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

Li Zefan
2009-09-25T01:00:47Z

>>> 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