The quilt patch titled
Subject: mm: compaction: fix the possible deadlock when isolating hugetlb pages
has been removed from the -mm tree. Its filename was
mm-compaction-fix-the-possible-deadlock-when-isolating-hugetlb-pages.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Subject: mm: compaction: fix the possible deadlock when isolating hugetlb pages
Date: Thu, 16 Mar 2023 19:06:47 +0800
When trying to isolate a migratable pageblock, it can contain several
normal pages or several hugetlb pages (e.g. CONT-PTE 64K hugetlb on arm64)
in a pageblock. That means we may hold the lru lock of a normal page to
continue to isolate the next hugetlb page by isolate_or_dissolve_huge_page()
in the same migratable pageblock.
However in the isolate_or_dissolve_huge_page(), it may allocate a new hugetlb
page and dissolve the old one by alloc_and_dissolve_hugetlb_folio() if the
hugetlb's refcount is zero. That means we can still enter the direct compaction
path to allocate a new hugetlb page under the current lru lock, which
may cause possible deadlock.
To avoid this possible deadlock, we should release the lru lock when
trying to isolate a hugetbl page. Moreover it does not make sense to take
the lru lock to isolate a hugetlb, which is not in the lru list.
Link: https://lkml.kernel.org/r/7ab3bffebe59fb419234a68dec1e4572a2518563.1678962352.git.baolin.wang@xxxxxxxxxxxxxxxxx
Fixes: 369fa227c219 ("mm: make alloc_contig_range handle free hugetlb pages")
Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: William Lam <william.lam@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/mm/compaction.c~mm-compaction-fix-the-possible-deadlock-when-isolating-hugetlb-pages
+++ a/mm/compaction.c
@@ -894,6 +894,11 @@ isolate_migratepages_block(struct compac
}
if (PageHuge(page) && cc->alloc_contig) {
+ if (locked) {
+ unlock_page_lruvec_irqrestore(locked, flags);
+ locked = NULL;
+ }
+
ret = isolate_or_dissolve_huge_page(page, &cc->migratepages);
/*
_
Patches currently in -mm which might be from baolin.wang@xxxxxxxxxxxxxxxxx are
