Re: [PATCH] fs: allow cross-vfsmount reflink/dedupe

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Feb 16, 2022 at 03:21:23PM -0500, Josef Bacik wrote:
> Currently we disallow reflink and dedupe if the two files aren't on the
> same vfsmount.  However we really only need to disallow it if they're
> not on the same super block.  It is very common for btrfs to have a main
> subvolume that is mounted and then different subvolumes mounted at
> different locations.  It's allowed to reflink between these volumes, but
> the vfsmount check disallows this.  Instead fix dedupe to check for the
> same superblock, and simply remove the vfsmount check for reflink as it
> already does the superblock check.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Seems pretty spiffy to /me/... ;)
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/ioctl.c       | 4 ----
>  fs/remap_range.c | 7 +------
>  2 files changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 1ed097e94af2..090bf47606ab 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -236,9 +236,6 @@ static long ioctl_file_clone(struct file *dst_file, unsigned long srcfd,
>  
>  	if (!src_file.file)
>  		return -EBADF;
> -	ret = -EXDEV;
> -	if (src_file.file->f_path.mnt != dst_file->f_path.mnt)
> -		goto fdput;
>  	cloned = vfs_clone_file_range(src_file.file, off, dst_file, destoff,
>  				      olen, 0);
>  	if (cloned < 0)
> @@ -247,7 +244,6 @@ static long ioctl_file_clone(struct file *dst_file, unsigned long srcfd,
>  		ret = -EINVAL;
>  	else
>  		ret = 0;
> -fdput:
>  	fdput(src_file);
>  	return ret;
>  }
> diff --git a/fs/remap_range.c b/fs/remap_range.c
> index 231159682907..bc5fb006dc79 100644
> --- a/fs/remap_range.c
> +++ b/fs/remap_range.c
> @@ -362,11 +362,6 @@ loff_t do_clone_file_range(struct file *file_in, loff_t pos_in,
>  
>  	WARN_ON_ONCE(remap_flags & REMAP_FILE_DEDUP);
>  
> -	/*
> -	 * FICLONE/FICLONERANGE ioctls enforce that src and dest files are on
> -	 * the same mount. Practically, they only need to be on the same file
> -	 * system.
> -	 */
>  	if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
>  		return -EXDEV;
>  
> @@ -458,7 +453,7 @@ loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
>  		goto out_drop_write;
>  
>  	ret = -EXDEV;
> -	if (src_file->f_path.mnt != dst_file->f_path.mnt)
> +	if (file_inode(src_file)->i_sb != file_inode(dst_file)->i_sb)
>  		goto out_drop_write;
>  
>  	ret = -EISDIR;
> -- 
> 2.26.3
>