Commit b0494532 authored May 11, 2015 by Ilya Dryomov

libceph: request a new osdmap if lingering request maps to no osd



This commit does two things.  First, if there are any homeless
lingering requests, we now request a new osdmap even if the osdmap that
is being processed brought no changes, i.e. if a given lingering
request turned homeless in one of the previous epochs and remained
homeless in the current epoch.  Not doing so leaves us with a stale
osdmap and as a result we may miss our window for reestablishing the
watch and lose notifies.

MON=1 OSD=1:

    # cat linger-needmap.sh
    #!/bin/bash
    rbd create --size 1 test
    DEV=$(rbd map test)
    ceph osd out 0
    rbd map dne/dne # obtain a new osdmap as a side effect (!)
    sleep 1
    ceph osd in 0
    rbd resize --size 2 test
    # rbd info test | grep size -> 2M
    # blockdev --getsize $DEV -> 1M

N.B.: Not obtaining a new osdmap in between "osd out" and "osd in"
above is enough to make it miss that resize notify, but that is a
bug^Wlimitation of ceph watch/notify v1.

Second, homeless lingering requests are now kicked just like those
lingering requests whose mapping has changed.  This is mainly to
recognize that a homeless lingering request makes no sense and to
preserve the invariant that a registered lingering request is not
sitting on any of r_req_lru_item lists.  This spares us a WARN_ON,
which commit ba9d114e ("libceph: clear r_req_lru_item in
__unregister_linger_request()") tried to fix the _wrong_ way.

Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>

parent e2608180

net/ceph/osd_client.c

+20 −11

Original line number	Diff line number	Diff line
		@@ -2017,21 +2017,30 @@ static void kick_requests(struct ceph_osd_client *osdc, bool force_resend,
		err = __map_request(osdc, req,
		force_resend \|\| force_resend_writes);
		dout("__map_request returned %d\n", err);
		if (err == 0)
		continue; /* no change and no osd was specified */
		if (err < 0)
		continue; /* hrm! */
		if (req->r_osd == NULL \|\| err > 0) {
		if (req->r_osd == NULL) {
		dout("tid %llu maps to no valid osd\n", req->r_tid);
		needmap++; /* request a newer map */
		continue;
		dout("lingering %p tid %llu maps to no osd\n",
		req, req->r_tid);
		/*
		* A homeless lingering request makes
		* no sense, as it's job is to keep
		* a particular OSD connection open.
		* Request a newer map and kick the
		* request, knowing that it won't be
		* resent until we actually get a map
		* that can tell us where to send it.
		*/
		needmap++;
		}

		dout("kicking lingering %p tid %llu osd%d\n", req, req->r_tid,
		req->r_osd ? req->r_osd->o_osd : -1);
		dout("kicking lingering %p tid %llu osd%d\n", req,
		req->r_tid, req->r_osd ? req->r_osd->o_osd : -1);
		__register_request(osdc, req);
		__unregister_linger_request(osdc, req);
		}
		}
		reset_changed_osds(osdc);
		mutex_unlock(&osdc->request_mutex);

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