| Message ID | 20220118162738.1366281-3-eesposit@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Removal of Aiocontext lock through drains: protect bdrv_replace_child_noperm. | expand |
On 1/18/22 17:27, Emanuele Giuseppe Esposito wrote: > Using bdrv_do_drained_begin_quiesce() in bdrv_child_cb_drained_end() bdrv_child_cb_drained_begin() > is not a good idea: the callback might be called when running > a drain in a coroutine, and bdrv_drained_begin_poll() does not > handle that case, resulting in assertion failure. > > Instead, bdrv_do_drained_begin with no recursion and poll > will accomplish the same thing (invoking bdrv_do_drained_begin_quiesce) > but will firstly check if we are already in a coroutine, and exit > from that via bdrv_co_yield_to_drain(). A better subject would be "fix bdrv_child_cb_drained_begin invocations from a coroutine". Paolo > Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> > --- > block.c | 2 +- > block/io.c | 7 ++++++- > include/block/block-io.h | 8 +++++--- > 3 files changed, 12 insertions(+), 5 deletions(-) > > diff --git a/block.c b/block.c > index 668986c879..08fde585f4 100644 > --- a/block.c > +++ b/block.c > @@ -1206,7 +1206,7 @@ static char *bdrv_child_get_parent_desc(BdrvChild *c) > static void bdrv_child_cb_drained_begin(BdrvChild *child) > { > BlockDriverState *bs = child->opaque; > - bdrv_do_drained_begin_quiesce(bs, NULL, false); > + bdrv_drained_begin_no_poll(bs); > } > > static bool bdrv_child_cb_drained_poll(BdrvChild *child) > diff --git a/block/io.c b/block/io.c > index 3be08cad29..5123b7b713 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -425,7 +425,7 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs, > } > } > > -void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, > +static void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, > BdrvChild *parent, bool ignore_bds_parents) > { > assert(!qemu_in_coroutine()); > @@ -487,6 +487,11 @@ void bdrv_subtree_drained_begin(BlockDriverState *bs) > bdrv_do_drained_begin(bs, true, NULL, false, true); > } > > +void bdrv_drained_begin_no_poll(BlockDriverState *bs) > +{ > + bdrv_do_drained_begin(bs, false, NULL, false, false); > +} > + > /** > * This function does not poll, nor must any of its recursively called > * functions. The *drained_end_counter pointee will be incremented > diff --git a/include/block/block-io.h b/include/block/block-io.h > index a69bc5bd36..34a991649c 100644 > --- a/include/block/block-io.h > +++ b/include/block/block-io.h > @@ -238,13 +238,15 @@ bool bdrv_drain_poll(BlockDriverState *bs, bool recursive, > void bdrv_drained_begin(BlockDriverState *bs); > > /** > - * bdrv_do_drained_begin_quiesce: > + * bdrv_drained_begin_no_poll: > * > * Quiesces a BDS like bdrv_drained_begin(), but does not wait for already > * running requests to complete. > + * Same as bdrv_drained_begin(), but do not poll for the subgraph to > + * actually become unquiesced. Therefore, no graph changes will occur > + * with this function. > */ > -void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, > - BdrvChild *parent, bool ignore_bds_parents); > +void bdrv_drained_begin_no_poll(BlockDriverState *bs); > > /** > * Like bdrv_drained_begin, but recursively begins a quiesced section for
diff --git a/block.c b/block.c index 668986c879..08fde585f4 100644 --- a/block.c +++ b/block.c @@ -1206,7 +1206,7 @@ static char *bdrv_child_get_parent_desc(BdrvChild *c) static void bdrv_child_cb_drained_begin(BdrvChild *child) { BlockDriverState *bs = child->opaque; - bdrv_do_drained_begin_quiesce(bs, NULL, false); + bdrv_drained_begin_no_poll(bs); } static bool bdrv_child_cb_drained_poll(BdrvChild *child) diff --git a/block/io.c b/block/io.c index 3be08cad29..5123b7b713 100644 --- a/block/io.c +++ b/block/io.c @@ -425,7 +425,7 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs, } } -void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, +static void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, BdrvChild *parent, bool ignore_bds_parents) { assert(!qemu_in_coroutine()); @@ -487,6 +487,11 @@ void bdrv_subtree_drained_begin(BlockDriverState *bs) bdrv_do_drained_begin(bs, true, NULL, false, true); } +void bdrv_drained_begin_no_poll(BlockDriverState *bs) +{ + bdrv_do_drained_begin(bs, false, NULL, false, false); +} + /** * This function does not poll, nor must any of its recursively called * functions. The *drained_end_counter pointee will be incremented diff --git a/include/block/block-io.h b/include/block/block-io.h index a69bc5bd36..34a991649c 100644 --- a/include/block/block-io.h +++ b/include/block/block-io.h @@ -238,13 +238,15 @@ bool bdrv_drain_poll(BlockDriverState *bs, bool recursive, void bdrv_drained_begin(BlockDriverState *bs); /** - * bdrv_do_drained_begin_quiesce: + * bdrv_drained_begin_no_poll: * * Quiesces a BDS like bdrv_drained_begin(), but does not wait for already * running requests to complete. + * Same as bdrv_drained_begin(), but do not poll for the subgraph to + * actually become unquiesced. Therefore, no graph changes will occur + * with this function. */ -void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, - BdrvChild *parent, bool ignore_bds_parents); +void bdrv_drained_begin_no_poll(BlockDriverState *bs); /** * Like bdrv_drained_begin, but recursively begins a quiesced section for
Using bdrv_do_drained_begin_quiesce() in bdrv_child_cb_drained_end() is not a good idea: the callback might be called when running a drain in a coroutine, and bdrv_drained_begin_poll() does not handle that case, resulting in assertion failure. Instead, bdrv_do_drained_begin with no recursion and poll will accomplish the same thing (invoking bdrv_do_drained_begin_quiesce) but will firstly check if we are already in a coroutine, and exit from that via bdrv_co_yield_to_drain(). Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> --- block.c | 2 +- block/io.c | 7 ++++++- include/block/block-io.h | 8 +++++--- 3 files changed, 12 insertions(+), 5 deletions(-)