[dm-devel] [regression] a potential issue for bow_target after "dm: delay registering the gendisk" applied

[Faqiang Zhu]

Hi Christoph,

 

Recently when I use kernel5.15 with android, an issue related to bow_target
is found with below log:

 

[    8.935429][    T1] kobject_add_internal failed for bow (error: -2
parent: (null))

 

The call trace to the preceding log is as below:

dm_ctl_ioctl

 -> ctl_ioctl

   -> lookup_ioctl    // returns the table_load function pointer

      table_load

        -> populate_table

             -> dm_table_add_target

                  -> dm_bow_ctr

                       -> kobject_init_and_add

                            -> kobject_add_varg

                                 -> kobject_add_internal

 

 

Compared to kernel5.10, then I found it's related to below patch. The
gendisk, it's not registered yet, its kobject is not in sysfs, so its child
"bow" kobject cannot be added to the kernel.

commit 89f871af1b26d98d983cba7ed0e86effa45ba5f8

Author: Christoph Hellwig  <mailto:hch at lst.de> hch at lst.de

Date:   Wed Aug 4 11:41:46 2021 +0200

 

    dm: delay registering the gendisk

 

 

Is this an issue? if it is, is there any patch to fix it? if it is not, then
what is the right way to use the bow_target in userspace?

 

 

Best Regards,

Zhu Faqiang.

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