diff options
author | Chuck Lever <chuck.lever@oracle.com> | 2023-11-21 11:40:13 -0500 |
---|---|---|
committer | Chuck Lever <chuck.lever@oracle.com> | 2024-01-07 17:54:26 -0500 |
commit | b541dd554bc0442f7ff8c6cab6c5460c044913c8 (patch) | |
tree | 83e59092c037fea239bcf6b5a5e8bee49d2f90e0 /include | |
parent | 52e89100754b2e888cb63bf2d19e65d809497cd6 (diff) | |
download | linux-stable-b541dd554bc0442f7ff8c6cab6c5460c044913c8.tar.gz linux-stable-b541dd554bc0442f7ff8c6cab6c5460c044913c8.tar.bz2 linux-stable-b541dd554bc0442f7ff8c6cab6c5460c044913c8.zip |
svcrdma: Eliminate allocation of recv_ctxt objects in backchannel
The svc_rdma_recv_ctxt free list uses a lockless list to avoid the
need for a spin lock in the fast path. llist_del_first(), which is
used by svc_rdma_recv_ctxt_get(), requires serialization, however,
when there are multiple list producers that are unserialized.
I mistakenly thought there was only one caller of
svc_rdma_recv_ctxt_get() (svc_rdma_refresh_recvs()), thus explicit
serialization would not be necessary. But there is another caller:
svc_rdma_bc_sendto(), and these two are not serialized against each
other. I haven't seen ill effects that I could directly ascribe to
a lack of serialization. It's just an observation based on code
audit.
When DMA-mapping before sending a Reply, the passed-in struct
svc_rdma_recv_ctxt is used only for its write and reply PCLs. These
are currently always empty in the backchannel case. So, instead of
passing a full svc_rdma_recv_ctxt object to
svc_rdma_map_reply_msg(), let's pass in just the Write and Reply
PCLs.
This change makes it unnecessary for the backchannel to acquire a
dummy svc_rdma_recv_ctxt object when sending an RPC Call. The need
for svc_rdma_recv_ctxt free list serialization is now completely
avoided.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/sunrpc/svc_rdma.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h index a5ee0af2a310..4ac32895a058 100644 --- a/include/linux/sunrpc/svc_rdma.h +++ b/include/linux/sunrpc/svc_rdma.h @@ -200,7 +200,8 @@ extern int svc_rdma_send(struct svcxprt_rdma *rdma, struct svc_rdma_send_ctxt *ctxt); extern int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma, struct svc_rdma_send_ctxt *sctxt, - const struct svc_rdma_recv_ctxt *rctxt, + const struct svc_rdma_pcl *write_pcl, + const struct svc_rdma_pcl *reply_pcl, const struct xdr_buf *xdr); extern void svc_rdma_send_error_msg(struct svcxprt_rdma *rdma, struct svc_rdma_send_ctxt *sctxt, |