btrfs: qgroup: correctly model root qgroup rsv in convert

commit 141fb8cd206ace23c02cd2791c6da52c1d77d42a upstream.

We use add_root_meta_rsv and sub_root_meta_rsv to track prealloc and
pertrans reservations for subvolumes when quotas are enabled. The
convert function does not properly increment pertrans after decrementing
prealloc, so the count is not accurate.

Note: we check that the fs is not read-only to mirror the logic in
qgroup_convert_meta, which checks that before adding to the pertrans rsv.

Fixes: 8287475a2055 ("btrfs: qgroup: Use root::qgroup_meta_rsv_* to record qgroup meta reserved space")
CC: stable@vger.kernel.org # 6.1+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 34278cb5f9643cf0f33d4fea1a45a0a0b621d839..c50cabf69415f08f605596165767f165192b0922 100644 (file)
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -4080,6 +4080,8 @@ void btrfs_qgroup_convert_reserved_meta(struct btrfs_root *root, int num_bytes)
                                      BTRFS_QGROUP_RSV_META_PREALLOC);
        trace_qgroup_meta_convert(root, num_bytes);
        qgroup_convert_meta(fs_info, root->root_key.objectid, num_bytes);
+       if (!sb_rdonly(fs_info->sb))
+               add_root_meta_rsv(root, num_bytes, BTRFS_QGROUP_RSV_META_PERTRANS);
 }
 
 /*