libceph: add an epoch_barrier field to struct ceph_osd_client

Cephfs can get cap update requests that contain a new epoch barrier in
them. When that happens we want to pause all OSD traffic until the right
map epoch arrives.

Add an epoch_barrier field to ceph_osd_client that is protected by the
osdc->lock rwsem. When the barrier is set, and the current OSD map
epoch is below that, pause the request target when submitting the
request or when revisiting it. Add a way for upper layers (cephfs)
to update the epoch_barrier as well.

If we get a new map, compare the new epoch against the barrier before
kicking requests and request another map if the map epoch is still lower
than the one we want.

If we get a map with a full pool, or at quota condition, then set the
barrier to the current epoch value.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

include/linux/ceph/osd_client.h

@@ -267,6 +267,7 @@ struct ceph_osd_client {
 	struct rb_root         osds;          /* osds */
 	struct list_head       osd_lru;       /* idle osds */
 	spinlock_t             osd_lru_lock;
+	u32		       epoch_barrier;
 	struct ceph_osd        homeless_osd;
 	atomic64_t             last_tid;      /* tid of last request */
 	u64                    last_linger_id;
@@ -305,6 +306,7 @@ extern void ceph_osdc_handle_reply(struct ceph_osd_client *osdc,
 				   struct ceph_msg *msg);
 extern void ceph_osdc_handle_map(struct ceph_osd_client *osdc,
 				 struct ceph_msg *msg);
+void ceph_osdc_update_epoch_barrier(struct ceph_osd_client *osdc, u32 eb);
 
 extern void osd_req_op_init(struct ceph_osd_request *osd_req,
 			    unsigned int which, u16 opcode, u32 flags);

net/ceph/debugfs.c

@@ -62,7 +62,8 @@ static int osdmap_show(struct seq_file *s, void *p)
 		return 0;
 
 	down_read(&osdc->lock);
-	seq_printf(s, "epoch %d flags 0x%x\n", map->epoch, map->flags);
+	seq_printf(s, "epoch %u barrier %u flags 0x%x\n", map->epoch,
+			osdc->epoch_barrier, map->flags);
 
 	for (n = rb_first(&map->pg_pools); n; n = rb_next(n)) {
 		struct ceph_pg_pool_info *pi =

net/ceph/osd_client.c

@@ -1298,8 +1298,9 @@ static bool target_should_be_paused(struct ceph_osd_client *osdc,
 		       __pool_full(pi);
 
 	WARN_ON(pi->id != t->base_oloc.pool);
-	return (t->flags & CEPH_OSD_FLAG_READ && pauserd) ||
-	       (t->flags & CEPH_OSD_FLAG_WRITE && pausewr);
+	return ((t->flags & CEPH_OSD_FLAG_READ) && pauserd) ||
+	       ((t->flags & CEPH_OSD_FLAG_WRITE) && pausewr) ||
+	       (osdc->osdmap->epoch < osdc->epoch_barrier);
 }
 
 enum calc_target_result {
@@ -1654,8 +1655,13 @@ static void __submit_request(struct ceph_osd_request *req, bool wrlocked)
 		goto promote;
 	}
 
-	if ((req->r_flags & CEPH_OSD_FLAG_WRITE) &&
-	    ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSEWR)) {
+	if (osdc->osdmap->epoch < osdc->epoch_barrier) {
+		dout("req %p epoch %u barrier %u\n", req, osdc->osdmap->epoch,
+		     osdc->epoch_barrier);
+		req->r_t.paused = true;
+		maybe_request_map(osdc);
+	} else if ((req->r_flags & CEPH_OSD_FLAG_WRITE) &&
+		   ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSEWR)) {
 		dout("req %p pausewr\n", req);
 		req->r_t.paused = true;
 		maybe_request_map(osdc);
@@ -1807,19 +1813,77 @@ static void abort_request(struct ceph_osd_request *req, int err)
 	complete_request(req, err);
 }
 
+static void update_epoch_barrier(struct ceph_osd_client *osdc, u32 eb)
+{
+	if (likely(eb > osdc->epoch_barrier)) {
+		dout("updating epoch_barrier from %u to %u\n",
+				osdc->epoch_barrier, eb);
+		osdc->epoch_barrier = eb;
+		/* Request map if we're not to the barrier yet */
+		if (eb > osdc->osdmap->epoch)
+			maybe_request_map(osdc);
+	}
+}
+
+void ceph_osdc_update_epoch_barrier(struct ceph_osd_client *osdc, u32 eb)
+{
+	down_read(&osdc->lock);
+	if (unlikely(eb > osdc->epoch_barrier)) {
+		up_read(&osdc->lock);
+		down_write(&osdc->lock);
+		update_epoch_barrier(osdc, eb);
+		up_write(&osdc->lock);
+	} else {
+		up_read(&osdc->lock);
+	}
+}
+EXPORT_SYMBOL(ceph_osdc_update_epoch_barrier);
+
 /*
  * Drop all pending requests that are stalled waiting on a full condition to
- * clear, and complete them with ENOSPC as the return code.
+ * clear, and complete them with ENOSPC as the return code. Set the
+ * osdc->epoch_barrier to the latest map epoch that we've seen if any were
+ * cancelled.
  */
 static void ceph_osdc_abort_on_full(struct ceph_osd_client *osdc)
 {
 	struct rb_node *n;
+	bool victims = false;
 
 	dout("enter abort_on_full\n");
 
 	if (!ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL) && !have_pool_full(osdc))
 		goto out;
 
+	/* Scan list and see if there is anything to abort */
+	for (n = rb_first(&osdc->osds); n; n = rb_next(n)) {
+		struct ceph_osd *osd = rb_entry(n, struct ceph_osd, o_node);
+		struct rb_node *m;
+
+		m = rb_first(&osd->o_requests);
+		while (m) {
+			struct ceph_osd_request *req = rb_entry(m,
+					struct ceph_osd_request, r_node);
+			m = rb_next(m);
+
+			if (req->r_abort_on_full) {
+				victims = true;
+				break;
+			}
+		}
+		if (victims)
+			break;
+	}
+
+	if (!victims)
+		goto out;
+
+	/*
+	 * Update the barrier to current epoch if it's behind that point,
+	 * since we know we have some calls to be aborted in the tree.
+	 */
+	update_epoch_barrier(osdc, osdc->osdmap->epoch);
+
 	for (n = rb_first(&osdc->osds); n; n = rb_next(n)) {
 		struct ceph_osd *osd = rb_entry(n, struct ceph_osd, o_node);
 		struct rb_node *m;
@@ -1837,7 +1901,7 @@ static void ceph_osdc_abort_on_full(struct ceph_osd_client *osdc)
 		}
 	}
 out:
-	dout("return abort_on_full\n");
+	dout("return abort_on_full barrier=%u\n", osdc->epoch_barrier);
 }
 
 static void check_pool_dne(struct ceph_osd_request *req)
@@ -3293,7 +3357,8 @@ void ceph_osdc_handle_map(struct ceph_osd_client *osdc, struct ceph_msg *msg)
 	pausewr = ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSEWR) ||
 		  ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL) ||
 		  have_pool_full(osdc);
-	if (was_pauserd || was_pausewr || pauserd || pausewr)
+	if (was_pauserd || was_pausewr || pauserd || pausewr ||
+	    osdc->osdmap->epoch < osdc->epoch_barrier)
 		maybe_request_map(osdc);
 
 	kick_requests(osdc, &need_resend, &need_resend_linger);