+ mm-hugetlb-correct-demote-page-offset-logic.patch added to mm-hotfixes-unstable branch

+ mm-hugetlb-correct-demote-page-offset-logic.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/hugetlb: correct demote page offset logic
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-hugetlb-correct-demote-page-offset-logic.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-correct-demote-page-offset-logic.patch

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

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------------------------------------------------------
From: Doug Berger <opendmb@gmail.com>
Subject: mm/hugetlb: correct demote page offset logic
Date: Wed, 14 Sep 2022 12:09:17 -0700

With gigantic pages it may not be true that struct page structures are
contiguous across the entire gigantic page.  The nth_page macro is used
here in place of direct pointer arithmetic to correct for this.

Link: https://lkml.kernel.org/r/20220914190917.3517663-1-opendmb@gmail.com
Fixes: 8531fc6f52f5 ("hugetlb: add hugetlb demote page support")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb.c |   14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlb-correct-demote-page-offset-logic
+++ a/mm/hugetlb.c
@@ -3420,6 +3420,7 @@ static int demote_free_huge_page(struct
 {
 	int i, nid = page_to_nid(page);
 	struct hstate *target_hstate;
+	struct page *subpage;
 	int rc = 0;
 
 	target_hstate = size_to_hstate(PAGE_SIZE << h->demote_order);
@@ -3453,15 +3454,16 @@ static int demote_free_huge_page(struct
 	mutex_lock(&target_hstate->resize_lock);
 	for (i = 0; i < pages_per_huge_page(h);
 				i += pages_per_huge_page(target_hstate)) {
+		subpage = nth_page(page, i);
 		if (hstate_is_gigantic(target_hstate))
-			prep_compound_gigantic_page_for_demote(page + i,
+			prep_compound_gigantic_page_for_demote(subpage,
 							target_hstate->order);
 		else
-			prep_compound_page(page + i, target_hstate->order);
-		set_page_private(page + i, 0);
-		set_page_refcounted(page + i);
-		prep_new_huge_page(target_hstate, page + i, nid);
-		put_page(page + i);
+			prep_compound_page(subpage, target_hstate->order);
+		set_page_private(subpage, 0);
+		set_page_refcounted(subpage);
+		prep_new_huge_page(target_hstate, subpage, nid);
+		put_page(subpage);
 	}
 	mutex_unlock(&target_hstate->resize_lock);
 
_

Patches currently in -mm which might be from opendmb@gmail.com are

mm-hugetlb-correct-demote-page-offset-logic.patch