Re: [PATCH] Add missing blk_trace_remove_sysfs to be in pair with blk_trace_init_sysfs

[Li Zefan <lizf@cn.fujitsu.com>]

>>> connection between kobj and sysfs. It's somewhat unclear why all the
>>> kobject operation are only within this if(){} block - so I've thought
>>> there is some reason...
>>> IMHO only elv_unregister_queue() should be probably in the if(){} block.
>>>
>> Seems it's a bug to put kobject_put(dev->kobj) in the if block.
>>
>> I created a stacked device (mdadm) and kmemleak still reported leaks
>> even after I fixed the blktrace issue. And then I moved kobejct_put()
>> outside the if, no more leaks reports.
>>
> 
> Ok - I didn't have a testcase where the request_fn would be NULL.

Here you are ;)

mdadm --create --level=linear --raid-devices=1 --force /dev/md0 /dev/sda6

> So in this case I propose this patch:
> 

Looks good.

Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>

> ---
> Add missing blk_trace_remove_sysfs to be in pair with blk_trace_init_sysfs
> introduced in commit 1d54ad6da9192fed5dd3b60224d9f2dfea0dcd82.
> Release kobject also in case the request_fn is NULL.
> 
> Problem was noticed via kmemleak backtrace when some sysfs entries were
> note properly destroyed during  device removal:
> 
> unreferenced object 0xffff88001aa76640 (size 80):
>   comm "lvcreate", pid 2120, jiffies 4294885144
>   hex dump (first 32 bytes):
>     01 00 00 00 00 00 00 00 f0 65 a7 1a 00 88 ff ff  .........e......
>     90 66 a7 1a 00 88 ff ff 86 1d 53 81 ff ff ff ff  .f........S.....
>   backtrace:
>     [<ffffffff813f9cc6>] kmemleak_alloc+0x26/0x60
>     [<ffffffff8111d693>] kmem_cache_alloc+0x133/0x1c0
>     [<ffffffff81195891>] sysfs_new_dirent+0x41/0x120
>     [<ffffffff81194b0c>] sysfs_add_file_mode+0x3c/0xb0
>     [<ffffffff81197c81>] internal_create_group+0xc1/0x1a0
>     [<ffffffff81197d93>] sysfs_create_group+0x13/0x20
>     [<ffffffff810d8004>] blk_trace_init_sysfs+0x14/0x20
>     [<ffffffff8123f45c>] blk_register_queue+0x3c/0xf0
>     [<ffffffff812447e4>] add_disk+0x94/0x160
>     [<ffffffffa00d8b08>] dm_create+0x598/0x6e0 [dm_mod]
>     [<ffffffffa00de951>] dev_create+0x51/0x350 [dm_mod]
>     [<ffffffffa00de823>] ctl_ioctl+0x1a3/0x240 [dm_mod]
>     [<ffffffffa00de8f2>] dm_compat_ctl_ioctl+0x12/0x20 [dm_mod]
>     [<ffffffff81177bfd>] compat_sys_ioctl+0xcd/0x4f0
>     [<ffffffff81036ed8>] sysenter_dispatch+0x7/0x2c
>     [<ffffffffffffffff>] 0xffffffffffffffff
> 
> Signed-off-by: Zdenek Kabelac <zkabelac@redhat.com>
> ---
>  block/blk-sysfs.c            |   11 ++++++-----
>  include/linux/blktrace_api.h |    2 ++
>  kernel/trace/blktrace.c      |    5 +++++
>  3 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index b78c9c3..8a6d81a 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -452,6 +452,7 @@ int blk_register_queue(struct gendisk *disk)
>  	if (ret) {
>  		kobject_uevent(&q->kobj, KOBJ_REMOVE);
>  		kobject_del(&q->kobj);
> +		blk_trace_remove_sysfs(disk_to_dev(disk));
>  		return ret;
>  	}
> 
> @@ -465,11 +466,11 @@ void blk_unregister_queue(struct gendisk *disk)
>  	if (WARN_ON(!q))
>  		return;
> 
> -	if (q->request_fn) {
> +	if (q->request_fn)
>  		elv_unregister_queue(q);
> 
> -		kobject_uevent(&q->kobj, KOBJ_REMOVE);
> -		kobject_del(&q->kobj);
> -		kobject_put(&disk_to_dev(disk)->kobj);
> -	}
> +	kobject_uevent(&q->kobj, KOBJ_REMOVE);
> +	kobject_del(&q->kobj);
> +	blk_trace_remove_sysfs(disk_to_dev(disk));
> +	kobject_put(&disk_to_dev(disk)->kobj);
>  }
> diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
> index 7e4350e..622939a 100644
> --- a/include/linux/blktrace_api.h
> +++ b/include/linux/blktrace_api.h
> @@ -198,6 +198,7 @@ extern int blk_trace_setup(struct request_queue
> *q, char *name, dev_t dev,
>  			   char __user *arg);
>  extern int blk_trace_startstop(struct request_queue *q, int start);
>  extern int blk_trace_remove(struct request_queue *q);
> +extern void blk_trace_remove_sysfs(struct device *dev);
>  extern int blk_trace_init_sysfs(struct device *dev);
> 
>  extern struct attribute_group blk_trace_attr_group;
> @@ -211,6 +212,7 @@ extern struct attribute_group blk_trace_attr_group;
>  # define blk_trace_startstop(q, start)			(-ENOTTY)
>  # define blk_trace_remove(q)				(-ENOTTY)
>  # define blk_add_trace_msg(q, fmt, ...)			do { } while (0)
> +# define blk_trace_remove_sysfs(struct device *dev)	do { } while (0)
>  static inline int blk_trace_init_sysfs(struct device *dev)
>  {
>  	return 0;
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index 3eb159c..60b5c5a 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -1657,6 +1657,11 @@ int blk_trace_init_sysfs(struct device *dev)
>  	return sysfs_create_group(&dev->kobj, &blk_trace_attr_group);
>  }
> 
> +void blk_trace_remove_sysfs(struct device *dev)
> +{
> +	sysfs_remove_group(&dev->kobj, &blk_trace_attr_group);
> +}
> +
>  #endif /* CONFIG_BLK_DEV_IO_TRACE */
> 
>  #ifdef CONFIG_EVENT_TRACING