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Date: Thu, 17 Nov 2011 10:48:20 +0530
From: Supriya Kannery <supriyak@linux.vnet.ibm.com>
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Subject: Re: [Qemu-devel] [v9 Patch 4/6]Qemu: Add commandline -drive option
 'hostcache'
Reply-To: supriyak@linux.vnet.ibm.com
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Luiz Capitulino <lcapitulino@redhat.com>, Christoph Hellwig <hch@lst.de>, qemu-devel@nongnu.org

On 11/17/2011 01:36 AM, Stefan Hajnoczi wrote:
> On Fri, Nov 11, 2011 at 6:48 AM, Supriya Kannery
> <supriyak@linux.vnet.ibm.com>  wrote:
>> +        if ((hostcache = qemu_opt_get_bool(opts, "hostcache", -1)) != -1) {
>
> This does not work.  qemu_opt_get_bool() takes a bool default argument
> and returns a bool.  (bool)-1 == true.  But (int)true == 1 and you
> cannot expect it to ever equal -1.
>
> Try this:
>
> if (qemu_opt_get(opts, "hostcache")&&
>      !qemu_opt_get_bool(opts, "hostcache", false)) {
>      bdrv_flags |= BDRV_O_NOCACHE;
> }
>
> Stefan
>

Thanks! for pointing this.
Does the following look ok?

  if ((hostcache = qemu_opt_get_bool(opts, "hostcache", 1) == 0) {
      bdrv_flags |= BDRV_O_NOCACHE;
  }

If either "hostcache" is not at all specified or it is specified
as "on", qemu_opt_get_bool will return 1, which can be ignored
as bdrv_flags is initialized to 0.