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block: drain from main loop thread in bdrv_co_yield_to_drain()

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For simplicity, always run BlockDevOps .drained_begin/end/poll()
callbacks in the main loop thread. This makes it easier to implement the
callbacks and avoids extra locks.

Move the function pointer declarations from the I/O Code section to the
Global State section for BlockDevOps, BdrvChildClass, and BlockDriver.

Narrow IO_OR_GS_CODE() to GLOBAL_STATE_CODE() where appropriate.

The test-bdrv-drain test case calls bdrv_drain() from an IOThread. This
is now only allowed from coroutine context, so update the test case to
run in a coroutine.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230516190238.8401-11-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2023-05-16 15:02:28 -04:00 • committed by Kevin Wolf
parent ff82b7835b
commit ab61335025
4 changed files with 67 additions and 58 deletions
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72
include/block/block_int-common.h
View file

@ -363,6 +363,21 @@ struct BlockDriver {
void (*bdrv_attach_aio_context)(BlockDriverState *bs,
AioContext *new_context);
/**
* bdrv_drain_begin is called if implemented in the beginning of a
* drain operation to drain and stop any internal sources of requests in
* the driver.
* bdrv_drain_end is called if implemented at the end of the drain.
*
* They should be used by the driver to e.g. manage scheduled I/O
* requests, or toggle an internal state. After the end of the drain new
* requests will continue normally.
*
* Implementations of both functions must not call aio_poll().
*/
void (*bdrv_drain_begin)(BlockDriverState *bs);
void (*bdrv_drain_end)(BlockDriverState *bs);
/**
* Try to get @bs's logical and physical block size.
* On success, store them in @bsz and return zero.
@ -758,21 +773,6 @@ struct BlockDriver {
void coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_io_unplug)(
BlockDriverState *bs);
/**
* bdrv_drain_begin is called if implemented in the beginning of a
* drain operation to drain and stop any internal sources of requests in
* the driver.
* bdrv_drain_end is called if implemented at the end of the drain.
*
* They should be used by the driver to e.g. manage scheduled I/O
* requests, or toggle an internal state. After the end of the drain new
* requests will continue normally.
*
* Implementations of both functions must not call aio_poll().
*/
void (*bdrv_drain_begin)(BlockDriverState *bs);
void (*bdrv_drain_end)(BlockDriverState *bs);
bool (*bdrv_supports_persistent_dirty_bitmap)(BlockDriverState *bs);
bool coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_can_store_new_dirty_bitmap)(
@ -955,6 +955,27 @@ struct BdrvChildClass {
void GRAPH_WRLOCK_PTR (*attach)(BdrvChild *child);
void GRAPH_WRLOCK_PTR (*detach)(BdrvChild *child);
/*
* If this pair of functions is implemented, the parent doesn't issue new
* requests after returning from .drained_begin() until .drained_end() is
* called.
*
* These functions must not change the graph (and therefore also must not
* call aio_poll(), which could change the graph indirectly).
*
* Note that this can be nested. If drained_begin() was called twice, new
* I/O is allowed only after drained_end() was called twice, too.
*/
void (*drained_begin)(BdrvChild *child);
void (*drained_end)(BdrvChild *child);
/*
* Returns whether the parent has pending requests for the child. This
* callback is polled after .drained_begin() has been called until all
* activity on the child has stopped.
*/
bool (*drained_poll)(BdrvChild *child);
/*
* Notifies the parent that the filename of its child has changed (e.g.
* because the direct child was removed from the backing chain), so that it
@ -984,27 +1005,6 @@ struct BdrvChildClass {
const char *(*get_name)(BdrvChild *child);
AioContext *(*get_parent_aio_context)(BdrvChild *child);
/*
* If this pair of functions is implemented, the parent doesn't issue new
* requests after returning from .drained_begin() until .drained_end() is
* called.
*
* These functions must not change the graph (and therefore also must not
* call aio_poll(), which could change the graph indirectly).
*
* Note that this can be nested. If drained_begin() was called twice, new
* I/O is allowed only after drained_end() was called twice, too.
*/
void (*drained_begin)(BdrvChild *child);
void (*drained_end)(BdrvChild *child);
/*
* Returns whether the parent has pending requests for the child. This
* callback is polled after .drained_begin() has been called until all
* activity on the child has stopped.
*/
bool (*drained_poll)(BdrvChild *child);
};
extern const BdrvChildClass child_of_bds;