Snapshot creation with btrfs_qgroup_inherit structure can easily lead to
qgroup inconsistent.
The inconsistency itself is not a big deal, but due to the limitation of
the ioctl, we can't inform user space to do a rescan.
Thus it's recommended to use BTRFS_IOC_QGROUP_ASSIGN to assign qgroup
relation other than do it in snapshot creation.
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
---
include/uapi/linux/btrfs.h | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index dc8675d892a4..b8881910bde3 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -132,6 +132,17 @@ struct btrfs_ioctl_vol_args_v2 {
union {
struct {
__u64 size;
+ /*
+ * WARNING: Don't use this structure to assign qgroup
+ * for snapshot creation.
+ *
+ * Such inheritance for snapshot can lead to qgroup
+ * inconsistent due to massive extent ownership change.
+ *
+ * Due to the limitation of snapshot creation ioctl, we
+ * can't inform user space to do a rescan.
+ * Please use BTRFS_IOC_QGROUP_ASSIGN instead.
+ */
struct btrfs_qgroup_inherit __user *qgroup_inherit;
};
__u64 unused[4];
--
2.26.2
