Re: [PATCH 1/2] iomap: Separate out generic_write_sync() from iomap_dio_complete()

[Dave Chinner <david@fromorbit.com>]

On Tue, Dec 15, 2020 at 12:06:35PM -0600, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> This introduces a separate function __iomap_dio_complte() which
> completes the Direct I/O without performing the write sync.
> 
> Filesystems such as btrfs which require an inode_lock for sync can call
> __iomap_dio_complete() and must perform sync on their own after unlock.
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> ---
>  fs/iomap/direct-io.c  | 16 +++++++++++++---
>  include/linux/iomap.h |  2 +-
>  2 files changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 933f234d5bec..11a108f39fd9 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -76,7 +76,7 @@ static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
>  		dio->submit.cookie = submit_bio(bio);
>  }
>  
> -ssize_t iomap_dio_complete(struct iomap_dio *dio)
> +ssize_t __iomap_dio_complete(struct iomap_dio *dio)
>  {
>  	const struct iomap_dio_ops *dops = dio->dops;
>  	struct kiocb *iocb = dio->iocb;
> @@ -119,18 +119,28 @@ ssize_t iomap_dio_complete(struct iomap_dio *dio)
>  	}
>  
>  	inode_dio_end(file_inode(iocb->ki_filp));
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(__iomap_dio_complete);
> +
> +ssize_t iomap_dio_complete(struct iomap_dio *dio)
> +{
> +	ssize_t ret;
> +
> +	ret = __iomap_dio_complete(dio);
>  	/*
>  	 * If this is a DSYNC write, make sure we push it to stable storage now
>  	 * that we've written data.
>  	 */
>  	if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
> -		ret = generic_write_sync(iocb, ret);
> +		ret = generic_write_sync(dio->iocb, ret);
>  
>  	kfree(dio);
>  
>  	return ret;
>  }
> -EXPORT_SYMBOL_GPL(iomap_dio_complete);
> +

NACK.

If you don't want iomap_dio_complete to do O_DSYNC work after
successfully writing data, strip those flags out of the kiocb
before you call iomap_dio_rw() and do it yourself after calling
iomap_dio_complete().

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com