Am 10.11.2022 um 17:11 hat Hanna Reitz geschrieben: > On 10.11.22 15:01, Kevin Wolf wrote: > > Am 07.11.2022 um 16:13 hat Hanna Reitz geschrieben: > > > Hi, > > > > > > v1 cover letter: > > > https://lists.nongnu.org/archive/html/qemu-block/2022-09/msg00389.html > > > > > > bdrv_replace_child_noperm() drains the child via > > > bdrv_parent_drained_{begin,end}_single(). When it removes a child, the > > > bdrv_parent_drained_end_single() at its end will be called on an empty > > > child, making the BDRV_POLL_WHILE() in it poll the main AioContext > > > (because c->bs is NULL). > > > > > > That’s wrong, though, because it’s supposed to operate on the parent. > > > bdrv_parent_drained_end_single_no_poll() will have scheduled any BHs in > > > the parents’ AioContext, which may be anything, not necessarily the main > > > context. Therefore, we must poll the parent’s context. > > > > > > Patch 3 does this for both bdrv_parent_drained_{begin,end}_single(). > > > Patch 1 ensures that we can legally call > > > bdrv_child_get_parent_aio_context() from those I/O context functions, > > > and patch 2 fixes blk_do_set_aio_context() to not cause an assertion > > > failure if it beginning a drain can end up in blk_get_aio_context() > > > before blk->ctx has been updated. > > Thanks, applied to the block branch. > > Thanks! > > I tested your drain series, and it does indeed fix the bug, too. > (Sorry for the delay, I thought it’d take less time to write an > iotest...)
Thanks for testing, it's good to have this confirmed. > > I would still be interested in a test case as a follow-up. > > Got it working now and sent as “tests/stream-under-throttle: New test”. Great! I'll take a look. Kevin
