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

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: 9fcd6d2e052e ("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>

diff --git a/mm/compaction.c b/mm/compaction.c
index a40550a33aee691b08bbebec36336b30abcd65d6..9ecbfbc695e5f68d8a211f32032beb75b32093eb 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -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 @@ isolate_fail:
                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;