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mm/compaction: correctly return failure with bogus compound_order in strict mode

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In strict mode, we should return 0 if there is any hole in pageblock.  If
we successfully isolated pages at beginning at pageblock and then have a
bogus compound_order outside pageblock in next page.  We will abort search
loop with blockpfn > end_pfn.  Although we will limit blockpfn to end_pfn,
we will treat it as a successful isolation in strict mode as blockpfn is
not < end_pfn and return partial isolated pages.  Then
isolate_freepages_range may success unexpectly with hole in isolated
range.

Link: https://lkml.kernel.org/r/20230901155141.249860-4-shikemeng@huaweicloud.com
Fixes: 9fcd6d2e05 ("mm, compaction: skip compound pages by order in free scanner")
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Kemeng Shi 2023-09-01 23:51:38 +08:00 committed by Andrew Morton
parent 4c17989116
commit 3da0272a4c
1 changed files with 3 additions and 3 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

6
mm/compaction.c
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@ -626,11 +626,12 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
if (PageCompound(page)) {
const unsigned int order = compound_order(page);
if (likely(order <= MAX_ORDER)) {
if (blockpfn + (1UL << order) <= end_pfn) {
blockpfn += (1UL << order) - 1;
page += (1UL << order) - 1;
nr_scanned += (1UL << order) - 1;
}
goto isolate_fail;
}
@ -678,8 +679,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
spin_unlock_irqrestore(&cc->zone->lock, flags);
/*
* There is a tiny chance that we have read bogus compound_order(),
* so be careful to not go outside of the pageblock.
* Be careful to not go outside of the pageblock.
*/
if (unlikely(blockpfn > end_pfn))
blockpfn = end_pfn;