+ mm-shmem-swap-fix-softlockup-with-mthp-swapin-v3.patch added to mm-hotfixes-unstable branch

+ mm-shmem-swap-fix-softlockup-with-mthp-swapin-v3.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm-shmem-swap-fix-softlockup-with-mthp-swapin-v3
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-shmem-swap-fix-softlockup-with-mthp-swapin-v3.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-shmem-swap-fix-softlockup-with-mthp-swapin-v3.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: Kairui Song <kasong@tencent.com>
Subject: mm-shmem-swap-fix-softlockup-with-mthp-swapin-v3
Date: Wed, 11 Jun 2025 02:16:45 +0800

add comment

Link: https://lkml.kernel.org/r/20250610181645.45922-1-ryncsn@gmail.com
Fixes: 1dd44c0af4fa1 ("mm: shmem: skip swapcache for swapin of synchronous swap device")
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/shmem.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/shmem.c~mm-shmem-swap-fix-softlockup-with-mthp-swapin-v3
+++ a/mm/shmem.c
@@ -2273,6 +2273,8 @@ static int shmem_swapin_folio(struct ino
 		 * If uffd is active for the vma, we need per-page fault
 		 * fidelity to maintain the uffd semantics, then fallback
 		 * to swapin order-0 folio, as well as for zswap case.
+		 * Any existing sub folio in the swap cache also blocks
+		 * mTHP swapin.
 		 */
 		if (order > 0 && ((vma && unlikely(userfaultfd_armed(vma))) ||
 				  !zswap_never_enabled() ||
_

Patches currently in -mm which might be from kasong@tencent.com are

mm-userfaultfd-fix-race-of-userfaultfd_move-and-swap-cache.patch
mm-shmem-swap-fix-softlockup-with-mthp-swapin.patch
mm-shmem-swap-fix-softlockup-with-mthp-swapin-v3.patch
mm-list_lru-refactor-the-locking-code.patch