From: Mel Gorman <mgorman@techsingularity.net>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org,
Andrea Arcangeli <aarcange@redhat.com>,
David Hildenbrand <david@redhat.com>,
Michal Hocko <mhocko@kernel.org>, Mike Rapoport <rppt@kernel.org>,
stable@vger.kernel.org
Subject: Re: [PATCH] mm, compaction: make fast_isolate_freepages() stay within zone
Date: Wed, 17 Feb 2021 18:50:16 +0000 [thread overview]
Message-ID: <20210217185015.GF3697@techsingularity.net> (raw)
In-Reply-To: <20210217173300.6394-1-vbabka@suse.cz>
On Wed, Feb 17, 2021 at 06:33:00PM +0100, Vlastimil Babka wrote:
> Compaction always operates on pages from a single given zone when isolating
> both pages to migrate and freepages. Pageblock boundaries are intersected with
> zone boundaries to be safe in case zone starts or ends in the middle of
> pageblock. The use of pageblock_pfn_to_page() protects against non-contiguous
> pageblocks.
>
> The functions fast_isolate_freepages() and fast_isolate_around() don't
> currently protect the fast freepage isolation thoroughly enough against these
> corner cases, and can result in freepage isolation operate outside of zone
> boundaries:
>
> - in fast_isolate_freepages() if we get a pfn from the first pageblock of a
> zone that starts in the middle of that pageblock, 'highest' can be a pfn
> outside of the zone. If we fail to isolate anything in this function, we
> may then call fast_isolate_around() on a pfn outside of the zone and there
> effectively do a set_pageblock_skip(page_to_pfn(highest)) which may currently
> hit a VM_BUG_ON() in some configurations
> - fast_isolate_around() checks only the zone end boundary and not beginning,
> nor that the pageblock is contiguous (with pageblock_pfn_to_page()) so it's
> possible that we end up calling isolate_freepages_block() on a range of pfn's
> from two different zones and end up e.g. isolating freepages under the wrong
> zone's lock.
>
> This patch should fix the above issues.
>
> Fixes: 5a811889de10 ("mm, compaction: use free lists to quickly locate a migration target")
Acked-by: Mel Gorman <mgorman@techsingularity.net>
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2021-02-17 18:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 17:33 [PATCH] mm, compaction: make fast_isolate_freepages() stay within zone Vlastimil Babka
2021-02-17 18:16 ` David Rientjes
2021-02-17 18:50 ` Mel Gorman [this message]
2021-02-18 17:42 ` Vlastimil Babka
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