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[4.2.y-ckt,203/273] libceph: don't bail early from try_read() when skipping a message

Message ID 1457391064-6660-204-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa March 7, 2016, 10:49 p.m. UTC 
4.2.8-ckt5 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Ilya Dryomov <idryomov@gmail.com>

commit e7a88e82fe380459b864e05b372638aeacb0f52d upstream.

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.

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: Kamal Mostafa <kamal@canonical.com>
---
 net/ceph/messenger.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
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Patch

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index ec564c5..1d47fa3 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2328,7 +2328,7 @@  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);
@@ -2361,7 +2361,7 @@  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);