Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1034765AbcKAHn7 (ORCPT ); Tue, 1 Nov 2016 03:43:59 -0400 Received: from mail-pf0-f196.google.com ([209.85.192.196]:35377 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1034733AbcKAHn6 (ORCPT ); Tue, 1 Nov 2016 03:43:58 -0400 From: Eryu Guan To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: viro@zeniv.linux.org.uk, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Eryu Guan Subject: [PATCH v2] mm/filemap: don't allow partially uptodate page for pipes Date: Tue, 1 Nov 2016 15:43:07 +0800 Message-Id: <1477986187-12717-1-git-send-email-guaneryu@gmail.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2504 Lines: 60 Starting from 4.9-rc1 kernel, I started noticing some test failures of sendfile(2) and splice(2) (sendfile0N and splice01 from LTP) when testing on sub-page block size filesystems (tested both XFS and ext4), these syscalls start to return EIO in the tests. e.g. sendfile02 1 TFAIL : sendfile02.c:133: sendfile(2) failed to return expected value, expected: 26, got: -1 sendfile02 2 TFAIL : sendfile02.c:133: sendfile(2) failed to return expected value, expected: 24, got: -1 sendfile02 3 TFAIL : sendfile02.c:133: sendfile(2) failed to return expected value, expected: 22, got: -1 sendfile02 4 TFAIL : sendfile02.c:133: sendfile(2) failed to return expected value, expected: 20, got: -1 This is because that in sub-page block size cases, we don't need the whole page to be uptodate, only the part we care about is uptodate is OK (if fs has ->is_partially_uptodate defined). But page_cache_pipe_buf_confirm() doesn't have the ability to check the partially-uptodate case, it needs the whole page to be uptodate. So it returns EIO in this case. This is a regression introduced by commit 82c156f85384 ("switch generic_file_splice_read() to use of ->read_iter()"). Prior to the change, generic_file_splice_read() doesn't allow partially-uptodate page either, so it worked fine. Fix it by skipping the partially-uptodate check if we're working on a pipe in do_generic_file_read(), so we read the whole page from disk as long as the page is not uptodate. Signed-off-by: Eryu Guan --- I think the other way to fix it is to add the ability to check & allow partially-uptodate page to page_cache_pipe_buf_confirm(), but that is much harder to do and seems gain little. v2: - Update summary a little bit - Update commit log - Add comment to the code - Add more people/list to cc v1: http://marc.info/?l=linux-mm&m=147756897431777&w=2 mm/filemap.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index 849f459..670264d 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1734,6 +1734,9 @@ static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos, if (inode->i_blkbits == PAGE_SHIFT || !mapping->a_ops->is_partially_uptodate) goto page_not_up_to_date; + /* pipes can't handle partially uptodate pages */ + if (unlikely(iter->type & ITER_PIPE)) + goto page_not_up_to_date; if (!trylock_page(page)) goto page_not_up_to_date; /* Did it get truncated before we got the lock? */ -- 2.7.4