linux-kernel - Re: sk_lock: inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM

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Message-Id: <20090714.090432.13343695.davem@davemloft.net>
Date:	Tue, 14 Jul 2009 09:04:32 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	fengguang.wu@...el.com, linux-kernel@...r.kernel.org,
	linux-nfs@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: sk_lock: inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W}
 usage

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Fri, 10 Jul 2009 16:02:47 +0800

> On Fri, Jul 10, 2009 at 04:00:17PM +0800, Wu Fengguang wrote:
>> 
>> The (sk_allocation & ~__GFP_WAIT) cases should be rare, but I guess
>> the networking code shall do it anyway, because sk_allocation defaults
>> to GFP_KERNEL. It seems that currently the networking code simply uses
>> a lot of GFP_ATOMIC, do they really mean "I cannot sleep"?
> 
> Yep because they're done from softirq context.

Yes, this is the core issue.

All of Wu's talk about how "GFP_ATOMIC will wake up kswapd and
therefore can succeed just as well as GFP_KERNEL" is not relevant,
because GFP_ATOMIC means sleeping is not allowed.
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