Date: Wed, 18 May 2011 18:09:50 -0700 From: "Zack Kirsch" <zack.kirsch@isilon.com> To: "Rick Macklem" <rmacklem@uoguelph.ca>, "FreeBSD FS" <freebsd-fs@freebsd.org> Subject: RE: adding a lock flags argument to VFS_FHTOVP() for FreeBSD9 Message-ID: <476FC2247D6C7843A4814ED64344560C03EC9A5E@seaxch10.desktop.isilon.com> In-Reply-To: <256284561.428250.1305590315172.JavaMail.root@erie.cs.uoguelph.ca> References: <256284561.428250.1305590315172.JavaMail.root@erie.cs.uoguelph.ca>
next in thread | previous in thread | raw e-mail | index | archive | help
Btw, we've implemented exactly this at Isilon and do take SHARED locks instead of EXCLUSIVE for many operations. I'm definitely in support of the idea. Zack -----Original Message----- From: owner-freebsd-fs@freebsd.org [mailto:owner-freebsd-fs@freebsd.org] On Behalf Of Rick Macklem Sent: Monday, May 16, 2011 4:59 PM To: FreeBSD FS Subject: RFC: adding a lock flags argument to VFS_FHTOVP() for FreeBSD9 Hi, Down the road, I would like the NFS server to be able to do a VFS_FHTOVP(mp, &fhp->fh_fid, LK_SHARED, vpp); similar to what is already supported for VFS_VGET(). The reason is that, currently, when a client does read-aheads, these reads are basically serialized because the VFS_FHTOVP() gets an LK_EXCLUSIVE locked vnode for each RPC on the server. Like VFS_VGET(), the underlying file system can still choose to return a LK_EXCLUSIVE locked vnode even when LK_SHARED is specified. (Some file systems, such as FFS, just call VFS_VGET() in VFS_FHTOVP(), so all that happens is that the flag is passed through to VFS_VGET() for those ones.) To minimize the risk of the patch breaking something, I have it setting LK_EXCLUSIVE for all VFS_FHTOVP() calls so that the semantics don't actually change. (Changing the NFS server to use LK_SHARED is a trivial patch, but will need extensive testing, so I'm not planning on that change for 9.0.) If you are interested, my current patch is at: http://people.freebsd.org/~rmacklem/fhtovp.patch So, does this sound like a reasonable thing to commit, once the patch is reviewed? rick _______________________________________________ freebsd-fs@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-fs To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org"
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?476FC2247D6C7843A4814ED64344560C03EC9A5E>