| Message ID | 20220121170544.2049944-10-eesposit@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | block layer: split block APIs in global state and I/O | expand |
Am 21.01.2022 um 18:05 hat Emanuele Giuseppe Esposito geschrieben: > We want to be sure that the functions that write the child and > parent list of a bs are under BQL and drain. > > BQL prevents from concurrent writings from the GS API, while > drains protect from I/O. > > TODO: drains are missing in some functions using this assert. > Therefore a proper assertion will fail. Because adding drains > requires additional discussions, they will be added in future > series. > > Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> > diff --git a/block/io.c b/block/io.c > index cb095deeec..3be08cad29 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -734,6 +734,17 @@ void bdrv_drain_all(void) > bdrv_drain_all_end(); > } > > +void assert_bdrv_graph_writable(BlockDriverState *bs) > +{ > + /* > + * TODO: this function is incomplete. Because the users of this > + * assert lack the necessary drains, check only for BQL. > + * Once the necessary drains are added, > + * assert also for qatomic_read(&bs->quiesce_counter) > 0 > + */ > + assert(qemu_in_main_thread()); > +} This looks like a trivial function that could easily be static inline. Kevin
diff --git a/block.c b/block.c index d0a6fb2937..5ac0bf024a 100644 --- a/block.c +++ b/block.c @@ -1415,6 +1415,7 @@ static void bdrv_child_cb_attach(BdrvChild *child) { BlockDriverState *bs = child->opaque; + assert_bdrv_graph_writable(bs); QLIST_INSERT_HEAD(&bs->children, child, next); if (child->role & BDRV_CHILD_COW) { @@ -1434,6 +1435,7 @@ static void bdrv_child_cb_detach(BdrvChild *child) bdrv_unapply_subtree_drain(child, bs); + assert_bdrv_graph_writable(bs); QLIST_REMOVE(child, next); } @@ -2814,6 +2816,7 @@ static void bdrv_replace_child_noperm(BdrvChild **childp, if (child->klass->detach) { child->klass->detach(child); } + assert_bdrv_graph_writable(old_bs); QLIST_REMOVE(child, next_parent); } @@ -2823,6 +2826,7 @@ static void bdrv_replace_child_noperm(BdrvChild **childp, } if (new_bs) { + assert_bdrv_graph_writable(new_bs); QLIST_INSERT_HEAD(&new_bs->parents, child, next_parent); /* diff --git a/block/io.c b/block/io.c index cb095deeec..3be08cad29 100644 --- a/block/io.c +++ b/block/io.c @@ -734,6 +734,17 @@ void bdrv_drain_all(void) bdrv_drain_all_end(); } +void assert_bdrv_graph_writable(BlockDriverState *bs) +{ + /* + * TODO: this function is incomplete. Because the users of this + * assert lack the necessary drains, check only for BQL. + * Once the necessary drains are added, + * assert also for qatomic_read(&bs->quiesce_counter) > 0 + */ + assert(qemu_in_main_thread()); +} + /** * Remove an active request from the tracked requests list * diff --git a/include/block/block_int-global-state.h b/include/block/block_int-global-state.h index bd64ad0c7f..512a8fd88e 100644 --- a/include/block/block_int-global-state.h +++ b/include/block/block_int-global-state.h @@ -309,4 +309,12 @@ void bdrv_remove_aio_context_notifier(BlockDriverState *bs, */ void bdrv_drain_all_end_quiesce(BlockDriverState *bs); +/** + * Make sure that the function is running under both drain and BQL. + * The latter protects from concurrent writings + * from the GS API, while the former prevents concurrent reads + * from I/O. + */ +void assert_bdrv_graph_writable(BlockDriverState *bs); + #endif /* BLOCK_INT_GLOBAL_STATE */
We want to be sure that the functions that write the child and parent list of a bs are under BQL and drain. BQL prevents from concurrent writings from the GS API, while drains protect from I/O. TODO: drains are missing in some functions using this assert. Therefore a proper assertion will fail. Because adding drains requires additional discussions, they will be added in future series. Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> --- block.c | 4 ++++ block/io.c | 11 +++++++++++ include/block/block_int-global-state.h | 8 ++++++++ 3 files changed, 23 insertions(+)