+ mm-rmap-fix-two-comments-related-to-huge_pmd_unshare.patch added to mm-new branch

+ mm-rmap-fix-two-comments-related-to-huge_pmd_unshare.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/rmap: fix two comments related to huge_pmd_unshare()
has been added to the -mm mm-new branch.  Its filename is
     mm-rmap-fix-two-comments-related-to-huge_pmd_unshare.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-rmap-fix-two-comments-related-to-huge_pmd_unshare.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

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------------------------------------------------------
From: "David Hildenbrand (Red Hat)" <david@kernel.org>
Subject: mm/rmap: fix two comments related to huge_pmd_unshare()
Date: Fri, 12 Dec 2025 08:10:18 +0100

PMD page table unsharing no longer touches the refcount of a PMD page
table.  Also, it is not about dropping the refcount of a "PMD page" but
the "PMD page table".

Let's just simplify by saying that the PMD page table was unmapped,
consequently also unmapping the folio that was mapped into this page.

This code should be deduplicated in the future.

Link: https://lkml.kernel.org/r/20251212071019.471146-4-david@kernel.org
Fixes: 59d9094df3d7 ("mm: hugetlb: independent PMD page table shared count")
Signed-off-by: David Hildenbrand (Red Hat) <david@kernel.org>
Reviewed-by: Rik van Riel <riel@surriel.com>
Tested-by: Laurence Oberman <loberman@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Oscar Salvador <osalvador@suse.de>
Cc: Liu Shixin <liushixin2@huawei.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Harry Yoo <harry.yoo@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Prakash Sangappa <prakash.sangappa@oracle.com>
Cc: Uschakow, Stanislav" <suschako@amazon.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/rmap.c |   20 ++++----------------
 1 file changed, 4 insertions(+), 16 deletions(-)

--- a/mm/rmap.c~mm-rmap-fix-two-comments-related-to-huge_pmd_unshare
+++ a/mm/rmap.c
@@ -2016,14 +2016,8 @@ static bool try_to_unmap_one(struct foli
 					flush_tlb_range(vma,
 						range.start, range.end);
 					/*
-					 * The ref count of the PMD page was
-					 * dropped which is part of the way map
-					 * counting is done for shared PMDs.
-					 * Return 'true' here.  When there is
-					 * no other sharing, huge_pmd_unshare
-					 * returns false and we will unmap the
-					 * actual page and drop map count
-					 * to zero.
+					 * The PMD table was unmapped,
+					 * consequently unmapping the folio.
 					 */
 					goto walk_done;
 				}
@@ -2416,14 +2410,8 @@ static bool try_to_migrate_one(struct fo
 						range.start, range.end);
 
 					/*
-					 * The ref count of the PMD page was
-					 * dropped which is part of the way map
-					 * counting is done for shared PMDs.
-					 * Return 'true' here.  When there is
-					 * no other sharing, huge_pmd_unshare
-					 * returns false and we will unmap the
-					 * actual page and drop map count
-					 * to zero.
+					 * The PMD table was unmapped,
+					 * consequently unmapping the folio.
 					 */
 					page_vma_mapped_walk_done(&pvmw);
 					break;
_

Patches currently in -mm which might be from david@kernel.org are

mm-hugetlb-fix-hugetlb_pmd_shared.patch
mm-hugetlb-fix-two-comments-related-to-huge_pmd_unshare.patch
mm-rmap-fix-two-comments-related-to-huge_pmd_unshare.patch
mm-hugetlb-fix-excessive-ipi-broadcasts-when-unsharing-pmd-tables-using-mmu_gather.patch