diff options
| author | David Stevens <stevensd@chromium.org> | 2023-04-18 17:40:31 +0900 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-12-12 17:20:19 -0800 |
| commit | 55ac8bbe358bdd2f3c044c12f249fd22d48fe015 (patch) | |
| tree | 9ce5d9290c1f8159bcf17a608afcc7a392f8082d /mm | |
| parent | 43e8832fed08438e2a27afed9bac21acd0ceffe5 (diff) | |
mm/shmem: fix race in shmem_undo_range w/THP
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>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/shmem.c | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index 91e2620148b2..0d1ce70bce38 100644 --- a/mm/shmem.c +++ b/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); } |