From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Layton Subject: Re: [PATCH 0/6] kernel tinification: optionally compile out splice family of syscalls (splice, vmsplice, tee and sendfile) Date: Sun, 23 Nov 2014 19:28:10 -0500 Message-ID: <20141123192810.682a223e@tlielax.poochiereds.net> References: <1416752468-1626-1-git-send-email-pieter@boesman.nl> <20141123.134623.2061031332250984539.davem@davemloft.net> <20141123194326.GB8517@thin> <20141123203040.GB26749@smipidev> <20141123233637.GC12456@thin> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20141123233637.GC12456@thin> Sender: netdev-owner@vger.kernel.org To: Josh Triplett Cc: Pieter Smith , David Miller , alexander.h.duyck@intel.com, viro@zeniv.linux.org.uk, ast@plumgrid.com, akpm@linux-foundation.org, beber@meleeweb.net, catalina.mocanu@gmail.com, dborkman@redhat.com, edumazet@google.com, ebiederm@xmission.com, fabf@skynet.be, fuse-devel@lists.sourceforge.net, geert@linux-m68k.org, hughd@google.com, iulia.manda21@gmail.com, JBeulich@suse.com, bfields@fieldses.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, mcgrof@suse.com, mattst88@gmail.com, mgorman@suse.de, mst@redhat.com, miklos@szeredi.hu, netdev@vger.kernel.org, oleg@redhat.com, Paul.Durrant@citrix.com, paulmck@linux.vnet.ibm.com, pefoley2@pefoley.com, tgraf@suug.ch, therbert@google.com, willemb@google.com, xiaoguangrong@linux.vnet.ibm.com, zhenglong.cai@cs2c.com.cn List-Id: linux-api@vger.kernel.org On Sun, 23 Nov 2014 15:36:37 -0800 Josh Triplett wrote: > On Sun, Nov 23, 2014 at 09:30:40PM +0100, Pieter Smith wrote: > > On Sun, Nov 23, 2014 at 11:43:26AM -0800, Josh Triplett wrote: > > > On Sun, Nov 23, 2014 at 01:46:23PM -0500, David Miller wrote: > > > > Truly removing sendfile/sendpage means that you can't even compile NFS > > > > into the tree. > > > > > > If you mean the in-kernel nfsd (CONFIG_NFSD), that already has a large > > > stack of "select" and "depends on", both directly and indirectly; adding > > > a "select SPLICE_SYSCALL" to it seems fine. (That select does need > > > adding, though. Pieter, you need to test-compile more than just > > > tinyconfig and defconfig. Try an allyesconfig with *just* splice turned > > > off, and make sure that compiles.) > > > > Did exacly that. Took forever on my hardware, but no problems. > > Ah, I see. Looking more closely at nfsd, it looks like it already has a > code path for filesystems that don't do splice. I think, rather than > making nfsd select SPLICE_SYSCALL, that it would suffice to change the > "rqstp->rq_splice_ok = true;" in svc_process_common (net/sunrpc/svc.c) > to: > > rqstp->rq_splice_ok = IS_ENABLED(CONFIG_SPLICE_SYSCALL); > > Then nfsd should simply *always* fall back to its non-splice support. > I'd probably prefer the above, actually. We have to keep supporting non-splice enabled fs' for the forseeable future, so we may as well allow people to run nfsd in such configurations. It could even be useful for testing the non-splice-enabled codepaths. > That said, given that it seems exceedingly unlikely that anyone would > use the in-kernel nfsd on a system trying to minimize kernel size, it > still seems cleaner to just "select SPLICE_SYSCALL" from NFSD in > Kconfig. That avoids making any changes at all to the nfsd source in > this patch series. > -- Jeff Layton