[lkml]   [2012]   [Aug]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
SubjectRe: 3.0+ NFS issues (bisected)
On Fri, Aug 17, 2012 at 04:08:07PM -0400, J. Bruce Fields wrote:
> Wait a minute, that assumption's a problem because that calculation
> depends in part on xpt_reserved, which is changed here....
> In particular, svc_xprt_release() calls svc_reserve(rqstp, 0), which
> subtracts rqstp->rq_reserved and then calls svc_xprt_enqueue, now with a
> lower xpt_reserved value. That could well explain this.

So, maybe something like this?


commit c8136c319ad85d0db870021fc3f9074d37f26d4a
Author: J. Bruce Fields <>
Date: Fri Aug 17 17:31:53 2012 -0400

svcrpc: don't add to xpt_reserved till we receive

The rpc server tries to ensure that there will be room to send a reply
before it receives a request.

It does this by tracking, in xpt_reserved, an upper bound on the total
size of the replies that is has already committed to for the socket.

Currently it is adding in the estimate for a new reply *before* it
checks whether there is space available. If it finds that there is not
space, it then subtracts the estimate back out.

This may lead the subsequent svc_xprt_enqueue to decide that there is
space after all.

The results is a svc_recv() that will repeatedly return -EAGAIN, causing
server threads to loop without doing any actual work.

Reported-by: Michael Tokarev <>
Signed-off-by: J. Bruce Fields <>

diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index ec99849a..59ff3a3 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -366,8 +366,6 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
rqstp, rqstp->rq_xprt);
rqstp->rq_xprt = xprt;
- rqstp->rq_reserved = serv->sv_max_mesg;
- atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
} else {
@@ -644,8 +642,6 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
if (xprt) {
rqstp->rq_xprt = xprt;
- rqstp->rq_reserved = serv->sv_max_mesg;
- atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);

/* As there is a shortage of threads and this request
* had to be queued, don't allow the thread to wait so
@@ -743,6 +739,10 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
len = xprt->xpt_ops->xpo_recvfrom(rqstp);
dprintk("svc: got len=%d\n", len);
+ if (len > 0) {
+ rqstp->rq_reserved = serv->sv_max_mesg;
+ atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
+ }

/* No data, incomplete (TCP) read, or accept() */

 \ /
  Last update: 2012-08-18 01:01    [W:0.066 / U:3.528 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site