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mm: compaction: fix the possible deadlock when isolating hugetlb pages
authorBaolin Wang <baolin.wang@linux.alibaba.com>
Thu, 16 Mar 2023 11:06:47 +0000 (19:06 +0800)
committerAndrew Morton <akpm@linux-foundation.org>
Thu, 6 Apr 2023 02:42:50 +0000 (19:42 -0700)
commit1c06b6a599b5b7be74a6baffafa00b0f70cbe523
treeaed24bb201db0eef17bda869537ac711bd8ee356
parent56d48d8dbefb1cae3aeae54284f7d6f52a41ec23
mm: compaction: fix the possible deadlock when isolating hugetlb pages

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