linux-kernel - Re: [PATCH v2 2/7] mm/migrate: correct failure handling if !hugepage_migration

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Message-ID: <20131210083825.GB24992@lge.com>
Date:	Tue, 10 Dec 2013 17:38:25 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Rafael Aquini <aquini@...hat.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Vlastimil Babka <vbabka@...e.cz>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>
Subject: Re: [PATCH v2 2/7] mm/migrate: correct failure handling if
 !hugepage_migration_support()

On Mon, Dec 09, 2013 at 04:17:32PM +0000, Christoph Lameter wrote:
> On Mon, 9 Dec 2013, Joonsoo Kim wrote:
> 
> > We should remove the page from the list if we fail without ENOSYS,
> > since migrate_pages() consider error cases except -ENOMEM and -EAGAIN
> > as permanent failure and it assumes that the page would be removed from
> > the list. Without this patch, we could overcount number of failure.
> 
> Ok what does the patch do about this? I dont see any modifications. Remove
> this part of the description?

Description is slightly wrong.
Following is correct one.

"We should remove the page from the list if we fail *with* ENOSYS,"

And this patch do this by adding putback_active_hugepage(hpage)
on ENOSYS case.

> 
> > In addition, we should put back the new hugepage if
> > !hugepage_migration_support(). If not, we would leak hugepage memory.
> 
> Ok looks like that is fixed by this patch.
> 
> Acked-by: Christoph Lameter <cl@...ux.com>

Thanks.
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