btrfs: delete chunk allocation attemp when setting block group ro

Below test will fail currently:
      mkfs.ext4 -F /dev/sda
      btrfs-convert /dev/sda
      mount /dev/sda /mnt
      btrfs device add -f /dev/sdb /mnt
      btrfs balance start -v -dconvert=raid1 -mconvert=raid1 /mnt

The reason is there are some block groups with usage 0, but the whole
disk hasn't free space to allocate new chunk, so we even can't set such
block group readonly. This patch deletes the chunk allocation when
setting block group ro. For META, we already have reserve. But for
SYSTEM, we don't have, so the check_system_chunk is still required.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 857a859948a35bf7c964fe57cb05d3b3f1d366c5..50de1fa6fc9e73075052130530535db29796feb0 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8482,14 +8482,6 @@ int btrfs_set_block_group_ro(struct btrfs_root *root,
        if (IS_ERR(trans))
                return PTR_ERR(trans);
 
-       alloc_flags = update_block_group_flags(root, cache->flags);
-       if (alloc_flags != cache->flags) {
-               ret = do_chunk_alloc(trans, root, alloc_flags,
-                                    CHUNK_ALLOC_FORCE);
-               if (ret < 0)
-                       goto out;
-       }
-
        ret = set_block_group_ro(cache, 0);
        if (!ret)
                goto out;
@@ -8500,6 +8492,11 @@ int btrfs_set_block_group_ro(struct btrfs_root *root,
                goto out;
        ret = set_block_group_ro(cache, 0);
 out:
+       if (cache->flags & BTRFS_BLOCK_GROUP_SYSTEM) {
+               alloc_flags = update_block_group_flags(root, cache->flags);
+               check_system_chunk(trans, root, alloc_flags);
+       }
+
        btrfs_end_transaction(trans, root);
        return ret;
 }