On Sun, Mar 1, 2015 at 8:20 PM, Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> wrote: > On Sun, Mar 1, 2015 at 8:06 PM, Bruce James Fields <bfields@xxxxxxxxxxxx> wrote: >> On Sun, Mar 01, 2015 at 07:52:28PM -0500, Trond Myklebust wrote: >>> Hi Bruce, >>> >>> On Sun, Mar 1, 2015 at 2:14 PM, Trond Myklebust >>> <trond.myklebust@xxxxxxxxxxxxxxx> wrote: >>> > Hi, >>> > >>> > When doing testing of NFSv3 loopback mounts (client and server are on >>> > the same IP address), I'm seeing a very reproducible hang in which the >>> > client stops receiving data from the server. The TCP connection is still >>> > marked as established, and the server appears to continue to receive and >>> > send data, however the client does not. >>> > >>> > So far, I've reproduced on both v4.0-rc1, and the Fedora v3.18.7 kernel. >>> > >>> > The reproducer is simply to loopback mount using NFSv3, and then run the >>> > 'fsx' filesystem exerciser. I'm usually able to trigger the hang with >>> > "fsx -N 100000 foobar". >>> > >>> > I've attached a couple of wireshark trace of a few frames just before >>> > and during the hang in case it jogs any memories. >>> >>> This bug appears to go away when I disable the splice()-based reads by >>> clearing the RQ_SPLICE_OK flag. >>> >>> I noticed that it always involved a combination of a READ and a >>> truncating SETATTR call. Are you sure that it is safe to share >>> pagecache pages directly with sendpage() in this way? As far as I can >>> tell, there is no locking to prevent them from being modified while in >>> the TCP send queue. >> >> This is the stable-pages problem that we've had forever, isn't it? Or >> is this a different problem? > > It is causing the TCP socket to hang, so it goes beyond the usual > stable pages issue. > Confirming that clearing RQ_SPLICE_OK fixes the issue on all kernel that I've tested so far. -- Trond Myklebust Linux NFS client maintainer, PrimaryData trond.myklebust@xxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
