Message-ID: <4B5FADE8.30803@theptrgroup.com>
Date: Tue, 26 Jan 2010 22:07:20 -0500
From: Jeff Angielski <jeff@theptrgroup.com>
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To: Matt Mackall <mpm@selenic.com>
CC: Herbert Xu <herbert@gondor.apana.org.au>, linux-mtd@lists.infradead.org,
       LKML <linux-kernel@vger.kernel.org>, dedekind1@gmail.com
Subject: Re: UBIFS assert failed in ubifs_dirty_inode
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Matt Mackall wrote:
> On Tue, 2010-01-26 at 20:44 -0500, Jeff Angielski wrote:
>> Artem Bityutskiy wrote:
>>> On Mon, 2010-01-25 at 23:48 -0600, Matt Mackall wrote:
>>>> Hmm. I'd just as soon drop it entirely. Here's a patch. Herbert, you
>>>> want to send this through your crypto tree?
>>>>
>>>>
>>>> random: drop weird m_time/a_time manipulation
>>>>
>>>> No other driver does anything remotely like this that I know of except
>>>> for the tty drivers, and I can't see any reason for random/urandom to do
>>>> it. In fact, it's a (trivial, harmless) timing information leak. And
>>>> obviously, it generates power- and flash-cycle wasting I/O, especially
>>>> if combined with something like hwrngd. Also, it breaks ubifs's
>>>> expectations.
>>>>
>>>> Signed-off-by: Matt Mackall <mpm@selenic.com>
>>>>
>>>> diff -r 29db0c391ce8 drivers/char/random.c
>>>> --- a/drivers/char/random.c	Sun Jan 17 11:01:16 2010 -0800
>>>> +++ b/drivers/char/random.c	Mon Jan 25 23:32:00 2010 -0600
>>>> @@ -1051,12 +1051,6 @@
>>>>  				/* like a named pipe */
>>>>  	}
>>>>  
>>>> -	/*
>>>> -	 * If we gave the user some bytes, update the access time.
>>>> -	 */
>>>> -	if (count)
>>>> -		file_accessed(file);
>>>> -
>>>>  	return (count ? count : retval);
>>>>  }
>>>>  
>>>> @@ -1116,8 +1110,6 @@
>>>>  	if (ret)
>>>>  		return ret;
>>>>  
>>>> -	inode->i_mtime = current_fs_time(inode->i_sb);
>>>> -	mark_inode_dirty(inode);
>>>>  	return (ssize_t)count;
>>>>  }
>>> It may brake other FSes expectations, theoretically, as well.
>>>
>>> Anyway, I'm perfectly fine if this is removed.
>>>
>>> Jeff, could you please try Matt's patch and report back if you still
>>> have issues or not. If no, you can use this as a temporary work-around
>>> until a proper fix hits upstream or ubifs-2.6.git.
>> Matt's patch did not compile as written.  I tried to implement what I 
>> think he was trying to do and created this patch (it seems to match the 
>> guts of what inode_setattr() was looking for):
>>
>>
>> diff --git a/drivers/char/random.c b/drivers/char/random.c
>> index 8258982..70f16c7 100644
>> --- a/drivers/char/random.c
>> +++ b/drivers/char/random.c
>> @@ -1108,6 +1108,7 @@ static ssize_t random_write(struct file *file, 
>> const char __user *buffer,
>>   {
>>   	size_t ret;
>>   	struct inode *inode = file->f_path.dentry->d_inode;
>> +	struct iattr attr;
>>
>>   	ret = write_pool(&blocking_pool, buffer, count);
>>   	if (ret)
>> @@ -1116,8 +1117,12 @@ static ssize_t random_write(struct file *file, 
>> const char __user *buffer,
>>   	if (ret)
>>   		return ret;
>>
>> -	inode->i_mtime = current_fs_time(inode->i_sb);
>> -	mark_inode_dirty(inode);
>> +	attr.ia_mtime = current_fs_time(inode->i_sb);
>> +	attr.ia_valid = ATTR_MTIME;
>> +	ret = inode_setattr(inode, &attr);
>> +	if (ret)
>> +		return ret;
>> +
>>   	return (ssize_t)count;
>>   }
>>
>> However, this patch does not fix the problem.  I still see the same 
>> errors.  Matt, is this what you were trying to do?
> 
> That doesn't look anything like my patch? And mine was test compiled.

Ahh, you would be right.  I mixed up authors.  My bad.  ;)

Matt's patch that removes the offending code works fine.

Artem's patch that tries to fix the offending code (and does not compile 
as posted) does not work.


-- 
Jeff Angielski
The PTR Group
www.theptrgroup.com
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