Re: [Qemu-devel] [PATCH] Disable O_DIRECT for physical CDROM/DVD drives

[Jes Sorensen]

On 07/20/10 17:40, Kevin Wolf wrote:
>> diff --git a/block/raw-posix.c b/block/raw-posix.c
>> index 291699f..0ea79b6 100644
>> --- a/block/raw-posix.c
>> +++ b/block/raw-posix.c
>> @@ -1139,6 +1139,11 @@ static int cdrom_open(BlockDriverState *bs, const 
>> char *filename, int flags)
>>      BDRVRawState *s = bs->opaque;
>>  
>>      s->type = FTYPE_CD;
>> +    if (flags & BDRV_O_NOCACHE) {
>> +        fprintf(stderr, "Disabling unsupported O_DIRECT (cache=none) for "
>> +                "CDROM/DVD device (%s)\n", filename);
>> +        flags &= ~BDRV_O_NOCACHE;
>> +    }
> 
> Good point. Just one detail: We should probably change bs->open_flags,
> too, to keep things consistent.

Thats effectively what my patch does. cdrom_open() calls
raw_open_common() which has this part:

    /* Use O_DSYNC for write-through caching, no flags for write-back
caching,
     * and O_DIRECT for no caching. */
    if ((bdrv_flags & BDRV_O_NOCACHE))
        s->open_flags |= O_DIRECT;

Cheers,
Jes