From: Peter Zijlstra <peterz@infradead.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
". James Morris" <jmorris@namei.org>,
linux-security-module@vger.kernel.org,
linux-kernel <linux-kernel@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>,
David Miller <davem@davemloft.net>
Subject: Re: deferring __fput()
Date: Mon, 25 Jun 2012 15:19:56 +0200 [thread overview]
Message-ID: <1340630396.2507.66.camel@laptop> (raw)
In-Reply-To: <20120625121436.GU14083@ZenIV.linux.org.uk>
On Mon, 2012-06-25 at 13:14 +0100, Al Viro wrote:
> You mean, doing that from RCU callbacks?
Indirectly, yeah, but the RCU callback would schedule it or whatever.
> Still a bad idea, IMO; you will end up with a context
> switch and unpleasantness with delayed user-visible effects of syscalls. With aio we did have
> a delayed execution of fput() anyway; all that has changed there is that we use generic
> mechanism instead of home-grown analog thereof.
Right, the delayed effect is the main concern. The example in the
referred thread was unmount() returning -EBUSY after the last
close()/munmap().
> I'll need to reread that thread to comment on the specifics (had been too long ago; I don't
> remember the details), but... See Linus' objections to full-async fput() circa this April
> or March. There's a reason why this patchset uses task_work_add() whenever possible.
Ok, I'll try and find that thread, so the advantage of task_work_add()
is that you'll keep the work in the task that caused it wherever
possible, right -- provided its actually sitll around.
If we make fput() deferable in general we'll be sure to grow some 'fun'
cases. So are we going to add a sync against unmount someplace to avoid
these un-expected -EBUSY things?
next prev parent reply other threads:[~2012-06-25 13:20 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-22 12:44 deferring __fput() Mimi Zohar
2012-06-23 9:20 ` Al Viro
2012-06-23 19:45 ` Al Viro
2012-06-23 20:38 ` Oleg Nesterov
2012-06-23 21:01 ` Al Viro
2012-06-23 21:11 ` Al Viro
2012-06-24 4:16 ` Al Viro
2012-06-24 10:09 ` Al Viro
2012-06-24 16:54 ` Oleg Nesterov
2012-06-24 15:33 ` Oleg Nesterov
2012-06-25 6:03 ` Al Viro
2012-06-25 15:18 ` Oleg Nesterov
2012-06-27 18:37 ` [PATCH 0/4] Was: " Oleg Nesterov
2012-06-27 18:37 ` [PATCH 1/4] task_work: use the single-linked list to shrink sizeof(task_work) Oleg Nesterov
2012-06-27 18:37 ` [PATCH 2/4] task_work: don't rely on PF_EXITING Oleg Nesterov
2012-06-27 18:38 ` [PATCH 3/4] task_work: deal with task_work callbacks adding more work Oleg Nesterov
2012-06-27 18:38 ` [PATCH 4/4] task_work: kill task_work->data Oleg Nesterov
2012-06-27 19:05 ` Oleg Nesterov
2012-06-28 4:38 ` [PATCH 0/4] Was: deferring __fput() Al Viro
2012-06-28 16:22 ` Oleg Nesterov
2012-06-28 16:45 ` Oleg Nesterov
2012-06-30 6:24 ` Al Viro
2012-06-30 17:41 ` Oleg Nesterov
2012-06-29 5:30 ` Mimi Zohar
2012-06-29 8:33 ` Al Viro
2012-06-29 13:02 ` Mimi Zohar
2012-06-29 17:41 ` Al Viro
2012-06-29 21:38 ` Mimi Zohar
2012-06-29 23:56 ` Mimi Zohar
2012-06-30 5:02 ` Al Viro
2012-07-01 19:50 ` Mimi Zohar
2012-07-01 20:57 ` Al Viro
2012-07-02 1:46 ` Mimi Zohar
2012-07-02 3:43 ` Al Viro
2012-07-02 5:11 ` Al Viro
2012-07-02 11:49 ` Mimi Zohar
2012-07-02 12:02 ` Al Viro
2012-07-02 13:01 ` Mimi Zohar
2012-07-02 13:33 ` Al Viro
2012-07-02 14:50 ` Mimi Zohar
2012-08-21 13:05 ` [PATCH] task_work: add a scheduling point in task_work_run() Eric Dumazet
2012-08-21 20:37 ` Mimi Zohar
2012-08-21 21:32 ` Eric Dumazet
2012-08-22 3:13 ` Mimi Zohar
2012-08-22 5:27 ` Michael Wang
2012-08-22 5:38 ` Al Viro
2012-06-23 20:57 ` deferring __fput() Al Viro
2012-06-23 21:33 ` Al Viro
2012-06-24 15:20 ` Oleg Nesterov
2012-06-24 18:11 ` Oleg Nesterov
2012-06-25 12:03 ` Peter Zijlstra
2012-06-25 12:14 ` Al Viro
2012-06-25 13:19 ` Peter Zijlstra [this message]
2012-06-25 13:53 ` Al Viro
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