+ mm-memory-failure-fix-deadlock-when-hugetlb_optimize_vmemmap-is-enabled-v2.patch added to mm-hotfixes-unstable branch

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

The patch titled
     Subject: mm/memory-failure: fix deadlock when hugetlb_optimize_vmemmap is enabled
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-memory-failure-fix-deadlock-when-hugetlb_optimize_vmemmap-is-enabled-v2.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-fix-deadlock-when-hugetlb_optimize_vmemmap-is-enabled-v2.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: Miaohe Lin <linmiaohe@huawei.com>
Subject: mm/memory-failure: fix deadlock when hugetlb_optimize_vmemmap is enabled
Date: Fri, 12 Apr 2024 10:57:54 +0800

extend comment per Oscar

Link: https://lkml.kernel.org/r/20240412025754.1897615-1-linmiaohe@huawei.com
Fixes: a6b40850c442 ("mm: hugetlb: replace hugetlb_free_vmemmap_enabled with a static_key")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Oscar Salvador <osalvador@suse.de>
Cc: <stable@vger.kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

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

--- a/mm/memory-failure.c~mm-memory-failure-fix-deadlock-when-hugetlb_optimize_vmemmap-is-enabled-v2
+++ a/mm/memory-failure.c
@@ -159,6 +159,10 @@ static int __page_handle_poison(struct p
 	 * dissolve_free_huge_page() might hold cpu_hotplug_lock via static_key_slow_dec()
 	 * when hugetlb vmemmap optimization is enabled. This will break current lock
 	 * dependency chain and leads to deadlock.
+	 * Disabling pcp before dissolving the page was a deterministic approach because
+	 * we made sure that those pages cannot end up in any PCP list. Draining PCP lists
+	 * expels those pages to the buddy system, but nothing guarantees that those pages
+	 * do not get back to a PCP queue if we need to refill those.
 	 */
 	ret = dissolve_free_huge_page(page);
 	if (!ret) {
_

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

mm-memory-failure-fix-deadlock-when-hugetlb_optimize_vmemmap-is-enabled.patch
mm-memory-failure-fix-deadlock-when-hugetlb_optimize_vmemmap-is-enabled-v2.patch
fork-defer-linking-file-vma-until-vma-is-fully-initialized.patch