Message-ID: <4C42B98E.4020208@vflare.org>
Date: Sun, 18 Jul 2010 13:51:34 +0530
From: Nitin Gupta <ngupta@vflare.org>
Reply-To: ngupta@vflare.org
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To: Pekka Enberg <penberg@cs.helsinki.fi>
CC: Hugh Dickins <hugh.dickins@tiscali.co.uk>,
        Andrew Morton <akpm@linux-foundation.org>, Greg KH <greg@kroah.com>,
        Dan Magenheimer <dan.magenheimer@oracle.com>,
        Rik van Riel <riel@redhat.com>, Avi Kivity <avi@redhat.com>,
        Christoph Hellwig <hch@infradead.org>,
        Minchan Kim <minchan.kim@gmail.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        linux-mm <linux-mm@kvack.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 7/8] Use xvmalloc to store compressed chunks
References: <1279283870-18549-1-git-send-email-ngupta@vflare.org> <1279283870-18549-8-git-send-email-ngupta@vflare.org> <4C42B2E4.4040504@cs.helsinki.fi>
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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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