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381a3ce1c0
IO operations may be needed before md_run(), such as updating metadata
after writing sysfs. Without bioset, this triggers a NULL pointer
dereference as below:
BUG: kernel NULL pointer dereference, address: 0000000000000020
Call Trace:
md_update_sb+0x658/0xe00
new_level_store+0xc5/0x120
md_attr_store+0xc9/0x1e0
sysfs_kf_write+0x6f/0xa0
kernfs_fop_write_iter+0x141/0x2a0
vfs_write+0x1fc/0x5a0
ksys_write+0x79/0x180
__x64_sys_write+0x1d/0x30
x64_sys_call+0x2818/0x2880
do_syscall_64+0xa9/0x580
entry_SYSCALL_64_after_hwframe+0x4b/0x53
Reproducer
```
mdadm -CR /dev/md0 -l1 -n2 /dev/sd[cd]
echo inactive > /sys/block/md0/md/array_state
echo 10 > /sys/block/md0/md/new_level
```
mddev_init() can only be called once per mddev, no need to test if bioset
has been initialized anymore.
Link: https://lore.kernel.org/linux-raid/20251103125757.1405796-3-linan666@huaweicloud.com
Fixes: d981ed8419 ("md: Add new_level sysfs interface")
Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.