libceph, rbd: ceph_osd_linger_request, watch/notify v2

This adds support and switches rbd to a new, more reliable version of
watch/notify protocol.  As with the OSD client update, this is mostly
about getting the right structures linked into the right places so that
reconnects are properly sent when needed.  watch/notify v2 also
requires sending regular pings to the OSDs - send_linger_ping().

A major change from the old watch/notify implementation is the
introduction of ceph_osd_linger_request - linger requests no longer
piggy back on ceph_osd_request.  ceph_osd_event has been merged into
ceph_osd_linger_request.

All the details are now hidden within libceph, the interface consists
of a simple pair of watch/unwatch functions and ceph_osdc_notify_ack().
ceph_osdc_watch() does return ceph_osd_linger_request, but only to keep
the lifetime management simple.

ceph_osdc_notify_ack() accepts an optional data payload, which is
relayed back to the notifier.

Portions of this patch are loosely based on work by Douglas Fuller
<dfuller@redhat.com> and Mike Christie <michaelc@cs.wisc.edu>.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/include/linux/ceph/rados.h b/include/linux/ceph/rados.h
index 28740a58f32c..204c8c944703 100644
--- a/include/linux/ceph/rados.h
+++ b/include/linux/ceph/rados.h
@@ -427,7 +427,17 @@ enum {
 	CEPH_OSD_CMPXATTR_MODE_U64    = 2
 };
 
-#define RADOS_NOTIFY_VER	1
+enum {
+	CEPH_OSD_WATCH_OP_UNWATCH = 0,
+	CEPH_OSD_WATCH_OP_LEGACY_WATCH = 1,
+	/* note: use only ODD ids to prevent pre-giant code from
+	   interpreting the op as UNWATCH */
+	CEPH_OSD_WATCH_OP_WATCH = 3,
+	CEPH_OSD_WATCH_OP_RECONNECT = 5,
+	CEPH_OSD_WATCH_OP_PING = 7,
+};
+
+const char *ceph_osd_watch_op_name(int o);
 
 /*
  * an individual object operation.  each may be accompanied by some data
@@ -462,8 +472,9 @@ struct ceph_osd_op {
 	        } __attribute__ ((packed)) snap;
 		struct {
 			__le64 cookie;
-			__le64 ver;
-			__u8 flag;	/* 0 = unwatch, 1 = watch */
+			__le64 ver;     /* no longer used */
+			__u8 op;	/* CEPH_OSD_WATCH_OP_* */
+			__le32 gen;     /* registration generation */
 		} __attribute__ ((packed)) watch;
 		struct {
 			__le64 offset, length;