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block: remove AIOCBInfo->get_aio_context()

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The synchronous bdrv_aio_cancel() function needs the acb's AioContext so
it can call aio_poll() to wait for cancellation.

It turns out that all users run under the BQL in the main AioContext, so
this callback is not needed.

Remove the callback, mark bdrv_aio_cancel() GLOBAL_STATE_CODE just like
its blk_aio_cancel() caller, and poll the main loop AioContext.

The purpose of this cleanup is to identify bdrv_aio_cancel() as an API
that does not work with the multi-queue block layer.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230912231037.826804-2-stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2023-09-12 19:10:33 -04:00 • committed by Kevin Wolf
parent 52b10c9c0c
commit 652b0dd808
8 changed files with 10 additions and 57 deletions
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23
block/io.c
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@ -2950,25 +2950,18 @@ int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf,
/**************************************************************/
/* async I/Os */
/**
* Synchronously cancels an acb. Must be called with the BQL held and the acb
* must be processed with the BQL held too (IOThreads are not allowed).
*
* Use bdrv_aio_cancel_async() instead when possible.
*/
void bdrv_aio_cancel(BlockAIOCB *acb)
{
IO_CODE();
GLOBAL_STATE_CODE();
qemu_aio_ref(acb);
bdrv_aio_cancel_async(acb);
while (acb->refcnt > 1) {
if (acb->aiocb_info->get_aio_context) {
aio_poll(acb->aiocb_info->get_aio_context(acb), true);
} else if (acb->bs) {
/* qemu_aio_ref and qemu_aio_unref are not thread-safe, so
* assert that we're not using an I/O thread. Thread-safe
* code should use bdrv_aio_cancel_async exclusively.
*/
assert(bdrv_get_aio_context(acb->bs) == qemu_get_aio_context());
aio_poll(bdrv_get_aio_context(acb->bs), true);
} else {
abort();
}
}
AIO_WAIT_WHILE_UNLOCKED(NULL, acb->refcnt > 1);
qemu_aio_unref(acb);
}