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Date: Tue, 17 May 2011 10:39:48 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [RFC Patch 1/3]Qemu: Enhance "info block" to
 display cache setting
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To: Supriya Kannery <supriyak@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>, qemu-devel@nongnu.org, Prerna Saxena <prerna@linux.vnet.ibm.com>

Am 16.05.2011 20:10, schrieb Supriya Kannery:
> Enhance "info block" to display cache setting
> 
> Example:
> (qemu) info block
> ide0-hd0: type=hd removable=0 file=../rhel6-32.qcow2 ro=0 drv=qcow2 
> encrypted=0
> 
> Enhanced to include "cache" setting:
> (qemu) info block
> ide0-hd0: type=hd removable=0 cache=none file=../rhel6-32.qcow2 ro=0 
> drv=qcow2 encrypted=0
> 
> Signed-off-by: Supriya Kannery <supriyak@in.ibm.com>
> Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
> 
> ---
>  block.c |   18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> Index: qemu/block.c
> ===================================================================
> --- qemu.orig/block.c
> +++ qemu/block.c
> @@ -1713,6 +1713,19 @@ static void bdrv_print_dict(QObject *obj
>          monitor_printf(mon, " locked=%d", qdict_get_bool(bs_dict, "locked"));
>      }
>  
> +    if (qdict_haskey(bs_dict, "open_flags")) {
> +        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"));
>  
> @@ -1762,9 +1775,10 @@ void bdrv_info(Monitor *mon, QObject **r
>          }
>  
>          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);
>  
>          if (bs->drv) {
>              QObject *obj;

bs->open_flags is a purely internal thing and its meaning is not
guaranteed to be stable. Exposing it to the user is wrong.

Kevin