Messages in this thread Patch in this message | | | From | Baolin Wang <> | Subject | [PATCH v2 2/2] mm: compaction: fix the possible deadlock when isolating hugetlb pages | Date | Thu, 16 Mar 2023 19:06:47 +0800 |
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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.
Fixes: 369fa227c219 ("mm: make alloc_contig_range handle free hugetlb pages") Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> --- Changes from v1: - Collect reviewed tags. Thanks Mike and Vlastimil. --- mm/compaction.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/mm/compaction.c b/mm/compaction.c index 7e645cdfc2e9..3df076716691 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -894,6 +894,11 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, } 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); /* -- 2.27.0
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