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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 82c156f853 ("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 <guaneryu@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Eryu Guan 2016-11-01 15:43:07 +08:00 committed by Al Viro
parent 70fe2f4815
commit 6d6d36bc6e
1 changed files with 3 additions and 0 deletions
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3
mm/filemap.c
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@ -1732,6 +1732,9 @@ 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? */