The quilt patch titled Subject: mm/shmem: fix race in shmem_undo_range w/THP has been removed from the -mm tree. Its filename was mm-shmem-fix-race-in-shmem_undo_range-w-thp.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------ From: David Stevens stevensd@chromium.org Subject: mm/shmem: fix race in shmem_undo_range w/THP Date: Tue, 18 Apr 2023 17:40:31 +0900
Split folios during the second loop of shmem_undo_range. It's not sufficient to only split folios when dealing with partial pages, since it's possible for a THP to be faulted in after that point. Calling truncate_inode_folio in that situation can result in throwing away data outside of the range being targeted.
[akpm@linux-foundation.org: tidy up comment layout] Link: https://lkml.kernel.org/r/20230418084031.3439795-1-stevensd@google.com Fixes: b9a8a4195c7d ("truncate,shmem: Handle truncates that split large folios") Signed-off-by: David Stevens stevensd@chromium.org Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Suleiman Souhlal suleiman@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/shmem.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-)
--- a/mm/shmem.c~mm-shmem-fix-race-in-shmem_undo_range-w-thp +++ a/mm/shmem.c @@ -1080,7 +1080,24 @@ whole_folios: } VM_BUG_ON_FOLIO(folio_test_writeback(folio), folio); - truncate_inode_folio(mapping, folio); + + if (!folio_test_large(folio)) { + truncate_inode_folio(mapping, folio); + } else if (truncate_inode_partial_folio(folio, lstart, lend)) { + /* + * If we split a page, reset the loop so + * that we pick up the new sub pages. + * Otherwise the THP was entirely + * dropped or the target range was + * zeroed, so just continue the loop as + * is. + */ + if (!folio_test_large(folio)) { + folio_unlock(folio); + index = start; + break; + } + } } folio_unlock(folio); } _
Patches currently in -mm which might be from stevensd@chromium.org are