[PATCH 3.14 116/130] libceph: dont bail early from try_read() when skipping a message

[Greg Kroah-Hartman]

3.14-stable review patch.  If anyone has any objections, please let me know.

--

From: Ilya Dryomov 

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 
Signed-off-by: Ilya Dryomov 
Tested-by: Varada Kari 
Reviewed-by: Alex Elder 
Signed-off-by: Greg Kroah-Hartman 

---
 net/ceph/messenger.c |4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2279,7 +2279,7 @@ static int read_partial_message(struct c
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);
@@ -2312,7 +2312,7 @@ static int read_partial_message(struct c
sizeof(m->footer);
con->in_tag = CEPH_MSGR_TAG_READY;
con->in_seq++;
-   return 0;
+   return 1;
}
 
BUG_ON(!con->in_msg);

[PATCH 3.14 116/130] libceph: dont bail early from try_read() when skipping a message

[Greg Kroah-Hartman]

3.14-stable review patch.  If anyone has any objections, please let me know.

--

From: Ilya Dryomov 

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 
Signed-off-by: Ilya Dryomov 
Tested-by: Varada Kari 
Reviewed-by: Alex Elder 
Signed-off-by: Greg Kroah-Hartman 

---
 net/ceph/messenger.c |4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2279,7 +2279,7 @@ static int read_partial_message(struct c
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);
@@ -2312,7 +2312,7 @@ static int read_partial_message(struct c
sizeof(m->footer);
con->in_tag = CEPH_MSGR_TAG_READY;
con->in_seq++;
-   return 0;
+   return 1;
}
 
BUG_ON(!con->in_msg);