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block: introduce assert_bdrv_graph_writable

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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>
Message-Id: <20220303151616.325444-15-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Emanuele Giuseppe Esposito 2022-03-03 10:15:59 -05:00 • committed by Kevin Wolf
parent 967d7905d1
commit 696bf4c78c
2 changed files with 21 additions and 0 deletions
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17
include/block/block_int-global-state.h
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@ -309,4 +309,21 @@ 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.
*/
static inline 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());
}
#endif /* BLOCK_INT_GLOBAL_STATE */