Re: [PATCH 03/11] vfs: no fallback for ->copy_file_range

Amir Goldstein
2018-12-03T10:22:36Z

On Mon, Dec 3, 2018 at 10:34 AM Dave Chinner <david@fromorbit.com> wrote:
>
> From: Dave Chinner <dchinner@redhat.com>
>
> Now that we have generic_copy_file_range(), remove it as a fallback
> case when offloads fail. This puts the responsibility for executing
> fallbacks on the filesystems that implement ->copy_file_range and
> allows us to add operational validity checks to
> generic_copy_file_range().
>
> Rework vfs_copy_file_range() to call a new do_copy_file_range()
> helper to exceute the copying callout, and move calls to
> generic_file_copy_range() into filesystem methods where they
> currently return failures.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>

You may add
Reviewed-by: Amir Goldstein <amir73il@gmail.com>

After fixing the overlayfs issue below.
...

> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index 84dd957efa24..68736e5d6a56 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -486,8 +486,15 @@ 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,
> + ssize_t ret;
> +
> + ret = ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
> OVL_COPY);
> +
> + if (ret == -EOPNOTSUPP)
> + ret = generic_copy_file_range(file_in, pos_in, file_out,
> + pos_out, len, flags);
> + return ret;
> }
>

This is unneeded, because ovl_copyfile(OVL_COPY) is implemented
by calling vfs_copy_file_range() (on the underlying files) and it is
not possible
to get EOPNOTSUPP from vfs_copy_file_range().

Thanks,
Amir.