ceph: carry snapshot creation time with inodes

MDS InodeStat v3 wire structures include a trailing snapshot creation
time member. Unmarshall this and retain it for a future vxattr.
Signed-off-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/inode.c

@@ -813,6 +813,7 @@ static int fill_inode(struct inode *inode, struct page *locked_page,
 		dout("%p mode 0%o uid.gid %d.%d\n", inode, inode->i_mode,
 		     from_kuid(&init_user_ns, inode->i_uid),
 		     from_kgid(&init_user_ns, inode->i_gid));
+		ceph_decode_timespec64(&ci->i_snap_btime, &iinfo->snap_btime);
 	}
 
 	if ((new_version || (new_issued & CEPH_CAP_LINK_SHARED)) &&

fs/ceph/mds_client.c

@@ -166,6 +166,15 @@ static int parse_reply_info_in(void **p, void *end,
 			info->dir_pin = -ENODATA;
 		}
 
+		/* snapshot birth time, remains zero for v<=2 */
+		if (struct_v >= 3) {
+			ceph_decode_need(p, end, sizeof(info->snap_btime), bad);
+			ceph_decode_copy(p, &info->snap_btime,
+					 sizeof(info->snap_btime));
+		} else {
+			memset(&info->snap_btime, 0, sizeof(info->snap_btime));
+		}
+
 		*p = end;
 	} else {
 		if (features & CEPH_FEATURE_MDS_INLINE_DATA) {
@@ -198,6 +207,7 @@ static int parse_reply_info_in(void **p, void *end,
 		}
 
 		info->dir_pin = -ENODATA;
+		/* info->snap_btime remains zero */
 	}
 	return 0;
 bad:

fs/ceph/mds_client.h

@@ -69,6 +69,7 @@ struct ceph_mds_reply_info_in {
 	u64 max_bytes;
 	u64 max_files;
 	s32 dir_pin;
+	struct ceph_timespec snap_btime;
 };
 
 struct ceph_mds_reply_dir_entry {

fs/ceph/super.h

@@ -384,6 +384,7 @@ struct ceph_inode_info {
 	int i_snap_realm_counter; /* snap realm (if caps) */
 	struct list_head i_snap_realm_item;
 	struct list_head i_snap_flush_item;
+	struct timespec64 i_snap_btime;
 
 	struct work_struct i_work;
 	unsigned long  i_work_mask;