RE: [PATCH] migration: Move bitmap_mutex out of migration_bitmap_clear_dirty()

["Wang, Wei W" <wei.w.wang@intel.com>]

On Wednesday, July 7, 2021 1:47 AM, Peter Xu wrote:
> On Sat, Jul 03, 2021 at 02:53:27AM +0000, Wang, Wei W wrote:
> > +       do {
> > +            page_to_clear = start + (i++ << block->clear_bmap_shift);
> 
> Why "i" needs to be shifted?

Just move to the next clear chunk, no?
For example, (1 << 18) pages chunk (i.e. 1GB).

> 
> > +            migration_clear_memory_region_dirty_bitmap(ram_state,
> > +                                                       block,
> > +
> page_to_clear);
> > +       } while (i <= npages >> block->clear_bmap_shift);
> 
> I agree with David that this should be better put into the mutex section, if so
> we'd also touch up comment for bitmap_mutex.  Or is it a reason to explicitly
> not do so?

clear_bmap_test_and_clear already uses atomic operation on clear_bmap.
But it's also OK to me if you guys feel safer to move it under the lock.

Best,
Wei