Re: [Qemu-block] [Qemu-devel] [PATCH 16/17] block: protect modification of dirty bitmaps with a mutex

[Paolo Bonzini]

On 04/05/2017 10:05, Fam Zheng wrote:
>>      /* Writing to the list requires the BQL _and_ the dirty_bitmap_mutex.
>>       * Reading from the list can be done with either the BQL or the
>> -     * dirty_bitmap_mutex.  Modifying a bitmap requires the AioContext
>> -     * lock.  */
>> +     * dirty_bitmap_mutex.  Modifying a bitmap only requires
>> +     * dirty_bitmap_mutex.  */
> I'm confused by this comment. What's added in this patch is bitmap->mutex, not
> dirty_bitmap_mutex. Is it a mistake?

bitmap->mutex is a pointer that points to the (single) per-BDS mutex.

This patch changes the modification of bitmaps to require bitmap->mutex
(which points to bs->dirty_bitmap_mutex) instead of the AioContext lock.

Paolo

>>      QemuMutex dirty_bitmap_mutex;