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Date: Mon, 28 Feb 2011 16:15:28 +0100
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [RFC][PATCH 2/2] Extend monitor command 'info block'
	to display cache settings for block devices.
References: <20110228171956.05a84fb9@zephyr> <20110228174132.769fe22f@zephyr>
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To: Prerna Saxena <prerna@linux.vnet.ibm.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, Ananth Narayan <ananth@linux.vnet.ibm.com>, qemu-devel <qemu-devel@nongnu.org>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

Am 28.02.2011 13:11, schrieb Prerna Saxena:
> (qemu)info block
> SAMPLE output :
> ide0-hd0: type=hd removable=0 cache=none file=/tmp/abc.img ro=0
> drv=qcow2 encrypted=0
> 
> ---
>  block.c |   22 ++++++++++++++++++++--
>  1 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/block.c b/block.c
> index f7d91a2..c717888 100644
> --- a/block.c
> +++ b/block.c
> @@ -1707,6 +1707,23 @@ static void bdrv_print_dict(QObject *obj, void *opaque)
>          monitor_printf(mon, " locked=%d", qdict_get_bool(bs_dict, "locked"));
>      }
>  
> +    if (qdict_haskey(bs_dict, "open_flags") &&
> +        !strcmp(qdict_get_str(bs_dict, "type"), "hd")) {
> +        int open_flags = qdict_get_int(bs_dict, "open_flags");
> +        if (open_flags & BDRV_O_NOCACHE) {
> +            monitor_printf(mon, " cache=none");
> +        } else if (open_flags & BDRV_O_CACHE_WB) {
> +            if (open_flags & BDRV_O_NO_FLUSH) {
> +                monitor_printf(mon, " cache=unsafe");
> +            }
> +            else {
> +                monitor_printf(mon, " cache=writeback");
> +            }
> +        } else {
> +            monitor_printf(mon, " cache=writethrough");
> +        }
> +    }
> +
>      if (qdict_haskey(bs_dict, "inserted")) {
>          QDict *qdict = qobject_to_qdict(qdict_get(bs_dict, "inserted"));
>  
> @@ -1756,9 +1773,10 @@ void bdrv_info(Monitor *mon, QObject **ret_data)
>          }
>  
>          bs_obj = qobject_from_jsonf("{ 'device': %s, 'type': %s, "
> -                                    "'removable': %i, 'locked': %i }",
> +                                    "'removable': %i, 'locked': %i, "
> +                                    "'open_flags': %d }",
>                                      bs->device_name, type, bs->removable,
> -                                    bs->locked);
> +                                    bs->locked, bs->open_flags);

IIUC, this is the structure that a QMP client will receive for a
query-block command. The open_flags bitmask is not considered an ABI and
completely meaningless outside qemu.

Kevin