Re: [PATCH] Cleanup: Remove unused __REQ_NR_BITS from enum rq_flag_bits

[Jens Axboe <jens.axboe@oracle.com>]

On Mon, Apr 27 2009, Nikanth Karthikesan wrote:
> On Monday 27 April 2009 17:16:33 Jens Axboe wrote:
> > On Mon, Apr 27 2009, Nikanth Karthikesan wrote:
> > > The __REQ_NR_BITS  was being used by blk_dump_rq_flags() long back, while
> > > printing the individual request flag bits as strings to limit to the used
> > > bits. But it does not use it now. Remove unused enum.
> > >
> > > Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>
> > >
> > > ---
> > >
> > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> > > index ba54c83..f41abbb 100644
> > > --- a/include/linux/blkdev.h
> > > +++ b/include/linux/blkdev.h
> > > @@ -118,7 +118,6 @@ enum rq_flag_bits {
> > >  	__REQ_COPY_USER,	/* contains copies of user pages */
> > >  	__REQ_INTEGRITY,	/* integrity metadata has been remapped */
> > >  	__REQ_NOIDLE,		/* Don't anticipate more IO after this one */
> > > -	__REQ_NR_BITS,		/* stops here */
> > >  };
> > >
> > >  #define REQ_RW		(1 << __REQ_RW)
> >
> > Lets turn it into something useful instead. It's meant to catch someone
> > adding too many flags, how about something like this:
> >
> > Untested ;-)
> >
> > diff --git a/block/blk-core.c b/block/blk-core.c
> > index d73eb76..e62ef94 100644
> > --- a/block/blk-core.c
> > +++ b/block/blk-core.c
> > @@ -2159,6 +2159,8 @@ EXPORT_SYMBOL(kblockd_schedule_work);
> >
> >  int __init blk_dev_init(void)
> >  {
> > +	BUILD_BUG_ON(__REQ_NR_BITS > 8 * sizeof(int));
> > +
> >  	kblockd_workqueue = create_workqueue("kblockd");
> >  	if (!kblockd_workqueue)
> >  		panic("Failed to create kblockd\n");
> 
> Good idea. How about this?

That's fine, better explains the check. It doesn't matter in practice
though, since we will be restricted to 32 flags even on 64-bit archs (as
long as we support 32-bit archs).

I'll add it, thanks.

-- 
Jens Axboe