linux-kernel - Re: [PATCH] lowmemorykiller: prevent multiple instances of low memory killer

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Date:	Mon, 15 Apr 2013 17:13:59 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	"Dolkow, Snild" <Snild.Dolkow@...ymobile.com>
Cc:	"Anderö, Oskar" <Oskar.Andero@...ymobile.com>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Lekanovic, Radovan" <Radovan.Lekanovic@...ymobile.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Brian Swetland <swetland@...gle.com>
Subject: Re: [PATCH] lowmemorykiller: prevent multiple instances of low
 memory killer

On Mon, Apr 15, 2013 at 03:38:08PM +0200, Dolkow, Snild wrote:
> >Where is lowmem_shrink called from?  I only see shrink called from the
> >bcache sysfs handler __bch_cache_set().  The return value isn't checked
> >there.
> >
> >Up to now this function has only returns positive numbers.
> >
> >There isn't a place which check LMK_BUSY so maybe it's best to just
> >return zero?
> 
> Hey Dan,
> 
> lowmem_shrink is assigned to a shrinker struct
> (include/linux/shrinker.h) and called in do_shrinker_shrink() in
> mm/vmscan.c. That, in turn, is called and checked in a few places
> in vmscan.c.
>
> >From the comments in shrinker.h: 
> "It should return the number of objects which remain in the
> cache. If it returns -1, it means it cannot do any scanning at
> this time (eg. there is a risk of deadlock). The callback must not
> return -1 if nr_to_scan is zero."

Ah.  Good.  -1 is the right return.

But really should be a #define in shrinker.h instead of in
drivers/staging/android/.

regards,
dan carpenter

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