On 2/21/22 11:42, Mike Snitzer wrote:
On Mon, Feb 21 2022 at 5:36P -0500,
Faqiang Zhu <faqiang.zhu@xxxxxxx> 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@xxxxxx> hch@xxxxxx
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().
Might also be able to just move the sysfs initialization to first
preresume time, as the out-of-tree module VDO does?
https://github.com/dm-vdo/kvdo/commit/27bf63255af9e01736ca657df2fa1a03dcf124b8
Sweet Tea
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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