On 8/26/2023 11:36 PM, Kemeng Shi wrote:
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.
Fixes: 9fcd6d2e052ee ("mm, compaction: skip compound pages by order in free scanner")
Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
LGTM.
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index a40550a33aee..b4d03c9ffe7c 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -631,6 +631,14 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
page += (1UL << order) - 1;
nr_scanned += (1UL << order) - 1;
}
+ /*
+ * There is a tiny chance that we have read bogus
+ * compound_order(), so be careful to not go outside
+ * of the pageblock.
+ */
+ if (unlikely(blockpfn >= end_pfn))
+ blockpfn = end_pfn - 1;
+
goto isolate_fail;
}
@@ -678,8 +686,7 @@ 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;
