Re: [PATCH 06/15] btrfs: initialize sysfs devid and device link for seed device

[Nikolay Borisov <nborisov@suse.com>]

On 3.09.20 г. 3:57 ч., Anand Jain wrote:
> The following test case leads to null kobject-being-freed error.
> 
>  mount seed /mnt
>  add sprout to /mnt
>  umount /mnt
>  mount sprout to /mnt
>  delete seed

This patch warrants an fstests alongside it!

> 
>  kobject: '(null)' (00000000dd2b87e4): is not initialized, yet kobject_put() is being called.
>  WARNING: CPU: 1 PID: 15784 at lib/kobject.c:736 kobject_put+0x80/0x350
>  RIP: 0010:kobject_put+0x80/0x350
>  ::
>  Call Trace:
>  btrfs_sysfs_remove_devices_dir+0x6e/0x160 [btrfs]
>  btrfs_rm_device.cold+0xa8/0x298 [btrfs]
>  btrfs_ioctl+0x206c/0x22a0 [btrfs]
>  ksys_ioctl+0xe2/0x140
>  __x64_sys_ioctl+0x1e/0x29
>  do_syscall_64+0x96/0x150
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>  RIP: 0033:0x7f4047c6288b
>  ::
> 
> This is because, at the end of the seed device-delete, we try to remove
> the seed's devid sysfs entry. But for the seed devices under the sprout
> fs, we don't initialize the devid kobject yet. So this patch initializes
> the seed device devid kobject and the device link in the sysfs. This takes
> care of the Warning.
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
>  fs/btrfs/sysfs.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index 9853b9acd4bd..98ce955a0879 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -938,9 +938,15 @@ void btrfs_sysfs_remove_fsid(struct btrfs_fs_devices *fs_devs)
>  void btrfs_sysfs_remove_fs_devices(struct btrfs_fs_devices *fs_devices)
>  {
>  	struct btrfs_device *device;
> +	struct btrfs_fs_devices *seed;
>  
>  	list_for_each_entry(device, &fs_devices->devices, dev_list)
>  		btrfs_sysfs_remove_device(device);
> +
> +	list_for_each_entry(seed, &fs_devices->seed_list, seed_list) {
> +		list_for_each_entry(device, &seed->devices, dev_list)
> +			btrfs_sysfs_remove_device(device);
> +	}
>  }
>  
>  void btrfs_sysfs_remove_mounted(struct btrfs_fs_info *fs_info)
> @@ -1314,6 +1320,7 @@ int btrfs_sysfs_add_fs_devices(struct btrfs_fs_devices *fs_devices)
>  {
>  	int ret;
>  	struct btrfs_device *device;
> +	struct btrfs_fs_devices *seed;
>  
>  	list_for_each_entry(device, &fs_devices->devices, dev_list) {
>  		ret = btrfs_sysfs_add_device(device);
> @@ -1321,6 +1328,14 @@ int btrfs_sysfs_add_fs_devices(struct btrfs_fs_devices *fs_devices)
>  			return ret;
>  	}
>  
> +	list_for_each_entry(seed, &fs_devices->seed_list, seed_list) {
> +		list_for_each_entry(device, &seed->devices, dev_list) {
> +			ret = btrfs_sysfs_add_device(device);
> +			if (ret)
> +				return ret;
> +		}
> +	}
> +
>  	return 0;
>  }
>  
>