Date: Fri, 27 Mar 2015 12:24:14 +0100 (CET)
From: "Mkrtchyan, Tigran" <tigran.mkrtchyan@desy.de>
To: linux-nfs list <linux-nfs@vger.kernel.org>
Message-ID: <61504045.542929.1427455454361.JavaMail.zimbra@desy.de>
Subject: pNFS layout, ROC and multiple opens
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Sender: linux-nfs-owner@vger.kernel.org


Hi folks,

we run into following issue:

on a client host we have two processes - A and B.
Process A opens a file and reads some data:

OPEN -> LAYOUTGET -> READ.
Notice, that layout has a roc set to true.

Process B opens the same file:

OPEN -> READ.

Client obviously re-used layout information.
Now, process A closes the file and as a result,
layout becomes invalid. Nevertheless, process B
still assumes that layout still valid:

I thinks this is the source of the problem:

fs/nfs/pnfs.c:

1074         list_for_each_entry(ctx, &nfsi->open_files, list) {
1075                 state = ctx->state;
1076                 /* Don't return layout if there is open file state */
1077                 if (state != NULL && state->state != 0)
1078                         goto out_noroc;
1079         }
1080 


this is with 3.19. The RHEL7 kernel send yet another LAYOUTGET when the process A
closes the file.

Tigran.