linux-kernel - Re: [PATCH 3/3] tracing: clean up splice code

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Date:	Mon, 09 Feb 2009 20:26:20 +0200
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
CC:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 3/3] tracing: clean up splice code

Eduard - Gabriel Munteanu wrote:
>> @@ -2573,45 +2607,25 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
>>  		ret = iter->trace->splice_read(iter, filp,
>>  					       ppos, pipe, len, flags);
>>  		if (ret)
>> -			goto out;
>> +			goto out_err;
>>  	}
>>  
>>  	ret = tracing_wait_pipe(filp);
>>  	if (ret <= 0)
>> -		goto out;
>> +		goto out_err;
>>  
>>  	if (!iter->ent && !find_next_entry_inc(iter)) {
>>  		ret = -EFAULT;
>> -		goto out;
>> +		goto out_err;
>>  	}
>>  
>>  	/* Fill as many pages as possible. */
>>  	for (i = 0, rem = len; i < PIPE_BUFFERS && rem; i++) {
>>  		pages[i] = alloc_page(GFP_KERNEL);
>> +		if (!pages[i])
>> +			break;
> 
> I believe you should decrement 'i' before breaking, since we fill
> spd.nr_pages just after the loop. In case the current page couldn't be
> allocated, spd.nr_pages will be one too many (that is, 'i').

But, but, if we fail for i == 1, for example, we want ->nr_pages == 1, no?

			Pekka
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