ceph: support getting ceph.dir.rsnaps vxattr

Add support for grabbing the rsnaps value out of the inode info in
traces, and exposing that via ceph.dir.rsnaps xattr.
Signed-off-by: Yanhu Cao <gmayyyha@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/inode.c

@@ -895,6 +895,7 @@ int ceph_fill_inode(struct inode *inode, struct page *locked_page,
 			ci->i_rfiles = le64_to_cpu(info->rfiles);
 			ci->i_rsubdirs = le64_to_cpu(info->rsubdirs);
 			ci->i_dir_pin = iinfo->dir_pin;
+			ci->i_rsnaps = iinfo->rsnaps;
 			ceph_decode_timespec64(&ci->i_rctime, &info->rctime);
 		}
 	}

fs/ceph/mds_client.c

@@ -176,6 +176,13 @@ static int parse_reply_info_in(void **p, void *end,
 			memset(&info->snap_btime, 0, sizeof(info->snap_btime));
 		}
 
+		/* snapshot count, remains zero for v<=3 */
+		if (struct_v >= 4) {
+			ceph_decode_64_safe(p, end, info->rsnaps, bad);
+		} else {
+			info->rsnaps = 0;
+		}
+
 		*p = end;
 	} else {
 		if (features & CEPH_FEATURE_MDS_INLINE_DATA) {
@@ -214,7 +221,7 @@ static int parse_reply_info_in(void **p, void *end,
 		}
 
 		info->dir_pin = -ENODATA;
-		/* info->snap_btime remains zero */
+		/* info->snap_btime and info->rsnaps remain zero */
 	}
 	return 0;
 bad:

fs/ceph/mds_client.h

@@ -88,6 +88,7 @@ struct ceph_mds_reply_info_in {
 	s32 dir_pin;
 	struct ceph_timespec btime;
 	struct ceph_timespec snap_btime;
+	u64 rsnaps;
 	u64 change_attr;
 };
 

fs/ceph/super.h

@@ -334,7 +334,7 @@ struct ceph_inode_info {
 
 	/* for dirs */
 	struct timespec64 i_rctime;
-	u64 i_rbytes, i_rfiles, i_rsubdirs;
+	u64 i_rbytes, i_rfiles, i_rsubdirs, i_rsnaps;
 	u64 i_files, i_subdirs;
 
 	/* quotas */

fs/ceph/xattr.c

@@ -233,6 +233,12 @@ static ssize_t ceph_vxattrcb_dir_rsubdirs(struct ceph_inode_info *ci, char *val,
 	return ceph_fmt_xattr(val, size, "%lld", ci->i_rsubdirs);
 }
 
+static ssize_t ceph_vxattrcb_dir_rsnaps(struct ceph_inode_info *ci, char *val,
+					  size_t size)
+{
+	return ceph_fmt_xattr(val, size, "%lld", ci->i_rsnaps);
+}
+
 static ssize_t ceph_vxattrcb_dir_rbytes(struct ceph_inode_info *ci, char *val,
 					size_t size)
 {
@@ -384,6 +390,7 @@ static struct ceph_vxattr ceph_dir_vxattrs[] = {
 	XATTR_RSTAT_FIELD(dir, rentries),
 	XATTR_RSTAT_FIELD(dir, rfiles),
 	XATTR_RSTAT_FIELD(dir, rsubdirs),
+	XATTR_RSTAT_FIELD(dir, rsnaps),
 	XATTR_RSTAT_FIELD(dir, rbytes),
 	XATTR_RSTAT_FIELD(dir, rctime),
 	{