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authorUlrich Drepper <drepper@redhat.com>1997-08-27 20:26:10 +0000
committerUlrich Drepper <drepper@redhat.com>1997-08-27 20:26:10 +0000
commit92f1da4da04a7a86ddee91be5eaf0b10c333ac64 (patch)
tree2a10ce9e4e407e7e5b5ca092ca0947d234b5ff60 /db2/include/mp.h
parent22be878ecbc66606371bd33258f56e6711e6ba7a (diff)
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1997-08-10 19:17  Philip Blundell  <Philip.Blundell@pobox.com>

	* nss/nss_db/db-XXX.c: Include <db_185.h> not <db.h>.  Somebody
	should update this to use the new db API.
	* nss/nss_db/db-netgrp.c: Likewise.
	* nss/nss_db/db-alias.c: Likewise.
	* db2/Makefile: Makefile for db-2.x in glibc.

1997-08-27 21:20  Ulrich Drepper  <drepper@cygnus.com>

	* csu/Makefile (before-compile): New goal.  Make sure abi-tag.h
	is generated.
	[$(elf)=yes] (asm-CPPFLAGS): Make sure abi-tag.h file can be found.

	* Makeconfig [$(build-omitfp)=yes] (CFLAGS-.o): Add
	-D__USE_STRING_INLINES.
	* string/string.f: Move strnlen optimization after inclusion of
	<bits/string.h>.  Include <bits/string.h> only if __USE_STRING_INLINES
	is defined.
	* sysdeps/generic/memcpy.c: Undef memcpy to allow macro of this name
	in <bits/string.h>.
	* sysdeps/generic/memset.c: Likewise.
	* sysdeps/i386/string.h: i386 optimized string functions.
	* sysdeps/i386/i486string.h: i486+ optimized string functions.

	* Makefile (subdirs): Change db to db2.
	* shlib-versions: Bump libdb verion number to 3.
	* include/db.h: Include from db2 directory.
	* include/db_185.h: New file.
	* sysdeps/i386/Makefile [$(subdirs)=db2] (CPPFLAGS): Add macros
	to provide spinlock information for db2.
	* sysdeps/m68k/m68020/Makefile: New file.  Likewise.
	* sysdeps/sparc/Makefile: New file.  Likewise.
	* sysdeps/unix/sysv/linux/Makefile [$(subdirs)=db2] (CPPFLAGS):
	Add -DHAVE_LLSEEK.
	* db2/config.h: Hand-edited config file for db2 in glibc.
	* db2/compat.h: New file from db-2.3.4.
	* db2/db.h: Likewise.
	* db2/db_185.h: Likewise.
	* db2/db_int.h: Likewise.
	* db2/makedb.c: Likewise.
	* db2/btree/bt_close.c: Likewise.
	* db2/btree/bt_compare.c: Likewise.
	* db2/btree/bt_conv.c: Likewise.
	* db2/btree/bt_cursor.c: Likewise.
	* db2/btree/bt_delete.c: Likewise.
	* db2/btree/bt_open.c: Likewise.
	* db2/btree/bt_page.c: Likewise.
	* db2/btree/bt_put.c: Likewise.
	* db2/btree/bt_rec.c: Likewise.
	* db2/btree/bt_recno.c: Likewise.
	* db2/btree/btree_auto.c: Likewise.
	* db2/btree/bt_rsearch.c: Likewise.
	* db2/btree/bt_search.c: Likewise.
	* db2/btree/bt_split.c: Likewise.
	* db2/btree/bt_stat.c: Likewise.
	* db2/btree/btree.src: Likewise.
	* db2/common/db_appinit.c: Likewise.
	* db2/common/db_err.c: Likewise.
	* db2/common/db_byteorder.c: Likewise.
	* db2/common/db_apprec.c: Likewise.
	* db2/common/db_salloc.c: Likewise.
	* db2/common/db_log2.c: Likewise.
	* db2/common/db_region.c: Likewise.
	* db2/common/db_shash.c: Likewise.
	* db2/db/db.c: Likewise.
	* db2/db/db.src: Likewise.
	* db2/db/db_conv.c: Likewise.
	* db2/db/db_dispatch.c: Likewise.
	* db2/db/db_dup.c: Likewise.
	* db2/db/db_overflow.c: Likewise.
	* db2/db/db_pr.c: Likewise.
	* db2/db/db_rec.c: Likewise.
	* db2/db/db_ret.c: Likewise.
	* db2/db/db_thread.c: Likewise.
	* db2/db/db_auto.c: Likewise.
	* db2/db185/db185.c: Likewise.
	* db2/db185/db185_int.h: Likewise.
	* db2/dbm/dbm.c: Likewise.
	* db2/hash/hash.c: Likewise.
	* db2/hash/hash.src: Likewise.
	* db2/hash/hash_page.c: Likewise.
	* db2/hash/hash_conv.c: Likewise.
	* db2/hash/hash_debug.c: Likewise.
	* db2/hash/hash_stat.c: Likewise.
	* db2/hash/hash_rec.c: Likewise.
	* db2/hash/hash_dup.c: Likewise.
	* db2/hash/hash_func.c: Likewise.
	* db2/hash/hash_auto.c: Likewise.
	* db2/include/mp.h: Likewise.
	* db2/include/btree.h: Likewise.
	* db2/include/db.h.src: Likewise.
	* db2/include/db_int.h.src: Likewise.
	* db2/include/db_shash.h: Likewise.
	* db2/include/db_swap.h: Likewise.
	* db2/include/db_185.h.src: Likewise.
	* db2/include/txn.h: Likewise.
	* db2/include/db_am.h: Likewise.
	* db2/include/shqueue.h: Likewise.
	* db2/include/hash.h: Likewise.
	* db2/include/db_dispatch.h: Likewise.
	* db2/include/lock.h: Likewise.
	* db2/include/db_page.h: Likewise.
	* db2/include/log.h: Likewise.
	* db2/include/db_auto.h: Likewise.
	* db2/include/btree_auto.h: Likewise.
	* db2/include/hash_auto.h: Likewise.
	* db2/include/log_auto.h: Likewise.
	* db2/include/txn_auto.h: Likewise.
	* db2/include/db_ext.h: Likewise.
	* db2/include/btree_ext.h: Likewise.
	* db2/include/clib_ext.h: Likewise.
	* db2/include/common_ext.h: Likewise.
	* db2/include/hash_ext.h: Likewise.
	* db2/include/lock_ext.h: Likewise.
	* db2/include/log_ext.h: Likewise.
	* db2/include/mp_ext.h: Likewise.
	* db2/include/mutex_ext.h: Likewise.
	* db2/include/os_ext.h: Likewise.
	* db2/include/txn_ext.h: Likewise.
	* db2/include/cxx_int.h: Likewise.
	* db2/include/db_cxx.h: Likewise.
	* db2/include/queue.h: Likewise.
	* db2/lock/lock.c: Likewise.
	* db2/lock/lock_conflict.c: Likewise.
	* db2/lock/lock_util.c: Likewise.
	* db2/lock/lock_deadlock.c: Likewise.
	* db2/log/log.c: Likewise.
	* db2/log/log_get.c: Likewise.
	* db2/log/log.src: Likewise.
	* db2/log/log_compare.c: Likewise.
	* db2/log/log_put.c: Likewise.
	* db2/log/log_rec.c: Likewise.
	* db2/log/log_archive.c: Likewise.
	* db2/log/log_register.c: Likewise.
	* db2/log/log_auto.c: Likewise.
	* db2/log/log_findckp.c: Likewise.
	* db2/mp/mp_bh.c: Likewise.
	* db2/mp/mp_fget.c: Likewise.
	* db2/mp/mp_fopen.c: Likewise.
	* db2/mp/mp_fput.c: Likewise.
	* db2/mp/mp_fset.c: Likewise.
	* db2/mp/mp_open.c: Likewise.
	* db2/mp/mp_region.c: Likewise.
	* db2/mp/mp_pr.c: Likewise.
	* db2/mp/mp_sync.c: Likewise.
	* db2/mutex/68020.gcc: Likewise.
	* db2/mutex/mutex.c: Likewise.
	* db2/mutex/README: Likewise.
	* db2/mutex/x86.gcc: Likewise.
	* db2/mutex/sparc.gcc: Likewise.
	* db2/mutex/uts4.cc.s: Likewise.
	* db2/mutex/alpha.dec: Likewise.
	* db2/mutex/alpha.gcc: Likewise.
	* db2/mutex/parisc.gcc: Likewise.
	* db2/mutex/parisc.hp: Likewise.
	* db2/os/db_os_abs.c: Likewise.
	* db2/os/db_os_dir.c: Likewise.
	* db2/os/db_os_fid.c: Likewise.
	* db2/os/db_os_lseek.c: Likewise.
	* db2/os/db_os_mmap.c: Likewise.
	* db2/os/db_os_open.c: Likewise.
	* db2/os/db_os_rw.c: Likewise.
	* db2/os/db_os_sleep.c: Likewise.
	* db2/os/db_os_stat.c: Likewise.
	* db2/os/db_os_unlink.c: Likewise.
	* db2/txn/txn.c: Likewise.
	* db2/txn/txn.src: Likewise.
	* db2/txn/txn_rec.c: Likewise.
	* db2/txn/txn_auto.c: Likewise.
	* db2/clib/getlong.c: Likewise.
	* db2/progs/db_archive/db_archive.c: Likewise.
	* db2/progs/db_checkpoint/db_checkpoint.c: Likewise.
	* db2/progs/db_deadlock/db_deadlock.c: Likewise.
	* db2/progs/db_dump/db_dump.c: Likewise.
	* db2/progs/db_dump185/db_dump185.c: Likewise.
	* db2/progs/db_load/db_load.c: Likewise.
	* db2/progs/db_printlog/db_printlog.c: Likewise.
	* db2/progs/db_recover/db_recover.c: Likewise.
	* db2/progs/db_stat/db_stat.c: Likewise.

	* libio/stdio.h [__cplusplus] (__STDIO_INLINE): Define as inline.

	* po/de.po, po/sv.po: Update from 2.0.5 translations.

	* sysdeps/unix/sysv/linux/netinet/tcp.h: Pretty print.

	* sunrpc/rpc/xdr.h (XDR): Don't define argument of x_destroy callback
	as const.
	* sunrpc/xdr_mem.c (xdrmem_destroy): Don't define argument as const.
	* sunrpx/xdr_rec.c (xdrrec_destroy): Likewise.
	* sunrpx/xdr_stdio.c (xdrstdio_destroy): Likewise.

1997-08-27 18:47  Ulrich Drepper  <drepper@cygnus.com>

	* sysdeps/unix/sysv/linux/if_index.c: Include <errno.h>.
	Reported by Benjamin Kosnik <bkoz@cygnus.com>.

1997-08-27 02:27  Roland McGrath  <roland@baalperazim.frob.com>

	* abi-tags: New file.
	* csu/Makefile (distribute): Remove abi-tag.h.
	($(objpfx)abi-tag.h): New target.
	* Makefile (distribute): Add abi-tags.
	* sysdeps/unix/sysv/linux/abi-tag.h: File removed.
	* sysdeps/mach/hurd/abi-tag.h: File removed.
	* sysdeps/stub/abi-tag.h: File removed.

1997-08-25  Andreas Schwab  <schwab@issan.informatik.uni-dortmund.de>

	* sysdeps/unix/make-syscalls.sh: Change output so that it
	generates compilation rules only for the currently selected object
	suffixes.

1997-08-25  Andreas Schwab  <schwab@issan.informatik.uni-dortmund.de>

	* sysdeps/m68k/dl-machine.h (RTLD_START): Switch back to previous
	section to avoid confusing the compiler.
	* sysdeps/alpha/dl-machine.h (RTLD_START): Likewise.
	* sysdeps/i386/dl-machine.h (RTLD_START): Likewise.
	* sysdeps/mips/dl-machine.h (RTLD_START): Likewise.
	* sysdeps/mips/mips64/dl-machine.h (RTLD_START): Likewise.
	* sysdeps/sparc/sparc32/dl-machine.h (RTLD_START): Likewise.

	* sysdeps/m68k/dl-machine.h (elf_machine_load_address): Use a GOT
	relocation instead of a constant to avoid text relocation.
	(ELF_MACHINE_BEFORE_RTLD_RELOC): Removed.
	(RTLD_START): Declare global labels as functions and add size
	directive.

1997-08-25 17:01  Ulrich Drepper  <drepper@cygnus.com>

	* sysdeps/i386/bits/select.h: Correct assembler versions to work even
	for descriptors >= 32.

	* stdlib/alloca.h: Don't define alloca to __alloca since if gcc
	is used __alloca is not defined to __builtin_alloca and so might
	not be available.
	Reported by Uwe Ohse <uwe@ohse.de>.

	* sysdeps/unix/sysv/linux/sys/sysmacros.h: Define macros in a special
	way if gcc is not used and so dev_t is an array.
	Reported by Uwe Ohse <uwe@ohse.de>.

1997-08-23  Andreas Schwab  <schwab@issan.informatik.uni-dortmund.de>

	* manual/libc.texinfo: Reorder chapters to match logical order.

1997-08-25 12:22  Ulrich Drepper  <drepper@cygnus.com>

	* sunrpc/rpc/xdr.h: Change name of parameters in prototypes of
	xdr_reference, xdrmem_create, and xdrstdio_create because of clash
	with g++ internal symbols.
	Patch by Sudish Joseph <sj@eng.mindspring.net>.

	* elf/dl-deps.c: Implement handling of DT_FILTER.
Diffstat (limited to 'db2/include/mp.h')
-rw-r--r--db2/include/mp.h266
1 files changed, 266 insertions, 0 deletions
diff --git a/db2/include/mp.h b/db2/include/mp.h
new file mode 100644
index 0000000000..4872596f83
--- /dev/null
+++ b/db2/include/mp.h
@@ -0,0 +1,266 @@
+/*-
+ * See the file LICENSE for redistribution information.
+ *
+ * Copyright (c) 1996, 1997
+ *	Sleepycat Software.  All rights reserved.
+ *
+ *	@(#)mp.h	10.14 (Sleepycat) 8/18/97
+ */
+
+struct __bh;		typedef struct __bh BH;
+struct __db_mpreg;	typedef struct __db_mpreg DB_MPREG;
+struct __mpool;		typedef struct __mpool MPOOL;
+struct __mpoolfile;	typedef struct __mpoolfile MPOOLFILE;
+
+					/* Default mpool name. */
+#define	DB_DEFAULT_MPOOL_FILE	"__db_mpool.share"
+
+/*
+ *  We default to 128K (16 8K pages) if the user doesn't specify, and
+ * require a minimum of 20K.
+ */
+#define	DB_CACHESIZE_DEF	(128 * 1024)
+#define	DB_CACHESIZE_MIN	( 20 * 1024)
+
+/* Macro to return per-process address, offsets. */
+#define	ADDR(base, offset)	((void *)((u_int8_t *)((base)->addr) + offset))
+#define	OFFSET(base, p)		((u_int8_t *)(p) - (u_int8_t *)(base)->addr)
+
+#define	INVALID		0		/* Invalid shared memory offset. */
+#define	TEMPORARY	"<tmp>"		/* Temporary file name. */
+
+/*
+ * There are two kinds of locks in the mpool code.  The first is the region
+ * lock, used to serialize modifications to all data structures.  The second
+ * is a per-buffer header lock.  The locking order is as follows:
+ *
+ * Process searching for a buffer:
+ *	Acquire the region lock.
+ *	Find the buffer header.
+ *	Increment the reference count (guarantee the buffer stays).
+ *	If the BH_LOCKED flag is set:
+ *		Release the region lock.
+ *		Acquire the buffer lock.
+ *		Release the buffer lock.
+ *		Acquire the region lock.
+ *	Return the buffer.
+ *
+ * Process reading/writing a buffer:
+ *	Acquire the region lock.
+ *	Find/create the buffer header.
+ *	If reading, increment the reference count (guarantee the buffer stays).
+ *	Set the BH_LOCKED flag.
+ *	Acquire the buffer lock (guaranteed not to block).
+ *	Release the region lock.
+ *	Do the I/O and/or initialize buffer contents.
+ *	Acquire the region lock.
+ *	Clear the BH_LOCKED flag.
+ *	Release the region lock.
+ *	Release the buffer lock.
+ *	If reading, return the buffer.
+ *
+ * Pointers to DB_MPOOL, MPOOL, DB_MPOOLFILE and MPOOLFILE structures are not
+ * reacquired when a region lock is reacquired because they couldn't have been
+ * closed/discarded and because they never move in memory.
+ */
+#define	LOCKINIT(dbmp, mutexp)						\
+	if (F_ISSET(dbmp, MP_LOCKHANDLE | MP_LOCKREGION))		\
+		(void)__db_mutex_init(mutexp, (dbmp)->fd)
+
+#define	LOCKHANDLE(dbmp, mutexp)					\
+	if (F_ISSET(dbmp, MP_LOCKHANDLE))				\
+		(void)__db_mutex_lock(mutexp, (dbmp)->fd,		\
+		(dbmp)->dbenv == NULL ? NULL : (dbmp)->dbenv->db_yield)
+#define	UNLOCKHANDLE(dbmp, mutexp)					\
+	if (F_ISSET(dbmp, MP_LOCKHANDLE))				\
+		(void)__db_mutex_unlock(mutexp, (dbmp)->fd)
+
+#define	LOCKREGION(dbmp)						\
+	if (F_ISSET(dbmp, MP_LOCKREGION))				\
+		(void)__db_mutex_lock(&((RLAYOUT *)(dbmp)->mp)->lock,	\
+		    (dbmp)->fd,						\
+		    (dbmp)->dbenv == NULL ? NULL : (dbmp)->dbenv->db_yield)
+#define	UNLOCKREGION(dbmp)						\
+	if (F_ISSET(dbmp, MP_LOCKREGION))				\
+		(void)__db_mutex_unlock(&((RLAYOUT *)(dbmp)->mp)->lock,	\
+		(dbmp)->fd)
+
+#define	LOCKBUFFER(dbmp, bhp)						\
+	if (F_ISSET(dbmp, MP_LOCKREGION))				\
+		(void)__db_mutex_lock(&(bhp)->mutex, (dbmp)->fd,	\
+		    (dbmp)->dbenv == NULL ? NULL : (dbmp)->dbenv->db_yield)
+#define	UNLOCKBUFFER(dbmp, bhp)						\
+	if (F_ISSET(dbmp, MP_LOCKREGION))				\
+		(void)__db_mutex_unlock(&(bhp)->mutex, (dbmp)->fd)
+
+/*
+ * DB_MPOOL --
+ *	Per-process memory pool structure.
+ */
+struct __db_mpool {
+/* These fields need to be protected for multi-threaded support. */
+	db_mutex_t	mutex;		/* Structure lock. */
+
+					/* List of pgin/pgout routines. */
+	LIST_HEAD(__db_mpregh, __db_mpreg) dbregq;
+
+					/* List of DB_MPOOLFILE's. */
+	TAILQ_HEAD(__db_mpoolfileh, __db_mpoolfile) dbmfq;
+
+/* These fields are not protected. */
+	DB_ENV     *dbenv;		/* Reference to error information. */
+
+	MPOOL	   *mp;			/* Address of the shared MPOOL. */
+
+	void	   *maddr;		/* Address of mmap'd region. */
+	void	   *addr;		/* Address of shalloc() region. */
+
+	DB_HASHTAB *htab;		/* Hash table of bucket headers. */
+
+	int	    fd;			/* Underlying mmap'd fd. */
+
+
+#define	MP_ISPRIVATE	0x01		/* Private, so local memory. */
+#define	MP_LOCKHANDLE	0x02		/* Threaded, lock handles and region. */
+#define	MP_LOCKREGION	0x04		/* Concurrent access, lock region. */
+	u_int32_t  flags;
+};
+
+/*
+ * DB_MPREG --
+ *	DB_MPOOL registry of pgin/pgout functions.
+ */
+struct __db_mpreg {
+	LIST_ENTRY(__db_mpreg) q;	/* Linked list. */
+
+	int ftype;			/* File type. */
+					/* Pgin, pgout routines. */
+	int (*pgin) __P((db_pgno_t, void *, DBT *));
+	int (*pgout) __P((db_pgno_t, void *, DBT *));
+};
+
+/*
+ * DB_MPOOLFILE --
+ *	Per-process DB_MPOOLFILE information.
+ */
+struct __db_mpoolfile {
+/* These fields need to be protected for multi-threaded support. */
+	db_mutex_t	mutex;		/* Structure lock. */
+
+	int	   fd;			/* Underlying file descriptor. */
+
+	u_int32_t pinref;		/* Pinned block reference count. */
+
+/* These fields are not protected. */
+	TAILQ_ENTRY(__db_mpoolfile) q;	/* Linked list of DB_MPOOLFILE's. */
+
+	char	  *path;		/* Initial file path. */
+	DB_MPOOL  *dbmp;		/* Overlying DB_MPOOL. */
+	MPOOLFILE *mfp;			/* Underlying MPOOLFILE. */
+
+	void	  *addr;		/* Address of mmap'd region. */
+	size_t	   len;			/* Length of mmap'd region. */
+
+#define	MP_PATH_ALLOC	0x01		/* Path is allocated memory. */
+#define	MP_PATH_TEMP	0x02		/* Backing file is a temporary. */
+#define	MP_READONLY	0x04		/* File is readonly. */
+	u_int32_t  flags;
+};
+
+/*
+ * MPOOL --
+ *	Shared memory pool region.  One of these is allocated in shared
+ *	memory, and describes the pool.
+ */
+struct __mpool {
+	RLAYOUT	    rlayout;		/* General region information. */
+
+	SH_TAILQ_HEAD(__bhq) bhq;	/* LRU list of buckets. */
+	SH_TAILQ_HEAD(__bhfq) bhfq;	/* Free buckets. */
+	SH_TAILQ_HEAD(__mpfq) mpfq;	/* List of MPOOLFILEs. */
+
+	/*
+	 * We make the assumption that the early pages of the file are far
+	 * more likely to be retrieved than the later pages, which means
+	 * that the top bits are more interesting for hashing since they're
+	 * less likely to collide.  On the other hand, since 512 4K pages
+	 * represents a 2MB file, only the bottom 9 bits of the page number
+	 * are likely to be set.  We XOR in the offset in the MPOOL of the
+	 * MPOOLFILE that backs this particular page, since that should also
+	 * be unique for the page.
+	 */
+#define	BUCKET(mp, mf_offset, pgno)					\
+	(((pgno) ^ ((mf_offset) << 9)) % (mp)->htab_buckets)
+
+	size_t	    htab;		/* Hash table offset. */
+	size_t	    htab_buckets;	/* Number of hash table entries. */
+
+	DB_LSN	    lsn;		/* Maximum checkpoint LSN. */
+	int	    lsn_cnt;		/* Checkpoint buffers left to write. */
+
+	DB_MPOOL_STAT stat;		/* Global mpool statistics. */
+
+#define	MP_LSN_RETRY	0x01		/* Retry all BH_WRITE buffers. */
+	u_int32_t  flags;
+};
+
+/*
+ * MPOOLFILE --
+ *	Shared DB_MPOOLFILE information.
+ */
+struct __mpoolfile {
+	SH_TAILQ_ENTRY  q;		/* List of MPOOLFILEs */
+
+	u_int32_t ref;			/* Reference count. */
+
+	int	  ftype;		/* File type. */
+	int	  can_mmap;		/* If the file can be mmap'd. */
+
+	int	  lsn_off;		/* Page's LSN offset. */
+
+	size_t	  path_off;		/* File name location. */
+
+	size_t	  fileid_off;		/* File identification location. */
+
+	size_t	  pgcookie_len;		/* Pgin/pgout cookie length. */
+	size_t	  pgcookie_off;		/* Pgin/pgout cookie location. */
+
+	int	  lsn_cnt;		/* Checkpoint buffers left to write. */
+
+	DB_MPOOL_FSTAT stat;		/* Per-file mpool statistics. */
+};
+
+/*
+ * BH --
+ *	Buffer header.
+ */
+struct __bh {
+	db_mutex_t	mutex;		/* Structure lock. */
+
+	u_int16_t	ref;		/* Reference count. */
+
+#define	BH_CALLPGIN	0x001		/* Page needs to be reworked... */
+#define	BH_DIRTY	0x002		/* Page was modified. */
+#define	BH_DISCARD	0x004		/* Page is useless. */
+#define	BH_LOCKED	0x008		/* Page is locked (I/O in progress). */
+#define	BH_TRASH	0x010		/* Page is garbage. */
+#define	BH_WRITE	0x020		/* Page scheduled for writing. */
+	u_int16_t  flags;
+
+	SH_TAILQ_ENTRY	q;		/* LRU list of bucket headers. */
+	SH_TAILQ_ENTRY	mq;		/* MPOOLFILE list of bucket headers. */
+
+	db_pgno_t pgno;			/* Underlying MPOOLFILE page number. */
+	size_t	  mf_offset;		/* Associated MPOOLFILE offset. */
+
+	/*
+	 * !!!
+	 * This array must be size_t aligned -- the DB access methods put PAGE
+	 * and other structures into it, and expect to be able to access them
+	 * directly.  (We guarantee size_t alignment in the db_mpool(3) manual
+	 * page as well.)
+	 */
+	u_int8_t   buf[1];		/* Variable length data. */
+};
+
+#include "mp_ext.h"