From: Linus Torvalds <torvalds@linux-foundation.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org, James Morris <jmorris@namei.org>,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org,
David Safford <safford@linux.vnet.ibm.com>,
Dmitry Kasatkin <dmitry.kasatkin@intel.com>,
Mimi Zohar <zohar@linux.vnet.ibm.com>,
David Miller <davem@davemloft.net>
Subject: Re: [RFC] situation with fput() locking (was Re: [PULL REQUEST] : ima-appraisal patches)
Date: Fri, 20 Apr 2012 08:56:57 -0700 [thread overview]
Message-ID: <CA+55aFxia+u3VAf0qN-2wv7DyAQZK-Z8=n=cqUvo--+C905aFg@mail.gmail.com> (raw)
In-Reply-To: <20120420080914.GF6871@ZenIV.linux.org.uk>
On Fri, Apr 20, 2012 at 1:09 AM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> Note that we do *not* need to bother with fput_light() - even if it does
> fput(), that fput() won't usually be the final one.
Ack. Most of the time the fput_light()->fput will just decrement the use count.
> We also get something else out of that - AFAICS, the kludge in __scm_destroy()
> can be killed after that. We did it to prevent recursion on fput(), right?
> Now that recursion will be gone...
Hmm.. That points out that we may have a *lot* of these pending final
fput's, though. So the deferral queueing should be fairly light. What
were your particular plans for it?
This actually sounds like a fairly good usage-case for Oleg's new
task_work_add() thing. That would defer the final fput, but at the
same time guarantee that it gets done before returning to user space -
in case there are any issues with synchronous actions. Have you looked
at Oleg's series? You weren't cc'd because it didn't affect you, but
look at lkml for "task_work_add()" to find it.
NOTE! If pure kernel threads do fput() deferral (and maybe they do -
I'm thinking nfsd etc), then the task-work thing might need some extra
thought.
Linus
WARNING: multiple messages have this Message-ID (diff)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org, James Morris <jmorris@namei.org>,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org,
David Safford <safford@linux.vnet.ibm.com>,
Dmitry Kasatkin <dmitry.kasatkin@intel.com>,
Mimi Zohar <zohar@linux.vnet.ibm.com>,
David Miller <davem@davemloft.net>
Subject: Re: [RFC] situation with fput() locking (was Re: [PULL REQUEST] : ima-appraisal patches)
Date: Fri, 20 Apr 2012 08:56:57 -0700 [thread overview]
Message-ID: <CA+55aFxia+u3VAf0qN-2wv7DyAQZK-Z8=n=cqUvo--+C905aFg@mail.gmail.com> (raw)
In-Reply-To: <20120420080914.GF6871@ZenIV.linux.org.uk>
On Fri, Apr 20, 2012 at 1:09 AM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> Note that we do *not* need to bother with fput_light() - even if it does
> fput(), that fput() won't usually be the final one.
Ack. Most of the time the fput_light()->fput will just decrement the use count.
> We also get something else out of that - AFAICS, the kludge in __scm_destroy()
> can be killed after that. We did it to prevent recursion on fput(), right?
> Now that recursion will be gone...
Hmm.. That points out that we may have a *lot* of these pending final
fput's, though. So the deferral queueing should be fairly light. What
were your particular plans for it?
This actually sounds like a fairly good usage-case for Oleg's new
task_work_add() thing. That would defer the final fput, but at the
same time guarantee that it gets done before returning to user space -
in case there are any issues with synchronous actions. Have you looked
at Oleg's series? You weren't cc'd because it didn't affect you, but
look at lkml for "task_work_add()" to find it.
NOTE! If pure kernel threads do fput() deferral (and maybe they do -
I'm thinking nfsd etc), then the task-work thing might need some extra
thought.
Linus
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next prev parent reply other threads:[~2012-04-20 15:57 UTC|newest]
Thread overview: 105+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-18 13:04 [PULL REQUEST] : ima-appraisal patches Mimi Zohar
2012-04-18 15:02 ` James Morris
2012-04-18 18:07 ` Mimi Zohar
2012-04-18 18:39 ` Al Viro
2012-04-18 20:56 ` Mimi Zohar
2012-04-19 19:57 ` Mimi Zohar
2012-04-20 0:43 ` [RFC] situation with fput() locking (was Re: [PULL REQUEST] : ima-appraisal patches) Al Viro
2012-04-20 2:31 ` Linus Torvalds
2012-04-20 2:31 ` Linus Torvalds
2012-04-20 2:54 ` Al Viro
2012-04-20 2:58 ` Linus Torvalds
2012-04-20 2:58 ` Linus Torvalds
2012-04-20 8:09 ` Al Viro
2012-04-20 15:56 ` Linus Torvalds [this message]
2012-04-20 15:56 ` Linus Torvalds
2012-04-20 16:08 ` Al Viro
2012-04-20 16:42 ` Al Viro
2012-04-20 17:21 ` Linus Torvalds
2012-04-20 17:21 ` Linus Torvalds
2012-04-20 18:07 ` Al Viro
2012-04-23 18:01 ` [RFC] TIF_NOTIFY_RESUME, arch/*/*/*signal*.c and all such Al Viro
2012-04-23 18:37 ` Oleg Nesterov
2012-04-24 7:26 ` Al Viro
2012-04-25 3:06 ` Al Viro
2012-04-25 12:37 ` Oleg Nesterov
2012-04-25 12:50 ` Al Viro
2012-04-25 13:03 ` Oleg Nesterov
2012-04-25 13:32 ` Oleg Nesterov
2012-04-25 13:32 ` Al Viro
2012-04-25 14:52 ` Oleg Nesterov
2012-04-25 15:46 ` Oleg Nesterov
2012-04-25 16:10 ` Al Viro
2012-04-25 17:02 ` Oleg Nesterov
2012-04-25 17:51 ` Al Viro
2012-04-26 7:15 ` Martin Schwidefsky
2012-04-26 7:25 ` David Miller
2012-04-26 13:52 ` Oleg Nesterov
2012-04-26 14:31 ` Martin Schwidefsky
2012-04-26 13:22 ` Oleg Nesterov
2012-04-26 18:37 ` Oleg Nesterov
2012-04-26 23:19 ` Al Viro
2012-04-27 17:24 ` Oleg Nesterov
2012-04-27 17:54 ` Oleg Nesterov
2012-05-02 10:37 ` Matt Fleming
2012-05-02 14:14 ` Al Viro
2012-04-27 18:45 ` Al Viro
2012-04-27 19:14 ` Geert Uytterhoeven
2012-04-27 19:34 ` Al Viro
2012-04-29 22:51 ` Al Viro
2012-04-30 6:39 ` Greg Ungerer
2012-04-30 6:39 ` Greg Ungerer
2012-04-27 19:42 ` Al Viro
2012-04-27 20:20 ` Roland McGrath
2012-04-27 21:12 ` Al Viro
2012-04-27 21:27 ` Roland McGrath
2012-04-27 23:15 ` Al Viro
2012-04-27 23:32 ` Al Viro
2012-04-29 4:12 ` Al Viro
2012-04-30 8:06 ` Martin Schwidefsky
2012-04-27 23:50 ` Al Viro
2012-04-28 18:51 ` [PATCH] arch/tile: avoid calling do_signal() after fork from a kernel thread Chris Metcalf
2012-04-28 18:51 ` Chris Metcalf
2012-04-28 20:55 ` Al Viro
2012-04-28 21:46 ` Chris Metcalf
2012-04-28 21:46 ` Chris Metcalf
2012-04-29 0:55 ` Al Viro
2012-04-28 18:51 ` [PATCH v2] arch/tile: fix up some issues in calling do_work_pending() Chris Metcalf
2012-04-28 18:51 ` Chris Metcalf
2012-04-29 3:49 ` [PATCH] arch/tile: avoid calling do_signal() after fork from a kernel thread Chris Metcalf
2012-04-29 3:49 ` Chris Metcalf
2012-04-28 2:42 ` [RFC] TIF_NOTIFY_RESUME, arch/*/*/*signal*.c and all such Al Viro
2012-04-28 3:32 ` Al Viro
2012-04-28 3:36 ` Al Viro
2012-04-29 16:33 ` Oleg Nesterov
2012-04-29 16:18 ` Oleg Nesterov
2012-04-29 18:05 ` Al Viro
2012-05-01 4:31 ` Al Viro
2012-05-01 5:06 ` Mike Frysinger
2012-05-01 5:52 ` Al Viro
2012-05-02 17:24 ` Al Viro
2012-05-02 18:30 ` Oleg Nesterov
2012-04-29 16:41 ` Oleg Nesterov
2012-04-29 18:09 ` Al Viro
2012-04-29 18:25 ` Oleg Nesterov
2012-04-20 3:15 ` [RFC] situation with fput() locking (was Re: [PULL REQUEST] : ima-appraisal patches) Al Viro
2012-04-20 18:54 ` Hugh Dickins
2012-04-20 19:04 ` Al Viro
2012-04-20 19:18 ` Linus Torvalds
2012-04-20 19:32 ` Hugh Dickins
2012-04-20 19:58 ` Al Viro
2012-04-20 21:12 ` Linus Torvalds
2012-04-20 21:12 ` Linus Torvalds
2012-04-20 22:13 ` Al Viro
2012-04-20 22:35 ` Linus Torvalds
2012-04-20 22:35 ` Linus Torvalds
2012-04-27 7:35 ` Kasatkin, Dmitry
2012-04-27 17:34 ` Al Viro
2012-04-27 18:52 ` Kasatkin, Dmitry
2012-04-27 18:52 ` Kasatkin, Dmitry
2012-04-27 19:15 ` Kasatkin, Dmitry
2012-04-30 14:32 ` Mimi Zohar
2012-04-30 14:32 ` Mimi Zohar
2012-05-03 4:23 ` James Morris
2012-05-03 4:23 ` James Morris
2012-04-20 19:37 ` Al Viro
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