Re: [PATCH v4] btrfs: allocate raid type kobjects dynamically

From: Chris Mason <clm@fb.com>
To: Jeff Mahoney <jeffm@suse.com>,
	linux-btrfs <linux-btrfs@vger.kernel.org>,
	David Sterba <dsterba@suse.cz>
Subject: Re: [PATCH v4] btrfs: allocate raid type kobjects dynamically
Date: Tue, 27 May 2014 13:22:33 -0400	[thread overview]
Message-ID: <5384C9D9.9000705@fb.com> (raw)
In-Reply-To: <5384C68C.507@fb.com>

On 05/27/2014 01:08 PM, Chris Mason wrote:
> On 05/27/2014 12:59 PM, Jeff Mahoney wrote:
>> We are currently allocating space_info objects in an array when we
>> allocate space_info. When a user does something like:
>>
>> # btrfs balance start -mconvert=raid1 -dconvert=raid1 /mnt
>> # btrfs balance start -mconvert=single -dconvert=single /mnt -f
>> # btrfs balance start -mconvert=raid1 -dconvert=raid1 /
>>
>> We can end up with memory corruption since the kobject hasn't
>> been reinitialized properly and the name pointer was left set.
>>
>> The rationale behind allocating them statically was to avoid
>> creating a separate kobject container that just contained the
>> raid type. It used the index in the array to determine the index.
>>
>> Ultimately, though, this wastes more memory than it saves in all
>> but the most complex scenarios and introduces kobject lifetime
>> questions.
>>
>> This patch allocates the kobjects dynamically instead. Note that
>> we also remove the kobject_get/put of the parent kobject since
>> kobject_add and kobject_del do that internally.
>>
>> Signed-off-by: Jeff Mahoney <jeffm@suse.com>
> 
> Lets see how smart patchwork is:
> 
> Reported-by:David Sterba <dsterba@suse.cz>

For future reference, not that smart.

-chris