Re: [Qemu-devel] PATCH: Control over drive open modes for backing file

[Blue Swirl]

On 7/31/08, Daniel P. Berrange <address@hidden> wrote:
> On Thu, Jul 31, 2008 at 02:46:55PM +0100, Paul Brook wrote:
>  > > +#define BDRV_O_RDONLY      0x0001 /* Force read-only */
>  > > +#define BDRV_O_WRONLY      0x0002 /* Force writeable, no fallback */
>  > > +#define BDRV_O_RDWR        0x0003 /* Try writeable, fallback to 
> read-only
>  > > */
>  >
>  > This is IMHO really misleading.  Normal O_* are not bitflags. The code uses
>  > these as bitflags sometimes, which means your descriptions are 
> contradictory.
>
>
> One alternative approach I considered would be to not have an explicit
>  flag for writable, and instead have a flag to explicitly indicate that
>  fallback to read-only shouldn't be attempted.
>
>
>    #define BDRV_O_RDONLY            0x0001
>
>    #define BDRV_O_NO_RO_FALLBACK    0x0002
>
>  This would probably make the patch smaller because I won't need to update
>  all the callers which assume flags of '0'  gives a writable file, falling
>  back to RO.
>
>  Other suggestions welcome too...

Write-only should mean that only writing is allowed, read access
should not be needed.