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block: remove AioContext locking

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This is the big patch that removes
aio_context_acquire()/aio_context_release() from the block layer and
affected block layer users.

There isn't a clean way to split this patch and the reviewers are likely
the same group of people, so I decided to do it in one patch.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Message-ID: <20231205182011.1976568-7-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2023-12-05 13:20:03 -05:00 • committed by Kevin Wolf
parent 6bc30f1949
commit b49f4755c7
41 changed files with 104 additions and 1169 deletions
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45
block/io.c
View file

@ -294,8 +294,6 @@ static void bdrv_co_drain_bh_cb(void *opaque)
BlockDriverState *bs = data->bs;
if (bs) {
AioContext *ctx = bdrv_get_aio_context(bs);
aio_context_acquire(ctx);
bdrv_dec_in_flight(bs);
if (data->begin) {
bdrv_do_drained_begin(bs, data->parent, data->poll);
@ -303,7 +301,6 @@ static void bdrv_co_drain_bh_cb(void *opaque)
assert(!data->poll);
bdrv_do_drained_end(bs, data->parent);
}
aio_context_release(ctx);
} else {
assert(data->begin);
bdrv_drain_all_begin();
@ -320,8 +317,6 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs,
{
BdrvCoDrainData data;
Coroutine *self = qemu_coroutine_self();
AioContext *ctx = bdrv_get_aio_context(bs);
AioContext *co_ctx = qemu_coroutine_get_aio_context(self);
/* Calling bdrv_drain() from a BH ensures the current coroutine yields and
* other coroutines run if they were queued by aio_co_enter(). */
@ -340,17 +335,6 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs,
bdrv_inc_in_flight(bs);
}
/*
* Temporarily drop the lock across yield or we would get deadlocks.
* bdrv_co_drain_bh_cb() reaquires the lock as needed.
*
* When we yield below, the lock for the current context will be
* released, so if this is actually the lock that protects bs, don't drop
* it a second time.
*/
if (ctx != co_ctx) {
aio_context_release(ctx);
}
replay_bh_schedule_oneshot_event(qemu_get_aio_context(),
bdrv_co_drain_bh_cb, &data);
@ -358,11 +342,6 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs,
/* If we are resumed from some other event (such as an aio completion or a
* timer callback), it is a bug in the caller that should be fixed. */
assert(data.done);
/* Reacquire the AioContext of bs if we dropped it */
if (ctx != co_ctx) {
aio_context_acquire(ctx);
}
}
static void bdrv_do_drained_begin(BlockDriverState *bs, BdrvChild *parent,
@ -478,13 +457,12 @@ static bool bdrv_drain_all_poll(void)
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
/* bdrv_drain_poll() can't make changes to the graph and we are holding the
* main AioContext lock, so iterating bdrv_next_all_states() is safe. */
/*
* bdrv_drain_poll() can't make changes to the graph and we hold the BQL,
* so iterating bdrv_next_all_states() is safe.
*/
while ((bs = bdrv_next_all_states(bs))) {
AioContext *aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
result |= bdrv_drain_poll(bs, NULL, true);
aio_context_release(aio_context);
}
return result;
@ -525,11 +503,7 @@ void bdrv_drain_all_begin_nopoll(void)
/* Quiesce all nodes, without polling in-flight requests yet. The graph
* cannot change during this loop. */
while ((bs = bdrv_next_all_states(bs))) {
AioContext *aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
bdrv_do_drained_begin(bs, NULL, false);
aio_context_release(aio_context);
}
}
@ -588,11 +562,7 @@ void bdrv_drain_all_end(void)
}
while ((bs = bdrv_next_all_states(bs))) {
AioContext *aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
bdrv_do_drained_end(bs, NULL);
aio_context_release(aio_context);
}
assert(qemu_get_current_aio_context() == qemu_get_aio_context());
@ -2368,15 +2338,10 @@ int bdrv_flush_all(void)
}
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
AioContext *aio_context = bdrv_get_aio_context(bs);
int ret;
aio_context_acquire(aio_context);
ret = bdrv_flush(bs);
int ret = bdrv_flush(bs);
if (ret < 0 && !result) {
result = ret;
}
aio_context_release(aio_context);
}
return result;