Re: [PATCH v2 1/5] md/md-bitmap: call md_bitmap_create,destroy in location_store

[Su Yue <l@damenly.org>]

aOn Mon 13 Apr 2026 at 15:47, Li Nan <linan666@huaweicloud.com> 
wrote:

> 在 2026/4/7 18:26, Su Yue 写道:
>> If bitmap/location is present, mdadm will call 
>> update_array_info()
>> while growing bitmap from none to internal via 
>> location_store().
>> md_bitmap_create() is needed to set mddev->bitmap_ops otherwise
>> mddev->bitmap_ops->get_stats() in update_array_info() will 
>> trigger
>> kernel NULL pointer dereference.
>> Fixes: fb8cc3b0d9db ("md/md-bitmap: delay registration of 
>> bitmap_ops until
>> creating bitmap")
>> Signed-off-by: Su Yue <glass.su@suse.com>
>> ---
>>   drivers/md/md-bitmap.c | 11 ++++++++---
>>   drivers/md/md.c        |  4 ++--
>>   drivers/md/md.h        |  2 ++
>>   3 files changed, 12 insertions(+), 5 deletions(-)
>> diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
>> index 83378c033c72..2f24aae05552 100644
>> --- a/drivers/md/md-bitmap.c
>> +++ b/drivers/md/md-bitmap.c
>> @@ -2618,7 +2618,7 @@ location_store(struct mddev *mddev, const 
>> char *buf, size_t len)
>>   			goto out;
>>   		}
>>   -		bitmap_destroy(mddev);
>> +		md_bitmap_destroy(mddev);
>>   		mddev->bitmap_info.offset = 0;
>>   		if (mddev->bitmap_info.file) {
>>   			struct file *f = mddev->bitmap_info.file;
>> @@ -2653,15 +2653,20 @@ location_store(struct mddev *mddev, 
>> const char *buf, size_t len)
>>   				goto out;
>>   			}
>>   +			/*
>> +			 * lockless bitmap shoudle have set bitmap_id
>> +			 * using bitmap_type, so always ID_BITMAP.
>> +			 */
>> +			mddev->bitmap_id = ID_BITMAP;
>>   			mddev->bitmap_info.offset = offset;
>> -			rv = bitmap_create(mddev);
>> +			rv = md_bitmap_create(mddev);
>>   			if (rv)
>>   				goto out;
>>     			rv = bitmap_load(mddev);
>
> mddev->bitmap_ops->load() should also be used here.

/NOD.
location_store() is only used for ID_BITMAP_NONE and ID_BITMAP, so
mddev->bitmap_ops->load() is always bitmap_load().
But for code consistency, mddev->bitmap_ops->load() is better, 
will fix it.

--
Su