From 6d6d36bc6e77f8b1f86d81884ad5149931bb4acd Mon Sep 17 00:00:00 2001 From: Eryu Guan Date: Tue, 1 Nov 2016 15:43:07 +0800 Subject: [PATCH] mm/filemap: don't allow partially uptodate page for pipes 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 Signed-off-by: Al Viro --- mm/filemap.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index c7fe2f16503f..50b52fe51937 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1732,6 +1732,9 @@ find_page: 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? */ -- 2.30.2