Date: Sun, 30 Oct 2011 02:36:49 +0000 (UTC) From: Rick Macklem <rmacklem@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-8@freebsd.org Subject: svn commit: r226926 - stable/8/sys/kern Message-ID: <201110300236.p9U2anfA044044@svn.freebsd.org>
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Author: rmacklem Date: Sun Oct 30 02:36:49 2011 New Revision: 226926 URL: http://svn.freebsd.org/changeset/base/226926 Log: MFC: r225537 Modify vfs_register() to use a hash calculation on vfc_name to set vfc_typenum, so that vfc_typenum doesn't change when file systems are loaded in different orders. This keeps NFS file handles from changing, for file systems that use vfc_typenum in their fsid. This change is controlled via a loader.conf variable called vfs.typenumhash, since vfc_typenum will change once when this is enabled. It defaults to 1 for 9.0, but will default to 0 when MFC'd to stable/8. Modified: stable/8/sys/kern/vfs_init.c Directory Properties: stable/8/sys/ (props changed) stable/8/sys/amd64/include/xen/ (props changed) stable/8/sys/cddl/contrib/opensolaris/ (props changed) stable/8/sys/contrib/dev/acpica/ (props changed) stable/8/sys/contrib/pf/ (props changed) Modified: stable/8/sys/kern/vfs_init.c ============================================================================== --- stable/8/sys/kern/vfs_init.c Sun Oct 30 02:19:39 2011 (r226925) +++ stable/8/sys/kern/vfs_init.c Sun Oct 30 02:36:49 2011 (r226926) @@ -39,6 +39,7 @@ __FBSDID("$FreeBSD$"); #include <sys/param.h> #include <sys/systm.h> +#include <sys/fnv_hash.h> #include <sys/kernel.h> #include <sys/linker.h> #include <sys/mount.h> @@ -65,6 +66,18 @@ int maxvfsconf = VFS_GENERIC + 1; struct vfsconfhead vfsconf = TAILQ_HEAD_INITIALIZER(vfsconf); /* + * Loader.conf variable vfs.typenumhash enables setting vfc_typenum using a hash + * calculation on vfc_name, so that it doesn't change when file systems are + * loaded in a different order. This will avoid the NFS server file handles from + * changing for file systems that use vfc_typenum in their fsid. + */ +static int vfs_typenumhash = 0; +TUNABLE_INT("vfs.typenumhash", &vfs_typenumhash); +SYSCTL_INT(_vfs, OID_AUTO, typenumhash, CTLFLAG_RDTUN, &vfs_typenumhash, 0, + "Set vfc_typenum using a hash calculation on vfc_name, so that it does not" + "change when file systems are loaded in a different order."); + +/* * A Zen vnode attribute structure. * * Initialized when the first filesystem registers by vfs_register(). @@ -138,6 +151,9 @@ vfs_register(struct vfsconf *vfc) struct sysctl_oid *oidp; struct vfsops *vfsops; static int once; + struct vfsconf *tvfc; + uint32_t hashval; + int secondpass; if (!once) { vattr_null(&va_null); @@ -152,7 +168,34 @@ vfs_register(struct vfsconf *vfc) if (vfs_byname(vfc->vfc_name) != NULL) return EEXIST; - vfc->vfc_typenum = maxvfsconf++; + if (vfs_typenumhash != 0) { + /* + * Calculate a hash on vfc_name to use for vfc_typenum. Unless + * all of 1<->255 are assigned, it is limited to 8bits since + * that is what ZFS uses from vfc_typenum and is also the + * preferred range for vfs_getnewfsid(). + */ + hashval = fnv_32_str(vfc->vfc_name, FNV1_32_INIT); + hashval &= 0xff; + secondpass = 0; + do { + /* Look for and fix any collision. */ + TAILQ_FOREACH(tvfc, &vfsconf, vfc_list) { + if (hashval == tvfc->vfc_typenum) { + if (hashval == 255 && secondpass == 0) { + hashval = 1; + secondpass = 1; + } else + hashval++; + break; + } + } + } while (tvfc != NULL); + vfc->vfc_typenum = hashval; + if (vfc->vfc_typenum >= maxvfsconf) + maxvfsconf = vfc->vfc_typenum + 1; + } else + vfc->vfc_typenum = maxvfsconf++; TAILQ_INSERT_TAIL(&vfsconf, vfc, vfc_list); /*
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