linux-kernel - Re: [PATCH v2 21/35] ovl: add reflink/copyfile/dedup support

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Message-ID: <20180507204350.GB9510@magnolia>
Date:   Mon, 7 May 2018 13:43:50 -0700
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Miklos Szeredi <mszeredi@...hat.com>
Cc:     linux-unionfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 21/35] ovl: add reflink/copyfile/dedup support

On Mon, May 07, 2018 at 10:37:53AM +0200, Miklos Szeredi wrote:
> Since set of arguments are so similar, handle in a common helper.
> 
> Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
> ---
>  fs/overlayfs/file.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 88 insertions(+)
> 
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index ce871a15e185..2ac95c95e8e6 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -382,6 +382,90 @@ static long ovl_compat_ioctl(struct file *file, unsigned int cmd,
>  	return ovl_ioctl(file, cmd, arg);
>  }
>  
> +enum ovl_copyop {
> +	OVL_COPY,
> +	OVL_CLONE,
> +	OVL_DEDUPE,
> +};
> +
> +static s64 ovl_copyfile(struct file *file_in, loff_t pos_in,
> +			struct file *file_out, loff_t pos_out,
> +			u64 len, unsigned int flags, enum ovl_copyop op)
> +{
> +	struct inode *inode_out = file_inode(file_out);
> +	struct fd real_in, real_out;
> +	const struct cred *old_cred;
> +	s64 ret;
> +
> +	ret = ovl_real_fdget(file_out, &real_out);
> +	if (ret)
> +		return ret;
> +
> +	ret = ovl_real_fdget(file_in, &real_in);
> +	if (ret) {
> +		fdput(real_out);
> +		return ret;
> +	}
> +
> +	old_cred = ovl_override_creds(file_inode(file_out)->i_sb);
> +	switch (op) {
> +	case OVL_COPY:
> +		ret = vfs_copy_file_range(real_in.file, pos_in,
> +					  real_out.file, pos_out, len, flags);
> +		break;
> +
> +	case OVL_CLONE:
> +		ret = vfs_clone_file_range(real_in.file, pos_in,
> +					   real_out.file, pos_out, len);
> +		break;
> +
> +	case OVL_DEDUPE:
> +		ret = vfs_dedupe_file_range_one(real_in.file, pos_in,
> +						real_out.file, pos_out, len);
> +		break;
> +	}
> +	revert_creds(old_cred);
> +
> +	/* Update size */
> +	ovl_copyattr(ovl_inode_real(inode_out), inode_out);
> +
> +	fdput(real_in);
> +	fdput(real_out);
> +
> +	return ret;
> +}
> +
> +static ssize_t ovl_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 ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
> +			    OVL_COPY);
> +}
> +
> +static int ovl_clone_file_range(struct file *file_in, loff_t pos_in,
> +				struct file *file_out, loff_t pos_out, u64 len)
> +{
> +	return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, 0,
> +			    OVL_CLONE);
> +}
> +
> +static s64 ovl_dedupe_file_range(struct file *file_in, loff_t pos_in,
> +				 struct file *file_out, loff_t pos_out,
> +				 u64 len)
> +{
> +	/*
> +	 * Don't copy up because of a dedupe request, this wouldn't make sense
> +	 * most of the time (data would be duplicated instead of deduplicated).
> +	 */
> +	if (!ovl_inode_upper(file_inode(file_in)) ||
> +	    !ovl_inode_upper(file_inode(file_out)))
> +		return -EPERM;

/me wonders, why not EOPNOTSUPP?  That's what we've been using (in xfs
anyway) for "filesystem doesn't want to let you do this".

(Or I guess EXDEV, but "cross-device link not supported" might not be
quite what you want users to see...)

--D

> +
> +	return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, 0,
> +			    OVL_DEDUPE);
> +}
> +
>  const struct file_operations ovl_file_operations = {
>  	.open		= ovl_open,
>  	.release	= ovl_release,
> @@ -393,4 +477,8 @@ const struct file_operations ovl_file_operations = {
>  	.fallocate	= ovl_fallocate,
>  	.unlocked_ioctl	= ovl_ioctl,
>  	.compat_ioctl	= ovl_compat_ioctl,
> +
> +	.copy_file_range	= ovl_copy_file_range,
> +	.clone_file_range	= ovl_clone_file_range,
> +	.dedupe_file_range	= ovl_dedupe_file_range,
>  };
> -- 
> 2.14.3
>