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

[supriya kannery]

Stefan Hajnoczi wrote:
> On Tue, Nov 22, 2011 at 9:45 AM, supriya kannery <address@hidden> wrote:
>   
> > supriya kannery wrote:
> >     
> > > Stefan Hajnoczi wrote:
> > >       
> > > > On Fri, Nov 11, 2011 at 6:48 AM, Supriya Kannery
> > > > <address@hidden> 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
>
>