Re: [Qemu-devel] [PATCH 14/19] block: insert event-tap to bdrv_aio_writev() and bdrv_aio_flush().

[Kevin Wolf]

Am 19.01.2011 06:44, schrieb Yoshiaki Tamura:
> event-tap function is called only when it is on, and requests sent
> from device emulators.
> 
> Signed-off-by: Yoshiaki Tamura <address@hidden>
> ---
>  block.c |   11 +++++++++++
>  1 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/block.c b/block.c
> index ff2795b..85bd8b8 100644
> --- a/block.c
> +++ b/block.c
> @@ -28,6 +28,7 @@
>  #include "block_int.h"
>  #include "module.h"
>  #include "qemu-objects.h"
> +#include "event-tap.h"
>  
>  #ifdef CONFIG_BSD
>  #include <sys/types.h>
> @@ -2111,6 +2112,11 @@ BlockDriverAIOCB *bdrv_aio_writev(BlockDriverState 
> *bs, int64_t sector_num,
>      if (bdrv_check_request(bs, sector_num, nb_sectors))
>          return NULL;
>  
> +    if (bs->device_name && event_tap_is_on()) {
> +        return event_tap_bdrv_aio_writev(bs, sector_num, qiov, nb_sectors,
> +                                         cb, opaque);
> +    }
> +
>      if (bs->dirty_bitmap) {
>          blk_cb_data = blk_dirty_cb_alloc(bs, sector_num, nb_sectors, cb,
>                                           opaque);

Just noticed the context here... Does this patch break block migration
when event-tap is on?

Another question that came to my mind is if we really hook everything we
need. I think we'll need to have a hook in bdrv_flush as well. I don't
know if you do hook qemu_aio_flush and friends -  does a call cause
event-tap to flush its queue? If not, a call to qemu_aio_flush might
hang qemu because it's waiting for requests to complete which are
actually stuck in the event-tap queue.

Kevin