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UPSTREAM: mm/thp: fix deferred split queue not partially_mapped: fix

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Though even more elusive than before, list_del corruption has still been
seen on THP's deferred split queue.

The idea in commit e66f3185fa04 was right, but its implementation wrong.
The context omitted an important comment just before the critical test:
"split_folio() removes folio from list on success." In ignoring that
comment, when a THP split succeeded, the code went on to release the
preceding safe folio, preserving instead an irrelevant (formerly head)
folio: which gives no safety because it's not on the list.  Fix the logic.

Link: https://lkml.kernel.org/r/3c995a30-31ce-0998-1b9f-3a2cb9354c91@google.com
Fixes: e66f3185fa04 ("mm/thp: fix deferred split queue not partially_mapped")
Change-Id: I582667f7dc86e306a3f68519de2c5ce8573baf6c
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Usama Arif <usamaarif642@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit a3477c9e02cc9d62a7c8bfc4e7453f5af9a175aa)
Bug: 419599659
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
This commit is contained in:
Hugh Dickins
2024-11-10 13:11:21 -08:00
committed by Kalesh Singh
parent 3a8faa5b25
commit 374babecde
1 changed files with 3 additions and 1 deletions
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4
mm/huge_memory.c
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@@ -3797,7 +3797,9 @@ next:
* in the case it was underused, then consider it used and * in the case it was underused, then consider it used and
* don't add it back to split_queue. * don't add it back to split_queue.
*/ */
if (!did_split && !folio_test_partially_mapped(folio)) { if (did_split) {
; /* folio already removed from list */
} else if (!folio_test_partially_mapped(folio)) {
list_del_init(&folio->_deferred_list); list_del_init(&folio->_deferred_list);
removed++; removed++;
} else { } else {