On Mon, Sep 12, 2016 at 06:06:41PM +0300, Amir Goldstein wrote:
> When copying up within the same fs, try to use vfs_clone_file_range().
> This is very efficient when lower and upper are on the same fs
> with file reflink support. If vfs_clone_file_range() fails because
> lower and upper are not on the same fs or if fs has no reflink support,
> copy up falls back to the regular data copy code.
>
> Tested correct behavior when lower and upper are on:
> 1. same ext4 (copy)
> 2. same xfs + reflink patches + mkfs.xfs (copy)
> 3. same xfs + reflink patches + mkfs.xfs -m reflink=1 (clone)
> 4. different xfs + reflink patches + mkfs.xfs -m reflink=1 (copy)
>
> For comparison, on my laptop, xfstest overlay/001 (copy up of large
> sparse files) takes less than 1 second in the xfs reflink setup vs.
> 25 seconds on the rest of the setups.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/overlayfs/copy_up.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index 43fdc27..e432d7e 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -136,6 +136,16 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
> goto out_fput;
> }
>
> + /*
> + * Try to use clone_file_range to clone up within the same fs.
> + * On failure to clone entire file, fallback to copy loop.
> + */
> + error = vfs_clone_file_range(old_file, 0, new_file, 0, len);
> + if (error == -EXDEV || error == -EOPNOTSUPP)
> + error = 0;
> + else
> + len = 0;
> +
> /* FIXME: copy up sparse files efficiently */
> while (len) {
> size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
That's nasty. Just use a goto to skip the code that doesn't need to
be run if vfs_clone_file_range() succeeds. This is much better, IMO:
if (!error)
goto out_done;
if (error != -EXDEV && error != -EOPNOTSUPP)
goto out_error;
/* Can't clone, so now we try to copy the data */
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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