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SubjectRe: [PATCH 3/3] mm: fix return value in __alloc_contig_migrate_range()
Date
Joonsoo Kim <js1304@gmail.com> 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@gmail.com>
> Cc: Michal Nazarewicz <mina86@mina86.com>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Christoph Lameter <cl@linux.com>

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.
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 4403009..02d4519 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5673,7 +5673,6 @@ static int __alloc_contig_migrate_range(unsigned long start, unsigned long end)
> }
> tries = 0;
> } else if (++tries == 5) {
> - ret = ret < 0 ? ret : -EBUSY;
> break;
> }
>
> @@ -5683,7 +5682,7 @@ static int __alloc_contig_migrate_range(unsigned long start, unsigned long end)
> }
>
> putback_lru_pages(&cc.migratepages);
> - return ret > 0 ? 0 : ret;
> + return ret <= 0 ? ret : -EBUSY;
> }
>
> /*

--
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.o. | Liege of Serenly Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michal "mina86" Nazarewicz (o o)
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