linux-ext4 - Re: [PATCH 1/3] direct-io: always call ->end

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Message-ID: <20160203000510.GB5854@birch.djwong.org>
Date:	Tue, 2 Feb 2016 16:05:10 -0800
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	Christoph Hellwig <hch@....de>
Cc:	linux-fsdevel@...r.kernel.org, xfs@....sgi.com,
	linux-ext4@...r.kernel.org, ocfs2-devel@....oracle.com
Subject: Re: [PATCH 1/3] direct-io: always call ->end_io if non-NULL

On Tue, Feb 02, 2016 at 09:17:35PM +0100, Christoph Hellwig wrote:
> See http://www.infradead.org/rpr.html

Ick. ^^^

> This way we can pass back errors to the file system, and allow for
> cleanup required for all direct I/O invocations.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  fs/dax.c          | 2 +-
>  fs/direct-io.c    | 4 ++--
>  fs/ext4/inode.c   | 3 +++
>  fs/ocfs2/aops.c   | 3 +++
>  fs/xfs/xfs_aops.c | 3 +++
>  5 files changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index 4fd6b0c..e47d1ba 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -267,7 +267,7 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
>  	if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
>  		inode_unlock(inode);
>  
> -	if ((retval > 0) && end_io)
> +	if (end_io)
>  		end_io(iocb, pos, retval, bh.b_private);
>  
>  	if (!(flags & DIO_SKIP_DIO_COUNT))
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 1b2f7ff..ead7ac1 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -253,8 +253,8 @@ static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret,
>  	if (ret == 0)
>  		ret = transferred;
>  
> -	if (dio->end_io && dio->result)
> -		dio->end_io(dio->iocb, offset, transferred, dio->private);
> +	if (dio->end_io)
> +		dio->end_io(dio->iocb, offset, ret, dio->private);

Could we make end_io return an int so that errors during completion can be
stuffed into ret to be picked up by whatever's calling directio?  Something
like this:

if (dio->end_io) {
	int ret2;

	ret2 = dio->end_io(dio->iocb, offset, ret, dio->private);
	if (ret2 && !ret)
		ret = ret2;
}

That way I can capture IO errors during the CoW remapping step and pass them to
userland either via dio_complete()'s return value or through ki_complete.

(If ret itself is an error code then obviously we don't bother with the
post-CoW remap.)

--D

>  
>  	if (!(dio->flags & DIO_SKIP_DIO_COUNT))
>  		inode_dio_end(dio->inode);
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 83bc8bf..d04555b 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3166,6 +3166,9 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
>  {
>          ext4_io_end_t *io_end = iocb->private;
>  
> +	if (size <= 0)
> +		return;
> +
>  	/* if not async direct IO just return */
>  	if (!io_end)
>  		return;
> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
> index 794fd15..1eeb804 100644
> --- a/fs/ocfs2/aops.c
> +++ b/fs/ocfs2/aops.c
> @@ -628,6 +628,9 @@ static void ocfs2_dio_end_io(struct kiocb *iocb,
>  	struct inode *inode = file_inode(iocb->ki_filp);
>  	int level;
>  
> +	if (bytes <= 0)
> +		return;
> +
>  	/* this io's submitter should not have unlocked this before we could */
>  	BUG_ON(!ocfs2_iocb_is_rw_locked(iocb));
>  
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 379c089..c318e9f 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -1655,6 +1655,9 @@ xfs_end_io_direct_write(
>  	struct inode		*inode = file_inode(iocb->ki_filp);
>  	struct xfs_ioend	*ioend = private;
>  
> +	if (size <= 0)
> +		return;
> +
>  	trace_xfs_gbmap_direct_endio(XFS_I(inode), offset, size,
>  				     ioend ? ioend->io_type : 0, NULL);
>  
> -- 
> 2.1.4
> 
> --
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