From: Chuck Lever <chuck.lever@oracle.com>
To: Jason L Tibbitts III <tibbs@math.uh.edu>,
Benjamin Coddington <bcodding@redhat.com>
Cc: Bruce Fields <bfields@fieldses.org>,
Wolfgang Walter <linux@stwm.de>,
Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
km@cm4all.com, linux-kernel@vger.kernel.org
Subject: Re: Regression in 5.1.20: Reading long directory fails
Date: Fri, 6 Sep 2019 16:50:36 -0400 [thread overview]
Message-ID: <75F810C6-E99E-40C3-B5E1-34BA2CC42773@oracle.com> (raw)
In-Reply-To: <ufapnkdw3s3.fsf@epithumia.math.uh.edu>
> On Sep 6, 2019, at 4:47 PM, Jason L Tibbitts III <tibbs@math.uh.edu> wrote:
>
>>>>>> "JBF" == J Bruce Fields <bfields@fieldses.org> writes:
>
> JBF> Those readdir changes were client-side, right? Based on that I'd
> JBF> been assuming a client bug, but maybe it'd be worth getting a full
> JBF> packet capture of the readdir reply to make sure it's legit.
>
> I have been working with bcodding on IRC for the past couple of days on
> this. Fortunately I was able to come up with way to fill up a directory
> in such a way that it will fail with certainty and as a bonus doesn't
> include any user data so I can feel OK about sharing packet captures. I
> have a capture alongside a kernel trace of the problematic operation in
> https://www.math.uh.edu/~tibbs/nfs/. Not that I can particularly tell
> anything useful from that, but bcodding says that it seems to point to
> some issue in sunrpc.
>
> And because I can easily reproduce this and I was able to do a bisect:
>
> 2c94b8eca1a26cd46010d6e73a23da5f2e93a19d is the first bad commit
> commit 2c94b8eca1a26cd46010d6e73a23da5f2e93a19d
> Author: Chuck Lever <chuck.lever@oracle.com>
> Date: Mon Feb 11 11:25:41 2019 -0500
>
> SUNRPC: Use au_rslack when computing reply buffer size
>
> au_rslack is significantly smaller than (au_cslack << 2). Using
> that value results in smaller receive buffers. In some cases this
> eliminates an extra segment in Reply chunks (RPC/RDMA).
>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
>
> :040000 040000 d4d1ce2fbe0035c5bd9df976b8c448df85dcb505 7011a792dfe72ff9cd70d66e45d353f3d7817e3e M net
>
> But of course, I can't say whether this is the actual bad commit or
> whether it just introduced a behavior change which alters the conditions
> under which the problem appears.
The first place I'd start looking is the XDR constants at the head of fs/nfs/nfs4xdr.c
having to do with READDIR.
The report of behavior changes with the use of krb5p also makes this commit plausible.
> And just to make sure that the blame doesn't lie with the old RHEL7
> kernel, I rsynced over the problematic directory to a machine running
> something slightly more modern (5.1.11, which I know I need to update,
> but it's already set up to do kerberised NFS) and the same problem
> exists, though the directory listing does fail at a different place.
>
> - J<
--
Chuck Lever
next prev parent reply other threads:[~2019-09-06 20:53 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <ufak1bhyuew.fsf@epithumia.math.uh.edu>
2019-08-22 19:39 ` Regression in 5.1.20: Reading long directory fails Jason L Tibbitts III
2019-08-28 17:46 ` J. Bruce Fields
2019-08-28 18:29 ` Jason L Tibbitts III
2019-08-28 18:33 ` J. Bruce Fields
2019-09-03 15:49 ` Jason L Tibbitts III
2019-09-03 18:02 ` Wolfgang Walter
2019-09-03 19:06 ` Jason L Tibbitts III
2019-09-03 19:08 ` Chuck Lever
2019-09-03 21:37 ` Wolfgang Walter
2019-09-04 1:50 ` Jason L Tibbitts III
2019-09-06 14:48 ` J. Bruce Fields
2019-09-06 20:47 ` Jason L Tibbitts III
2019-09-06 20:50 ` Chuck Lever [this message]
2019-09-08 11:39 ` Benjamin Coddington
2019-09-08 15:19 ` Trond Myklebust
2019-09-08 15:48 ` Chuck Lever
2019-09-08 16:47 ` Trond Myklebust
2019-09-08 16:51 ` Chuck Lever
2019-09-11 16:25 ` Benjamin Coddington
2019-09-11 16:39 ` Chuck Lever
2019-09-11 17:26 ` Benjamin Coddington
2019-09-11 17:27 ` Benjamin Coddington
2019-09-11 17:29 ` Chuck Lever
2019-09-11 17:40 ` Benjamin Coddington
2019-09-11 17:43 ` Chuck Lever
2019-09-11 17:59 ` Benjamin Coddington
2019-09-11 17:50 ` Benjamin Coddington
2019-09-11 17:54 ` Chuck Lever
2019-09-12 12:29 ` Benjamin Coddington
2019-09-12 12:53 ` Trond Myklebust
2019-09-12 13:08 ` Benjamin Coddington
2019-09-12 13:13 ` J. Bruce Fields
2019-09-12 13:25 ` Trond Myklebust
2019-09-12 13:35 ` Benjamin Coddington
2019-09-12 13:14 ` Trond Myklebust
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