On 2/25/2018 3:21 PM, Sowmini Varadhan wrote:
This commit is an optimization over commit 01883eda72bd
("rds: support for zcopy completion notification") for PF_RDS sockets.
RDS applications are predominantly request-response transactions, so
it is more efficient to reduce the number of system calls and have
zerocopy completion notification delivered as ancillary data on the
POLLIN channel.
Cookies are passed up as ancillary data (at level SOL_RDS) in a
struct rds_zcopy_cookies when the returned value of recvmsg() is
greater than, or equal to, 0. A max of RDS_MAX_ZCOOKIES may be passed
with each message.
This commit removes support for zerocopy completion notification on
MSG_ERRQUEUE for PF_RDS sockets.
Signed-off-by: Sowmini Varadhan <sowmini.varad...@oracle.com>
---
v2: remove sk_error_queue path; lot of cautionary checks rds_recvmsg_zcookie()
and callers to make sure we dont remove cookies from the queue and then
fail to pass it up to caller
v3:
- bounds check on skb->cb to make sure there is enough room for
struct rds_zcopy_cookies as well as the rds_znotifier;
- Refactor cautionary checks in rds_recvmsg_zcookie: if no msg_control
has been passed, or if there not enough msg_controllen for a
a rds_zcopy_cookies, return silently (do not return error, as the
caller may have wanted other ancillary data which may happen to fit
in the space provided)
- return bool form rds_recvmsg_zcookie, some other code cleanup
Just in case you haven't seen yet, Dan Carpenter reported skb deref
warning on previous version of the patch. Not sure why it wasn't sent
on netdev.
smatch warnings:
net/rds/recv.c:605 rds_recvmsg_zcookie() warn: variable dereferenced
before check 'skb' (see line 596)
With that addressed,
Acked-by: Santosh Shilimkar <santosh.shilim...@oracle.com>
