Re: [PATCH v2 07/10] iomap: Introduce iomap_apply2() for operations on two files

[Darrick J. Wong]

On Fri, Feb 26, 2021 at 08:20:27AM +0800, Shiyang Ruan wrote:
> Some operations, such as comparing a range of data in two files under
> fsdax mode, requires nested iomap_open()/iomap_end() on two file.  Thus,
> we introduce iomap_apply2() to accept arguments from two files and
> iomap_actor2_t for actions on two files.
> 
> Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
> ---
>  fs/iomap/apply.c      | 51 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/iomap.h |  7 +++++-
>  2 files changed, 57 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/iomap/apply.c b/fs/iomap/apply.c
> index 26ab6563181f..fd2f8bde5791 100644
> --- a/fs/iomap/apply.c
> +++ b/fs/iomap/apply.c
> @@ -97,3 +97,54 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
>  
>  	return written ? written : ret;
>  }
> +
> +loff_t
> +iomap_apply2(struct inode *ino1, loff_t pos1, struct inode *ino2, loff_t pos2,
> +		loff_t length, unsigned int flags, const struct iomap_ops *ops,
> +		void *data, iomap_actor2_t actor)
> +{
> +	struct iomap smap = { .type = IOMAP_HOLE };
> +	struct iomap dmap = { .type = IOMAP_HOLE };
> +	loff_t written = 0, ret;
> +
> +	ret = ops->iomap_begin(ino1, pos1, length, 0, &smap, NULL);
> +	if (ret)
> +		goto out_src;
> +	if (WARN_ON(smap.offset > pos1)) {
> +		written = -EIO;
> +		goto out_src;
> +	}
> +	if (WARN_ON(smap.length == 0)) {
> +		written = -EIO;
> +		goto out_src;
> +	}
> +
> +	ret = ops->iomap_begin(ino2, pos2, length, 0, &dmap, NULL);
> +	if (ret)
> +		goto out_dest;
> +	if (WARN_ON(dmap.offset > pos2)) {
> +		written = -EIO;
> +		goto out_dest;
> +	}
> +	if (WARN_ON(dmap.length == 0)) {
> +		written = -EIO;
> +		goto out_dest;
> +	}
> +
> +	/* make sure extent length of two file is equal */
> +	if (WARN_ON(smap.length != dmap.length)) {

Why not set smap.length and dmap.length to min(smap.length, dmap.length) ?

--D

> +		written = -EIO;
> +		goto out_dest;
> +	}
> +
> +	written = actor(ino1, pos1, ino2, pos2, length, data, &smap, &dmap);
> +
> +out_dest:
> +	if (ops->iomap_end)
> +		ret = ops->iomap_end(ino2, pos2, length, 0, 0, &dmap);
> +out_src:
> +	if (ops->iomap_end)
> +		ret = ops->iomap_end(ino1, pos1, length, 0, 0, &smap);
> +
> +	return ret;
> +}
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 5bd3cac4df9c..913f98897a77 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -148,10 +148,15 @@ struct iomap_ops {
>   */
>  typedef loff_t (*iomap_actor_t)(struct inode *inode, loff_t pos, loff_t len,
>  		void *data, struct iomap *iomap, struct iomap *srcmap);
> -
> +typedef loff_t (*iomap_actor2_t)(struct inode *ino1, loff_t pos1,
> +		struct inode *ino2, loff_t pos2, loff_t len, void *data,
> +		struct iomap *smap, struct iomap *dmap);
>  loff_t iomap_apply(struct inode *inode, loff_t pos, loff_t length,
>  		unsigned flags, const struct iomap_ops *ops, void *data,
>  		iomap_actor_t actor);
> +loff_t iomap_apply2(struct inode *ino1, loff_t pos1, struct inode *ino2,
> +		loff_t pos2, loff_t length, unsigned int flags,
> +		const struct iomap_ops *ops, void *data, iomap_actor2_t actor);
>  
>  ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from,
>  		const struct iomap_ops *ops);
> -- 
> 2.30.1
> 
> 
>