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>
(cherry picked from commit 2f0810880f082fa8ba66ab2c33b02e4ff9770a5e)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index f461ffa3fa3e61fd67ad2d9ebdf14efe962d514f..9d2e5818993c407d6cb4f672fb1b136e1555d209 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8483,14 +8483,6 @@ 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;
@@ -8501,6 +8493,11 @@ 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;
 }