From: Al Viro <viro@ZenIV.linux.org.uk>
To: Hugh Dickins <hughd@google.com>
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>,
Linus Torvalds <torvalds@linux-foundation.org>,
David Miller <davem@davemloft.net>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC] situation with fput() locking (was Re: [PULL REQUEST] : ima-appraisal patches)
Date: Fri, 20 Apr 2012 20:04:18 +0100 [thread overview]
Message-ID: <20120420190418.GK6871@ZenIV.linux.org.uk> (raw)
In-Reply-To: <alpine.LSU.2.00.1204201133340.1450@eggly.anvils>
On Fri, Apr 20, 2012 at 11:54:01AM -0700, Hugh Dickins wrote:
> I can see that the discussion has since moved on quite a way from here.
>
> But it looks to me fairly easy for mm to stop doing fput() under mmap_sem.
>
> That's already the case when exiting (no mmap_sem held), and shouldn't add
> observable cost when unmapping (we already work on a chain of vmas to be
> freed, and when unmapping that chain will usually just be of one: shouldn't
> matter to defer a final pass until after mmap_sem is dropped). Unless I'm
> mistaken, the fput() buried in vma_adjust() can never be a final fput.
>
> Is it worth my trying to implement that? Or do you see an immediate
> gotcha that I'm missing? Or are you happy enough with your deferred
> fput() ideas, that it would be a waste of time to rearrange the mm end?
Deferring the final pass after dropping ->mmap_sem is going to be
interesting; what would protect ->vm_next on those suckers? Locking
rules are already bloody complicated in mm/*; this will only add more
subtle fun. Note that right now both the dissolution of ->vm_next
list and freeing of VMAs happen under ->mmap_sem; changing that might
cost us a lot of headache...
next prev parent reply other threads:[~2012-04-20 19:04 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
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 [this message]
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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