On 10/16/2013 05:51 PM, Alexey Kardashevskiy wrote:
> On 10/10/2013 02:50 PM, Alexey Kardashevskiy wrote:
>> On 10/09/2013 06:47 PM, Paolo Bonzini wrote:
>>> Il 09/10/2013 09:15, Alexey Kardashevskiy ha scritto:
>>>> Sorry for my ignorance (I never ever touched this part of qemu) but how can
>>>> you possibly avoid block.c while doing savevm? The qcow2 driver must not
>>>> use posix read()/write(), right? So no matter how, all writes end up in
>>>> bdrv_co_do_writev() which changes blocks number. Or use
>>>> raw_aio_readv()/raw_aio_writev() API directly? Please give some more hints.
>>>> Thanks.
>>>
>>> I think Kevin was suggesting using qcow_aio_writev directly, or
>>> something like that. But it is not trivial, especially because
>>> save_vm_state takes byte offsets instead of sectors. So for now I'd
>>> still go for the more hacky solution.
>>
>> I failed to find qcow_aio_writev() or anything like that. qcow2_co_writev()
>> uses block.c. And I tried this:
>>
>> diff --git a/block/qcow2.c b/block/qcow2.c
>> index 4a9888c..17faf8b 100644
>> --- a/block/qcow2.c
>> +++ b/block/qcow2.c
>> @@ -1837,10 +1837,16 @@ static int qcow2_save_vmstate(BlockDriverState *bs,
>> QEMUIOVector *qiov,
>> BDRVQcowState *s = bs->opaque;
>> int growable = bs->growable;
>> int ret;
>> + int64_t total_sectors = bs->total_sectors;
>>
>> BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE);
>> bs->growable = 1;
>> ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov);
>> + /*
>> + * Setting @growable may cause underlying bdrv_co_do_writev()
>> + * to increase bs->total_sectors and we do not want this to happen.
>> + */
>> + bs->total_sectors = total_sectors;
>> bs->growable = growable;
>>
>> return ret;
>>
>>
>> It breaks loadvm in a different (weird) way, the error is something like
>> "ram" or "spapr/htab" (streams registered with register_savevm_live())
>> chunk cannot be read. Need to debug more...
>
>
> Just to keep the conversation going :) The patch below helps while the
> patch above creates snapshots which cannot be loaded.
>
> And there is no qcow_aio_writev-like API to fix it, what did you mean?
>
> Why not just revert the breaking patch?
Ping? Or it is all fixed now?
> Thanks.
>
> diff --git a/savevm.c b/savevm.c
> index e0c8aee..aeda0d1 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -42,6 +42,7 @@
> #include "qemu/iov.h"
> #include "block/snapshot.h"
> #include "block/qapi.h"
> +#include "block/block_int.h"
>
> #define SELF_ANNOUNCE_ROUNDS 5
>
> @@ -2389,6 +2390,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)
> qemu_timeval tv;
> struct tm tm;
> const char *name = qdict_get_try_str(qdict, "name");
> + int64_t total_sectors;
>
> /* Verify if there is a device that doesn't support snapshots and is
> writable */
> bs = NULL;
> @@ -2442,6 +2444,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)
> }
>
> /* save the VM state */
> + total_sectors = bs->total_sectors;
> f = qemu_fopen_bdrv(bs, 1);
> if (!f) {
> monitor_printf(mon, "Could not open VM state file\n");
> @@ -2450,6 +2453,11 @@ void do_savevm(Monitor *mon, const QDict *qdict)
> ret = qemu_savevm_state(f);
> vm_state_size = qemu_ftell(f);
> qemu_fclose(f);
> + /*
> + * Setting @growable may cause underlying bdrv_co_do_writev()
> + * to increase bs->total_sectors and we do not want this to happen.
> + */
> + bs->total_sectors = total_sectors;
> if (ret < 0) {
> monitor_printf(mon, "Error %d while writing VM\n", ret);
> goto the_end;
>
>
>
>
--
Alexey
