| From: Baolin Wang <baolin.wang@linux.alibaba.com> |
| 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@linux.alibaba.com |
| 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> |
| Acked-by: Mel Gorman <mgorman@techsingularity.net> |
| Cc: Oscar Salvador <osalvador@suse.de> |
| Cc: William Lam <william.lam@bytedance.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| 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); |
| |
| /* |
| _ |
