Re: [PATCH 1/2] loop: respect REQ_NOWAIT for memory allocation

["hch@lst.de" <hch@lst.de>]

On Sun, Nov 16, 2025 at 05:43:53AM +0000, Chaitanya Kulkarni wrote:
> On 11/15/25 19:50, Damien Le Moal wrote:
> > On 11/16/25 11:52, Chaitanya Kulkarni wrote:
> >>    6. Loop driver:
> >>     loop_queue_rq()
> >>      lo_rw_aio()
> >>       kmalloc_array(..., GFP_NOIO) <-- BLOCKS (REQ_NOWAIT violation)
> >>        -> Should use GFP_NOWAIT when rq->cmd_flags & REQ_NOWAIT
> > Same comment as for zloop. Re-read the code and see that loop_queue_rq() calls
> > loop_queue_work(). That function has a memory allocation that is already marked
> > with GFP_NOWAIT, and that this function does not directly execute lo_rw_aio() as
> > that is done from loop_workfn(), in the work item context.
> > So again, no blocking violation that I can see here.
> > As far as I can tell, this patch is not needed.
> >
> Thanks for pointing that out. Since REQ_NOWAIT is not valid in the
> workqueue, then REQ_NOWAIT flag needs to be cleared before
> handing it over to workqueue ? is that the right interpretation?

Having it cleared does seem useful as there is no need to skip blocking
operations.  I don't think it actually is required, just a lot more
efficient.