linux-kernel - [PATCH] mm: teach mincore

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Message-ID: <20230302222404.175303-1-jthoughton@google.com>
Date:   Thu,  2 Mar 2023 22:24:04 +0000
From:   James Houghton <jthoughton@...gle.com>
To:     Peter Xu <peterx@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     David Hildenbrand <david@...hat.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Anish Moorthy <amoorthy@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        James Houghton <jthoughton@...gle.com>
Subject: [PATCH] mm: teach mincore_hugetlb about pte markers

By checking huge_pte_none(), we incorrectly classify PTE markers as
"present". Instead, check huge_pte_none_mostly(), classifying PTE
markers the same as if the PTE were completely blank.

PTE markers, unlike other kinds of swap entries, don't reference any
physical page and don't indicate that a physical page was mapped
previously. As such, treat them as non-present for the sake of
mincore().

Fixes: 5c041f5d1f23 ("mm: teach core mm about pte markers")
Signed-off-by: James Houghton <jthoughton@...gle.com>
---
 mm/mincore.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mincore.c b/mm/mincore.c
index cd69b9db0081..d359650b0f75 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -33,7 +33,7 @@ static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
 	 * Hugepages under user process are always in RAM and never
 	 * swapped out, but theoretically it needs to be checked.
 	 */
-	present = pte && !huge_pte_none(huge_ptep_get(pte));
+	present = pte && !huge_pte_none_mostly(huge_ptep_get(pte));
 	for (; addr != end; vec++, addr += PAGE_SIZE)
 		*vec = present;
 	walk->private = vec;
-- 
2.40.0.rc0.216.gc4246ad0f0-goog