Currently (almost) all filesystems maintain a local inode hash table

to get from (mount + inode) to vnode.  These tables are mostly
copy&pasted from UFS, sized based on desiredvnodes and therefore
quite large (128K-512K).  Several filesystems are buggy enough that
they allocate the hash table even before they know if they will
ever be used or not.

Add "vfs_hash", a system wide hash table, which will replace all
the per-filesystem hash-tables.

The fields we add to struct vnode will more or less be saved in
the respective filesystems inodes.

Having one central implementation will save code and will allow us
to justify the complexity of code to dynamically (re)size the hash
at a later point.

1 files changed, 184 insertions, 0 deletions

diff --git a/sys/kern/vfs_hash.c b/sys/kern/vfs_hash.c
new file mode 100644
index 0000000..f62ee39
--- /dev/null
+++ b/sys/kern/vfs_hash.c
@@ -0,0 +1,184 @@
+/*-
+ * Copyright (c) 2005 Poul-Henning Kamp
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/malloc.h>
+#include <sys/vnode.h>
+
+#if 0
+#include "opt_mac.h"
+
+#include <sys/bio.h>
+#include <sys/buf.h>
+#include <sys/conf.h>
+#include <sys/event.h>
+#include <sys/eventhandler.h>
+#include <sys/extattr.h>
+#include <sys/fcntl.h>
+#include <sys/kdb.h>
+#include <sys/kthread.h>
+#include <sys/mac.h>
+#include <sys/mount.h>
+#include <sys/namei.h>
+#include <sys/reboot.h>
+#include <sys/sleepqueue.h>
+#include <sys/stat.h>
+#include <sys/sysctl.h>
+#include <sys/syslog.h>
+#include <sys/vmmeter.h>
+
+#include <machine/stdarg.h>
+
+#include <vm/vm.h>
+#include <vm/vm_object.h>
+#include <vm/vm_extern.h>
+#include <vm/pmap.h>
+#include <vm/vm_map.h>
+#include <vm/vm_page.h>
+#include <vm/vm_kern.h>
+#include <vm/uma.h>
+
+#endif
+
+static MALLOC_DEFINE(M_VFS_HASH, "VFS hash", "VFS hash table");
+
+static LIST_HEAD(vfs_hashhead, vnode)	*vfs_hash_tbl;
+static u_long				vfs_hash_mask;
+static struct mtx			vfs_hash_mtx;
+
+static void
+vfs_hashinit(void *dummy __unused)
+{
+
+	vfs_hash_tbl = hashinit(desiredvnodes, M_VFS_HASH, &vfs_hash_mask);
+	mtx_init(&vfs_hash_mtx, "vfs hash", NULL, MTX_DEF);
+}
+
+/* Must be SI_ORDER_SECOND so desiredvnodes is available */
+SYSINIT(vfs_hash, SI_SUB_VFS, SI_ORDER_SECOND, vfs_hashinit, NULL)
+
+int
+vfs_hash_get(struct mount *mp, u_int hash, int flags, struct thread *td, struct vnode **vpp)
+{
+	struct vnode *vp;
+	int error;
+
+	while (1) {
+		mtx_lock(&vfs_hash_mtx);
+		LIST_FOREACH(vp,
+		    &vfs_hash_tbl[hash & vfs_hash_mask], v_hashlist) {
+			if (vp->v_hash != hash)
+				continue;
+			if (vp->v_mount != mp)
+				continue;
+			VI_LOCK(vp);
+			mtx_unlock(&vfs_hash_mtx);
+			error = vget(vp, flags | LK_INTERLOCK, td);
+			if (error == ENOENT)
+				break;
+			if (error)
+				return (error);
+			*vpp = vp;
+			return (0);
+		}
+		if (vp == NULL) {
+			mtx_unlock(&vfs_hash_mtx);
+			*vpp = NULL;
+			return (0);
+		}
+	}
+}
+
+void
+vfs_hash_remove(struct vnode *vp)
+{
+
+	mtx_lock(&vfs_hash_mtx);
+	VI_LOCK(vp);
+	VNASSERT(vp->v_iflag & VI_HASHED, vp, ("vfs_hash_remove: not hashed"));
+	LIST_REMOVE(vp, v_hashlist);
+	vp->v_iflag &= ~VI_HASHED;
+	VI_UNLOCK(vp);
+	mtx_unlock(&vfs_hash_mtx);
+}
+
+int
+vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td, struct vnode **vpp)
+{
+	struct vnode *vp2;
+	int error;
+
+	while (1) {
+		mtx_lock(&vfs_hash_mtx);
+		LIST_FOREACH(vp2,
+		    &vfs_hash_tbl[hash & vfs_hash_mask], v_hashlist) {
+			if (vp2->v_hash != hash)
+				continue;
+			if (vp2->v_mount != vp->v_mount)
+				continue;
+			VI_LOCK(vp2);
+			mtx_unlock(&vfs_hash_mtx);
+			error = vget(vp2, flags | LK_INTERLOCK, td);
+			if (error == ENOENT)
+				break;
+			if (error)
+				return (error);
+			*vpp = vp2;
+			return (0);
+		}
+		if (vp2 == NULL)
+			break;
+			
+	}
+	VI_LOCK(vp);
+	VNASSERT(!(vp->v_iflag & VI_HASHED), vp,
+	    ("vfs_hash_insert: already hashed"));
+	vp->v_hash = hash;
+	LIST_INSERT_HEAD(&vfs_hash_tbl[hash & vfs_hash_mask], vp, v_hashlist);
+	vp->v_iflag |= VI_HASHED;
+	VI_UNLOCK(vp);
+	mtx_unlock(&vfs_hash_mtx);
+	*vpp = NULL;
+	return (0);
+}
+
+void
+vfs_hash_rehash(struct vnode *vp, u_int hash)
+{
+
+	mtx_lock(&vfs_hash_mtx);
+	VNASSERT(vp->v_iflag & VI_HASHED, vp, ("vfs_hash_rehash: not hashed"));
+	LIST_REMOVE(vp, v_hashlist);
+	LIST_INSERT_HEAD(&vfs_hash_tbl[hash & vfs_hash_mask], vp, v_hashlist);
+	vp->v_hash = hash;
+	mtx_unlock(&vfs_hash_mtx);
+}