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author | Vlastimil Babka <vbabka@suse.cz> | 2017-11-16 04:38:30 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-01-31 14:55:51 +0300 |
commit | 685cce58f1c2e4fb5dbc891edf3e1bbca217ed3e (patch) | |
tree | 14be73ef1946cfdceeb9bc033c92c1b188b68a0e /ipc | |
parent | 714c19ef57a5271c14ab6d1b5878f5662a0b3034 (diff) | |
download | linux-685cce58f1c2e4fb5dbc891edf3e1bbca217ed3e.tar.xz |
mm, page_alloc: fix potential false positive in __zone_watermark_ok
commit b050e3769c6b4013bb937e879fc43bf1847ee819 upstream.
Since commit 97a16fc82a7c ("mm, page_alloc: only enforce watermarks for
order-0 allocations"), __zone_watermark_ok() check for high-order
allocations will shortcut per-migratetype free list checks for
ALLOC_HARDER allocations, and return true as long as there's free page
of any migratetype. The intention is that ALLOC_HARDER can allocate
from MIGRATE_HIGHATOMIC free lists, while normal allocations can't.
However, as a side effect, the watermark check will then also return
true when there are pages only on the MIGRATE_ISOLATE list, or (prior to
CMA conversion to ZONE_MOVABLE) on the MIGRATE_CMA list. Since the
allocation cannot actually obtain isolated pages, and might not be able
to obtain CMA pages, this can result in a false positive.
The condition should be rare and perhaps the outcome is not a fatal one.
Still, it's better if the watermark check is correct. There also
shouldn't be a performance tradeoff here.
Link: http://lkml.kernel.org/r/20171102125001.23708-1-vbabka@suse.cz
Fixes: 97a16fc82a7c ("mm, page_alloc: only enforce watermarks for order-0 allocations")
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'ipc')
0 files changed, 0 insertions, 0 deletions