From mboxrd@z Thu Jan  1 00:00:00 1970
From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH]  fs null_blk: Null pointer deference problem in alloc_page_buffers
Date: Sat, 18 Jan 2014 00:05:00 +0530
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References: <1389950530-8903-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <x49sismzevl.fsf@segfault.boston.devel.redhat.com>
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Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	Matias Bjorling <m@bjorling.me>, Jens Axboe <axboe@kernel.dk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Yuanhan Liu <yuanhan.liu@linux.intel.com>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Jan Kara <jack@suse.cz>, Johannes Weiner <hannes@cmpxchg.org>,
	Zhang Yanfei <zhangyanfei@cn.fujitsu.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Sumanth <sumantk2@linux.vnet.ibm.com>
To: Jeff Moyer <jmoyer@redhat.com>
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On 01/17/2014 11:09 PM, Jeff Moyer wrote:
> Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> writes:
>
>> diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
>> index a2e69d2..6b0e049 100644
>> --- a/drivers/block/null_blk.c
>> +++ b/drivers/block/null_blk.c
>> @@ -535,6 +535,11 @@ static int null_add_dev(void)
>>   	if (!nullb)
>>   		return -ENOMEM;
>>
>> +	if (bs > PAGE_SIZE) {
>> +		WARN(1, "Invalid block size. Setting it to 4096\n");
>> +		bs = 4096;
>> +	}
>> +
>
> Why are you hard-coding 4k instead of just using PAGE_SIZE?
>

Thanks Jeff. Yes,that makes sense. will change.
(got same suggestion from reporter here too)