From: Andrew Morton <akpm@linux-foundation.org>
To: Hillf Danton <dhillf@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [PATCH] mm: hugetlb: undo change to page mapcount in fault handler
Date: Wed, 4 Jan 2012 15:16:32 -0800 [thread overview]
Message-ID: <20120104151632.05e6b3b0.akpm@linux-foundation.org> (raw)
In-Reply-To: <CAJd=RBBY0sKdtdx9d8KXTchjaN6au0_hvMfE2+9JkdhvJe7eAw@mail.gmail.com>
On Fri, 23 Dec 2011 21:00:41 +0800
Hillf Danton <dhillf@gmail.com> wrote:
> Page mapcount should be updated only if we are sure that the page ends
> up in the page table otherwise we would leak if we couldn't COW due to
> reservations or if idx is out of bounds.
It would be much nicer if we could run vma_needs_reservation() before
even looking up or allocating the page.
And afaict the interface is set up to do that: you run
vma_needs_reservation() before allocating the page and then
vma_commit_reservation() afterwards.
But hugetlb_no_page() and hugetlb_fault() appear to have forgotten to
run vma_commit_reservation() altogether. Why isn't this as busted as
it appears to be?
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WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Hillf Danton <dhillf@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [PATCH] mm: hugetlb: undo change to page mapcount in fault handler
Date: Wed, 4 Jan 2012 15:16:32 -0800 [thread overview]
Message-ID: <20120104151632.05e6b3b0.akpm@linux-foundation.org> (raw)
In-Reply-To: <CAJd=RBBY0sKdtdx9d8KXTchjaN6au0_hvMfE2+9JkdhvJe7eAw@mail.gmail.com>
On Fri, 23 Dec 2011 21:00:41 +0800
Hillf Danton <dhillf@gmail.com> wrote:
> Page mapcount should be updated only if we are sure that the page ends
> up in the page table otherwise we would leak if we couldn't COW due to
> reservations or if idx is out of bounds.
It would be much nicer if we could run vma_needs_reservation() before
even looking up or allocating the page.
And afaict the interface is set up to do that: you run
vma_needs_reservation() before allocating the page and then
vma_commit_reservation() afterwards.
But hugetlb_no_page() and hugetlb_fault() appear to have forgotten to
run vma_commit_reservation() altogether. Why isn't this as busted as
it appears to be?
next prev parent reply other threads:[~2012-01-04 23:16 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-22 13:36 [PATCH] mm: hugetlb: undo change to page mapcount in fault handler Hillf Danton
2011-12-22 13:36 ` Hillf Danton
2011-12-22 16:36 ` Michal Hocko
2011-12-22 16:36 ` Michal Hocko
2011-12-23 13:00 ` Hillf Danton
2011-12-23 13:00 ` Hillf Danton
2011-12-26 7:00 ` KAMEZAWA Hiroyuki
2011-12-26 7:00 ` KAMEZAWA Hiroyuki
2012-01-04 23:16 ` Andrew Morton [this message]
2012-01-04 23:16 ` Andrew Morton
2012-01-10 20:45 ` Andrew Morton
2012-01-10 20:45 ` Andrew Morton
2012-01-11 12:06 ` Hillf Danton
2012-01-11 12:06 ` Hillf Danton
2012-01-13 23:39 ` Andrew Morton
2012-01-13 23:39 ` Andrew Morton
2012-01-14 5:27 ` Hillf Danton
2012-01-14 5:27 ` Hillf Danton
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