From: Johannes Weiner <jweiner@redhat.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Minchan Kim <minchan.kim@gmail.com>
Subject: Re: [PATCH] thp+memcg-numa: fix BUG at include/linux/mm.h:370!
Date: Mon, 14 Mar 2011 20:58:23 +0100 [thread overview]
Message-ID: <20110314195823.GC2140@redhat.com> (raw)
In-Reply-To: <20110314171730.GF10696@random.random>
On Mon, Mar 14, 2011 at 06:17:31PM +0100, Andrea Arcangeli wrote:
> On Mon, Mar 14, 2011 at 09:56:10AM -0700, Linus Torvalds wrote:
> > Does mem_cgroup_newpage_charge() even _need_ the mmap_sem at all? And
> > if not, why not release the read-lock early? And even if it _does_
> > need it, why not do
[...]
> About mem_cgroup_newpage_charge I think you're right it won't need the
> mmap_sem. Running it under it is sure safe. But if it's not needed we
> can move the up_read before the mem_cgroup_newpage_charge like you
> suggested. Johannes/Minchan could you confirm the mmap_sem isn't
> needed around mem_cgroup_newpage_charge? The mm and new_page are
> stable without the mmap_sem, only the vma goes away but the memcg
> shouldn't care.
We don't care about the vma. It's all about assigning the physical
page to the memcg that mm->owner belongs to.
It would be the first callsite not holding the mmap_sem, but that is
only because all existing sites are fault handlers that don't drop the
lock for other reasons.
I am not aware of anything that would rely on the lock in there, or
would not deserve to break if it did.
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next prev parent reply other threads:[~2011-03-14 19:58 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-14 8:08 [PATCH] thp+memcg-numa: fix BUG at include/linux/mm.h:370! Hugh Dickins
2011-03-14 15:25 ` Minchan Kim
2011-03-14 15:52 ` Andrea Arcangeli
2011-03-14 16:37 ` Hugh Dickins
2011-03-14 16:56 ` Linus Torvalds
2011-03-14 17:17 ` Andrea Arcangeli
2011-03-14 19:58 ` Johannes Weiner [this message]
2011-03-14 23:42 ` KAMEZAWA Hiroyuki
2011-04-01 21:21 ` Andrea Arcangeli
2011-03-14 16:59 ` [PATCH] mm: PageBuddy and mapcount underflows robustness Andrea Arcangeli
2011-03-14 17:30 ` Linus Torvalds
2011-03-17 23:16 ` Andrea Arcangeli
2011-03-18 21:34 ` Hugh Dickins
2011-03-23 22:58 ` [stable] " Greg KH
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