linux-kernel - Re: Resend: [PATCH] blkdev: fix blkdev_issue

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Date:	Fri, 06 Aug 2010 13:24:05 +0200
From:	Jens Axboe <axboe@...nel.dk>
To:	Dmitry Monakhov <dmonakhov@...nvz.org>
CC:	linux-kernel@...r.kernel.org
Subject: Re: Resend: [PATCH] blkdev: fix blkdev_issue_zeroout return value

On 2010-08-06 13:15, Dmitry Monakhov wrote:
> Jens Axboe <axboe@...nel.dk> writes:
> 
>> On 2010-08-06 12:42, Dmitry Monakhov wrote:
>>> Hi Jens,
>>> Seems that my first mail was missed somewhere.  
>>> I've found couple of trivial issues in blkdev_issue_zeroout()
>>> implementation. Unfortunately I've miss during initial testing phase
>>> because always called it with BARRIER|WAIT flags.
>>
>> BTW, this:
>>
>> @@ -218,15 +222,18 @@ submit:
>>  		/* One of bios in the batch was completed with error.*/
>>  		ret = -EIO;
>>  
>> -	if (ret)
>> +	if (ret && ret != -ENOMEM)
>>  		goto out;
>>  
>>  	if (test_bit(BIO_EOPNOTSUPP, &bb.flags)) {
>>  		ret = -EOPNOTSUPP;
>>  		goto out;
>>  	}
>> -	if (nr_sects != 0)
>> +	if (nr_sects != 0) {
>> +		if (ret == -ENOMEM)
>> +			io_schedule();
>>  		goto submit;
>> +	}
>>  out:
>>  	return ret;
>>  }
>>
>> is broken. Either the caller sets __GFP_WAIT and then bio_alloc() will
>> not fail, or GFP_ATOMIC is used knowing that the call can fail and
>> return ENOMEM. Don't code in retry logic like this.
> Ok, my fault and in fact i've done in explicitly. I just thought
> that blk-layer is some times an exception from general GFP_ATOMIC rule
> because in some places in blk-layer we stick to GFP_NOFAIL semantics
> regardless to actual gfp flags.
> 
> New version attached.

Thanks that looks better, now really added.

-- 
Jens Axboe

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