FAILED: patch "[PATCH] mm: migrate: fix THP's mapcount on isolation" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Possible dependencies:

829ae0f81ce0 ("mm: migrate: fix THP's mapcount on isolation") 89f6c88a6ab4 ("mm: __isolate_lru_page_prepare() in isolate_migratepages_block()") c2135f7c570b ("mm/vmscan: __isolate_lru_page_prepare() cleanup") 9df41314390b ("mm/compaction: do page isolation first in compaction") d25b5bd8a8f4 ("mm/lru: introduce TestClearPageLRU()")
13805a88a9bd ("mm/mlock: remove __munlock_isolate_lru_page()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 829ae0f81ce093d674ff2256f66a714753e9ce32 Mon Sep 17 00:00:00 2001
From: Gavin Shan <[email protected]>
Date: Thu, 24 Nov 2022 17:55:23 +0800
Subject: [PATCH] mm: migrate: fix THP's mapcount on isolation

The issue is reported when removing memory through virtio_mem device. The transparent huge page, experienced copy-on-write fault, is wrongly regarded as pinned. The transparent huge page is escaped from being isolated in isolate_migratepages_block(). The transparent huge page can't be migrated and the corresponding memory block can't be put into offline state.

Fix it by replacing page_mapcount() with total_mapcount(). With this, the transparent huge page can be isolated and migrated, and the memory block can be put into offline state. Besides, The page's refcount is increased a bit earlier to avoid the page is released when the check is executed.

index c51f7f545afe..1f6da31dd9a5 100644
@@ -984,29 +984,29 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 			goto isolate_fail;
 		}
 
+		/*
+		 * Be careful not to clear PageLRU until after we're
+		 * sure the page is not being freed elsewhere -- the
+		 * page release code relies on it.
+		 */
+		if (unlikely(!get_page_unless_zero(page)))
+			goto isolate_fail;
+
 		/*
 		 * Migration will fail if an anonymous page is pinned in memory,
 		 * so avoid taking lru_lock and isolating it unnecessarily in an
 		 * admittedly racy check.
 		 */
 		mapping = page_mapping(page);
-		if (!mapping && page_count(page) > page_mapcount(page))
-			goto isolate_fail;
+		if (!mapping && (page_count(page) - 1) > total_mapcount(page))
+			goto isolate_fail_put;
 
 		/*
 		 * Only allow to migrate anonymous pages in GFP_NOFS context
 		 * because those do not depend on fs locks.
 		 */
 		if (!(cc->gfp_mask & __GFP_FS) && mapping)
-			goto isolate_fail;
-
-		/*
-		 * Be careful not to clear PageLRU until after we're
-		 * sure the page is not being freed elsewhere -- the
-		 * page release code relies on it.
-		 */
-		if (unlikely(!get_page_unless_zero(page)))
-			goto isolate_fail;
+			goto isolate_fail_put;
 
 		/* Only take pages on LRU: a check now makes later tests safe */
 		if (!PageLRU(page))