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Date: Mon, 30 Jul 2012 14:30:35 -0500 (CDT)
From: Christoph Lameter <cl@linux.com>
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To: JoonSoo Kim <js1304@gmail.com>
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        linux-mm@kvack.org, Sasha Levin <levinsasha928@gmail.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>
Subject: Re: [RESEND PATCH 2/4 v3] mm: fix possible incorrect return value
 of migrate_pages() syscall
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On Sat, 28 Jul 2012, JoonSoo Kim wrote:

> 2012/7/28 Christoph Lameter <cl@linux.com>:
> > On Sat, 28 Jul 2012, Joonsoo Kim wrote:
> >
> >> do_migrate_pages() can return the number of pages not migrated.
> >> Because migrate_pages() syscall return this value directly,
> >> migrate_pages() syscall may return the number of pages not migrated.
> >> In fail case in migrate_pages() syscall, we should return error value.
> >> So change err to -EBUSY
> >
> > Lets leave this alone. This would change the migrate_pages semantics
> > because a successful move of N out of M pages would be marked as a
> > total failure although pages were in fact moved.
> >
>
> Okay.
> Then, do we need to fix man-page of migrate_pages() syscall?
> According to man-page, only returning 0 or -1 is valid.
> Without this patch, it can return positive value.

Yes the manpage needs updating to say that it can return the number of
pages not migrated.