Commit 34251e49 authored Feb 17, 2016 by Ilya Dryomov Committed by Sasha Levin Mar 10, 2016

libceph: don't bail early from try_read() when skipping a message



[ Upstream commit e7a88e82fe380459b864e05b372638aeacb0f52d ]

The contract between try_read() and try_write() is that when called
each processes as much data as possible.  When instructed by osd_client
to skip a message, try_read() is violating this contract by returning
after receiving and discarding a single message instead of checking for
more.  try_write() then gets a chance to write out more requests,
generating more replies/skips for try_read() to handle, forcing the
messenger into a starvation loop.

Cc: stable@vger.kernel.org # 3.10+
Reported-by: Varada Kari <Varada.Kari@sandisk.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Tested-by: Varada Kari <Varada.Kari@sandisk.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

parent 9c8b0ac7

net/ceph/messenger.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -2287,7 +2287,7 @@ static int read_partial_message(struct ceph_connection *con)
		con->in_base_pos = -front_len - middle_len - data_len -
		sizeof(m->footer);
		con->in_tag = CEPH_MSGR_TAG_READY;
		return 0;
		return 1;
		} else if ((s64)seq - (s64)con->in_seq > 1) {
		pr_err("read_partial_message bad seq %lld expected %lld\n",
		seq, con->in_seq + 1);
		@@ -2320,7 +2320,7 @@ static int read_partial_message(struct ceph_connection *con)
		sizeof(m->footer);
		con->in_tag = CEPH_MSGR_TAG_READY;
		con->in_seq++;
		return 0;
		return 1;
		}

		BUG_ON(!con->in_msg);