On Thu, 5 Jun 2008 09:28:51 +0100 "Daniel J Blueman" <daniel.blueman@xxxxxxxxx> wrote: > On Thu, Jun 5, 2008 at 1:35 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > > On Thu, 5 Jun 2008 00:33:54 +0100 > > "Daniel J Blueman" <daniel.blueman@xxxxxxxxx> wrote: > > > >> Having experienced 'mount.nfs4: internal error' when mounting nfsv4 in > >> the past, I have a minimal test-case I sometimes run: > >> > >> $ while :; do mount -t nfs4 filer:/store /store; umount /store; done > >> > >> After ~100 iterations, I saw the 'mount.nfs4: internal error', > >> followed by symptoms of memory corruption [1], a locking issue with > >> the reporting [2] and another (related?) memory-corruption issue > >> (off-by-1?) [3]. A little analysis shows memory being overwritten by > >> (likely) a poison value, which gets complicated if it's not > >> use-after-free... > >> > >> Anyone dare confirm this issue? NFSv4 server is x86-64 Ubuntu 8.04 > >> 2.6.24-18, client U8.04 2.6.26-rc4; batteries included [4]. > >> > >> I'm happy to decode addresses, test patches etc. > >> > >> Daniel > >> > > > > Looks like it fell down while trying to take down the kthread during a > > failed mount attempt. I have to wonder if I might have introduced a > > race when I changed nfs4 callback thread to kthread API. I think we may > > need the BKL around the last 2 statements in the main callback thread > > function. If you can easily reproduce this, could you test the > > following patch and let me know if it helps? > > > > Note that this patch is entirely untested, so test it someplace > > non-critical ;-). > > > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > > > > > > diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c > > index c1e7c83..a3e83f9 100644 > > --- a/fs/nfs/callback.c > > +++ b/fs/nfs/callback.c > > @@ -90,9 +90,9 @@ nfs_callback_svc(void *vrqstp) > > preverr = err; > > svc_process(rqstp); > > } > > - unlock_kernel(); > > nfs_callback_info.task = NULL; > > svc_exit_thread(rqstp); > > + unlock_kernel(); > > return 0; > > } > > This doesn't resolve the issue, alas. I'll hunker down to the > bisection in the next few days. > > Thanks, > Daniel Yeah, after I sent that I went back and looked and it seemed like while we don't hold the BKL there, access to the callback info is still serialized via a semaphore. Thanks for testing it anyway... -- Jeff Layton <jlayton@xxxxxxxxxx> -- 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
