Re: [PATCH 1/2] iomap: split size and error for iomap_dio_rw ->end_io

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, Sep 03, 2019 at 03:03:26PM +0200, Christoph Hellwig wrote:
> From: Matthew Bobrowski <mbobrowski@mbobrowski.org>
> 
> Modify the calling convention for the iomap_dio_rw ->end_io() callback.
> Rather than passing either dio->error or dio->size as the 'size' argument,
> instead pass both the dio->error and the dio->size value separately.
> 
> In the instance that an error occurred during a write, we currently cannot
> determine whether any blocks have been allocated beyond the current EOF and
> data has subsequently been written to these blocks within the ->end_io()
> callback. As a result, we cannot judge whether we should take the truncate
> failed write path. Having both dio->error and dio->size will allow us to
> perform such checks within this callback.
> 
> Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
> [hch: minor cleanups]
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/iomap/direct-io.c  | 9 +++------
>  fs/xfs/xfs_file.c     | 8 +++++---
>  include/linux/iomap.h | 4 ++--
>  3 files changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 10517cea9682..2ccf1c6460d4 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -77,13 +77,10 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
>  	loff_t offset = iocb->ki_pos;
>  	ssize_t ret;
>  
> -	if (dio->end_io) {
> -		ret = dio->end_io(iocb,
> -				dio->error ? dio->error : dio->size,
> -				dio->flags);
> -	} else {
> +	if (dio->end_io)
> +		ret = dio->end_io(iocb, dio->size, dio->error, dio->flags);
> +	else
>  		ret = dio->error;
> -	}
>  
>  	if (likely(!ret)) {
>  		ret = dio->size;
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index d952d5962e93..3d8e6db9ef77 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -370,21 +370,23 @@ static int
>  xfs_dio_write_end_io(
>  	struct kiocb		*iocb,
>  	ssize_t			size,
> +	int			error,
>  	unsigned		flags)
>  {
>  	struct inode		*inode = file_inode(iocb->ki_filp);
>  	struct xfs_inode	*ip = XFS_I(inode);
>  	loff_t			offset = iocb->ki_pos;
>  	unsigned int		nofs_flag;
> -	int			error = 0;
>  
>  	trace_xfs_end_io_direct_write(ip, offset, size);
>  
>  	if (XFS_FORCED_SHUTDOWN(ip->i_mount))
>  		return -EIO;
>  
> -	if (size <= 0)
> -		return size;
> +	if (error)
> +		return error;
> +	if (!size)
> +		return 0;
>  
>  	/*
>  	 * Capture amount written on completion as we can't reliably account
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index bc499ceae392..50bb746d2216 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -188,8 +188,8 @@ sector_t iomap_bmap(struct address_space *mapping, sector_t bno,
>   */
>  #define IOMAP_DIO_UNWRITTEN	(1 << 0)	/* covers unwritten extent(s) */
>  #define IOMAP_DIO_COW		(1 << 1)	/* covers COW extent(s) */
> -typedef int (iomap_dio_end_io_t)(struct kiocb *iocb, ssize_t ret,
> -		unsigned flags);
> +typedef int (iomap_dio_end_io_t)(struct kiocb *iocb, ssize_t size, int error,
> +				 unsigned int flags);
>  ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  		const struct iomap_ops *ops, iomap_dio_end_io_t end_io);
>  int iomap_dio_iopoll(struct kiocb *kiocb, bool spin);
> -- 
> 2.20.1
>