From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38551) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zovz7-0002UQ-Fy for qemu-devel@nongnu.org; Wed, 21 Oct 2015 12:11:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zovz6-0007Kd-Hf for qemu-devel@nongnu.org; Wed, 21 Oct 2015 12:11:29 -0400 Date: Wed, 21 Oct 2015 12:11:18 -0400 From: Jeff Cody Message-ID: <20151021161118.GD6466@localhost.localdomain> References: <1445393209-26545-1-git-send-email-famz@redhat.com> <1445393209-26545-6-git-send-email-famz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1445393209-26545-6-git-send-email-famz@redhat.com> Subject: Re: [Qemu-devel] [Qemu-block] [PATCH v5 05/12] block: Introduce "drained begin/end" API List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Fam Zheng Cc: kwolf@redhat.com, pbonzini@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, stefanha@redhat.com On Wed, Oct 21, 2015 at 10:06:42AM +0800, Fam Zheng wrote: > The semantics is that after bdrv_drained_begin(bs), bs will not get new external > requests until the matching bdrv_drained_end(bs). > > Signed-off-by: Fam Zheng > --- > block/io.c | 17 +++++++++++++++++ > include/block/block.h | 21 +++++++++++++++++++++ > include/block/block_int.h | 2 ++ > 3 files changed, 40 insertions(+) > > diff --git a/block/io.c b/block/io.c > index 2fd7a1d..5ac6256 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -2624,3 +2624,20 @@ void bdrv_flush_io_queue(BlockDriverState *bs) > } > bdrv_start_throttled_reqs(bs); > } > + > +void bdrv_drained_begin(BlockDriverState *bs) > +{ > + if (!bs->quiesce_counter++) { > + aio_disable_external(bdrv_get_aio_context(bs)); > + } > + bdrv_drain(bs); > +} > + > +void bdrv_drained_end(BlockDriverState *bs) > +{ > + assert(bs->quiesce_counter > 0); > + if (--bs->quiesce_counter > 0) { > + return; > + } > + aio_enable_external(bdrv_get_aio_context(bs)); > +} Why do we need a quiesce counter, given that aio_{disable, enable}_external() increments / decrements a counter? > diff --git a/include/block/block.h b/include/block/block.h > index 28d903c..6d38b62 100644 > --- a/include/block/block.h > +++ b/include/block/block.h > @@ -610,4 +610,25 @@ void bdrv_io_plug(BlockDriverState *bs); > void bdrv_io_unplug(BlockDriverState *bs); > void bdrv_flush_io_queue(BlockDriverState *bs); > > +BlockAcctStats *bdrv_get_stats(BlockDriverState *bs); > + Is the above line from a bad rebase? > +/** > + * bdrv_drained_begin: > + * > + * Begin a quiesced section for exclusive access to the BDS, by disabling > + * external request sources including NBD server and device model. Note that > + * this doesn't block timers or coroutines from submitting more requests, which > + * means block_job_pause is still necessary. > + * > + * This function can be recursive. > + */ > +void bdrv_drained_begin(BlockDriverState *bs); > + > +/** > + * bdrv_drained_end: > + * > + * End a quiescent section started by bdrv_drained_begin(). > + */ > +void bdrv_drained_end(BlockDriverState *bs); > + > #endif > diff --git a/include/block/block_int.h b/include/block/block_int.h > index e472a03..e317b14 100644 > --- a/include/block/block_int.h > +++ b/include/block/block_int.h > @@ -448,6 +448,8 @@ struct BlockDriverState { > /* threshold limit for writes, in bytes. "High water mark". */ > uint64_t write_threshold_offset; > NotifierWithReturn write_threshold_notifier; > + > + int quiesce_counter; > }; > > struct BlockBackendRootState { > -- > 2.4.3 > >