From: Minchan Kim <minchan.kim@gmail.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Lameter <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>, Mel Gorman <mel@csn.ul.ie>
Subject: Re: [PATCH 1/3] When migrate_pages returns 0, all pages must have been released
Date: Sat, 22 Jan 2011 08:54:13 +0900 [thread overview]
Message-ID: <20110121235413.GA1703@barrios-desktop> (raw)
In-Reply-To: <20110121173618.GH9506@random.random>
On Fri, Jan 21, 2011 at 06:36:18PM +0100, Andrea Arcangeli wrote:
> On Fri, Jan 21, 2011 at 10:11:03AM -0600, Christoph Lameter wrote:
> > On Thu, 20 Jan 2011, Andrea Arcangeli wrote:
> >
> > > Which following putback_lru_page()? You mean
> > > putback_lru_page(newpage)? That is for the newly allocated page
> > > (allocated at the very top, so always needed), it's not relevant to
> > > the page_count(page) = 1. The page_count 1 is hold by the caller, so
> > > it's leaking memory right now (for everything but compaction).
> >
> > Ahh yes we removed the putback_lru_pages call from migrate_pages()
> > and broke the existing release logic. The caller has to call
> > putback_release_pages() as per commit
>
> putback_lru_paeges
>
> > cf608ac19c95804dc2df43b1f4f9e068aa9034ab
>
> That is the very commit that introduced the two bugs that I've fixed
> by code review.
>
> >
> > If that is still the case then we still have the double free.
>
> The caller only calls putback_lru_pages if ret != 0 (the two cases you
> refer to happen with ret = 0).
>
> Even if caller unconditionally calls putback_lru_pages (kind of what
> compaction did), it can't double free because migrate_pages already
> unlinked the pages before calling putback_lru_page(page), so there's
> no way to do a double free (however if the caller unconditionally
> called putback_lru_pages there would be no memleak to fix, but it
> doesn't).
>
> > Could we please document the calling conventions exactly in the source?
> > Right now it says that the caller should call putback_lru_pages().
>
> The caller should call putback_lru_pages only if ret != 0. Minchan
> this is your commit we're discussing can you check the commentary?
No problem.
I will send the patch.
Thanks Adnrea, Christoph.
>
> Thanks!
> Andrea
>
--
Kind regards,
Minchan Kim
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next prev parent reply other threads:[~2011-01-21 23:54 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-20 16:17 [PATCH 1/3] When migrate_pages returns 0, all pages must have been released Minchan Kim
2011-01-20 16:17 ` [PATCH 2/3] migration: Fix page corruption during hugepage migration Minchan Kim
2011-01-20 16:17 ` [PATCH 3/3] compaction: Check migrate_pages's return value instead of list_empty Minchan Kim
2011-01-26 8:18 ` Mel Gorman
2011-01-20 17:30 ` [PATCH 1/3] When migrate_pages returns 0, all pages must have been released Christoph Lameter
2011-01-20 18:24 ` Andrea Arcangeli
2011-01-20 18:49 ` Christoph Lameter
2011-01-20 21:28 ` Andrea Arcangeli
2011-01-21 16:11 ` Christoph Lameter
2011-01-21 17:36 ` Andrea Arcangeli
2011-01-21 23:54 ` Minchan Kim [this message]
2011-01-26 8:14 ` Mel Gorman
2011-01-26 23:06 ` Andrew Morton
2011-01-26 23:21 ` Minchan Kim
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