[PATCH v3 3/3] NFSD: Add support for encoding multiple segments

[Christoph Hellwig]

On Tue, Mar 24, 2015 at 08:43:31AM -0400, Anna Schumaker wrote:
> > I don't know, and don't have profiles.  I'll either try to reproduce or
> > wait till Anna's back from vacation.
> 
> I'm using whatever functions NFSD already uses for reading files,
> which I expect go through the VFS.  Is there a flag that controls
> cache behavior?

There's the O_DIRECT flag, but that's not what I mean.  If you just
wrote to it it's a cached read, if you did unmount the filesystem after
writing, or did an echo to /proc/sys/vm/drop_caches you get uncached
read behavior.