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Date: Mon, 29 Mar 2010 12:54:56 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 2/3] qemu-nbd: Extend read-only option to
	nbd	device file
References: <1269796032-9166-1-git-send-email-ozaki.ryota@gmail.com>
	<1269796032-9166-2-git-send-email-ozaki.ryota@gmail.com>
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To: Ryota Ozaki <ozaki.ryota@gmail.com>
Cc: qemu-devel@nongnu.org

Am 28.03.2010 19:07, schrieb Ryota Ozaki:
> This patch allows to operate on nbd device file
> without write permission for the file if read-only
> option is specified.
> 
> Signed-off-by: Ryota Ozaki <ozaki.ryota@gmail.com>

The help for -r should be changed, too. Currently it says:

-r, --read-only      export read-only

> ---
>  qemu-nbd.c |   10 +++++-----
>  1 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 00b8896..7ef409f 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -162,7 +162,7 @@ static int find_partition(BlockDriverState *bs, int partition,
>      return -1;
>  }
>  
> -static void show_parts(const char *device)
> +static void show_parts(const char *device, bool readonly)
>  {
>      if (fork() == 0) {
>          int nbd;
> @@ -172,7 +172,7 @@ static void show_parts(const char *device)
>           * but remember to load the module with max_part != 0 :
>           *     modprobe nbd max_part=63
>           */
> -        nbd = open(device, O_RDWR);
> +        nbd = open(device, readonly ? O_RDONLY : O_RDWR);
>          if (nbd != -1) {
>                close(nbd);
>          }

Can't we always use O_RDONLY here? Assuming that this is enough to
trigger a partition table update, I haven't tested it. But if it's not
enough, wouldn't be enough for readonly either.

Kevin