Re: [Qemu-devel] [PATCH] block: fix bdrv_ioctl called from coroutine
[ Cc: qemu-block ] Am 16.12.2015 um 19:33 hat Paolo Bonzini geschrieben: > When called from a coroutine, bdrv_ioctl must be asynchronous just like > e.g. bdrv_flush. The code was incorrectly making it synchronous, fix > it. > > Signed-off-by: Paolo Bonzini Thanks, applied to the block branch. Kevin
Re: [Qemu-devel] [PATCH] block: fix bdrv_ioctl called from coroutine
On Thu, 12/17 13:51, Paolo Bonzini wrote: > > > On 17/12/2015 13:33, Fam Zheng wrote: > > > In the coroutine case, the yield is hidden in the drivers, and it may or > > > may not happen. For example, qcow2_co_flush_to_os starts with > > > > > > qemu_co_mutex_lock(&s->lock); > > > > > > which can yield. > > > > bdrv_ioctl, on the contrary, is emulated with .bdrv_aio_ioctl, so it always > > yields (unless -ENOTSUP), that's why I think aio_poll() is necessary in both > > branches. > > But why should it yield, if called in coroutine context? bdrv_flush > doesn't yield if emulated with .bdrv_aio_flush *and* called in coroutine > context. bdrv_ioctl should do the same, I think. > Looking at bdrv_flush again I see what you mean. Thanks for explaining! Reviewed-by: Fam Zheng
Re: [Qemu-devel] [PATCH] block: fix bdrv_ioctl called from coroutine
On 17/12/2015 13:33, Fam Zheng wrote: > > In the coroutine case, the yield is hidden in the drivers, and it may or > > may not happen. For example, qcow2_co_flush_to_os starts with > > > > qemu_co_mutex_lock(&s->lock); > > > > which can yield. > > bdrv_ioctl, on the contrary, is emulated with .bdrv_aio_ioctl, so it always > yields (unless -ENOTSUP), that's why I think aio_poll() is necessary in both > branches. But why should it yield, if called in coroutine context? bdrv_flush doesn't yield if emulated with .bdrv_aio_flush *and* called in coroutine context. bdrv_ioctl should do the same, I think. Paolo
Re: [Qemu-devel] [PATCH] block: fix bdrv_ioctl called from coroutine
On Thu, 12/17 09:44, Paolo Bonzini wrote:
>
>
> On 17/12/2015 01:59, Fam Zheng wrote:
> > On Wed, 12/16 19:33, Paolo Bonzini wrote:
> >> When called from a coroutine, bdrv_ioctl must be asynchronous just like
> >> e.g. bdrv_flush. The code was incorrectly making it synchronous, fix
> >> it.
> >>
> >> Signed-off-by: Paolo Bonzini
> >> ---
> >> Fam, any reason why you did it this way? I don't see
> >> any coroutine caller, but it doesn't make much sense. :)
> >
> > That is a surprising question! From a coroutine, it is bdrv_flush ->
> > bdrv_flush_co_entry -> bdrv_co_flush, which I think is always synchronous,
> > especially, noticing the code around calling bs->bdrv_aio_flush:
> >
> > acb = bs->drv->bdrv_aio_flush(bs, bdrv_co_io_em_complete, &co);
> > if (acb == NULL) {
> > ret = -EIO;
> > } else {
> > qemu_coroutine_yield();
> > ret = co.ret;
> > }
> >
> > Am I missing something?
>
> In the coroutine case, the yield is hidden in the drivers, and it may or
> may not happen. For example, qcow2_co_flush_to_os starts with
>
> qemu_co_mutex_lock(&s->lock);
>
> which can yield.
bdrv_ioctl, on the contrary, is emulated with .bdrv_aio_ioctl, so it always
yields (unless -ENOTSUP), that's why I think aio_poll() is necessary in both
branches.
Fam
Re: [Qemu-devel] [PATCH] block: fix bdrv_ioctl called from coroutine
On 17/12/2015 01:59, Fam Zheng wrote:
> On Wed, 12/16 19:33, Paolo Bonzini wrote:
>> When called from a coroutine, bdrv_ioctl must be asynchronous just like
>> e.g. bdrv_flush. The code was incorrectly making it synchronous, fix
>> it.
>>
>> Signed-off-by: Paolo Bonzini
>> ---
>> Fam, any reason why you did it this way? I don't see
>> any coroutine caller, but it doesn't make much sense. :)
>
> That is a surprising question! From a coroutine, it is bdrv_flush ->
> bdrv_flush_co_entry -> bdrv_co_flush, which I think is always synchronous,
> especially, noticing the code around calling bs->bdrv_aio_flush:
>
> acb = bs->drv->bdrv_aio_flush(bs, bdrv_co_io_em_complete, &co);
> if (acb == NULL) {
> ret = -EIO;
> } else {
> qemu_coroutine_yield();
> ret = co.ret;
> }
>
> Am I missing something?
In the coroutine case, the yield is hidden in the drivers, and it may or
may not happen. For example, qcow2_co_flush_to_os starts with
qemu_co_mutex_lock(&s->lock);
which can yield.
Paolo
> Fam
>
>>
>> block/io.c | 7 ---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/block/io.c b/block/io.c
>> index e00fb5d..841f5b5 100644
>> --- a/block/io.c
>> +++ b/block/io.c
>> @@ -2614,10 +2614,11 @@ int bdrv_ioctl(BlockDriverState *bs, unsigned long
>> int req, void *buf)
>> bdrv_co_ioctl_entry(&data);
>> } else {
>> Coroutine *co = qemu_coroutine_create(bdrv_co_ioctl_entry);
>> +
>> qemu_coroutine_enter(co, &data);
>> -}
>> -while (data.ret == -EINPROGRESS) {
>> -aio_poll(bdrv_get_aio_context(bs), true);
>> +while (data.ret == -EINPROGRESS) {
>> +aio_poll(bdrv_get_aio_context(bs), true);
>> +}
>> }
>> return data.ret;
>> }
>> --
>> 2.5.0
>>
>
>
Re: [Qemu-devel] [PATCH] block: fix bdrv_ioctl called from coroutine
On Wed, 12/16 19:33, Paolo Bonzini wrote:
> When called from a coroutine, bdrv_ioctl must be asynchronous just like
> e.g. bdrv_flush. The code was incorrectly making it synchronous, fix
> it.
>
> Signed-off-by: Paolo Bonzini
> ---
> Fam, any reason why you did it this way? I don't see
> any coroutine caller, but it doesn't make much sense. :)
That is a surprising question! From a coroutine, it is bdrv_flush ->
bdrv_flush_co_entry -> bdrv_co_flush, which I think is always synchronous,
especially, noticing the code around calling bs->bdrv_aio_flush:
acb = bs->drv->bdrv_aio_flush(bs, bdrv_co_io_em_complete, &co);
if (acb == NULL) {
ret = -EIO;
} else {
qemu_coroutine_yield();
ret = co.ret;
}
Am I missing something?
Fam
>
> block/io.c | 7 ---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/block/io.c b/block/io.c
> index e00fb5d..841f5b5 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -2614,10 +2614,11 @@ int bdrv_ioctl(BlockDriverState *bs, unsigned long
> int req, void *buf)
> bdrv_co_ioctl_entry(&data);
> } else {
> Coroutine *co = qemu_coroutine_create(bdrv_co_ioctl_entry);
> +
> qemu_coroutine_enter(co, &data);
> -}
> -while (data.ret == -EINPROGRESS) {
> -aio_poll(bdrv_get_aio_context(bs), true);
> +while (data.ret == -EINPROGRESS) {
> +aio_poll(bdrv_get_aio_context(bs), true);
> +}
> }
> return data.ret;
> }
> --
> 2.5.0
>
[Qemu-devel] [PATCH] block: fix bdrv_ioctl called from coroutine
When called from a coroutine, bdrv_ioctl must be asynchronous just like
e.g. bdrv_flush. The code was incorrectly making it synchronous, fix
it.
Signed-off-by: Paolo Bonzini
---
Fam, any reason why you did it this way? I don't see
any coroutine caller, but it doesn't make much sense. :)
block/io.c | 7 ---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/block/io.c b/block/io.c
index e00fb5d..841f5b5 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2614,10 +2614,11 @@ int bdrv_ioctl(BlockDriverState *bs, unsigned long int
req, void *buf)
bdrv_co_ioctl_entry(&data);
} else {
Coroutine *co = qemu_coroutine_create(bdrv_co_ioctl_entry);
+
qemu_coroutine_enter(co, &data);
-}
-while (data.ret == -EINPROGRESS) {
-aio_poll(bdrv_get_aio_context(bs), true);
+while (data.ret == -EINPROGRESS) {
+aio_poll(bdrv_get_aio_context(bs), true);
+}
}
return data.ret;
}
--
2.5.0
