Am 25.11.2022 um 15:59 hat Vladimir Sementsov-Ogievskiy geschrieben: > On 11/18/22 20:41, Kevin Wolf wrote: > > We only need to call both the BlockDriver's callback and the parent > > callbacks when going from undrained to drained or vice versa. A second > > drain section doesn't make a difference for the driver or the parent, > > they weren't supposed to send new requests before and after the second > > drain. > > > > One thing that gets in the way is the 'ignore_bds_parents' parameter in > > bdrv_do_drained_begin_quiesce() and bdrv_do_drained_end(): It means that > > bdrv_drain_all_begin() increases bs->quiesce_counter, but does not > > quiesce the parent through BdrvChildClass callbacks. If an additional > > drain section is started now, bs->quiesce_counter will be non-zero, but > > we would still need to quiesce the parent through BdrvChildClass in > > order to keep things consistent (and unquiesce it on the matching > > bdrv_drained_end(), even though the counter would reach 0 yet as long as > > would reach -> would NOT reach > > if I understand correctly)
Yes, you're right. Thanks for catching it. Fixing this while applying the series. Kevin > > the bdrv_drain_all() section is still active). > > > > Instead of keeping track of this, let's just get rid of the parameter. > > It was introduced in commit 6cd5c9d7b2d as an optimisation so that > > during bdrv_drain_all(), we wouldn't recursively drain all parents up to > > the root for each node, resulting in quadratic complexity. As it happens, > > calling the callbacks only once solves the same problem, so as of this > > patch, we'll still have O(n) complexity and ignore_bds_parents is not > > needed any more. > > > > This patch only ignores the 'ignore_bds_parents' parameter. It will be > > removed in a separate patch. > > > > Signed-off-by: Kevin Wolf <[email protected]> > > Reviewed-by: Hanna Reitz <[email protected]> > > Reviewed-by: Vladimir Sementsov-Ogievskiy <[email protected]> > > > > > -- > Best regards, > Vladimir >
