Re: Small O_SYNC writes are no longer NFS_DATA_SYNC

[Trond Myklebust <Trond.Myklebust@netapp.com>]

On Tue, 2011-03-22 at 09:17 +1100, NeilBrown wrote:
> On Mon, 21 Mar 2011 17:02:00 -0400 Trond Myklebust
> <Trond.Myklebust@netapp.com> wrote:
> I must admit that I found the terminology a bit confusing for 
> FLUSH_COND_STABLE.
> What is means is "if this turns out to be part of a larger request, then clear
> FLUSH_STABLE" - which sounds a bit more like "FLUSH_COND_UNSTABLE" - i.e. if
> a condition is met, then make it unstable.
> But I don't think that change would help at all.
> 
> How about changing the test in nfs_write_rpcsetup to
> 	if (how & (FLUSH_STABLE|FLUSH_CONDSTABLE)) {
> 		data->args.stable = NFS_DATA_SYNC;
> 		if (!nfs_need_commit(NFS_I(inode)))
> 			data->args.stable = NFS_FILE_SYNC;
> 	}
> 
> and then just set either FLUSH_STABLE or FLUSH_COND_STABLE - never both -
> and when you test FLUSH_COND_STABLE and then some other condition, just
> clear FLUSH_COND_STABLE.
> 
> I would find that quite a bit more readable.

The reason why I opted not to go for that approach was because
nfs_write_rpcsetup() doesn't really know about whether or not there are
any more RPCs pending (and so having a 'conditional' flag being
interpreted there didn't appear to make sense), but if you feel that is
easier on the eyes then I'm happy to change my opinion.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com