On Wed, 2025-06-11 at 06:44 -0400, Mike Snitzer wrote: > On Tue, Jun 10, 2025 at 11:57:33PM -0700, Christoph Hellwig wrote: > > On Tue, Jun 10, 2025 at 04:57:32PM -0400, Mike Snitzer wrote: > > > Add 'enable-dontcache' to NFSD's debugfs interface so that: Any data > > > read or written by NFSD will either not be cached (thanks to O_DIRECT) > > > or will be removed from the page cache upon completion (DONTCACHE). > > > > > > enable-dontcache is 0 by default. It may be enabled with: > > > echo 1 > /sys/kernel/debug/nfsd/enable-dontcache > > > > Having this as a global debug-only interface feels a bit odd. > > > > I generally agree, I originally proposed nfsd.nfsd_dontcache=Y > modparam: > https://lore.kernel.org/linux-nfs/20250220171205.12092-1-snitzer@xxxxxxxxxx/ > > (and even implemented formal NFSD per-export "dontcache" control, > which Trond and I both think is probably needed). > > But (ab)using debugfs is the approach Chuck and Jeff would like to > take for experimental NFSD changes so that we can kick the tires > without having to support an interface until the end of time. See > commit 9fe5ea760e64 ("NFSD: Add /sys/kernel/debug/nfsd") for more on > the general thinking. First consumer was commit c9dcd1de7977 ("NFSD: > Add experimental setting to disable the use of splice read"). > > I'm fine with using debugfs, means to an end with no strings attached. > > Once we have confidence in what is needed we can pivot back to > a modparam or per-export controls or whatever. > Yeah. I think this will probably end up being a per-export setting. We're just hesitant to commit to an interface until we have a bit more experience with this. -- Jeff Layton <jlayton@xxxxxxxxxx>
