+ mm-memory_failure-allow-truncate_error_folio-to-return-mf_delayed.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: memory_failure: Allow truncate_error_folio to return MF_DELAYED
has been added to the -mm mm-new branch.  Its filename is
     mm-memory_failure-allow-truncate_error_folio-to-return-mf_delayed.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory_failure-allow-truncate_error_folio-to-return-mf_delayed.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.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Lisa Wang <wyihan@google.com>
Subject: mm: memory_failure: Allow truncate_error_folio to return MF_DELAYED
Date: Thu, 17 Sep 2026 20:43:48 +0000

The .error_remove_folio a_ops is used by different filesystems to handle
folio truncation upon discovery of a memory failure in the memory
associated with the given folio.

Currently, MF_DELAYED is treated as an error, causing "Failed to punch
page" to be written to the console.  MF_DELAYED is then relayed to the
caller of truncate_error_folio() as MF_FAILED.  This further causes
memory_failure() to return -EBUSY, which then always causes a SIGBUS.

This is also implies that regardless of whether the thread's memory
corruption kill policy is PR_MCE_KILL_EARLY or PR_MCE_KILL_LATE, a memory
failure with MF_DELAYED will always cause a SIGBUS.

Update truncate_error_folio() to return MF_DELAYED to the caller if the
.error_remove_folio() callback reports MF_DELAYED.

Link: https://lore.kernel.org/20260917-memory-failure-mf-delayed-fix-v6-2-4b00856b5364@google.com
Fixes: 6a46079cf57a ("HWPOISON: The high level memory error handler in the VM v7")
Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory")
Signed-off-by: Lisa Wang <wyihan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Ackerley Tng <ackerleytng@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Isaku Yamahata <isaku.yamahata@intel.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vishal Annapurve <vannapurve@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: Yu Zhang <yu.c.zhang@linux.intel.com>
---

 mm/memory-failure.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/mm/memory-failure.c~mm-memory_failure-allow-truncate_error_folio-to-return-mf_delayed
+++ a/mm/memory-failure.c
@@ -939,10 +939,12 @@ static int truncate_error_folio(struct f
 	if (mapping->a_ops->error_remove_folio) {
 		int err = mapping->a_ops->error_remove_folio(mapping, folio);
 
-		if (err != 0)
+		if (err == MF_DELAYED)
+			ret = err;
+		else if (err != 0)
 			pr_info("%#lx: Failed to punch page: %d\n", pfn, err);
 		else if (!filemap_release_folio(folio, GFP_NOIO))
-			pr_info("%#lx: failed to release buffers\n", pfn);
+			pr_info("%#lx: Failed to release buffers\n", pfn);
 		else
 			ret = MF_RECOVERED;
 	} else {
_

Patches currently in -mm which might be from wyihan@google.com are

mm-memory_failure-clarify-the-mf_delayed-definition.patch
mm-memory_failure-allow-truncate_error_folio-to-return-mf_delayed.patch
mm-shmem-update-shmem-handler-to-the-mf_delayed-definition.patch
mm-memory_failure-generalize-extra_pins-handling-to-all-mf_delayed-cases.patch
mm-selftests-add-shmem-into-memory-failure-test.patch