diff --git a/include/mpool.h b/include/mpool.h
index b5be330a0cc5..c74764d725f3 100644
--- a/include/mpool.h
+++ b/include/mpool.h
@@ -30,7 +30,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)mpool.h	8.2 (Berkeley) 7/14/94
+ *	@(#)mpool.h	8.4 (Berkeley) 11/2/95
  * $FreeBSD$
  */
 
@@ -47,7 +47,7 @@
  * pool is handed an opaque MPOOL cookie which stores all of this information.
  */
 #define	HASHSIZE	128
-#define	HASHKEY(pgno)	((pgno - 1) % HASHSIZE)
+#define	HASHKEY(pgno)	((pgno - 1 + HASHSIZE) % HASHSIZE)
 
 /* The BKT structures are the elements of the queues. */
 typedef struct _bkt {
@@ -58,6 +58,7 @@ typedef struct _bkt {
 
 #define	MPOOL_DIRTY	0x01		/* page needs to be written */
 #define	MPOOL_PINNED	0x02		/* page is pinned into memory */
+#define	MPOOL_INUSE	0x04		/* page address is valid */
 	u_int8_t flags;			/* flags */
 } BKT;
 
@@ -68,7 +69,7 @@ typedef struct MPOOL {
 	pgno_t	curcache;		/* current number of cached pages */
 	pgno_t	maxcache;		/* max number of cached pages */
 	pgno_t	npages;			/* number of pages in the file */
-	u_long	pagesize;		/* file page size */
+	unsigned long	pagesize;	/* file page size */
 	int	fd;			/* file descriptor */
 					/* page in conversion routine */
 	void    (*pgin)(void *, pgno_t, void *);
@@ -76,25 +77,32 @@ typedef struct MPOOL {
 	void    (*pgout)(void *, pgno_t, void *);
 	void	*pgcookie;		/* cookie for page in/out routines */
 #ifdef STATISTICS
-	u_long	cachehit;
-	u_long	cachemiss;
-	u_long	pagealloc;
-	u_long	pageflush;
-	u_long	pageget;
-	u_long	pagenew;
-	u_long	pageput;
-	u_long	pageread;
-	u_long	pagewrite;
+	unsigned long	cachehit;
+	unsigned long	cachemiss;
+	unsigned long	pagealloc;
+	unsigned long	pageflush;
+	unsigned long	pageget;
+	unsigned long	pagenew;
+	unsigned long	pageput;
+	unsigned long	pageread;
+	unsigned long	pagewrite;
 #endif
 } MPOOL;
 
+#define	MPOOL_IGNOREPIN	0x01		/* Ignore if the page is pinned. */
+#define	MPOOL_PAGE_REQUEST	0x01	/* Allocate a new page with a
+					   specific page number. */
+#define	MPOOL_PAGE_NEXT		0x02	/* Allocate a new page with the next
+					  page number. */
+
 __BEGIN_DECLS
 MPOOL	*mpool_open(void *, int, pgno_t, pgno_t);
 void	 mpool_filter(MPOOL *, void (*)(void *, pgno_t, void *),
 	    void (*)(void *, pgno_t, void *), void *);
-void	*mpool_new(MPOOL *, pgno_t *);
-void	*mpool_get(MPOOL *, pgno_t, u_int);
-int	 mpool_put(MPOOL *, void *, u_int);
+void	*mpool_new(MPOOL *, pgno_t *, unsigned int);
+void	*mpool_get(MPOOL *, pgno_t, unsigned int);
+int	 mpool_delete(MPOOL *, void *);
+int	 mpool_put(MPOOL *, void *, unsigned int);
 int	 mpool_sync(MPOOL *);
 int	 mpool_close(MPOOL *);
 #ifdef STATISTICS
diff --git a/lib/libc/db/Symbol.map b/lib/libc/db/Symbol.map
index 14df29f1ecc8..225fd401cb57 100644
--- a/lib/libc/db/Symbol.map
+++ b/lib/libc/db/Symbol.map
@@ -16,7 +16,6 @@ FBSD_1.0 {
 	dbm_dirfno;
 	mpool_open;
 	mpool_filter;
-	mpool_new;
 	mpool_get;
 	mpool_put;
 	mpool_close;
@@ -24,6 +23,11 @@ FBSD_1.0 {
 	mpool_stat;
 };
 
+FBSD_1.1 {
+	mpool_new;
+	mpool_delete;
+};
+
 FBSDprivate_1.0 {
 	__bt_open;
 	__dbpanic;
diff --git a/lib/libc/db/btree/bt_debug.c b/lib/libc/db/btree/bt_debug.c
index ff5357a5a814..dc8b83dbefa4 100644
--- a/lib/libc/db/btree/bt_debug.c
+++ b/lib/libc/db/btree/bt_debug.c
@@ -83,10 +83,9 @@ __bt_dump(DB *dbp)
 	}
 #undef X
 
-	for (i = P_ROOT; (h = mpool_get(t->bt_mp, i, 0)) != NULL; ++i) {
+	for (i = P_ROOT;
+	    (h = mpool_get(t->bt_mp, i, MPOOL_IGNOREPIN)) != NULL; ++i)
 		__bt_dpage(h);
-		(void)mpool_put(t->bt_mp, h, 0);
-	}
 }
 
 /*
@@ -135,10 +134,8 @@ __bt_dnpage(DB *dbp, pgno_t pgno)
 	PAGE *h;
 
 	t = dbp->internal;
-	if ((h = mpool_get(t->bt_mp, pgno, 0)) != NULL) {
+	if ((h = mpool_get(t->bt_mp, pgno, MPOOL_IGNOREPIN)) != NULL)
 		__bt_dpage(h);
-		(void)mpool_put(t->bt_mp, h, 0);
-	}
 }
 
 /*
@@ -257,7 +254,8 @@ __bt_stat(DB *dbp)
 	t = dbp->internal;
 	pcont = pinternal = pleaf = 0;
 	nkeys = ifree = lfree = 0;
-	for (i = P_ROOT; (h = mpool_get(t->bt_mp, i, 0)) != NULL; ++i) {
+	for (i = P_ROOT;
+	    (h = mpool_get(t->bt_mp, i, MPOOL_IGNOREPIN)) != NULL; ++i)
 		switch (h->flags & P_TYPE) {
 		case P_BINTERNAL:
 		case P_RINTERNAL:
@@ -274,22 +272,18 @@ __bt_stat(DB *dbp)
 			++pcont;
 			break;
 		}
-		(void)mpool_put(t->bt_mp, h, 0);
-	}
 
 	/* Count the levels of the tree. */
 	for (i = P_ROOT, levels = 0 ;; ++levels) {
-		h = mpool_get(t->bt_mp, i, 0);
+		h = mpool_get(t->bt_mp, i, MPOOL_IGNOREPIN);
 		if (h->flags & (P_BLEAF|P_RLEAF)) {
 			if (levels == 0)
 				levels = 1;
-			(void)mpool_put(t->bt_mp, h, 0);
 			break;
 		}
 		i = F_ISSET(t, R_RECNO) ?
 		    GETRINTERNAL(h, 0)->pgno :
 		    GETBINTERNAL(h, 0)->pgno;
-		(void)mpool_put(t->bt_mp, h, 0);
 	}
 
 	(void)fprintf(stderr, "%d level%s with %lu keys",
diff --git a/lib/libc/db/btree/bt_open.c b/lib/libc/db/btree/bt_open.c
index 7422ca4ca4a0..47f3646ac46a 100644
--- a/lib/libc/db/btree/bt_open.c
+++ b/lib/libc/db/btree/bt_open.c
@@ -352,18 +352,25 @@ nroot(BTREE *t)
 	PAGE *meta, *root;
 	pgno_t npg;
 
-	if ((meta = mpool_get(t->bt_mp, 0, 0)) != NULL) {
-		mpool_put(t->bt_mp, meta, 0);
-		return (RET_SUCCESS);
+	if ((root = mpool_get(t->bt_mp, 1, 0)) != NULL) {
+		if (root->lower == 0 &&
+		    root->pgno == 0 &&
+		    root->linp[0] == 0) {
+			mpool_delete(t->bt_mp, root);
+			errno = EINVAL;
+		} else {
+			mpool_put(t->bt_mp, root, 0);
+			return (RET_SUCCESS);
+		}
 	}
 	if (errno != EINVAL)		/* It's OK to not exist. */
 		return (RET_ERROR);
 	errno = 0;
 
-	if ((meta = mpool_new(t->bt_mp, &npg)) == NULL)
+	if ((meta = mpool_new(t->bt_mp, &npg, MPOOL_PAGE_NEXT)) == NULL)
 		return (RET_ERROR);
 
-	if ((root = mpool_new(t->bt_mp, &npg)) == NULL)
+	if ((root = mpool_new(t->bt_mp, &npg, MPOOL_PAGE_NEXT)) == NULL)
 		return (RET_ERROR);
 
 	if (npg != P_ROOT)
diff --git a/lib/libc/db/btree/bt_page.c b/lib/libc/db/btree/bt_page.c
index face4b139c91..ab5e359742ca 100644
--- a/lib/libc/db/btree/bt_page.c
+++ b/lib/libc/db/btree/bt_page.c
@@ -90,5 +90,5 @@ __bt_new(BTREE *t, pgno_t *npg)
 		F_SET(t, B_METADIRTY);
 		return (h);
 	}
-	return (mpool_new(t->bt_mp, npg));
+	return (mpool_new(t->bt_mp, npg, MPOOL_PAGE_NEXT));
 }
diff --git a/lib/libc/db/hash/README b/lib/libc/db/hash/README
index f29ccf7e1ba6..80d674396c0a 100644
--- a/lib/libc/db/hash/README
+++ b/lib/libc/db/hash/README
@@ -1,4 +1,5 @@
 #	@(#)README	8.1 (Berkeley) 6/4/93
+# $FreeBSD$
 
 This package implements a superset of the hsearch and dbm/ndbm libraries.
 
@@ -44,10 +45,6 @@ Test Programs:
 
 NOTES:
 
-The file search.h is provided for using the hsearch compatible interface
-on BSD systems.  On System V derived systems, search.h should appear in 
-/usr/include.
-
 The man page ../man/db.3 explains the interface to the hashing system.
 The file hash.ps is a postscript copy of a paper explaining
 the history, implementation, and performance of the hash package.
diff --git a/lib/libc/db/hash/hash_func.c b/lib/libc/db/hash/hash_func.c
index 2ca0a483180f..db32a75b7286 100644
--- a/lib/libc/db/hash/hash_func.c
+++ b/lib/libc/db/hash/hash_func.c
@@ -43,60 +43,57 @@ __FBSDID("$FreeBSD$");
 #include "page.h"
 #include "extern.h"
 
+#ifdef notdef
 static u_int32_t hash1(const void *, size_t) __unused;
 static u_int32_t hash2(const void *, size_t) __unused;
 static u_int32_t hash3(const void *, size_t) __unused;
+#endif
 static u_int32_t hash4(const void *, size_t);
 
-/* Global default hash function */
+/* Default hash function. */
 u_int32_t (*__default_hash)(const void *, size_t) = hash4;
 
+#ifdef notdef
 /*
- * HASH FUNCTIONS
- *
  * Assume that we've already split the bucket to which this key hashes,
  * calculate that bucket, and check that in fact we did already split it.
  *
- * This came from ejb's hsearch.
+ * EJB's original hsearch hash.
  */
-
 #define PRIME1		37
 #define PRIME2		1048583
 
-static u_int32_t
-hash1(keyarg, len)
-	const void *keyarg;
-	size_t len;
+u_int32_t
+hash1(const void *key, size_t len)
 {
-	const u_char *key;
 	u_int32_t h;
+	u_int8_t *k;
 
+	h = 0;
+	k = (u_int8_t *)key;
 	/* Convert string to integer */
-	for (key = keyarg, h = 0; len--;)
-		h = h * PRIME1 ^ (*key++ - ' ');
+	while (len--)
+		h = h * PRIME1 ^ (*k++ - ' ');
 	h %= PRIME2;
 	return (h);
 }
 
 /*
- * Phong's linear congruential hash
+ * Phong Vo's linear congruential hash
  */
 #define dcharhash(h, c)	((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
 
-static u_int32_t
-hash2(keyarg, len)
-	const void *keyarg;
-	size_t len;
+u_int32_t
+hash2(const void *key, size_t len)
 {
-	const u_char *e, *key;
 	u_int32_t h;
-	u_char c;
+	u_int8_t *e, c, *k;
 
-	key = keyarg;
-	e = key + len;
-	for (h = 0; key != e;) {
-		c = *key++;
-		if (!c && key > e)
+	k = (u_int8_t *)key;
+	e = k + len;
+	for (h = 0; k != e;) {
+		c = *k++;
+		if (!c && k > e)
 			break;
 		dcharhash(h, c);
 	}
@@ -110,101 +107,84 @@ hash2(keyarg, len)
  * all 8 bytes.  Essentially, this saves us 7 cmp & branch instructions.  If
  * this routine is heavily used enough, it's worth the ugly coding.
  *
- * OZ's original sdbm hash
+ * Ozan Yigit's original sdbm hash.
  */
-static u_int32_t
-hash3(keyarg, len)
-	const void *keyarg;
-	size_t len;
+u_int32_t
+hash3(const void *key, size_t len)
 {
-	const u_char *key;
-	size_t loop;
-	u_int32_t h;
+	u_int32_t n, loop;
+	u_int8_t *k;
 
-#define HASHC   h = *key++ + 65599 * h
+#define HASHC   n = *k++ + 65599 * n
 
-	h = 0;
-	key = keyarg;
+	n = 0;
+	k = (u_int8_t *)key;
 	if (len > 0) {
 		loop = (len + 8 - 1) >> 3;
 
 		switch (len & (8 - 1)) {
 		case 0:
-			do {
+			do {	/* All fall throughs */
 				HASHC;
-				/* FALLTHROUGH */
 		case 7:
 				HASHC;
-				/* FALLTHROUGH */
 		case 6:
 				HASHC;
-				/* FALLTHROUGH */
 		case 5:
 				HASHC;
-				/* FALLTHROUGH */
 		case 4:
 				HASHC;
-				/* FALLTHROUGH */
 		case 3:
 				HASHC;
-				/* FALLTHROUGH */
 		case 2:
 				HASHC;
-				/* FALLTHROUGH */
 		case 1:
 				HASHC;
 			} while (--loop);
 		}
+
 	}
-	return (h);
+	return (n);
 }
+#endif /* notdef */
 
-/* Hash function from Chris Torek. */
-static u_int32_t
-hash4(keyarg, len)
-	const void *keyarg;
-	size_t len;
+/* Chris Torek's hash function. */
+u_int32_t
+hash4(const void *key, size_t len)
 {
-	const u_char *key;
-	size_t loop;
-	u_int32_t h;
+	u_int32_t h, loop;
+	const u_int8_t *k;
 
-#define HASH4a   h = (h << 5) - h + *key++;
-#define HASH4b   h = (h << 5) + h + *key++;
+#define HASH4a   h = (h << 5) - h + *k++;
+#define HASH4b   h = (h << 5) + h + *k++;
 #define HASH4 HASH4b
 
 	h = 0;
-	key = keyarg;
+	k = key;
 	if (len > 0) {
 		loop = (len + 8 - 1) >> 3;
 
 		switch (len & (8 - 1)) {
 		case 0:
-			do {
+			do {	/* All fall throughs */
 				HASH4;
-				/* FALLTHROUGH */
 		case 7:
 				HASH4;
-				/* FALLTHROUGH */
 		case 6:
 				HASH4;
-				/* FALLTHROUGH */
 		case 5:
 				HASH4;
-				/* FALLTHROUGH */
 		case 4:
 				HASH4;
-				/* FALLTHROUGH */
 		case 3:
 				HASH4;
-				/* FALLTHROUGH */
 		case 2:
 				HASH4;
-				/* FALLTHROUGH */
 		case 1:
 				HASH4;
 			} while (--loop);
 		}
+
 	}
 	return (h);
 }
diff --git a/lib/libc/db/man/mpool.3 b/lib/libc/db/man/mpool.3
index e9918a9f0fdf..3de51c307370 100644
--- a/lib/libc/db/man/mpool.3
+++ b/lib/libc/db/man/mpool.3
@@ -28,7 +28,7 @@
 .\"	@(#)mpool.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd June 4, 1993
+.Dd February 25, 1999
 .Dt MPOOL 3
 .Os
 .Sh NAME
@@ -47,7 +47,9 @@
 .Fa "void *pgcookie"
 .Fc
 .Ft void *
-.Fn mpool_new "MPOOL *mp" "pgno_t *pgnoaddr"
+.Fn mpool_new "MPOOL *mp" "pgno_t *pgnoaddr" "u_int flags"
+.Ft int
+.Fn mpool_delete "MPOOL *mp" "void *page"
 .Ft void *
 .Fn mpool_get "MPOOL *mp" "pgno_t pgno" "u_int flags"
 .Ft int
@@ -99,11 +101,11 @@ Both functions are called with the
 .Fa pgcookie
 pointer, the page number and a pointer to the page to being read or written.
 .Pp
-The
+The function
 .Fn mpool_new
-function takes an
-.Ft MPOOL
-pointer and an address as arguments.
+takes an
+.Dv MPOOL
+pointer, an address, and a set of flags as arguments.
 If a new page can be allocated, a pointer to the page is returned and
 the page number is stored into the
 .Fa pgnoaddr
@@ -113,6 +115,24 @@ Otherwise,
 is returned and
 .Va errno
 is set.
+The flags value is formed by
+.Tn OR Ns 'ing
+the following values:
+.Bl -tag -width Ds
+.It Dv MPOOL_PAGE_REQUEST
+Allocate a new page with a specific page number.
+.It Dv MPOOL_PAGE_NEXT
+Allocate a new page with the next page number.
+.El
+.Pp
+The function
+.Fn mpool_delete
+deletes the specified page from a pool and frees the page.
+It takes an
+.Dv MPOOL
+pointer and a page as arguments.
+The page must have been generated by
+.Fn mpool_new .
 .Pp
 The
 .Fn mpool_get
diff --git a/lib/libc/db/mpool/Makefile.inc b/lib/libc/db/mpool/Makefile.inc
index 9fef71262b6d..832e54db6ae4 100644
--- a/lib/libc/db/mpool/Makefile.inc
+++ b/lib/libc/db/mpool/Makefile.inc
@@ -3,4 +3,4 @@
 
 .PATH: ${.CURDIR}/db/mpool
 
-SRCS+=	mpool.c
+SRCS+=	mpool.c mpool-compat.c
diff --git a/lib/libc/db/mpool/mpool-compat.c b/lib/libc/db/mpool/mpool-compat.c
new file mode 100644
index 000000000000..9df76ff0b5d2
--- /dev/null
+++ b/lib/libc/db/mpool/mpool-compat.c
@@ -0,0 +1,43 @@
+/*-
+ * Copyright (c) 2009 Xin LI <delphij@FreeBSD.org>
+ * 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 <db.h>
+#include <mpool.h>
+
+void *__mpool_new__44bsd(MPOOL *, pgno_t *);
+
+void *
+__mpool_new__44bsd(MPOOL *mp, pgno_t *pgnoaddr)
+{
+
+	return (mpool_new(mp, pgnoaddr, MPOOL_PAGE_NEXT));
+}
+
+__sym_compat(mpool_new, __mpool_new_44bsd, FBSD_1.0);
diff --git a/lib/libc/db/mpool/mpool.c b/lib/libc/db/mpool/mpool.c
index 5610eb5486cc..09f888b7ca11 100644
--- a/lib/libc/db/mpool/mpool.c
+++ b/lib/libc/db/mpool/mpool.c
@@ -110,9 +110,7 @@ mpool_filter(MPOOL *mp, void (*pgin) (void *, pgno_t, void *),
  *	Get a new page of memory.
  */
 void *
-mpool_new(mp, pgnoaddr)
-	MPOOL *mp;
-	pgno_t *pgnoaddr;
+mpool_new(MPOOL *mp, pgno_t *pgnoaddr, u_int flags)
 {
 	struct _hqh *head;
 	BKT *bp;
@@ -131,8 +129,13 @@ mpool_new(mp, pgnoaddr)
 	 */
 	if ((bp = mpool_bkt(mp)) == NULL)
 		return (NULL);
-	*pgnoaddr = bp->pgno = mp->npages++;
-	bp->flags = MPOOL_PINNED;
+	if (flags == MPOOL_PAGE_REQUEST) {
+		mp->npages++;
+		bp->pgno = *pgnoaddr;
+	} else
+		bp->pgno = *pgnoaddr = mp->npages++;
+
+	bp->flags = MPOOL_PINNED | MPOOL_INUSE;
 
 	head = &mp->hqh[HASHKEY(bp->pgno)];
 	TAILQ_INSERT_HEAD(head, bp, hq);
@@ -140,6 +143,32 @@ mpool_new(mp, pgnoaddr)
 	return (bp->page);
 }
 
+int
+mpool_delete(MPOOL *mp, void *page)
+{
+	struct _hqh *head;
+	BKT *bp;
+
+	bp = (BKT *)((char *)page - sizeof(BKT));
+
+#ifdef DEBUG
+	if (!(bp->flags & MPOOL_PINNED)) {
+		(void)fprintf(stderr,
+		    "mpool_delete: page %d not pinned\n", bp->pgno);
+		abort();
+	}
+#endif
+
+	/* Remove from the hash and lru queues. */
+	head = &mp->hqh[HASHKEY(bp->pgno)];
+	TAILQ_REMOVE(head, bp, hq);
+	TAILQ_REMOVE(&mp->lqh, bp, q);
+
+	free(bp);
+	mp->curcache--;
+	return (RET_SUCCESS);
+}	
+	
 /*
  * mpool_get
  *	Get a page.
@@ -154,12 +183,6 @@ mpool_get(MPOOL *mp, pgno_t pgno,
 	off_t off;
 	int nr;
 
-	/* Check for attempt to retrieve a non-existent page. */
-	if (pgno >= mp->npages) {
-		errno = EINVAL;
-		return (NULL);
-	}
-
 #ifdef STATISTICS
 	++mp->pageget;
 #endif
@@ -167,7 +190,7 @@ mpool_get(MPOOL *mp, pgno_t pgno,
 	/* Check for a page that is cached. */
 	if ((bp = mpool_look(mp, pgno)) != NULL) {
 #ifdef DEBUG
-		if (bp->flags & MPOOL_PINNED) {
+		if (!(flags & MPOOL_IGNOREPIN) && bp->flags & MPOOL_PINNED) {
 			(void)fprintf(stderr,
 			    "mpool_get: page %d already pinned\n", bp->pgno);
 			abort();
@@ -193,20 +216,38 @@ mpool_get(MPOOL *mp, pgno_t pgno,
 		return (NULL);
 
 	/* Read in the contents. */
+	off = mp->pagesize * pgno;
+	if ((nr = pread(mp->fd, bp->page, mp->pagesize, off)) != mp->pagesize) {
+		switch (nr) {
+		case -1:
+			/* errno is set for us by pread(). */
+			free(bp);
+			mp->curcache--;
+			return (NULL);
+		case 0:
+			/*
+			 * A zero-length read means you need to create a
+			 * new page.
+			 */
+			memset(bp->page, 0, mp->pagesize);
+			break;
+		default:
+			/* A partial read is definitely bad. */
+			free(bp);
+			mp->curcache--;
+			errno = EINVAL;
+			return (NULL);
+		}
+	}
 #ifdef STATISTICS
 	++mp->pageread;
 #endif
-	off = mp->pagesize * pgno;
-	nr = pread(mp->fd, bp->page, mp->pagesize, off);
-	if (nr != mp->pagesize) {
-		if (nr >= 0)
-			errno = EFTYPE;
-		return (NULL);
-	}
 
 	/* Set the page number, pin the page. */
 	bp->pgno = pgno;
-	bp->flags = MPOOL_PINNED;
+	if (!(flags & MPOOL_IGNOREPIN))
+		bp->flags = MPOOL_PINNED;
+	bp->flags |= MPOOL_INUSE;
 
 	/*
 	 * Add the page to the head of the hash chain and the tail
@@ -245,7 +286,8 @@ mpool_put(MPOOL *mp, void *page, u_int flags)
 	}
 #endif
 	bp->flags &= ~MPOOL_PINNED;
-	bp->flags |= flags & MPOOL_DIRTY;
+	if (flags & MPOOL_DIRTY)
+		bp->flags |= flags & MPOOL_DIRTY;
 	return (RET_SUCCESS);
 }
 
@@ -329,6 +371,7 @@ mpool_bkt(MPOOL *mp)
 				bp->page = spage;
 			}
 #endif
+			bp->flags = 0;
 			return (bp);
 		}
 
@@ -338,6 +381,7 @@ new:	if ((bp = (BKT *)calloc(1, sizeof(BKT) + mp->pagesize)) == NULL)
 	++mp->pagealloc;
 #endif
 	bp->page = (char *)bp + sizeof(BKT);
+	bp->flags = 0;
 	++mp->curcache;
 	return (bp);
 }
@@ -363,6 +407,15 @@ mpool_write(MPOOL *mp, BKT *bp)
 	if (pwrite(mp->fd, bp->page, mp->pagesize, off) != mp->pagesize)
 		return (RET_ERROR);
 
+	/*
+	 * Re-run through the input filter since this page may soon be
+	 * accessed via the cache, and whatever the user's output filter
+	 * did may screw things up if we don't let the input filter
+	 * restore the in-core copy.
+	 */
+	if (mp->pgin)
+		(mp->pgin)(mp->pgcookie, bp->pgno, bp->page);
+
 	bp->flags &= ~MPOOL_DIRTY;
 	return (RET_SUCCESS);
 }
@@ -379,7 +432,8 @@ mpool_look(MPOOL *mp, pgno_t pgno)
 
 	head = &mp->hqh[HASHKEY(pgno)];
 	TAILQ_FOREACH(bp, head, hq)
-		if (bp->pgno == pgno) {
+		if ((bp->pgno == pgno) &&
+			((bp->flags & MPOOL_INUSE) == MPOOL_INUSE)) {
 #ifdef STATISTICS
 			++mp->cachehit;
 #endif