Re: [PATCH] block/file-posix: don't use functions calling AIO_WAIT_WHILE in worker threads

[Kevin Wolf]

Am 09.02.2023 um 16:45 hat Emanuele Giuseppe Esposito geschrieben:
> When calling bdrv_getlength() in handle_aiocb_write_zeroes(), the
> function creates a new coroutine and then waits that it finishes using
> AIO_WAIT_WHILE.
> The problem is that this function could also run in a worker thread,
> that has a different AioContext from main loop and iothreads, therefore
> in AIO_WAIT_WHILE we will have in_aio_context_home_thread(ctx) == false
> and therefore
> assert(qemu_get_current_aio_context() == qemu_get_aio_context());
> in the else branch will fail, crashing QEMU.
> 
> Aside from that, bdrv_getlength() is wrong also conceptually, because
> it reads the BDS graph from another thread and is not protected by
> any lock.
> 
> Replace it with raw_co_getlength, that doesn't create a coroutine and
> doesn't read the BDS graph.
> 
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>

Thanks, applied to the block branch.

Kevin