly flag of block group

The access for ro in btrfs_block_group_cache should be protected
because of the racy lock in relocation.

Signed-off-by: Wu Bo <wu.bo@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index db2057f262ad..a4db88da125e 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -6549,8 +6549,6 @@ static int set_block_group_ro(struct btrfs_block_group_cache *cache, int force)
         u64 min_allocable_bytes;
         int ret = -ENOSPC;
 
-        if (cache->ro)
-                return 0;
 
         /*
          * We need some metadata space and system metadata space for
@@ -6566,6 +6564,12 @@ static int set_block_group_ro(struct btrfs_block_group_cache *cache, int force)
 
         spin_lock(&sinfo->lock);
         spin_lock(&cache->lock);
+
+        if (cache->ro) {
+                ret = 0;
+                goto out;
+        }
+
         num_bytes = cache->key.offset - cache->reserved - cache->pinned -
                     cache->bytes_super - btrfs_block_group_used(&cache->item);
 
@@ -6579,7 +6583,7 @@ static int set_block_group_ro(struct btrfs_block_group_cache *cache, int force)
                 cache->ro = 1;
                 ret = 0;
         }
-
+out:
         spin_unlock(&cache->lock);
         spin_unlock(&sinfo->lock);
         return ret;