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Date:   Wed, 29 Nov 2017 14:38:17 +0900
From:   Joonsoo Kim <>
To:     Mike Kravetz <>
        Vlastimil Babka <>,
        Michal Nazarewicz <>,
        Michal Hocko <>,
        Mel Gorman <>,
        Johannes Weiner <>,
        Andrew Morton <>,
Subject: Re: [PATCH v2] mm/cma: fix alloc_contig_range ret code/potential leak

On Wed, Nov 22, 2017 at 10:52:14AM -0800, Mike Kravetz wrote:
> If the call __alloc_contig_migrate_range() in alloc_contig_range
> returns -EBUSY, processing continues so that test_pages_isolated()
> is called where there is a tracepoint to identify the busy pages.
> However, it is possible for busy pages to become available between
> the calls to these two routines.  In this case, the range of pages
> may be allocated.   Unfortunately, the original return code (ret
> == -EBUSY) is still set and returned to the caller.  Therefore,
> the caller believes the pages were not allocated and they are leaked.
> Update comment to indicate that allocation is still possible even if
> __alloc_contig_migrate_range returns -EBUSY.  Also, clear return code
> in this case so that it is not accidentally used or returned to caller.
> Fixes: 8ef5849fa8a2 ("mm/cma: always check which page caused allocation failure")
> Cc: <>
> Signed-off-by: Mike Kravetz <>

Good catch!!

Acked-by: Joonsoo Kim <>


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