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@xxxxxxx>
>>
>> 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.
--
Jens Axboe
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