linux-kernel - Re: [PATCH] mm/vmscan: Do not block forever at shrink_inactive

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Message-ID: <20140520052452.GG18954@dastard>
Date:	Tue, 20 May 2014 15:24:52 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	riel@...hat.com, kosaki.motohiro@...fujitsu.com,
	fengguang.wu@...el.com, kamezawa.hiroyu@...fujitsu.com,
	linux-kernel@...r.kernel.org, xfs@....sgi.com
Subject: Re: [PATCH] mm/vmscan: Do not block forever at
 shrink_inactive_list().

On Tue, May 20, 2014 at 12:54:29PM +0900, Tetsuo Handa wrote:
> Dave Chinner wrote:
> > So, XFS should be passing kswapd context to the workqueue allocation
> > context. The patch below does this.
> > 
> > Tetsuo-san, when it comes to problems involving XFS, you should
> > really CC xfs@....sgi.com because very few people really know how
> > XFS works and even fewer still know how it is supposed to interact
> > with memory reclaim....
> 
> Thank you for the patch, but ...
> 
>   #define PF_KSWAPD       0x00040000      /* I am kswapd */
> 
>   static inline int current_is_kswapd(void)
>   {
>   	return current->flags & PF_KSWAPD;
>   }

> I think ((char) (current->flags & 0x00040000)) == 0.
> Your patch wants
> 
>   -args->kswapd = current_is_kswapd();
>   +args->kswapd = (current_is_kswapd() != 0);

Thanks for pointing that out, but I think:

-static inline int current_is_kswapd(void)
+static inline bool current_is_kswapd(void)

is a better solution. It can only be true or false.

But regardless, I need to change the boolean options in that XFS
structure to be, well, booleans.

Cheers,

dave.

-- 
Dave Chinner
david@...morbit.com
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