+ mm-compaction-correctly-return-failure-with-bogus-compound_order-in-strict-mode.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/compaction: correctly return failure with bogus compound_order in strict mode
has been added to the -mm mm-unstable branch.  Its filename is
     mm-compaction-correctly-return-failure-with-bogus-compound_order-in-strict-mode.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-compaction-correctly-return-failure-with-bogus-compound_order-in-strict-mode.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Kemeng Shi <shikemeng@huaweicloud.com>
Subject: mm/compaction: correctly return failure with bogus compound_order in strict mode
Date: Fri, 1 Sep 2023 23:51:38 +0800

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>
---

 mm/compaction.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/compaction.c~mm-compaction-correctly-return-failure-with-bogus-compound_order-in-strict-mode
+++ a/mm/compaction.c
@@ -626,11 +626,12 @@ static unsigned long isolate_freepages_b
 		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;
_

Patches currently in -mm which might be from shikemeng@huaweicloud.com are

mm-compaction-use-correct-list-in-move_freelist_head-tail.patch
mm-compaction-call-list_is_first-last-more-intuitively-in-move_freelist_head-tail.patch
mm-compaction-correctly-return-failure-with-bogus-compound_order-in-strict-mode.patch
mm-compaction-remove-repeat-compact_blockskip_flush-check-in-reset_isolation_suitable.patch
mm-compaction-improve-comment-of-is_via_compact_memory.patch
mm-compaction-factor-out-code-to-test-if-we-should-run-compaction-for-target-order.patch