+ mm-hugetlb-fix-set_max_huge_pages-when-there-are-surplus-pages.patch added to mm-unstable branch

+ mm-hugetlb-fix-set_max_huge_pages-when-there-are-surplus-pages.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/hugetlb: fix set_max_huge_pages() when there are surplus pages
has been added to the -mm mm-unstable branch.  Its filename is
     mm-hugetlb-fix-set_max_huge_pages-when-there-are-surplus-pages.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-fix-set_max_huge_pages-when-there-are-surplus-pages.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: Jinjiang Tu <tujinjiang@huawei.com>
Subject: mm/hugetlb: fix set_max_huge_pages() when there are surplus pages
Date: Tue, 25 Feb 2025 22:19:33 +0800

In set_max_huge_pages(), min_count should mean the acquired persistent
huge pages, but it contains surplus huge pages.  It will leads to failing
to freeing free huge pages for a Node.

Steps to reproduce:
1) create 5 huge pages in Node 0
2) run a program to use all the huge pages
3) create 5 huge pages in Node 1
4) echo 0 > nr_hugepages for Node 1 to free the huge pages

The result:
        Node 0    Node 1
Total     5         5
Free      0         5
Surp      5         5

Link: https://lkml.kernel.org/r/20250225141933.3852667-1-tujinjiang@huawei.com
Fixes: 9a30523066cd ("hugetlb: add per node hstate attributes")
Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/hugetlb.c~mm-hugetlb-fix-set_max_huge_pages-when-there-are-surplus-pages
+++ a/mm/hugetlb.c
@@ -3933,7 +3933,7 @@ static int set_max_huge_pages(struct hst
 	 * and won't grow the pool anywhere else. Not until one of the
 	 * sysctls are changed, or the surplus pages go out of use.
 	 */
-	min_count = h->resv_huge_pages + h->nr_huge_pages - h->free_huge_pages;
+	min_count = h->resv_huge_pages + persistent_huge_pages(h) - h->free_huge_pages;
 	min_count = max(count, min_count);
 	try_to_free_low(h, min_count, nodes_allowed);
 
_

Patches currently in -mm which might be from tujinjiang@huawei.com are

mm-hugetlb-fix-set_max_huge_pages-when-there-are-surplus-pages.patch