[dm-devel] a potential issue for bow_target after "dm: delay registering the gendisk" applied
Mike Snitzer
snitzer at redhat.com
Mon Feb 21 16:42:41 UTC 2022
On Mon, Feb 21 2022 at 5:36P -0500,
Faqiang Zhu <faqiang.zhu at nxp.com> wrote:
> 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?
>
It is an issue for this out-of-tree dm-bow target. Likely needs to be
fixed by adding a new DM target operation to 'struct target_type' that
would get called by DM core at end of dm_setup_md_queue().
Or dm-bow discontinues using sysfs for whatever and convert to using
DM messages (with .message) and exposing associated state via .status
Mike
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