diff options
Diffstat (limited to 'fs/btrfs/qgroup.c')
| -rw-r--r-- | fs/btrfs/qgroup.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index 6c037f1252b7..071f7334f818 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -940,6 +940,14 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info) int ret = 0; int slot; + /* + * We need to have subvol_sem write locked, to prevent races between + * concurrent tasks trying to enable quotas, because we will unlock + * and relock qgroup_ioctl_lock before setting fs_info->quota_root + * and before setting BTRFS_FS_QUOTA_ENABLED. + */ + lockdep_assert_held_write(&fs_info->subvol_sem); + mutex_lock(&fs_info->qgroup_ioctl_lock); if (fs_info->quota_root) goto out; @@ -1117,8 +1125,19 @@ out_add_root: goto out_free_path; } + mutex_unlock(&fs_info->qgroup_ioctl_lock); + /* + * Commit the transaction while not holding qgroup_ioctl_lock, to avoid + * a deadlock with tasks concurrently doing other qgroup operations, such + * adding/removing qgroups or adding/deleting qgroup relations for example, + * because all qgroup operations first start or join a transaction and then + * lock the qgroup_ioctl_lock mutex. + * We are safe from a concurrent task trying to enable quotas, by calling + * this function, since we are serialized by fs_info->subvol_sem. + */ ret = btrfs_commit_transaction(trans); trans = NULL; + mutex_lock(&fs_info->qgroup_ioctl_lock); if (ret) goto out_free_path; |