Re: [PATCH 3/3] mm: fix return value in__alloc_contig_migrate_range()

[Michal Nazarewicz]

On Mon, 16 Jul 2012 20:40:56 +0200, JoonSoo Kim <js1304@xxxxxxxxx> wrote:

> 2012/7/17 Michal Nazarewicz <mina86@xxxxxxxxxx>:
> > Joonsoo Kim <js1304@xxxxxxxxx> writes:
> >
> > > migrate_pages() would return positive value in some failure case,
> > > so 'ret > 0 ? 0 : ret' may be wrong.
> > > This fix it and remove one dead statement.
> > >
> > > Signed-off-by: Joonsoo Kim <js1304@xxxxxxxxx>
> > > Cc: Michal Nazarewicz <mina86@xxxxxxxxxx>
> > > Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> > > Cc: Minchan Kim <minchan@xxxxxxxxxx>
> > > Cc: Christoph Lameter <cl@xxxxxxxxx>
> >
> > Have you actually encountered this problem?  If migrate_pages() fails
> > with a positive value, the code that you are removing kicks in and
> > -EBUSY is assigned to ret (now that I look at it, I think that in the
> > current code the "return ret > 0 ? 0 : ret;" statement could be reduced
> > to "return ret;").  Your code seems to be cleaner, but the commit
> > message does not look accurate to me.
>
> I don't encounter this problem yet.
>
> If migrate_pages() with offlining false meets KSM page, then migration failed.
> In this case, failed page is removed from cc.migratepage list and
> return failed count.

Good point.

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