libceph: add support for CEPH_OSD_OP_SETALLOCHINT osd op

This is primarily for rbd's benefit and is supposed to combat
fragmentation:

"... knowing that rbd images have a 4m size, librbd can pass a hint
that will let the osd do the xfs allocation size ioctl on new files so
that they are allocated in 1m or 4m chunks.  We've seen cases where
users with rbd workloads have very high levels of fragmentation in xfs
and this would mitigate that and probably have a pretty nice
performance benefit."

SETALLOCHINT is considered advisory, so our backwards compatibility
mechanism here is to set FAILOK flag for all SETALLOCHINT ops.

Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
index e94f5da251d6..c42d1ada685f 100644
--- a/include/linux/ceph/osd_client.h
+++ b/include/linux/ceph/osd_client.h
@@ -103,6 +103,10 @@ struct ceph_osd_req_op {
 			u32 timeout;
 			__u8 flag;
 		} watch;
+		struct {
+			u64 expected_object_size;
+			u64 expected_write_size;
+		} alloc_hint;
 	};
 };
 
@@ -294,6 +298,10 @@ extern void osd_req_op_cls_init(struct ceph_osd_request *osd_req,
 extern void osd_req_op_watch_init(struct ceph_osd_request *osd_req,
 					unsigned int which, u16 opcode,
 					u64 cookie, u64 version, int flag);
+extern void osd_req_op_alloc_hint_init(struct ceph_osd_request *osd_req,
+				       unsigned int which,
+				       u64 expected_object_size,
+				       u64 expected_write_size);
 
 extern struct ceph_osd_request *ceph_osdc_alloc_request(struct ceph_osd_client *osdc,
 					       struct ceph_snap_context *snapc,