Re: [PATCH 1/2] iomap: fix a regression for partial write errors

[Ritesh Harjani (IBM) <ritesh.list@gmail.com>]

Christoph Hellwig <hch@lst.de> writes:

> When write* wrote some data it should return the amount of written data
> and not the error code that caused it to stop.  Fix a recent regression
> in iomap_file_buffered_write that caused it to return the errno instead.
>

Agreed. Reviewed the change and it looks right to me. 
Feel free to add - 

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

> Fixes: 219580eea1ee ("iomap: update ki_pos in iomap_file_buffered_write")
> Reported-by: kernel test robot <oliver.sang@intel.com>
> Reported-by: Cyril Hrubis <chrubis@suse.cz>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---

In case anyone wanted to see before and after test failures output of

./runltp -f syscalls -s writev07 -d /mnt1/test

<without this patch>
tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
writev07.c:50: TINFO: starting test with initial file offset: 0
writev07.c:73: TINFO: got EFAULT
writev07.c:78: TFAIL: file was written to
writev07.c:84: TPASS: offset stayed unchanged
writev07.c:50: TINFO: starting test with initial file offset: 65
writev07.c:73: TINFO: got EFAULT
writev07.c:78: TFAIL: file was written to
writev07.c:84: TPASS: offset stayed unchanged
writev07.c:50: TINFO: starting test with initial file offset: 4096
writev07.c:73: TINFO: got EFAULT
writev07.c:80: TPASS: file stayed untouched
writev07.c:84: TPASS: offset stayed unchanged
writev07.c:50: TINFO: starting test with initial file offset: 4097
writev07.c:73: TINFO: got EFAULT
writev07.c:80: TPASS: file stayed untouched
writev07.c:84: TPASS: offset stayed unchanged

Summary:
passed   6
failed   2
broken   0
skipped  0
warnings 0


<with this patch>
tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
writev07.c:50: TINFO: starting test with initial file offset: 0
writev07.c:94: TINFO: writev() has written 64 bytes
writev07.c:105: TPASS: file has expected content
writev07.c:116: TPASS: offset at 64 as expected
writev07.c:50: TINFO: starting test with initial file offset: 65
writev07.c:94: TINFO: writev() has written 64 bytes
writev07.c:105: TPASS: file has expected content
writev07.c:116: TPASS: offset at 129 as expected
writev07.c:50: TINFO: starting test with initial file offset: 4096
writev07.c:94: TINFO: writev() has written 64 bytes
writev07.c:105: TPASS: file has expected content
writev07.c:116: TPASS: offset at 4160 as expected
writev07.c:50: TINFO: starting test with initial file offset: 4097
writev07.c:94: TINFO: writev() has written 64 bytes
writev07.c:105: TPASS: file has expected content
writev07.c:116: TPASS: offset at 4161 as expected

Summary:
passed   8
failed   0
broken   0
skipped  0
warnings 0



>  fs/iomap/buffered-io.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index adb92cdb24b009..7cc9f7274883a5 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -872,7 +872,7 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
>  	while ((ret = iomap_iter(&iter, ops)) > 0)
>  		iter.processed = iomap_write_iter(&iter, i);
>  
> -	if (unlikely(ret < 0))
> +	if (unlikely(iter.pos == iocb->ki_pos))
>  		return ret;
>  	ret = iter.pos - iocb->ki_pos;
>  	iocb->ki_pos += ret;
> -- 
> 2.39.2

-ritesh