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Radix tree based inode caching

One of the perpetual scaling problems XFS has is indexing
it's incore inodes. We currently uses hashes and the default
hash sizes chosen can only ever be a tradeoff between memory
consumption and the maximum realistic size of the cache.

As a result, anyone who has millions of inodes cached on a
filesystem needs to tunes the size of the cache via the ihashsize
mount option to allow decent scalability with inode cache
operations.

A further problem is the separate inode cluster hash, whose size is
based on the ihashsize but is smaller, and so under certain
conditions (sparse cluster cache population) this can become
a limitation long before the inode hash is causing issues.

The following patchset removes the inode hash and cluster hash
and replaces them with radix trees to avoid the scalability
limitations of the hashes. It also reduces the size of the
inodes by 3 pointers....
Merge of xfs-linux-melb:xfs-kern:29481a by kenmcd.

  Convert xfs inode caches from hashes to radix trees.

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#ifndef __XFS_CLNT_H__
#define __XFS_CLNT_H__

/*
 * XFS arguments structure, constructed from the arguments we
 * are passed via the mount system call.
 *
 * NOTE: The mount system call is handled differently between
 * Linux and IRIX.  In IRIX we worked work with a binary data
 * structure coming in across the syscall interface from user
 * space (the mount userspace knows about each filesystem type
 * and the set of valid options for it, and converts the users
 * argument string into a binary structure _before_ making the
 * system call), and the ABI issues that this implies.
 *
 * In Linux, we are passed a comma separated set of options;
 * ie. a NULL terminated string of characters.  Userspace mount
 * code does not have any knowledge of mount options expected by
 * each filesystem type and so each filesystem parses its mount
 * options in kernel space.
 *
 * For the Linux port, we kept this structure pretty much intact
 * and use it internally (because the existing code groks it).
 */
struct xfs_mount_args {
	int	flags;		/* flags -> see XFSMNT_... macros below */
	int	flags2;		/* flags -> see XFSMNT2_... macros below */
	int	logbufs;	/* Number of log buffers, -1 to default */
	int	logbufsize;	/* Size of log buffers, -1 to default */
	char	fsname[MAXNAMELEN+1];	/* data device name */
	char	rtname[MAXNAMELEN+1];	/* realtime device filename */
	char	logname[MAXNAMELEN+1];	/* journal device filename */
	char	mtpt[MAXNAMELEN+1];	/* filesystem mount point */
	int	sunit;		/* stripe unit (BBs) */
	int	swidth;		/* stripe width (BBs), multiple of sunit */
	uchar_t iosizelog;	/* log2 of the preferred I/O size */
	int	ihashsize;	/* inode hash table size (buckets) */
};

/*
 * XFS mount option flags -- args->flags1
 */
#define	XFSMNT_ATTR2		0x00000001	/* allow ATTR2 EA format */
#define	XFSMNT_WSYNC		0x00000002	/* safe mode nfs mount
						 * compatible */
#define	XFSMNT_INO64		0x00000004	/* move inode numbers up
						 * past 2^32 */
#define XFSMNT_UQUOTA		0x00000008	/* user quota accounting */
#define XFSMNT_PQUOTA		0x00000010	/* IRIX prj quota accounting */
#define XFSMNT_UQUOTAENF	0x00000020	/* user quota limit
						 * enforcement */
#define XFSMNT_PQUOTAENF	0x00000040	/* IRIX project quota limit
						 * enforcement */
#define XFSMNT_QUIET		0x00000080	/* don't report mount errors */
#define XFSMNT_NOALIGN		0x00000200	/* don't allocate at
						 * stripe boundaries*/
#define XFSMNT_RETERR		0x00000400	/* return error to user */
#define XFSMNT_NORECOVERY	0x00000800	/* no recovery, implies
						 * read-only mount */
#define XFSMNT_SHARED		0x00001000	/* shared XFS mount */
#define XFSMNT_IOSIZE		0x00002000	/* optimize for I/O size */
#define XFSMNT_OSYNCISOSYNC	0x00004000	/* o_sync is REALLY o_sync */
						/* (osyncisdsync is default) */
#define XFSMNT_32BITINODES	0x00200000	/* restrict inodes to 32
						 * bits of address space */
#define XFSMNT_GQUOTA		0x00400000	/* group quota accounting */
#define XFSMNT_GQUOTAENF	0x00800000	/* group quota limit
						 * enforcement */
#define XFSMNT_NOUUID		0x01000000	/* Ignore fs uuid */
#define XFSMNT_DMAPI		0x02000000	/* enable dmapi/xdsm */
#define XFSMNT_BARRIER		0x04000000	/* use write barriers */
#define XFSMNT_IDELETE		0x08000000	/* inode cluster delete */
#define XFSMNT_SWALLOC		0x10000000	/* turn on stripe width
						 * allocation */
#define XFSMNT_DIRSYNC		0x40000000	/* sync creat,link,unlink,rename
						 * symlink,mkdir,rmdir,mknod */
#define XFSMNT_FLAGS2		0x80000000	/* more flags set in flags2 */

/*
 * XFS mount option flags -- args->flags2
 */
#define XFSMNT2_COMPAT_IOSIZE	0x00000001	/* don't report large preferred
						 * I/O size in stat(2) */
#define XFSMNT2_FILESTREAMS	0x00000002	/* enable the filestreams
						 * allocator */

#endif	/* __XFS_CLNT_H__ */