ceph: support getting ceph.dir.pin vxattr

Link: http://tracker.ceph.com/issues/37576
Signed-off-by: "Yan, Zheng" <[e-mail]>
Signed-off-by: Ilya Dryomov <[e-mail]>

fs/ceph/inode.c

···
 			ci->i_rbytes = le64_to_cpu(info->rbytes);
 			ci->i_rfiles = le64_to_cpu(info->rfiles);
 			ci->i_rsubdirs = le64_to_cpu(info->rsubdirs);
+			ci->i_dir_pin = iinfo->dir_pin;
 			ceph_decode_timespec64(&ci->i_rctime, &info->rctime);
 		}
 	}

fs/ceph/mds_client.c

···
 			ceph_decode_64_safe(p, end, change_attr, bad);
 		}
 
+		/* dir pin */
+		if (struct_v >= 2) {
+			ceph_decode_32_safe(p, end, info->dir_pin, bad);
+		} else {
+			info->dir_pin = -ENODATA;
+		}
+
 		*p = end;
 	} else {
 		if (features & CEPH_FEATURE_MDS_INLINE_DATA) {
···
 				*p += info->pool_ns_len;
 			}
 		}
+
+		info->dir_pin = -ENODATA;
 	}
 	return 0;
 bad:

fs/ceph/mds_client.h

···
 	char *pool_ns_data;
 	u64 max_bytes;
 	u64 max_files;
+	s32 dir_pin;
 };
 
 struct ceph_mds_reply_dir_entry {

fs/ceph/super.h

···
 	/* quotas */
 	u64 i_max_bytes, i_max_files;
 
+	s32 i_dir_pin;
+
 	struct rb_root i_fragtree;
 	int i_fragtree_nsplits;
 	struct mutex i_fragtree_mutex;

fs/ceph/xattr.c

···
 			ci->i_rctime.tv_nsec);
 }
 
-/* quotas */
+/* dir pin */
+static bool ceph_vxattrcb_dir_pin_exists(struct ceph_inode_info *ci)
+{
+	return ci->i_dir_pin != -ENODATA;
+}
 
+static size_t ceph_vxattrcb_dir_pin(struct ceph_inode_info *ci, char *val,
+                                    size_t size)
+{
+	return snprintf(val, size, "%d", (int)ci->i_dir_pin);
+}
+
+/* quotas */
 static bool ceph_vxattrcb_quota_exists(struct ceph_inode_info *ci)
 {
 	bool ret = false;
···
 	XATTR_RSTAT_FIELD(dir, rsubdirs),
 	XATTR_RSTAT_FIELD(dir, rbytes),
 	XATTR_RSTAT_FIELD(dir, rctime),
+	{
+		.name = "ceph.dir.pin",
+		.name_size = sizeof("ceph.dir_pin"),
+		.getxattr_cb = ceph_vxattrcb_dir_pin,
+		.exists_cb = ceph_vxattrcb_dir_pin_exists,
+		.flags = VXATTR_FLAG_HIDDEN,
+	},
 	{
 		.name = "ceph.quota",
 		.name_size = sizeof("ceph.quota"),