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SubjectRe: [PATCH 6/7 v3] overlay: hybrid overlay filesystem prototype
On Mon, Sep 20, 2010 at 08:04:10PM +0200, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@suse.cz>
>
> This overlay filesystem is a hybrid of entirely filesystem based
> (unionfs, aufs) and entierly VFS based (union mounts) solutions.

[...]

> +static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
> +{
> + struct file *old_file;
> + struct file *new_file;
> + int error = 0;
> +
> + if (len == 0)
> + return 0;
> +
> + old_file = path_open(old, O_RDONLY);
> + if (IS_ERR(old_file))
> + return PTR_ERR(old_file);
> +
> + new_file = path_open(new, O_WRONLY);
> + if (IS_ERR(new_file)) {
> + error = PTR_ERR(new_file);
> + goto out_fput;
> + }
> +
> + /* FIXME: copy up sparse files efficiently */
> + while (len) {
> + loff_t offset = new_file->f_pos;
> + size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
> + long bytes;
> +
> + if (len < this_len)
> + this_len = len;
> +
> + if (signal_pending_state(TASK_KILLABLE, current))
> + return -EINTR;
> +
> + bytes = do_splice_direct(old_file, &offset, new_file, this_len,
> + SPLICE_F_MOVE);

Interruptible copyup is good. But it looks like splice setup is kind
of heavyweight and we should do it as seldom as possible.

What about implementing splice flag SPLICE_F_INTERRUPTIBLE instead?

-VAL


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