Re: [PATCH v3] Fix race of "mdadm --add" and "mdadm --incremental"

[Jes Sorensen <jes@trained-monkey.org>]

On 9/7/23 07:37, Li Xiao Keng wrote:
> There is a raid1 with sda and sdb. And we add sdc to this raid,
> it may return -EBUSY.
> 
> The main process of --add:
> 1. dev_open（sdc) in Manage_add
> 2. store_super1(st, di->fd) in write_init_super1
> 3. fsync(fd) in store_super1
> 4. close(di->fd) in write_init_super1
> 5. ioctl(ADD_NEW_DISK)
> 
> Step 2 and 3 will add sdc to metadata of raid1. There will be
> udev(change of sdc) event after step4. Then "/usr/sbin/mdadm
> --incremental --export $devnode --offroot $env{DEVLINKS}"
> will be run, and the sdc will be added to the raid1. Then
> step 5 will return -EBUSY because it checks if device isn't
> claimed in md_import_device()->lock_rdev()->blkdev_get_by_dev()
> ->blkdev_get().
> 
> It will be confusing for users because sdc is added first time.
> The "incremental" will get map_lock before add sdc to raid1.
> So we add map_lock before write_init_super in "mdadm --add"
> to fix the race of "add" and "incremental".
> 
> Signed-off-by: Li Xiao Keng <lixiaokeng@huawei.com>
> Signed-off-by: Guanqin Miao <miaoguanqin@huawei.com>

Applied!

Thanks,
Jes