From: Linus Torvalds <torvalds@linux-foundation.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Dmitry Vyukov" <dvyukov@google.com>,
"Ian Kent" <raven@themaw.net>, "Mickaël Salaün" <mic@digikod.net>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
syzkaller <syzkaller@googlegroups.com>,
"Kostya Serebryany" <kcc@google.com>,
"Alexander Potapenko" <glider@google.com>,
"Sasha Levin" <sasha.levin@oracle.com>,
"David Howells" <dhowells@redhat.com>
Subject: Re: fs: NULL deref in atime_needs_update
Date: Mon, 29 Feb 2016 08:45:37 -0800 [thread overview]
Message-ID: <CA+55aFz3qdv+sEA_mk0mVQ8ZofkyberEzmh-ofVGXM4dciGEYA@mail.gmail.com> (raw)
In-Reply-To: <20160229130924.GV17997@ZenIV.linux.org.uk>
On Mon, Feb 29, 2016 at 5:09 AM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> The more I look at the situation with d_is_...() wrt barriers and ->d_seq,
> the less I understand it; outside of RCU mode we don't really need the
> barriers for that stuff and in RCU mode ->d_flags handling had been
> a serious headache all along...
Yeah, one of my least favorite "recent" vfs improvements.
> I'm tempted to do as below .. [ changing it to be unde the seqlock ]
>
> David, Linus, do you see any problems with that? To me it looks saner
> that way and as cheap as the current code, but I might be missing something
> here...
I'd absolutely love to see this. The memory ordering for the flags
updates and reading was always really confusing, and I hated how it
was hidden inside the random access functions. And apparently it
wasn't just confusing, it was buggy too.
But I'd love it _more_ if this also means that we can get rid of the
rmb's, which your patch didn't. Can we? Or does the ordering still
remain for some other issue?
Linus
next prev parent reply other threads:[~2016-02-29 16:45 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-05 21:11 fs: NULL deref in atime_needs_update Dmitry Vyukov
2016-02-16 23:40 ` Mickaël Salaün
2016-02-19 19:32 ` Dmitry Vyukov
2016-02-20 3:21 ` Al Viro
2016-02-20 3:54 ` Al Viro
2016-02-20 3:54 ` Al Viro
2016-02-20 13:25 ` Mickaël Salaün
2016-02-20 17:10 ` Al Viro
2016-02-20 17:10 ` Al Viro
2016-02-20 20:26 ` Mickaël Salaün
2016-02-20 20:50 ` Al Viro
2016-02-20 20:50 ` Al Viro
2016-02-22 11:20 ` Dmitry Vyukov
2016-02-22 17:23 ` Al Viro
2016-02-23 15:34 ` Dmitry Vyukov
2016-02-23 18:17 ` Al Viro
2016-02-20 10:36 ` Dmitry Vyukov
2016-02-24 3:12 ` Ian Kent
2016-02-24 4:46 ` Al Viro
2016-02-24 4:46 ` Al Viro
2016-02-24 10:03 ` Dmitry Vyukov
2016-02-24 10:15 ` Dmitry Vyukov
2016-02-24 13:35 ` Dmitry Vyukov
2016-02-24 15:15 ` Al Viro
2016-02-25 8:29 ` Dmitry Vyukov
2016-02-25 16:39 ` Al Viro
2016-02-26 21:21 ` Al Viro
2016-02-26 21:25 ` Dmitry Vyukov
2016-02-26 22:07 ` Al Viro
2016-02-26 22:07 ` Al Viro
2016-02-27 22:27 ` Al Viro
2016-02-27 22:27 ` Al Viro
2016-02-28 15:43 ` Dmitry Vyukov
2016-02-28 16:04 ` Dmitry Vyukov
2016-02-28 17:01 ` Al Viro
2016-02-28 20:01 ` Al Viro
2016-02-29 9:38 ` Dmitry Vyukov
2016-02-29 12:34 ` Dmitry Vyukov
2016-02-29 16:11 ` Al Viro
2016-02-29 13:09 ` Al Viro
2016-02-29 15:54 ` Dmitry Vyukov
2016-02-29 16:19 ` Al Viro
2016-02-29 18:19 ` Dmitry Vyukov
2016-03-01 8:59 ` Dmitry Vyukov
2016-02-29 16:45 ` Linus Torvalds [this message]
2016-02-29 16:50 ` Al Viro
2016-02-29 17:20 ` Al Viro
2016-02-29 17:24 ` Linus Torvalds
2016-02-29 13:43 ` David Howells
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