On 25.10.21 12:17, Emanuele Giuseppe Esposito wrote:
block.h currently contains a mix of functions:
some of them run under the BQL and modify the block layer graph,
others are instead thread-safe and perform I/O in iothreads.
It is not easy to understand which function is part of which
group (I/O vs GS), and this patch aims to clarify it.
The "GS" functions need the BQL, and often use
aio_context_acquire/release and/or drain to be sure they
can modify the graph safely.
The I/O function are instead thread safe, and can run in
any AioContext.
By splitting the header in two files, block-io.h
and block-global-state.h we have a clearer view on what
needs what kind of protection. block-common.h
contains common structures shared by both headers.
block.h is left there for legacy and to avoid changing
all includes in all c files that use the block APIs.
Assertions are added in the next patch.
Signed-off-by: Emanuele Giuseppe Esposito <eespo...@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
---
block.c | 3 +
block/meson.build | 7 +-
include/block/block-common.h | 389 +++++++++++++
include/block/block-global-state.h | 286 ++++++++++
include/block/block-io.h | 306 ++++++++++
include/block/block.h | 878 +----------------------------
6 files changed, 1012 insertions(+), 857 deletions(-)
create mode 100644 include/block/block-common.h
create mode 100644 include/block/block-global-state.h
create mode 100644 include/block/block-io.h
[...]
diff --git a/include/block/block-io.h b/include/block/block-io.h
new file mode 100644
index 0000000000..9af4609ccb
--- /dev/null
+++ b/include/block/block-io.h
[...]
+/*
+ * I/O API functions. These functions are thread-safe, and therefore
+ * can run in any thread as long as the thread has called
+ * aio_context_acquire/release().
+ */
+
+int bdrv_replace_child_bs(BdrvChild *child, BlockDriverState *new_bs,
+ Error **errp);
Why is this function here? Naïvely, I would’ve assumed as a
graph-modifying function it should be in block-global-state.h.
I mean, perhaps it’s thread-safe and then it can fit here, too. Still,
it surprises me a bit to find this here.
Hanna
