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Shutemov" Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, hannes@cmpxchg.org, clm@meta.com, linux-kernel@vger.kernel.org, willy@infradead.org References: <20241110152906.1747545-1-axboe@kernel.dk> <20241110152906.1747545-9-axboe@kernel.dk> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/11/24 2:15 AM, Kirill A. Shutemov wrote: >> @@ -2706,8 +2712,16 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter, >> } >> } >> put_folios: >> - for (i = 0; i < folio_batch_count(&fbatch); i++) >> - folio_put(fbatch.folios[i]); >> + for (i = 0; i < folio_batch_count(&fbatch); i++) { >> + struct folio *folio = fbatch.folios[i]; >> + >> + if (folio_test_uncached(folio)) { >> + folio_lock(folio); >> + invalidate_complete_folio2(mapping, folio, 0); >> + folio_unlock(folio); > > I am not sure it is safe. What happens if it races with page fault? > > The only current caller of invalidate_complete_folio2() unmaps the folio > explicitly before calling it. And folio lock prevents re-faulting. > > I think we need to give up PG_uncached if we see folio_mapped(). And maybe > also mark the page accessed. Ok thanks, let me take a look at that and create a test case that exercises that explicitly. >> diff --git a/mm/swap.c b/mm/swap.c >> index 835bdf324b76..f2457acae383 100644 >> --- a/mm/swap.c >> +++ b/mm/swap.c >> @@ -472,6 +472,8 @@ static void folio_inc_refs(struct folio *folio) >> */ >> void folio_mark_accessed(struct folio *folio) >> { >> + if (folio_test_uncached(folio)) >> + return; > > if (folio_test_uncached(folio)) { > if (folio_mapped(folio)) > folio_clear_uncached(folio); > else > return; > } Noted, thanks! -- Jens Axboe