Re: [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*()

Michal Hocko
2017-04-06T07:27:55Z

On Thu 06-04-17 09:33:44, Adrian Hunter wrote:
> On 05/04/17 14:39, Vlastimil Babka wrote:
> > On 04/05/2017 01:36 PM, Richard Weinberger wrote:
> >> Michal,
> >>
> >> Am 05.04.2017 um 13:31 schrieb Michal Hocko:
> >>> On Wed 05-04-17 09:47:00, Vlastimil Babka wrote:
> >>>> Nandsim has own functions set_memalloc() and clear_memalloc() for robust
> >>>> setting and clearing of PF_MEMALLOC. Replace them by the new generic helpers.
> >>>> No functional change.
> >>>
> >>> This one smells like an abuser. Why the hell should read/write path
> >>> touch memory reserves at all!
> >>
> >> Could be. Let's ask Adrian, AFAIK he wrote that code.
> >> Adrian, can you please clarify why nandsim needs to play with PF_MEMALLOC?
> >
> > I was thinking about it and concluded that since the simulator can be
> > used as a block device where reclaimed pages go to, writing the data out
> > is a memalloc operation. Then reading can be called as part of r-m-w
> > cycle, so reading as well.
>
> IIRC it was to avoid getting stuck with nandsim waiting on memory reclaim
> and memory reclaim waiting on nandsim.

I've got lost in the indirection. Could you describe how would reclaim
get stuck waiting on these paths please?

--
Michal Hocko
SUSE Labs

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