Re: [Qemu-devel] [PATCH 1/3] block: count bdrv_co_rw_vmstate() requests

[Eric Blake]

On 05/17/2017 12:09 PM, Stefan Hajnoczi wrote:
> Call bdrv_inc/dec_in_flight() for vmstate reads/writes.  This seems
> unnecessary at first glance because vmstate reads/writes are done
> synchronously while the guest is stopped.  But we need the bdrv_wakeup()
> in bdrv_dec_in_flight() so the main loop sees request completion.
> Besides, it's cleaner to count vmstate reads/writes like ordinary
> read/write requests.
> 
> The bdrv_wakeup() partially fixes a 'savevm' hang with -object iothread.
> 
> Signed-off-by: Stefan Hajnoczi 
> ---
>  block/io.c | 17 -
>  1 file changed, 12 insertions(+), 5 deletions(-)

Reviewed-by: Eric Blake 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.   +1-919-301-3266
Virtualization:  qemu.org | libvirt.org



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[Qemu-devel] [PATCH 1/3] block: count bdrv_co_rw_vmstate() requests

[Stefan Hajnoczi]

Call bdrv_inc/dec_in_flight() for vmstate reads/writes.  This seems
unnecessary at first glance because vmstate reads/writes are done
synchronously while the guest is stopped.  But we need the bdrv_wakeup()
in bdrv_dec_in_flight() so the main loop sees request completion.
Besides, it's cleaner to count vmstate reads/writes like ordinary
read/write requests.

The bdrv_wakeup() partially fixes a 'savevm' hang with -object iothread.

Signed-off-by: Stefan Hajnoczi 
---
 block/io.c | 17 -
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/block/io.c b/block/io.c
index fdd7485..cc56e90 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1988,17 +1988,24 @@ bdrv_co_rw_vmstate(BlockDriverState *bs, QEMUIOVector 
*qiov, int64_t pos,
bool is_read)
 {
 BlockDriver *drv = bs->drv;
+int ret = -ENOTSUP;
+
+bdrv_inc_in_flight(bs);
 
 if (!drv) {
-return -ENOMEDIUM;
+ret = -ENOMEDIUM;
 } else if (drv->bdrv_load_vmstate) {
-return is_read ? drv->bdrv_load_vmstate(bs, qiov, pos)
-   : drv->bdrv_save_vmstate(bs, qiov, pos);
+if (is_read) {
+ret = drv->bdrv_load_vmstate(bs, qiov, pos);
+} else {
+ret = drv->bdrv_save_vmstate(bs, qiov, pos);
+}
 } else if (bs->file) {
-return bdrv_co_rw_vmstate(bs->file->bs, qiov, pos, is_read);
+ret = bdrv_co_rw_vmstate(bs->file->bs, qiov, pos, is_read);
 }
 
-return -ENOTSUP;
+bdrv_dec_in_flight(bs);
+return ret;
 }
 
 static void coroutine_fn bdrv_co_rw_vmstate_entry(void *opaque)
-- 
2.9.3