Re: [Qemu-devel] [v9 Patch 6/6]Qemu: raw posix implementation of reopen functions

[supriya kannery <supriyak@in.ibm.com>]

Stefan Hajnoczi wrote:
> On Tue, Nov 22, 2011 at 9:45 AM, supriya kannery <supriyak@in.ibm.com> wrote:
>   
>> supriya kannery wrote:
>>     
>>> Stefan Hajnoczi wrote:
>>>       
>>>> On Fri, Nov 11, 2011 at 6:48 AM, Supriya Kannery
>>>> <supriyak@linux.vnet.ibm.com> wrote:
>>>>
>>>>         
>>>>> +        }
>>>>> +        if ((flags & BDRV_O_NOCACHE)) {
>>>>> +            raw_rs->reopen_state.reopen_flags |= O_DIRECT;
>>>>> +        } else {
>>>>> +            raw_rs->reopen_state.reopen_flags &= ~O_DIRECT;
>>>>> +        }
>>>>> +        ret = fcntl_setfl(raw_rs->reopen_fd,
>>>>> raw_rs->reopen_state.reopen_flags);
>>>>>
>>>>>           
>>>> I wonder if this works on Solaris, FreeBSD, etc?
>>>>
>>>> Perhaps there needs to be a fallback to the missing "else" case below...
>>>>
>>>>
>>>>         
>>> ok. Will look into whether this will work on Solaris, FreeBSD etc..
>>>
>>>       
>> This should work for all non-win Oses.
>> I have tested only in x86.
>>
>> #ifndef _WIN32
>> /* Sets a specific flag */
>> int fcntl_setfl(int fd, int flag)
>> {
>>   int flags;
>>
>>   flags = fcntl(fd, F_GETFL);
>>     
>
> Are you sure POSIX guarantees that O_DIRECT can be changed with
> F_SETFL?  I didn't find any statement in the specification.  It is
> possible that this code compiles but does not actually work on
> non-Linux OSes.  Did you run tests?
>   
I don't have FreeBSD and Solaris systems to use.
Referred the following man page links to verify that O_DIRECT in these
OSes can be changed using fcntl.
http://fuse4bsd.creo.hu/localcgi/man-cgi.cgi?fcntl+2
http://man-wiki.net/index.php/2:fcntl
If anybody with these systems can confirm, that would be very helpful.

-thanks, Supriya


> Stefan
>
>