linux-kernel - Re: [PATCH 0/3] fs/9p: fix setattr/getattr issues with open files

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Message-ID: <20160704141655.GA5799@u-isr-cdi-08>
Date:	Mon, 4 Jul 2016 16:16:55 +0200
From:	Dominique Martinet <dominique.martinet@....fr>
To:	Greg Kurz <groug@...d.org>
CC:	Eric Van Hensbergen <ericvh@...il.com>,
	Latchesar Ionkov <lucho@...kov.net>,
	<linux-kernel@...r.kernel.org>, <qemu-devel@...gnu.org>,
	<v9fs-developer@...ts.sourceforge.net>,
	Ron Minnich <rminnich@...dia.gov>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 0/3] fs/9p: fix setattr/getattr issues with open files

I *think* this introduces a race somewhere, I'm getting errors like:
cat: f.05: No such file or directory
cat: f.14: No such file or directory
cat: f.13: No such file or directory
cat: f.39: No such file or directory
cat: f.05: No such file or directory

when doing:
   for file in {01..50}; do touch f.${file}; done
   seq 1 1000 | xargs -n 1 -P 25 -I{} cat f.* > /dev/null

I don't get it everytime but close enough to. Server is bi-socket and
has some numa effects which help producing data-synchronization races,
it's probably harder to hit on a laptop.

I'm simply trying over a patched qemu for now, applied patches right on
top of 4.6.1, can't seem to reproduce with a vanilla 4.6.1 without any
change to qemu (still patched), so it looks kernel-side.

Can't say I've taken much time to look at the patches yet though,
sorry - I don't think it's too hard to debug though so I'll take a look
tomorrow as soon as I find time if you haven't gotten it by then.

-- 
Dominique