On Mon, Mar 29, 2010 at 10:22 PM, Trond Myklebust <trond.myklebust@xxxxxxxxxx> wrote: > On Mon, 2010-03-29 at 20:03 +0100, Al Viro wrote: >> On Mon, Mar 29, 2010 at 07:36:45PM +0100, Daniel J Blueman wrote: >> > Hi Trond, >> > >> > When open fails and should return EPERM [1], instead we see an oops >> > [2]. I see this on 2.6.34-rc1 and -rc2 mainline; NFS4 server is >> > mainline 2.6.33.1. >> > >> > Let me know if you can't reproduce it and I'll provide some analysis >> > from this end. >> >> Joy... ERR_PTR(-EPERM) in nd.intent.file, and whoever had called >> lookup_instantiate_filp() hadn't bothered to check the return value. >> >> OK, I think I see what's going on. Replace >> lookup_instantiate_filp(nd, (struct dentry *)state, NULL); >> return 1; >> with >> lookup_instantiate_filp(nd, (struct dentry *)state, NULL); >> return state; >> in fs/nfs/nfs4proc.c:nfs4_open_revalidate() and see if everything works >> properly (or just lose the lookup_instantiate_filp() in there and simply >> return state). > > So this raises a point. Originally, the d_revalidate() call was required > to return a boolean 0 or 1. Nowadays it allows the filesystem to return > an error value instead. > > Should we therefore rewrite the NFS implementation to propagate errors > like ESTALE (when it means the parent directory is gone), EACCES, EPERM > and EIO instead of the current behaviour of just dropping the dentry and > hence forcing a lookup? Passing the error back without forcing a lookup sounds like a good win, if it can avoid a comparatively expensive roundtrip to the server (iff the dentry is fresh enough). Is this possible? Talking of expensive, I see latencytop show >16000ms latency for writing pages when I have a workload that does large buffered I/O to an otherwise uncongested server. The gigabit network is saturated, and reads often stall for 1000-4000ms (!). Client has the default 16 TCP request slots, and server has 8 nfsds - the server is far from disk or processor-saturated. I'll see if there is any useful debugging I can get about this. Thanks, Daniel -- Daniel J Blueman -- 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
