btrfs: qgroup: set quota enabled bit if quota disable fails flushing reservations

Before waiting for the rescan worker to finish and flushing reservations,
we clear the BTRFS_FS_QUOTA_ENABLED flag from fs_info. If we fail flushing
reservations we leave with the flag not set which is not correct since
quotas are still enabled - we must set back the flag on error paths, such
as when we fail to start a transaction, except for error paths that abort
a transaction. The reservation flushing happens very early before we do
any operation that actually disables quotas and before we start a
transaction, so set back BTRFS_FS_QUOTA_ENABLED if it fails.

Fixes: af0e2aa ("btrfs: qgroup: flush reservations during quota disable")
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: fdmanana

fs/btrfs/qgroup.c

@@ -1334,11 +1334,14 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info)
 
 	/*
 	 * We have nothing held here and no trans handle, just return the error
-	 * if there is one.
+	 * if there is one and set back the quota enabled bit since we didn't
+	 * actually disable quotas.
 	 */
 	ret = flush_reservations(fs_info);
-	if (ret)
+	if (ret) {
+		set_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
 		return ret;
+	}
 
 	/*
 	 * 1 For the root item