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From: Michal Hocko <mhocko@kernel.org>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	Richard Weinberger <richard@nod.at>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Mel Gorman <mgorman@techsingularity.net>,
	Johannes Weiner <hannes@cmpxchg.org>,
	linux-block@vger.kernel.org, nbd-general@lists.sourceforge.net,
	open-iscsi@googlegroups.com, linux-scsi@vger.kernel.org,
	netdev@vger.kernel.org,
	Boris Brezillon <boris.brezillon@free-electrons.com>
Subject: Re: [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*()
Date: Thu, 6 Apr 2017 09:27:55 +0200
Message-ID: <20170406072754.GC5497@dhcp22.suse.cz> (raw)
In-Reply-To: <fe1c21a4-0bc6-529c-5446-382b01d4c99e@intel.com>

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

      reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-05  7:46 [PATCH 0/4] more robust PF_MEMALLOC handling Vlastimil Babka
2017-04-05  7:46 ` [PATCH 1/4] mm: prevent potential recursive reclaim due to clearing PF_MEMALLOC Vlastimil Babka
2017-04-05 11:21   ` Michal Hocko
2017-04-05 11:40   ` Andrey Ryabinin
2017-04-07  9:21     ` Vlastimil Babka
2017-04-07  7:33   ` Hillf Danton
2017-04-05  7:46 ` [PATCH 2/4] mm: introduce memalloc_noreclaim_{save,restore} Vlastimil Babka
2017-04-05 11:28   ` Michal Hocko
2017-04-07  7:38   ` Hillf Danton
2017-04-05  7:46 ` [PATCH 3/4] treewide: convert PF_MEMALLOC manipulations to new helpers Vlastimil Babka
2017-04-05 11:30   ` Michal Hocko
2017-04-06  6:38     ` [Nbd] " Wouter Verhelst
2017-04-06 11:25       ` Mel Gorman
2017-04-05  7:47 ` [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*() Vlastimil Babka
2017-04-05 11:31   ` Michal Hocko
2017-04-05 11:36     ` Richard Weinberger
2017-04-05 11:39       ` Vlastimil Babka
2017-04-05 12:09         ` Michal Hocko
2017-04-06  6:33         ` Adrian Hunter
2017-04-06  7:27           ` Michal Hocko [this message]

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