Message ID | 1445393209-26545-6-git-send-email-famz@redhat.com |
---|---|
State | New |
Headers | show |
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 <famz@redhat.com> > --- > 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 > >
On Wed, 10/21 12:11, Jeff Cody wrote: > 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 <famz@redhat.com> > > --- > > 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? No longer necessary in this version because we call bdrv_drain unconditionally, but this makes it possible to introducd bdrv_is_quiesced() and assertion on it, so I lean toward keeping it as it doesn't hurt. > > > 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? Yes, will remove.
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)); +} 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); + +/** + * 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 {
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 <famz@redhat.com> --- block/io.c | 17 +++++++++++++++++ include/block/block.h | 21 +++++++++++++++++++++ include/block/block_int.h | 2 ++ 3 files changed, 40 insertions(+)