linux-kernel - Re: [PATCH 7/8] Use xvmalloc to store compressed chunks

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Message-ID: <4C42B98E.4020208@vflare.org>
Date:	Sun, 18 Jul 2010 13:51:34 +0530
From:	Nitin Gupta <ngupta@...are.org>
To:	Pekka Enberg <penberg@...helsinki.fi>
CC:	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <greg@...ah.com>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Rik van Riel <riel@...hat.com>, Avi Kivity <avi@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/8] Use xvmalloc to store compressed chunks

On 07/18/2010 01:23 PM, Pekka Enberg wrote:
> Nitin Gupta wrote:
>> @@ -528,17 +581,32 @@ static int zcache_store_page(struct zcache_inode_rb *znode,
>>          goto out;
>>      }
>>  
>> -    dest_data = kmap_atomic(zpage, KM_USER0);
>> +    local_irq_save(flags);
> 
> Does xv_malloc() required interrupts to be disabled? If so, why doesn't the function do it by itself?
> 


xvmalloc itself doesn't require disabling interrupts but zcache needs that since
otherwise, we can have deadlock between xvmalloc pool lock and mapping->tree_lock
which zcache_put_page() is called. OTOH, zram does not require this disabling of
interrupts. So, interrupts are disable separately for zcache case.

Thanks,
Nitin
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