Re: [PATCH 2/4] SUNRPC: Widen rpc_task::tk_flags

[Trond Myklebust <trondmy@hammerspace.com>]

On Fri, 2022-07-22 at 17:55 +0000, Chuck Lever III wrote:
> 
> 
> > On Jul 22, 2022, at 1:53 PM, Trond Myklebust
> > <trondmy@hammerspace.com> wrote:
> > 
> > On Fri, 2022-07-22 at 13:25 -0400, Chuck Lever wrote:
> > > There is just one unused bit left in rpc_task::tk_flags, and I
> > > will
> > > need two in subsequent patches. Double the width of the field to
> > > accommodate more flag bits.
> > 
> > The values 0x8 and 0x40 are both free, so I'm not seeing why this
> > patch
> > is needed at this time.
> 
> It's not needed now, but as recently as last year, there were no free
> bits (and I needed them for RPC-with-TLS support at that time). We
> will
> have to widen this field sooner or later.
> 
> I don't have a problem dropping this one if you'd rather wait.
> 

I dropped it after applying the other v2 patches. As I said, I don't
see a need for this expansion yet, and if we do at some point run out
of bits, I can see other flags we can drop (RPC_TASK_ROOTCREDS and
RPC_TASK_NULLCREDS being obvious targets) before we need to consider
actually expanding the size of this field.

In fact, by not expanding it, we can trivially shrink the size of
struct rpc_task by 8 bytes on x86_64 simply by moving the field
tk_rpc_status to eliminate the current 4 byte hole. I've added a patch
to do just that.

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com