[dm-devel] [PATCH] dm-bufio

[Mikulas Patocka]

On Mon, 17 Oct 2011, Joe Thornber wrote:

> On Fri, Oct 14, 2011 at 03:14:34PM -0400, Mikulas Patocka wrote:
> @@ -999,15 +1013,19 @@ again:
>                  * someone is doing some writes simultaneously with us --- in
>                  * this case, stop dropping the lock.
>                  */
>                 if (dropped_lock)
>                         goto again;
>         }
>         wake_up(&c->free_buffer_wait);
>         dm_bufio_unlock(c);
> 
> -       a = xchg(&c->async_write_error, 0);
> +       if (likely(!c->async_write_error))
> +               a = 0;
> +       else
> +               a = xchg(&c->async_write_error, 0);
>         f = dm_bufio_issue_flush(c);
> 
> 
> I didn't change this.  Is it also fixing a preexisting issue?

It doesn't fix anything. It just bypasses xchg for the most common case.

Mikulas