Re: [PATCH] Btrfs: don't remove raid type sysfs entries until unmount

[Jeff Mahoney <jeffm@suse.com>]

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On 5/23/14, 10:32 AM, David Sterba wrote:
> On Fri, May 23, 2014 at 08:56:06AM -0400, Jeff Mahoney wrote:
>> Sigh. Yep. kobject_cleanup caches ->name before the release
>> function and ignores the cleared value. It seems the "free name
>> if we alloced it" comment in there was leftover from the middle
>> of a patch series Kay applied in late 2007. Commit 0f4dafc05 adds
>> the comment while adding a flag to indicate that
>> kobject_set_name_vargs set the name. The commit af5ca3f4e says
>> kobject names must be dynamic but didn't update the comment.
>> 
>> Ok, so we can't save the strdup.
> 
> The tests have been running fine for more than 40 minutes,
> previously it took a few minutes to trigger the bug.
> 
> my quick fix:
> 
> --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@
> -8354,7 +8354,8 @@ static void __link_block_group(struct
> btrfs_space_info *space_info, int ret;
> 
> kobject_get(&space_info->kobj); /* put in release */ -
> kobj->name = get_raid_name(index); +               kobj->name =
> kstrdup(get_raid_name(index), GFP_ATOMIC); +
> BUG_ON(!kobj->name); ret = kobject_init_and_add(kobj,
> &btrfs_raid_ktype, &space_info->kobj, NULL); if (ret) { diff --git
> a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index
> d742d7973d3e..ac26f91968a7 100644 --- a/fs/btrfs/sysfs.c +++
> b/fs/btrfs/sysfs.c @@ -288,7 +288,7 @@ static struct attribute
> *raid_attributes[] = {
> 
> static void release_raid_kobj(struct kobject *kobj) { -
> kobj->name = NULL; +       /* kobj->name = NULL; */ 
> kobject_put(kobj->parent); }
> 

I'm testing as well. I'm seeing:
kobject (ffff88033f847e78): tried to init an initialized object,
something is seriously wrong.

.. as well. A memset would clear this up, but perhaps that's not the
right solution after all.

- -Jeff

- -- 
Jeff Mahoney
SUSE Labs
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