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 20ed46c6ae268d654b3dfdf3e6dc89cc3825746e..3b2cf959f1bcf15b3a4079d92f76d998bbc39d7a 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;
 }