From: David Stevens stevensd@chromium.org
stable inclusion from stable-v6.6.8 commit 7a4ae7acd20805940307be98b304871a43288a01 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I8ST59
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 55ac8bbe358bdd2f3c044c12f249fd22d48fe015 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- mm/shmem.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/mm/shmem.c b/mm/shmem.c index 69595d341882..e826be732b9b 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1098,7 +1098,24 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, } 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); }