From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 8083B6B0270 for ; Thu, 27 Oct 2016 07:49:33 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id n85so6717191pfi.4 for ; Thu, 27 Oct 2016 04:49:33 -0700 (PDT) Received: from mail-pf0-x244.google.com (mail-pf0-x244.google.com. [2607:f8b0:400e:c00::244]) by mx.google.com with ESMTPS id d5si7583531pgh.128.2016.10.27.04.49.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 27 Oct 2016 04:49:32 -0700 (PDT) Received: by mail-pf0-x244.google.com with SMTP id n85so2475831pfi.3 for ; Thu, 27 Oct 2016 04:49:32 -0700 (PDT) From: Eryu Guan Subject: [PATCH] mm/filemap: don't check partially uptodate page for pipes Date: Thu, 27 Oct 2016 19:41:59 +0800 Message-Id: <1477568519-7891-1-git-send-email-guaneryu@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: akpm@linux-foundation.org, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, Eryu Guan After commit 82c156f85384 ("switch generic_file_splice_read() to use of ->read_iter()") 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. 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. mm/filemap.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index 849f459..ae9ef9a 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1734,6 +1734,8 @@ 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; + 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org