Re: [PATCH v2 1/8] vfs: introduce generic_copy_file_range()

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

On Sun, May 26, 2019 at 09:10:52AM +0300, Amir Goldstein wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> Right now if vfs_copy_file_range() does not use any offload
> mechanism, it falls back to calling do_splice_direct(). This fails
> to do basic sanity checks on the files being copied. Before we
> start adding this necessarily functionality to the fallback path,
> separate it out into generic_copy_file_range().
> 
> generic_copy_file_range() has the same prototype as
> ->copy_file_range() so that filesystems can use it in their custom
> ->copy_file_range() method if they so choose.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---

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

--D

>  fs/read_write.c    | 35 ++++++++++++++++++++++++++++++++---
>  include/linux/fs.h |  3 +++
>  2 files changed, 35 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/read_write.c b/fs/read_write.c
> index c543d965e288..676b02fae589 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1565,6 +1565,36 @@ COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
>  }
>  #endif
>  
> +/**
> + * generic_copy_file_range - copy data between two files
> + * @file_in:	file structure to read from
> + * @pos_in:	file offset to read from
> + * @file_out:	file structure to write data to
> + * @pos_out:	file offset to write data to
> + * @len:	amount of data to copy
> + * @flags:	copy flags
> + *
> + * This is a generic filesystem helper to copy data from one file to another.
> + * It has no constraints on the source or destination file owners - the files
> + * can belong to different superblocks and different filesystem types. Short
> + * copies are allowed.
> + *
> + * This should be called from the @file_out filesystem, as per the
> + * ->copy_file_range() method.
> + *
> + * Returns the number of bytes copied or a negative error indicating the
> + * failure.
> + */
> +
> +ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in,
> +				struct file *file_out, loff_t pos_out,
> +				size_t len, unsigned int flags)
> +{
> +	return do_splice_direct(file_in, &pos_in, file_out, &pos_out,
> +				len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
> +}
> +EXPORT_SYMBOL(generic_copy_file_range);
> +
>  /*
>   * copy_file_range() differs from regular file read and write in that it
>   * specifically allows return partial success.  When it does so is up to
> @@ -1632,9 +1662,8 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
>  			goto done;
>  	}
>  
> -	ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
> -			len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
> -
> +	ret = generic_copy_file_range(file_in, pos_in, file_out, pos_out, len,
> +				      flags);
>  done:
>  	if (ret > 0) {
>  		fsnotify_access(file_in);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index f7fdfe93e25d..ea17858310ff 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1889,6 +1889,9 @@ extern ssize_t vfs_readv(struct file *, const struct iovec __user *,
>  		unsigned long, loff_t *, rwf_t);
>  extern ssize_t vfs_copy_file_range(struct file *, loff_t , struct file *,
>  				   loff_t, size_t, unsigned int);
> +extern ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in,
> +				       struct file *file_out, loff_t pos_out,
> +				       size_t len, unsigned int flags);
>  extern int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
>  					 struct file *file_out, loff_t pos_out,
>  					 loff_t *count,
> -- 
> 2.17.1
>