| Message ID | 1412182919-9550-7-git-send-email-stefanha@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 01.10.2014 19:01, Stefan Hajnoczi wrote: > Now that op blockers are in use, we can ensure that no other sources are > generating I/O on a BlockDriverState. Therefore it is possible to drain > requests for a single BDS. > > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > block.c | 36 +++++++++++++++++++++++++++++------- > include/block/block.h | 1 + > 2 files changed, 30 insertions(+), 7 deletions(-) > > diff --git a/block.c b/block.c > index c5a251c..48305c4 100644 > --- a/block.c > +++ b/block.c > @@ -1918,6 +1918,34 @@ static bool bdrv_requests_pending(BlockDriverState *bs) > return false; > } > > +static bool bdrv_drain_one(BlockDriverState *bs) > +{ > + bool bs_busy; > + > + bdrv_flush_io_queue(bs); > + bdrv_start_throttled_reqs(bs); > + bs_busy = bdrv_requests_pending(bs); > + bs_busy |= aio_poll(bdrv_get_aio_context(bs), bs_busy); > + return bs_busy; > +} > + > +/* > + * Wait for pending requests to complete on a single BlockDriverState subtree > + * > + * See the warning in bdrv_drain_all(). This function can only be called if > + * you are sure nothing can generate I/O because you have op blockers > + * installed. Although that warning now sounds too harsh: "it is not possible to have a function to drain a single device's I/O queue." Apparently, under certain circumstances, it now *is* possible. ;-) Reviewed-by: Max Reitz <mreitz@redhat.com>
diff --git a/block.c b/block.c index c5a251c..48305c4 100644 --- a/block.c +++ b/block.c @@ -1918,6 +1918,34 @@ static bool bdrv_requests_pending(BlockDriverState *bs) return false; } +static bool bdrv_drain_one(BlockDriverState *bs) +{ + bool bs_busy; + + bdrv_flush_io_queue(bs); + bdrv_start_throttled_reqs(bs); + bs_busy = bdrv_requests_pending(bs); + bs_busy |= aio_poll(bdrv_get_aio_context(bs), bs_busy); + return bs_busy; +} + +/* + * Wait for pending requests to complete on a single BlockDriverState subtree + * + * See the warning in bdrv_drain_all(). This function can only be called if + * you are sure nothing can generate I/O because you have op blockers + * installed. + * + * Note that unlike bdrv_drain_all(), the caller must hold the BlockDriverState + * AioContext. + */ +void bdrv_drain(BlockDriverState *bs) +{ + while (bdrv_drain_one(bs)) { + /* Keep iterating */ + } +} + /* * Wait for pending requests to complete across all BlockDriverStates * @@ -1941,16 +1969,10 @@ void bdrv_drain_all(void) QTAILQ_FOREACH(bs, &bdrv_states, device_list) { AioContext *aio_context = bdrv_get_aio_context(bs); - bool bs_busy; aio_context_acquire(aio_context); - bdrv_flush_io_queue(bs); - bdrv_start_throttled_reqs(bs); - bs_busy = bdrv_requests_pending(bs); - bs_busy |= aio_poll(aio_context, bs_busy); + busy |= bdrv_drain_one(bs); aio_context_release(aio_context); - - busy |= bs_busy; } } } diff --git a/include/block/block.h b/include/block/block.h index 3318f0d..61df804 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -372,6 +372,7 @@ int bdrv_flush(BlockDriverState *bs); int coroutine_fn bdrv_co_flush(BlockDriverState *bs); int bdrv_flush_all(void); void bdrv_close_all(void); +void bdrv_drain(BlockDriverState *bs); void bdrv_drain_all(void); int bdrv_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors);
Now that op blockers are in use, we can ensure that no other sources are generating I/O on a BlockDriverState. Therefore it is possible to drain requests for a single BDS. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> --- block.c | 36 +++++++++++++++++++++++++++++------- include/block/block.h | 1 + 2 files changed, 30 insertions(+), 7 deletions(-)