Re: Understanding locking for buf

On Mon, Mar 20, 2023 at 11:25:30AM +0100, Alexander Lochmann wrote:
> 
> 
> On 16.03.23 12:24, Konstantin Belousov wrote:
> > > Is the following correct?
> > > The aforementioned accesses by 100033 in g_vfs_done() are no violations with
> > > respect to the locking rule because from a global perspective the buf is
> > > locked. It is the only concurrent access at that moment.
> > I would formulate it differently:
> >    No other thread might legitimately get access to the buffer using
> >    either bread() or getblk() until current io operation finishes.
> >    The io operation is handled in two contexts: top-level, where a thread
> >    used getblk() as usual to claim buffer ownership, and completion
> >    thread context (geom up thread). The completion code legitimately
> >    manipulates the buffer, because the top-level code expects that after
> >    the buffer strategy routine is called, effectively moving the ownership
> >    to the geom up thread.
> Thx. But the top-level thread, using getblk(), legitimately releases the
> lock. Am I right?
No.  It does not, please re-read what I wrote.