linux-ext4 - Re: [PATCH V2] ext4: handle optional-arg mount options better

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Date:	Tue, 16 Feb 2010 11:28:39 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	tytso@....edu
CC:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH V2] ext4: handle optional-arg mount options better

Eric Sandeen wrote:
> tytso@....edu wrote:
>> Ok, how about this, for even more explicit?
>>
>> 						- Ted
> 
> Sure, that looks even better.  Who knew args parsing was so hard ;)
> 
> -Eric
> 
>> commit 15121c18a22ae483279f76dc9e554334b800d0f7
>> Author: Eric Sandeen <sandeen@...hat.com>
>> Date:   Mon Feb 15 20:17:55 2010 -0500
>>
>>     ext4: Fix optional-arg mount options
>>     
>>     We have 2 mount options, "barrier" and "auto_da_alloc" which may or
>>     may not take a 1/0 argument.  This causes the ext4 superblock mount
>>     code to subtract uninitialized pointers and pass the result to
>>     kmalloc, which results in very noisy failures.
>>     
>>     Per Ted's suggestion, initialize the args struct so that
>>     we know whether match_token() found an argument for the
>>     option, and skip match_int() if not.
>>     
>>     Also, return error (0) from parse_options if we thought
>>     we found an argument, but match_int() Fails.
>>     
>>     Reported-by: Michael S. Tsirkin <mst@...hat.com>
>>     Signed-off-by: Eric Sandeen <sandeen@...hat.com>
>>     Signed-off-by: "Theodore Ts'o" <tytso@....edu>
>>
>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>> index 735c20d..68a55df 100644
>> --- a/fs/ext4/super.c
>> +++ b/fs/ext4/super.c
>> @@ -1229,6 +1229,11 @@ static int parse_options(char *options, struct super_block *sb,
>>  		if (!*p)
>>  			continue;
>>  
>> +		/*
>> +		 * Initialize args struct so we know whether arg was
>> +		 * found; some options take optional arguments.
>> +		 */
>> +		args[0].to = args[0].from = 0;

Unless it's already in, those should probably be "= NULL"
since they're pointers.

-Eric
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