Re: [Qemu-devel] [PATCH 1/4 for-2.11?] block/dirty-bitmap: add lock to bdrv_enable/disable_dirty_bitmap

[Vladimir Sementsov-Ogievskiy]

13.11.2017 20:50, Eric Blake wrote:
> On 11/13/2017 10:20 AM, Vladimir Sementsov-Ogievskiy wrote:
> > Like other setters here these functions should take a lock.
> >
> > Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> > ---
> >   block/dirty-bitmap.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> Should this patch be in 2.11?


these functions are unused now, so, no, it's not necessary

> > diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
> > index bd04e991b1..2a0bcd9e51 100644
> > --- a/block/dirty-bitmap.c
> > +++ b/block/dirty-bitmap.c
> > @@ -397,15 +397,19 @@ void bdrv_remove_persistent_dirty_bitmap(BlockDriverState 
> > *bs,
> >   /* Called with BQL taken.  */
> >   void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
> >   {
> > +    bdrv_dirty_bitmap_lock(bitmap);
> >       assert(!bdrv_dirty_bitmap_frozen(bitmap));
> >       bitmap->disabled = true;
> > +    bdrv_dirty_bitmap_unlock(bitmap);
> Why do we need this lock in addition to BQL?
>
> >   }
> >   
> >   /* Called with BQL taken.  */
> >   void bdrv_enable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
> >   {
> > +    bdrv_dirty_bitmap_lock(bitmap);
> >       assert(!bdrv_dirty_bitmap_frozen(bitmap));
> >       bitmap->disabled = false;
> > +    bdrv_dirty_bitmap_unlock(bitmap);
> Again, why do we need this in addition to BQL?
>
> The commit message needs more details about a scenario where our
> existing BQL lock is insufficient to prevent misuse of bitmap->disabled.


--
Best regards,
Vladimir