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SubjectRe: [PATCH 6/7 v3] overlay: hybrid overlay filesystem prototype
On Fri, Sep 24, 2010 at 04:33:05PM +0200, Jens Axboe wrote:
> On 2010-09-23 01:21, Valerie Aurora wrote:
> > 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?
>
> The pipe alloc and such? That is lazily done and sticks around.

Thanks! So this looks like a good way to implement interruptible
in-kernel file copyup?

-VAL


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