/*
 *   Copyright (C) International Business Machines Corp., 2000-2004
 *
 *   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; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will 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 to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

/*
 *      jfs_imap.c: inode allocation map manager
 *
 * Serialization:
 *   Each AG has a simple lock which is used to control the serialization of
 *      the AG level lists.  This lock should be taken first whenever an AG
 *      level list will be modified or accessed.
 *
 *   Each IAG is locked by obtaining the buffer for the IAG page.
 *
 *   There is also a inode lock for the inode map inode.  A read lock needs to
 *      be taken whenever an IAG is read from the map or the global level
 *      information is read.  A write lock needs to be taken whenever the global
 *      level information is modified or an atomic operation needs to be used.
 *
 *      If more than one IAG is read at one time, the read lock may not
 *      be given up until all of the IAG's are read.  Otherwise, a deadlock
 *      may occur when trying to obtain the read lock while another thread
 *      holding the read lock is waiting on the IAG already being held.
 *
 *   The control page of the inode map is read into memory by diMount().
 *      Thereafter it should only be modified in memory and then it will be
 *      written out when the filesystem is unmounted by diUnmount().
 */

#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <linux/pagemap.h>
#include <linux/quotaops.h>

#include "jfs_incore.h"
#include "jfs_inode.h"
#include "jfs_filsys.h"
#include "jfs_dinode.h"
#include "jfs_dmap.h"
#include "jfs_imap.h"
#include "jfs_metapage.h"
#include "jfs_superblock.h"
#include "jfs_debug.h"

/*
 * __mark_inode_dirty expects inodes to be hashed.  Since we don't want
 * special inodes in the fileset inode space, we hash them to a dummy head
 */
static HLIST_HEAD(aggregate_hash);

/*
 * imap locks
 */
/* iag free list lock */
#define IAGFREE_LOCK_INIT(imap)         mutex_init(&imap->im_freelock)
#define IAGFREE_LOCK(imap)              mutex_lock(&imap->im_freelock)
#define IAGFREE_UNLOCK(imap)            mutex_unlock(&imap->im_freelock)

/* per ag iag list locks */
#define AG_LOCK_INIT(imap,index)        mutex_init(&(imap->im_aglock[index]))
#define AG_LOCK(imap,agno)              mutex_lock(&imap->im_aglock[agno])
#define AG_UNLOCK(imap,agno)            mutex_unlock(&imap->im_aglock[agno])

/*
 * forward references
 */
static int diAllocAG(struct inomap *, int, bool, struct inode *);
static int diAllocAny(struct inomap *, int, bool, struct inode *);
static int diAllocBit(struct inomap *, struct iag *, int);
static int diAllocExt(struct inomap *, int, struct inode *);
static int diAllocIno(struct inomap *, int, struct inode *);
static int diFindFree(u32, int);
static int diNewExt(struct inomap *, struct iag *, int);
static int diNewIAG(struct inomap *, int *, int, struct metapage **);
static void duplicateIXtree(struct super_block *, s64, int, s64 *);

static int diIAGRead(struct inomap * imap, int, struct metapage **);
static int copy_from_dinode(struct dinode *, struct inode *);
static void copy_to_dinode(struct dinode *, struct inode *);

/*
 * NAME:        diMount()
 *
 * FUNCTION:    initialize the incore inode map control structures for
 *              a fileset or aggregate init time.
 *
 *              the inode map's control structure (dinomap) is
 *              brought in from disk and placed in virtual memory.
 *
 * PARAMETERS:
 *      ipimap  - pointer to inode map inode for the aggregate or fileset.
 *
 * RETURN VALUES:
 *      0       - success
 *      -ENOMEM - insufficient free virtual memory.
 *      -EIO    - i/o error.
 */
int diMount(struct inode *ipimap)
{
        struct inomap *imap;
        struct metapage *mp;
        int index;
        struct dinomap_disk *dinom_le;

        /*
         * allocate/initialize the in-memory inode map control structure
         */
        /* allocate the in-memory inode map control structure. */
        imap = kmalloc(sizeof(struct inomap), GFP_KERNEL);
        if (imap == NULL) {
                jfs_err("diMount: kmalloc returned NULL!");
                return -ENOMEM;
        }

        /* read the on-disk inode map control structure. */

        mp = read_metapage(ipimap,
                           IMAPBLKNO << JFS_SBI(ipimap->i_sb)->l2nbperpage,
                           PSIZE, 0);
        if (mp == NULL) {
                kfree(imap);
                return -EIO;
        }

        /* copy the on-disk version to the in-memory version. */
        dinom_le = (struct dinomap_disk *) mp->data;
        imap->im_freeiag = le32_to_cpu(dinom_le->in_freeiag);
        imap->im_nextiag = le32_to_cpu(dinom_le->in_nextiag);
        atomic_set(&imap->im_numinos, le32_to_cpu(dinom_le->in_numinos));
        atomic_set(&imap->im_numfree, le32_to_cpu(dinom_le->in_numfree));
        imap->im_nbperiext = le32_to_cpu(dinom_le->in_nbperiext);
        imap->im_l2nbperiext = le32_to_cpu(dinom_le->in_l2nbperiext);
        for (index = 0; index < MAXAG; index++) {
                imap->im_agctl[index].inofree =
                    le32_to_cpu(dinom_le->in_agctl[index].inofree);
                imap->im_agctl[index].extfree =
                    le32_to_cpu(dinom_le->in_agctl[index].extfree);
                imap->im_agctl[index].numinos =
                    le32_to_cpu(dinom_le->in_agctl[index].numinos);
                imap->im_agctl[index].numfree =
                    le32_to_cpu(dinom_le->in_agctl[index].numfree);
        }

        /* release the buffer. */
        release_metapage(mp);

        /*
         * allocate/initialize inode allocation map locks
         */
        /* allocate and init iag free list lock */
        IAGFREE_LOCK_INIT(imap);

        /* allocate and init ag list locks */
        for (index = 0; index < MAXAG; index++) {
                AG_LOCK_INIT(imap, index);
        }

        /* bind the inode map inode and inode map control structure
         * to each other.
         */
        imap->im_ipimap = ipimap;
        JFS_IP(ipimap)->i_imap = imap;

        return (0);
}


/*
 * NAME:        diUnmount()
 *
 * FUNCTION:    write to disk the incore inode map control structures for
 *              a fileset or aggregate at unmount time.
 *
 * PARAMETERS:
 *      ipimap  - pointer to inode map inode for the aggregate or fileset.
 *
 * RETURN VALUES:
 *      0       - success
 *      -ENOMEM - insufficient free virtual memory.
 *      -EIO    - i/o error.
 */
int diUnmount(struct inode *ipimap, int mounterror)
{
        struct inomap *imap = JFS_IP(ipimap)->i_imap;

        /*
         * update the on-disk inode map control structure
         */

        if (!(mounterror || isReadOnly(ipimap)))
                diSync(ipimap);

        /*
         * Invalidate the page cache buffers
         */
        truncate_inode_pages(ipimap->i_mapping, 0);

        /*
         * free in-memory control structure
         */
        kfree(imap);

        return (0);
}


/*
 *      diSync()
 */
int diSync(struct inode *ipimap)
{
        struct dinomap_disk *dinom_le;
        struct inomap *imp = JFS_IP(ipimap)->i_imap;
        struct metapage *mp;
        int index;

        /*
         * write imap global conrol page
         */
        /* read the on-disk inode map control structure */
        mp = get_metapage(ipimap,
                          IMAPBLKNO << JFS_SBI(ipimap->i_sb)->l2nbperpage,
                          PSIZE, 0);
        if (mp == NULL) {
                jfs_err("diSync: get_metapage failed!");
                return -EIO;
        }

        /* copy the in-memory version to the on-disk version */
        dinom_le = (struct dinomap_disk *) mp->data;
        dinom_le->in_freeiag = cpu_to_le32(imp->im_freeiag);
        dinom_le->in_nextiag = cpu_to_le32(imp->im_nextiag);
        dinom_le->in_numinos = cpu_to_le32(atomic_read(&imp->im_numinos));
        dinom_le->in_numfree = cpu_to_le32(atomic_read(&imp->im_numfree));
        dinom_le->in_nbperiext = cpu_to_le32(imp->im_nbperiext);
        dinom_le->in_l2nbperiext = cpu_to_le32(imp->im_l2nbperiext);
        for (index = 0; index < MAXAG; index++) {
                dinom_le->in_agctl[index].inofree =
                    cpu_to_le32(imp->im_agctl[index].inofree);
                dinom_le->in_agctl[index].extfree =
                    cpu_to_le32(imp->im_agctl[index].extfree);
                dinom_le->in_agctl[index].numinos =
                    cpu_to_le32(imp->im_agctl[index].numinos);
                dinom_le->in_agctl[index].numfree =
                    cpu_to_le32(imp->im_agctl[index].numfree);
        }

        /* write out the control structure */
        write_metapage(mp);

        /*
         * write out dirty pages of imap
         */
        filemap_write_and_wait(ipimap->i_mapping);

        diWriteSpecial(ipimap, 0);

        return (0);
}


/*
 * NAME:        diRead()
 *
 * FUNCTION:    initialize an incore inode from disk.
 *
 *              on entry, the specifed incore inode should itself
 *              specify the disk inode number corresponding to the
 *              incore inode (i.e. i_number should be initialized).
 *
 *              this routine handles incore inode initialization for
 *              both "special" and "regular" inodes.  special inodes
 *              are those required early in the mount process and
 *              require special handling since much of the file system
 *              is not yet initialized.  these "special" inodes are
 *              identified by a NULL inode map inode pointer and are
 *              actually initialized by a call to diReadSpecial().
 *
 *              for regular inodes, the iag describing the disk inode
 *              is read from disk to determine the inode extent address
 *              for the disk inode.  with the inode extent address in
 *              hand, the page of the extent that contains the disk
 *              inode is read and the disk inode is copied to the
 *              incore inode.
 *
 * PARAMETERS:
 *      ip      -  pointer to incore inode to be initialized from disk.
 *
 * RETURN VALUES:
 *      0       - success
 *      -EIO    - i/o error.
 *      -ENOMEM - insufficient memory
 *
 */
int diRead(struct inode *ip)
{
        struct jfs_sb_info *sbi = JFS_SBI(ip->i_sb);
        int iagno, ino, extno, rc;
        struct inode *ipimap;
        struct dinode *dp;
        struct iag *iagp;
        struct metapage *mp;
        s64 blkno, agstart;
        struct inomap *imap;
        int block_offset;
        int inodes_left;
        unsigned long pageno;
        int rel_inode;

        jfs_info("diRead: ino = %ld", ip->i_ino);

        ipimap = sbi->ipimap;
        JFS_IP(ip)->ipimap = ipimap;

        /* determine the iag number for this inode (number) */
        iagno = INOTOIAG(ip->i_ino);

        /* read the iag */
        imap = JFS_IP(ipimap)->i_imap;
        IREAD_LOCK(ipimap, RDWRLOCK_IMAP);
        rc = diIAGRead(imap, iagno, &mp);
        IREAD_UNLOCK(ipimap);
        if (rc) {
                jfs_err("diRead: diIAGRead returned %d", rc);
                return (rc);
        }

        iagp = (struct iag *) mp->data;

        /* determine inode extent that holds the disk inode */
        ino = ip->i_ino & (INOSPERIAG - 1);
        extno = ino >> L2INOSPEREXT;

        if ((lengthPXD(&iagp->inoext[extno]) != imap->im_nbperiext) ||
            (addressPXD(&iagp->inoext[extno]) == 0)) {
                release_metapage(mp);
                return -ESTALE;
        }

        /* get disk block number of the page within the inode extent
         * that holds the disk inode.
         */
        blkno = INOPBLK(&iagp->inoext[extno], ino, sbi->l2nbperpage);

        /* get the ag for the iag */
        agstart = le64_to_cpu(iagp->agstart);

        release_metapage(mp);

        rel_inode = (ino & (INOSPERPAGE - 1));
        pageno = blkno >> sbi->l2nbperpage;

        if ((block_offset = ((u32) blkno & (sbi->nbperpage - 1)))) {
                /*
                 * OS/2 didn't always align inode extents on page boundaries
                 */
                inodes_left =
                     (sbi->nbperpage - block_offset) << sbi->l2niperblk;

                if (rel_inode < inodes_left)
                        rel_inode += block_offset << sbi->l2niperblk;
                else {
                        pageno += 1;
                        rel_inode -= inodes_left;
                }
        }

        /* read the page of disk inode */
        mp = read_metapage(ipimap, pageno << sbi->l2nbperpage, PSIZE, 1);
        if (mp == 0) {
                jfs_err("diRead: read_metapage failed");
                return -EIO;
        }

        /* locate the disk inode requested */
        dp = (struct dinode *) mp->data;
        dp += rel_inode;

        if (ip->i_ino != le32_to_cpu(dp->di_number)) {
                jfs_error(ip->i_sb, "diRead: i_ino != di_number");
                rc = -EIO;
        } else if (le32_to_cpu(dp->di_nlink) == 0)
                rc = -ESTALE;
        else
                /* copy the disk inode to the in-memory inode */
                rc = copy_from_dinode(dp, ip);

        release_metapage(mp);

        /* set the ag for the inode */
        JFS_IP(ip)->agno = BLKTOAG(agstart, sbi);
        JFS_IP(ip)->active_ag = -1;

        return (rc);
}


/*
 * NAME:        diReadSpecial()
 *
 * FUNCTION:    initialize a 'special' inode from disk.
 *
 *              this routines handles aggregate level inodes.  The
 *              inode cache cannot differentiate between the
 *              aggregate inodes and the filesystem inodes, so we
 *              handle these here.  We don't actually use the aggregate
 *              inode map, since these inodes are at a fixed location
 *              and in some cases the aggregate inode map isn't initialized
 *              yet.
 *
 * PARAMETERS:
 *      sb - filesystem superblock
 *      inum - aggregate inode number
 *      secondary - 1 if secondary aggregate inode table
 *
 * RETURN VALUES:
 *      new inode       - success
 *      NULL            - i/o error.
 */
struct inode *diReadSpecial(struct super_block *sb, ino_t inum, int secondary)
{
        struct jfs_sb_info *sbi = JFS_SBI(sb);
        uint address;
        struct dinode *dp;
        struct inode *ip;
        struct metapage *mp;

        ip = new_inode(sb);
        if (ip == NULL) {
                jfs_err("diReadSpecial: new_inode returned NULL!");
                return ip;
        }

        if (secondary) {
                address = addressPXD(&sbi->ait2) >> sbi->l2nbperpage;
                JFS_IP(ip)->ipimap = sbi->ipaimap2;
        } else {
                address = AITBL_OFF >> L2PSIZE;
                JFS_IP(ip)->ipimap = sbi->ipaimap;
        }

        ASSERT(inum < INOSPEREXT);

        ip->i_ino = inum;

        address += inum >> 3;   /* 8 inodes per 4K page */

        /* read the page of fixed disk inode (AIT) in raw mode */
        mp = read_metapage(ip, address << sbi->l2nbperpage, PSIZE, 1);
        if (mp == NULL) {
                ip->i_nlink = 1;        /* Don't want iput() deleting it */
                iput(ip);
                return (NULL);
        }

        /* get the pointer to the disk inode of interest */
        dp = (struct dinode *) (mp->data);
        dp += inum % 8;         /* 8 inodes per 4K page */

        /* copy on-disk inode to in-memory inode */
        if ((copy_from_dinode(dp, ip)) != 0) {
                /* handle bad return by returning NULL for ip */
                ip->i_nlink = 1;        /* Don't want iput() deleting it */
                iput(ip);
                /* release the page */
                release_metapage(mp);
                return (NULL);

        }

        ip->i_mapping->a_ops = &jfs_metapage_aops;
        mapping_set_gfp_mask(ip->i_mapping, GFP_NOFS);

        /* Allocations to metadata inodes should not affect quotas */
        ip->i_flags |= S_NOQUOTA;

        if ((inum == FILESYSTEM_I) && (JFS_IP(ip)->ipimap == sbi->ipaimap)) {
                sbi->gengen = le32_to_cpu(dp->di_gengen);
                sbi->inostamp = le32_to_cpu(dp->di_inostamp);
        }

        /* release the page */
        release_metapage(mp);

        hlist_add_head(&ip->i_hash, &aggregate_hash);

        return (ip);
}

/*
 * NAME:        diWriteSpecial()
 *
 * FUNCTION:    Write the special inode to disk
 *
 * PARAMETERS:
 *      ip - special inode
 *      secondary - 1 if secondary aggregate inode table
 *
 * RETURN VALUES: none
 */

void diWriteSpecial(struct inode *ip, int secondary)
{
        struct jfs_sb_info *sbi = JFS_SBI(ip->i_sb);
        uint address;
        struct dinode *dp;
        ino_t inum = ip->i_ino;
        struct metapage *mp;

        if (secondary)
                address = addressPXD(&sbi->ait2) >> sbi->l2nbperpage;
        else
                address = AITBL_OFF >> L2PSIZE;

        ASSERT(inum < INOSPEREXT);

        address += inum >> 3;   /* 8 inodes per 4K page */

        /* read the page of fixed disk inode (AIT) in raw mode */
        mp = read_metapage(ip, address << sbi->l2nbperpage, PSIZE, 1);
        if (mp == NULL) {
                jfs_err("diWriteSpecial: failed to read aggregate inode "
                        "extent!");
                return;
        }

        /* get the pointer to the disk inode of interest */
        dp = (struct dinode *) (mp->data);
        dp += inum % 8;         /* 8 inodes per 4K page */

        /* copy on-disk inode to in-memory inode */
        copy_to_dinode(dp, ip);
        memcpy(&dp->di_xtroot, &JFS_IP(ip)->i_xtroot, 288);

        if (inum == FILESYSTEM_I)
                dp->di_gengen = cpu_to_le32(sbi->gengen);

        /* write the page */
        write_metapage(mp);
}

/*
 * NAME:        diFreeSpecial()
 *
 * FUNCTION:    Free allocated space for special inode
 */
void diFreeSpecial(struct inode *ip)
{
        if (ip == NULL) {
                jfs_err("diFreeSpecial called with NULL ip!");
                return;
        }
        filemap_write_and_wait(ip->i_mapping);
        truncate_inode_pages(ip->i_mapping, 0);
        iput(ip);
}



/*
 * NAME:        diWrite()
 *
 * FUNCTION:    write the on-disk inode portion of the in-memory inode
 *              to its corresponding on-disk inode.
 *
 *              on entry, the specifed incore inode should itself
 *              specify the disk inode number corresponding to the
 *              incore inode (i.e. i_number should be initialized).
 *
 *              the inode contains the inode extent address for the disk
 *              inode.  with the inode extent address in hand, the
 *              page of the extent that contains the disk inode is
 *              read and the disk inode portion of the incore inode
 *              is copied to the disk inode.
 *
 * PARAMETERS:
 *      tid -  transacation id
 *      ip  -  pointer to incore inode to be written to the inode extent.
 *
 * RETURN VALUES:
 *      0       - success
 *      -EIO    - i/o error.
 */
int diWrite(tid_t tid, struct inode *ip)
{
        struct jfs_sb_info *sbi = JFS_SBI(ip->i_sb);
        struct jfs_inode_info *jfs_ip = JFS_IP(ip);
        int rc = 0;
        s32 ino;
        struct dinode *dp;
        s64 blkno;
        int block_offset;
        int inodes_left;
        struct metapage *mp;
        unsigned long pageno;
        int rel_inode;
        int dioffset;
        struct inode *ipimap;
        uint type;
        lid_t lid;
        struct tlock *ditlck, *tlck;
        struct linelock *dilinelock, *ilinelock;
        struct lv *lv;
        int n;

        ipimap = jfs_ip->ipimap;

        ino = ip->i_ino & (INOSPERIAG - 1);

        if (!addressPXD(&(jfs_ip->ixpxd)) ||
            (lengthPXD(&(jfs_ip->ixpxd)) !=
             JFS_IP(ipimap)->i_imap->im_nbperiext)) {
                jfs_error(ip->i_sb, "diWrite: ixpxd invalid");
                return -EIO;
        }

        /*
         * read the page of disk inode containing the specified inode:
         */
        /* compute the block address of the page */
        blkno = INOPBLK(&(jfs_ip->ixpxd), ino, sbi->l2nbperpage);

        rel_inode = (ino & (INOSPERPAGE - 1));
        pageno = blkno >> sbi->l2nbperpage;

        if ((block_offset = ((u32) blkno & (sbi->nbperpage - 1)))) {
                /*
                 * OS/2 didn't always align inode extents on page boundaries
                 */
                inodes_left =
                    (sbi->nbperpage - block_offset) << sbi->l2niperblk;

                if (rel_inode < inodes_left)
                        rel_inode += block_offset << sbi->l2niperblk;
                else {
                        pageno += 1;
                        rel_inode -= inodes_left;
                }
        }
        /* read the page of disk inode */
      retry:
        mp = read_metapage(ipimap, pageno << sbi->l2nbperpage, PSIZE, 1);
        if (mp == 0)
                return -EIO;

        /* get the pointer to the disk inode */
        dp = (struct dinode *) mp->data;
        dp += rel_inode;

        dioffset = (ino & (INOSPERPAGE - 1)) << L2DISIZE;

        /*
         * acquire transaction lock on the on-disk inode;
         * N.B. tlock is acquired on ipimap not ip;
         */
        if ((ditlck =
             txLock(tid, ipimap, mp, tlckINODE | tlckENTRY)) == NULL)
                goto retry;
        dilinelock = (struct linelock *) & ditlck->lock;

        /*
         * copy btree root from in-memory inode to on-disk inode
         *
         * (tlock is taken from inline B+-tree root in in-memory
         * inode when the B+-tree root is updated, which is pointed
         * by jfs_ip->blid as well as being on tx tlock list)
         *
         * further processing of btree root is based on the copy
         * in in-memory inode, where txLog() will log from, and,
         * for xtree root, txUpdateMap() will update map and reset
         * XAD_NEW bit;
         */

        if (S_ISDIR(ip->i_mode) && (lid = jfs_ip->xtlid)) {
                /*
                 * This is the special xtree inside the directory for storing
                 * the directory table
                 */
                xtpage_t *p, *xp;
                xad_t *xad;

                jfs_ip->xtlid = 0;
                tlck = lid_to_tlock(lid);
                assert(tlck->type & tlckXTREE);
                tlck->type |= tlckBTROOT;
                tlck->mp = mp;
                ilinelock = (struct linelock *) & tlck->lock;

                /*
                 * copy xtree root from inode to dinode:
                 */
                p = &jfs_ip->i_xtroot;
                xp = (xtpage_t *) &dp->di_dirtable;
                lv = ilinelock->lv;
                for (n = 0; n < ilinelock->index; n++, lv++) {
                        memcpy(&xp->xad[lv->offset], &p->xad[lv->offset],
                               lv->length << L2XTSLOTSIZE);
                }

                /* reset on-disk (metadata page) xtree XAD_NEW bit */
                xad = &xp->xad[XTENTRYSTART];
                for (n = XTENTRYSTART;
                     n < le16_to_cpu(xp->header.nextindex); n++, xad++)
                        if (xad->flag & (XAD_NEW | XAD_EXTENDED))
                                xad->flag &= ~(XAD_NEW | XAD_EXTENDED);
        }

        if ((lid = jfs_ip->blid) == 0)
                goto inlineData;
        jfs_ip->blid = 0;

        tlck = lid_to_tlock(lid);
        type = tlck->type;
        tlck->type |= tlckBTROOT;
        tlck->mp = mp;
        ilinelock = (struct linelock *) & tlck->lock;

        /*
         *      regular file: 16 byte (XAD slot) granularity
         */
        if (type & tlckXTREE) {
                xtpage_t *p, *xp;
                xad_t *xad;

                /*
                 * copy xtree root from inode to dinode:
                 */
                p = &jfs_ip->i_xtroot;
                xp = &dp->di_xtroot;
                lv = ilinelock->lv;
                for (n = 0; n < ilinelock->index; n++, lv++) {
                        memcpy(&xp->xad[lv->offset], &p->xad[lv->offset],
                               lv->length << L2XTSLOTSIZE);
                }

                /* reset on-disk (metadata page) xtree XAD_NEW bit */
                xad = &xp->xad[XTENTRYSTART];
                for (n = XTENTRYSTART;
                     n < le16_to_cpu(xp->header.nextindex); n++, xad++)
                        if (xad->flag & (XAD_NEW | XAD_EXTENDED))
                                xad->flag &= ~(XAD_NEW | XAD_EXTENDED);
        }
        /*
         *      directory: 32 byte (directory entry slot) granularity
         */
        else if (type & tlckDTREE) {
                dtpage_t *p, *xp;

                /*
                 * copy dtree root from inode to dinode:
                 */
                p = (dtpage_t *) &jfs_ip->i_dtroot;
                xp = (dtpage_t *) & dp->di_dtroot;
                lv = ilinelock->lv;
                for (n = 0; n < ilinelock->index; n++, lv++) {
                        memcpy(&xp->slot[lv->offset], &p->slot[lv->offset],
                               lv->length << L2DTSLOTSIZE);
                }
        } else {
                jfs_err("diWrite: UFO tlock");
        }

      inlineData:
        /*
         * copy inline symlink from in-memory inode to on-disk inode
         */
        if (S_ISLNK(ip->i_mode) && ip->i_size < IDATASIZE) {
                lv = & dilinelock->lv[dilinelock->index];
                lv->offset = (dioffset + 2 * 128) >> L2INODESLOTSIZE;
                lv->length = 2;
                memcpy(&dp->di_fastsymlink, jfs_ip->i_inline, IDATASIZE);
                dilinelock->index++;
        }
        /*
         * copy inline data from in-memory inode to on-disk inode:
         * 128 byte slot granularity
         */
        if (test_cflag(COMMIT_Inlineea, ip)) {
                lv = & dilinelock->lv[dilinelock->index];
                lv->offset = (dioffset + 3 * 128) >> L2INODESLOTSIZE;
                lv->length = 1;
                memcpy(&dp->di_inlineea, jfs_ip->i_inline_ea, INODESLOTSIZE);
                dilinelock->index++;

                clear_cflag(COMMIT_Inlineea, ip);
        }

        /*
         *      lock/copy inode base: 128 byte slot granularity
         */
        lv = & dilinelock->lv[dilinelock->index];
        lv->offset = dioffset >> L2INODESLOTSIZE;
        copy_to_dinode(dp, ip);
        if (test_and_clear_cflag(COMMIT_Dirtable, ip)) {
                lv->length = 2;
                memcpy(&dp->di_dirtable, &jfs_ip->i_dirtable, 96);
        } else
                lv->length = 1;
        dilinelock->index++;

        /* release the buffer holding the updated on-disk inode.
         * the buffer will be later written by commit processing.
         */
        write_metapage(mp);

        return (rc);
}


/*
 * NAME:        diFree(ip)
 *
 * FUNCTION:    free a specified inode from the inode working map
 *              for a fileset or aggregate.
 *
 *              if the inode to be freed represents the first (only)
 *              free inode within the iag, the iag will be placed on
 *              the ag free inode list.
 *
 *              freeing the inode will cause the inode extent to be
 *              freed if the inode is the only allocated inode within
 *              the extent.  in this case all the disk resource backing
 *              up the inode extent will be freed. in addition, the iag
 *              will be placed on the ag extent free list if the extent
 *              is the first free extent in the iag.  if freeing the
 *              extent also means that no free inodes will exist for
 *              the iag, the iag will also be removed from the ag free
 *              inode list.
 *
 *              the iag describing the inode will be freed if the extent
 *              is to be freed and it is the only backed extent within
 *              the iag.  in this case, the iag will be removed from the
 *              ag free extent list and ag free inode list and placed on
 *              the inode map's free iag list.
 *
 *              a careful update approach is used to provide consistency
 *              in the face of updates to multiple buffers.  under this
 *              approach, all required buffers are obtained before making
 *              any updates and are held until all updates are complete.
 *
 * PARAMETERS:
 *      ip      - inode to be freed.
 *
 * RETURN VALUES:
 *      0       - success
 *      -EIO    - i/o error.
 */
int diFree(struct inode *ip)
{
        int rc;
        ino_t inum = ip->i_ino;
        struct iag *iagp, *aiagp, *biagp, *ciagp, *diagp;
        struct metapage *mp, *amp, *bmp, *cmp, *dmp;
        int iagno, ino, extno, bitno, sword, agno;
        int back, fwd;
        u32 bitmap, mask;
        struct inode *ipimap = JFS_SBI(ip->i_sb)->ipimap;
        struct inomap *imap = JFS_IP(ipimap)->i_imap;
        pxd_t freepxd;
        tid_t tid;
        struct inode *iplist[3];
        struct tlock *tlck;
        struct pxd_lock *pxdlock;

        /*
         * This is just to suppress compiler warnings.  The same logic that
         * references these variables is used to initialize them.
         */
        aiagp = biagp = ciagp = diagp = NULL;

        /* get the iag number containing the inode.
         */
        iagno = INOTOIAG(inum);

        /* make sure that the iag is contained within
         * the map.
         */
        if (iagno >= imap->im_nextiag) {
                print_hex_dump(KERN_ERR, "imap: ", DUMP_PREFIX_ADDRESS, 16, 4,
                               imap, 32, 0);
                jfs_error(ip->i_sb,
                          "diFree: inum = %d, iagno = %d, nextiag = %d",
                          (uint) inum, iagno, imap->im_nextiag);
                return -EIO;
        }

        /* get the allocation group for this ino.
         */
        agno = JFS_IP(ip)->agno;

        /* Lock the AG specific inode map information
         */
        AG_LOCK(imap, agno);

        /* Obtain read lock in imap inode.  Don't release it until we have
         * read all of the IAG's that we are going to.
         */
        IREAD_LOCK(ipimap, RDWRLOCK_IMAP);

        /* read the iag.
         */
        if ((rc = diIAGRead(imap, iagno, &mp))) {
                IREAD_UNLOCK(ipimap);
                AG_UNLOCK(imap, agno);
                return (rc);
        }
        iagp = (struct iag *) mp->data;

        /* get the inode number and extent number of the inode within
         * the iag and the inode number within the extent.
         */
        ino = inum & (INOSPERIAG - 1);
        extno = ino >> L2INOSPEREXT;
        bitno = ino & (INOSPEREXT - 1);
        mask = HIGHORDER >> bitno;

        if (!(le32_to_cpu(iagp->wmap[extno]) & mask)) {
                jfs_error(ip->i_sb,
                          "diFree: wmap shows inode already free");
        }

        if (!addressPXD(&iagp->inoext[extno])) {
                release_metapage(mp);
                IREAD_UNLOCK(ipimap);
                AG_UNLOCK(imap, agno);
                jfs_error(ip->i_sb, "diFree: invalid inoext");
                return -EIO;
        }

        /* compute the bitmap for the extent reflecting the freed inode.
         */
        bitmap = le32_to_cpu(iagp->wmap[extno]) & ~mask;

        if (imap->im_agctl[agno].numfree > imap->im_agctl[agno].numinos) {
                release_metapage(mp);
                IREAD_UNLOCK(ipimap);
                AG_UNLOCK(imap, agno);
                jfs_error(ip->i_sb, "diFree: numfree > numinos");
                return -EIO;
        }
        /*
         *      inode extent still has some inodes or below low water mark:
         *      keep the inode extent;
         */
        if (bitmap ||
            imap->im_agctl[agno].numfree < 96 ||
            (imap->im_agctl[agno].numfree < 288 &&
             (((imap->im_agctl[agno].numfree * 100) /
               imap->im_agctl[agno].numinos) <= 25))) {
                /* if the iag currently has no free inodes (i.e.,
                 * the inode being freed is the first free inode of iag),
                 * insert the iag at head of the inode free list for the ag.
                 */
                if (iagp->nfreeinos == 0) {
                        /* check if there are any iags on the ag inode
                         * free list.  if so, read the first one so that
                         * we can link the current iag onto the list at
                         * the head.
                         */
                        if ((fwd = imap->im_agctl[agno].inofree) >= 0) {
                                /* read the iag that currently is the head
                                 * of the list.
                                 */
                                if ((rc = diIAGRead(imap, fwd, &amp))) {
                                        IREAD_UNLOCK(ipimap);
                                        AG_UNLOCK(imap, agno);
                                        release_metapage(mp);
                                        return (rc);
                                }
                                aiagp = (struct iag *) amp->data;

                                /* make current head point back to the iag.
                                 */
                                aiagp->inofreeback = cpu_to_le32(iagno);

                                write_metapage(amp);
                        }

                        /* iag points forward to current head and iag
                         * becomes the new head of the list.
                         */
                        iagp->inofreefwd =
                            cpu_to_le32(imap->im_agctl[agno].inofree);
                        iagp->inofreeback = cpu_to_le32(-1);
                        imap->im_agctl[agno].inofree = iagno;
                }

                IREAD_UNLOCK(ipimap);

                /* update the free inode summary map for the extent if
                 * freeing the inode means the extent will now have free
                 * inodes (i.e., the inode being freed is the first free
                 * inode of extent),
                 */
                if (iagp->wmap[extno] == cpu_to_le32(ONES)) {
                        sword = extno >> L2EXTSPERSUM;
                        bitno = extno & (EXTSPERSUM - 1);
                        iagp->inosmap[sword] &=
                            cpu_to_le32(~(HIGHORDER >> bitno));
                }

                /* update the bitmap.
                 */
                iagp->wmap[extno] = cpu_to_le32(bitmap);

                /* update the free inode counts at the iag, ag and
                 * map level.
                 */
                iagp->nfreeinos =
                    cpu_to_le32(le32_to_cpu(iagp->nfreeinos) + 1);
                imap->im_agctl[agno].numfree += 1;
                atomic_inc(&imap->im_numfree);

                /* release the AG inode map lock
                 */
                AG_UNLOCK(imap, agno);

                /* write the iag */
                write_metapage(mp);

                return (0);
        }


        /*
         *      inode extent has become free and above low water mark:
         *      free the inode extent;
         */

        /*
         *      prepare to update iag list(s) (careful update step 1)
         */
        amp = bmp = cmp = dmp = NULL;
        fwd = back = -1;

        /* check if the iag currently has no free extents.  if so,
         * it will be placed on the head of the ag extent free list.
         */
        if (iagp->nfreeexts == 0) {
                /* check if the ag extent free list has any iags.
                 * if so, read the iag at the head of the list now.
                 * this (head) iag will be updated later to reflect
                 * the addition of the current iag at the head of
                 * the list.
                 */
                if ((fwd = imap->im_agctl[agno].extfree) >= 0) {
                        if ((rc = diIAGRead(imap, fwd, &amp)))
                                goto error_out;
                        aiagp = (struct iag *) amp->data;
                }
        } else {
                /* iag has free extents. check if the addition of a free
                 * extent will cause all extents to be free within this
                 * iag.  if so, the iag will be removed from the ag extent
                 * free list and placed on the inode map's free iag list.
                 */
                if (iagp->nfreeexts == cpu_to_le32(EXTSPERIAG - 1)) {
                        /* in preparation for removing the iag from the
                         * ag extent free list, read the iags preceeding
                         * and following the iag on the ag extent free
                         * list.
                         */
                        if ((fwd = le32_to_cpu(iagp->extfreefwd)) >= 0) {
                                if ((rc = diIAGRead(imap, fwd, &amp)))
                                        goto error_out;
                                aiagp = (struct iag *) amp->data;
                        }

                        if ((back = le32_to_cpu(iagp->extfreeback)) >= 0) {
                                if ((rc = diIAGRead(imap, back, &bmp)))
                                        goto error_out;
                                biagp = (struct iag *) bmp->data;
                        }
                }
        }

        /* remove the iag from the ag inode free list if freeing
         * this extent cause the iag to have no free inodes.
         */
        if (iagp->nfreeinos == cpu_to_le32(INOSPEREXT - 1)) {
                int inofreeback = le32_to_cpu(iagp->inofreeback);
                int inofreefwd = le32_to_cpu(iagp->inofreefwd);

                /* in preparation for removing the iag from the
                 * ag inode free list, read the iags preceeding
                 * and following the iag on the ag inode free
                 * list.  before reading these iags, we must make
                 * sure that we already don't have them in hand
                 * from up above, since re-reading an iag (buffer)
                 * we are currently holding would cause a deadlock.
                 */
                if (inofreefwd >= 0) {

                        if (inofreefwd == fwd)
                                ciagp = (struct iag *) amp->data;
                        else if (inofreefwd == back)
                                ciagp = (struct iag *) bmp->data;
                        else {
                                if ((rc =
                                     diIAGRead(imap, inofreefwd, &cmp)))
                                        goto error_out;
                                ciagp = (struct iag *) cmp->data;
                        }
                        assert(ciagp != NULL);
                }

                if (inofreeback >= 0) {
                        if (inofreeback == fwd)
                                diagp = (struct iag *) amp->data;
                        else if (inofreeback == back)
                                diagp = (struct iag *) bmp->data;
                        else {
                                if ((rc =
                                     diIAGRead(imap, inofreeback, &dmp)))
                                        goto error_out;
                                diagp = (struct iag *) dmp->data;
                        }
                        assert(diagp != NULL);
                }
        }

        IREAD_UNLOCK(ipimap);

        /*
         * invalidate any page of the inode extent freed from buffer cache;
         */
        freepxd = iagp->inoext[extno];
        invalidate_pxd_metapages(ip, freepxd);

        /*
         *      update iag list(s) (careful update step 2)
         */
        /* add the iag to the ag extent free list if this is the
         * first free extent for the iag.
         */
        if (iagp->nfreeexts == 0) {
                if (fwd >= 0)
                        aiagp->extfreeback = cpu_to_le32(iagno);

                iagp->extfreefwd =
                    cpu_to_le32(imap->im_agctl[agno].extfree);
                iagp->extfreeback = cpu_to_le32(-1);
                imap->im_agctl[agno].extfree = iagno;
        } else {
                /* remove the iag from the ag extent list if all extents
                 * are now free and place it on the inode map iag free list.
                 */
                if (iagp->nfreeexts == cpu_to_le32(EXTSPERIAG - 1)) {
                        if (fwd >= 0)
                                aiagp->extfreeback = iagp->extfreeback;

                        if (back >= 0)
                                biagp->extfreefwd = iagp->extfreefwd;
                        else
                                imap->im_agctl[agno].extfree =
                                    le32_to_cpu(iagp->extfreefwd);

                        iagp->extfreefwd = iagp->extfreeback = cpu_to_le32(-1);

                        IAGFREE_LOCK(imap);
                        iagp->iagfree = cpu_to_le32(imap->im_freeiag);
                        imap->im_freeiag = iagno;
                        IAGFREE_UNLOCK(imap);
                }
        }

        /* remove the iag from the ag inode free list if freeing
         * this extent causes the iag to have no free inodes.
         */
        if (iagp->nfreeinos == cpu_to_le32(INOSPEREXT - 1)) {
                if ((int) le32_to_cpu(iagp->inofreefwd) >= 0)
                        ciagp->inofreeback = iagp->inofreeback;

                if ((int) le32_to_cpu(iagp->inofreeback) >= 0)
                        diagp->inofreefwd = iagp->inofreefwd;
                else
                        imap->im_agctl[agno].inofree =
                            le32_to_cpu(iagp->inofreefwd);

                iagp->inofreefwd = iagp->inofreeback = cpu_to_le32(-1);
        }

        /* update the inode extent address and working map
         * to reflect the free extent.
         * the permanent map should have been updated already
         * for the inode being freed.
         */
        if (iagp->pmap[extno] != 0) {
                jfs_error(ip->i_sb, "diFree: the pmap does not show inode free");
        }
        iagp->wmap[extno] = 0;
        PXDlength(&iagp->inoext[extno], 0);
        PXDaddress(&iagp->inoext[extno], 0);

        /* update the free extent and free inode summary maps
         * to reflect the freed extent.
         * the inode summary map is marked to indicate no inodes
         * available for the freed extent.
         */
        sword = extno >> L2EXTSPERSUM;
        bitno = extno & (EXTSPERSUM - 1);
        mask = HIGHORDER >> bitno;
        iagp->inosmap[sword] |= cpu_to_le32(mask);
        iagp->extsmap[sword] &= cpu_to_le32(~mask);

        /* update the number of free inodes and number of free extents
         * for the iag.
         */
        iagp->nfreeinos = cpu_to_le32(le32_to_cpu(iagp->nfreeinos) -
                                      (INOSPEREXT - 1));
        iagp->nfreeexts = cpu_to_le32(le32_to_cpu(iagp->nfreeexts) + 1);

        /* update the number of free inodes and backed inodes
         * at the ag and inode map level.
         */
        imap->im_agctl[agno].numfree -= (INOSPEREXT - 1);
        imap->im_agctl[agno].numinos -= INOSPEREXT;
        atomic_sub(INOSPEREXT - 1, &imap->im_numfree);
        atomic_sub(INOSPEREXT, &imap->im_numinos);

        if (amp)
                write_metapage(amp);
        if (bmp)
                write_metapage(bmp);
        if (cmp)
                write_metapage(cmp);
        if (dmp)
                write_metapage(dmp);

        /*
         * start transaction to update block allocation map
         * for the inode extent freed;
         *
         * N.B. AG_LOCK is released and iag will be released below, and
         * other thread may allocate inode from/reusing the ixad freed
         * BUT with new/different backing inode extent from the extent
         * to be freed by the transaction;
         */
        tid = txBegin(ipimap->i_sb, COMMIT_FORCE);
        mutex_lock(&JFS_IP(ipimap)->commit_mutex);

        /* acquire tlock of the iag page of the freed ixad
         * to force the page NOHOMEOK (even though no data is
         * logged from the iag page) until NOREDOPAGE|FREEXTENT log
         * for the free of the extent is committed;
         * write FREEXTENT|NOREDOPAGE log record
         * N.B. linelock is overlaid as freed extent descriptor;
         */
        tlck = txLock(tid, ipimap, mp, tlckINODE | tlckFREE);
        pxdlock = (struct pxd_lock *) & tlck->lock;
        pxdlock->flag = mlckFREEPXD;
        pxdlock->pxd = freepxd;
        pxdlock->index = 1;

        write_metapage(mp);

        iplist[0] = ipimap;

        /*
         * logredo needs the IAG number and IAG extent index in order
         * to ensure that the IMap is consistent.  The least disruptive
         * way to pass these values through  to the transaction manager
         * is in the iplist array.
         *
         * It's not pretty, but it works.
         */
        iplist[1] = (struct inode *) (size_t)iagno;
        iplist[2] = (struct inode *) (size_t)extno;

        rc = txCommit(tid, 1, &iplist[0], COMMIT_FORCE);

        txEnd(tid);
        mutex_unlock(&JFS_IP(ipimap)->commit_mutex);

        /* unlock the AG inode map information */
        AG_UNLOCK(imap, agno);

        return (0);

      error_out:
        IREAD_UNLOCK(ipimap);

        if (amp)
                release_metapage(amp);
        if (bmp)
                release_metapage(bmp);
        if (cmp)
                release_metapage(cmp);
        if (dmp)
                release_metapage(dmp);

        AG_UNLOCK(imap, agno);

        release_metapage(mp);

        return (rc);
}

/*
 * There are several places in the diAlloc* routines where we initialize
 * the inode.
 */
static inline void
diInitInode(struct inode *ip, int iagno, int ino, int extno, struct iag * iagp)
{
        struct jfs_sb_info *sbi = JFS_SBI(ip->i_sb);
        struct jfs_inode_info *jfs_ip = JFS_IP(ip);

        ip->i_ino = (iagno << L2INOSPERIAG) + ino;
        jfs_ip->ixpxd = iagp->inoext[extno];
        jfs_ip->agno = BLKTOAG(le64_to_cpu(iagp->agstart), sbi);
        jfs_ip->active_ag = -1;
}


/*
 * NAME:        diAlloc(pip,dir,ip)
 *
 * FUNCTION:    allocate a disk inode from the inode working map
 *              for a fileset or aggregate.
 *
 * PARAMETERS:
 *      pip     - pointer to incore inode for the parent inode.
 *      dir     - 'true' if the new disk inode is for a directory.
 *      ip      - pointer to a new inode
 *
 * RETURN VALUES:
 *      0       - success.
 *      -ENOSPC - insufficient disk resources.
 *      -EIO    - i/o error.
 */
int diAlloc(struct inode *pip, bool dir, struct inode *ip)
{
        int rc, ino, iagno, addext, extno, bitno, sword;
        int nwords, rem, i, agno;
        u32 mask, inosmap, extsmap;
        struct inode *ipimap;
        struct metapage *mp;
        ino_t inum;
        struct iag *iagp;
        struct inomap *imap;

        /* get the pointers to the inode map inode and the
         * corresponding imap control structure.
         */
        ipimap = JFS_SBI(pip->i_sb)->ipimap;
        imap = JFS_IP(ipimap)->i_imap;
        JFS_IP(ip)->ipimap = ipimap;
        JFS_IP(ip)->fileset = FILESYSTEM_I;

        /* for a directory, the allocation policy is to start
         * at the ag level using the preferred ag.
         */
        if (dir) {
                agno = dbNextAG(JFS_SBI(pip->i_sb)->ipbmap);
                AG_LOCK(imap, agno);
                goto tryag;
        }

        /* for files, the policy starts off by trying to allocate from
         * the same iag containing the parent disk inode:
         * try to allocate the new disk inode close to the parent disk
         * inode, using parent disk inode number + 1 as the allocation
         * hint.  (we use a left-to-right policy to attempt to avoid
         * moving backward on the disk.)  compute the hint within the
         * file system and the iag.
         */

        /* get the ag number of this iag */
        agno = JFS_IP(pip)->agno;

        if (atomic_read(&JFS_SBI(pip->i_sb)->bmap->db_active[agno])) {
                /*
                 * There is an open file actively growing.  We want to
                 * allocate new inodes from a different ag to avoid
                 * fragmentation problems.
                 */
                agno = dbNextAG(JFS_SBI(pip->i_sb)->ipbmap);
                AG_LOCK(imap, agno);
                goto tryag;
        }

        inum = pip->i_ino + 1;
        ino = inum & (INOSPERIAG - 1);

        /* back off the hint if it is outside of the iag */
        if (ino == 0)
                inum = pip->i_ino;

        /* lock the AG inode map information */
        AG_LOCK(imap, agno);

        /* Get read lock on imap inode */
        IREAD_LOCK(ipimap, RDWRLOCK_IMAP);

        /* get the iag number and read the iag */
        iagno = INOTOIAG(inum);
        if ((rc = diIAGRead(imap, iagno, &mp))) {
                IREAD_UNLOCK(ipimap);
                AG_UNLOCK(imap, agno);
                return (rc);
        }
        iagp = (struct iag *) mp->data;

        /* determine if new inode extent is allowed to be added to the iag.
         * new inode extent can be added to the iag if the ag
         * has less than 32 free disk inodes and the iag has free extents.
         */
        addext = (imap->im_agctl[agno].numfree < 32 && iagp->nfreeexts);

        /*
         *      try to allocate from the IAG
         */
        /* check if the inode may be allocated from the iag
         * (i.e. the inode has free inodes or new extent can be added).
         */
        if (iagp->nfreeinos || addext) {
                /* determine the extent number of the hint.
                 */
                extno = ino >> L2INOSPEREXT;

                /* check if the extent containing the hint has backed
                 * inodes.  if so, try to allocate within this extent.
                 */
                if (addressPXD(&iagp->inoext[extno])) {
                        bitno = ino & (INOSPEREXT - 1);
                        if ((bitno =
                             diFindFree(le32_to_cpu(iagp->wmap[extno]),
                                        bitno))
                            < INOSPEREXT) {
                                ino = (extno << L2INOSPEREXT) + bitno;

                                /* a free inode (bit) was found within this
                                 * extent, so allocate it.
                                 */
                                rc = diAllocBit(imap, iagp, ino);
                                IREAD_UNLOCK(ipimap);
                                if (rc) {
                                        assert(rc == -EIO);
                                } else {
                                        /* set the results of the allocation
                                         * and write the iag.
                                         */
                                        diInitInode(ip, iagno, ino, extno,
                                                    iagp);
                                        mark_metapage_dirty(mp);
                                }
                                release_metapage(mp);

                                /* free the AG lock and return.
                                 */
                                AG_UNLOCK(imap, agno);
                                return (rc);
                        }

                        if (!addext)
                                extno =
                                    (extno ==
                                     EXTSPERIAG - 1) ? 0 : extno + 1;
                }

                /*
                 * no free inodes within the extent containing the hint.
                 *
                 * try to allocate from the backed extents following
                 * hint or, if appropriate (i.e. addext is true), allocate
                 * an extent of free inodes at or following the extent
                 * containing the hint.
                 *
                 * the free inode and free extent summary maps are used
                 * here, so determine the starting summary map position
                 * and the number of words we'll have to examine.  again,
                 * the approach is to allocate following the hint, so we
                 * might have to initially ignore prior bits of the summary
                 * map that represent extents prior to the extent containing
                 * the hint and later revisit these bits.
                 */
                bitno = extno & (EXTSPERSUM - 1);
                nwords = (bitno == 0) ? SMAPSZ : SMAPSZ + 1;
                sword = extno >> L2EXTSPERSUM;

                /* mask any prior bits for the starting words of the
                 * summary map.
                 */
                mask = ONES << (EXTSPERSUM - bitno);
                inosmap = le32_to_cpu(iagp->inosmap[sword]) | mask;
                extsmap = le32_to_cpu(iagp->extsmap[sword]) | mask;

                /* scan the free inode and free extent summary maps for
                 * free resources.
                 */
                for (i = 0; i < nwords; i++) {
                        /* check if this word of the free inode summary
                         * map describes an extent with free inodes.
                         */
                        if (~inosmap) {
                                /* an extent with free inodes has been
                                 * found. determine the extent number
                                 * and the inode number within the extent.
                                 */
                                rem = diFindFree(inosmap, 0);
                                extno = (sword << L2EXTSPERSUM) + rem;
                                rem = diFindFree(le32_to_cpu(iagp->wmap[extno]),
                                                 0);
                                if (rem >= INOSPEREXT) {
                                        IREAD_UNLOCK(ipimap);
                                        release_metapage(mp);
                                        AG_UNLOCK(imap, agno);
                                        jfs_error(ip->i_sb,
                                                  "diAlloc: can't find free bit "
                                                  "in wmap");
                                        return EIO;
                                }

                                /* determine the inode number within the
                                 * iag and allocate the inode from the
                                 * map.
                                 */
                                ino = (extno << L2INOSPEREXT) + rem;
                                rc = diAllocBit(imap, iagp, ino);
                                IREAD_UNLOCK(ipimap);
                                if (rc)
                                        assert(rc == -EIO);
                                else {
                                        /* set the results of the allocation
                                         * and write the iag.
                                         */
                                        diInitInode(ip, iagno, ino, extno,
                                                    iagp);
                                        mark_metapage_dirty(mp);
                                }
                                release_metapage(mp);

                                /* free the AG lock and return.
                                 */
                                AG_UNLOCK(imap, agno);
                                return (rc);

                        }

                        /* check if we may allocate an extent of free
                         * inodes and whether this word of the free
                         * extents summary map describes a free extent.
                         */
                        if (addext && ~extsmap) {
                                /* a free extent has been found.  determine
                                 * the extent number.
                                 */
                                rem = diFindFree(extsmap, 0);
                                extno = (sword << L2EXTSPERSUM) + rem;

                                /* allocate an extent of free inodes.
                                 */
                                if ((rc = diNewExt(imap, iagp, extno))) {
                                        /* if there is no disk space for a
                                         * new extent, try to allocate the
                                         * disk inode from somewhere else.
                                         */
                                        if (rc == -ENOSPC)
                                                break;

                                        assert(rc == -EIO);
                                } else {
                                        /* set the results of the allocation
                                         * and write the iag.
                                         */
                                        diInitInode(ip, iagno,
                                                    extno << L2INOSPEREXT,
                                                    extno, iagp);
                                        mark_metapage_dirty(mp);
                                }
                                release_metapage(mp);
                                /* free the imap inode & the AG lock & return.
                                 */
                                IREAD_UNLOCK(ipimap);
                                AG_UNLOCK(imap, agno);
                                return (rc);
                        }

                        /* move on to the next set of summary map words.
                         */
                        sword = (sword == SMAPSZ - 1) ? 0 : sword + 1;
                        inosmap = le32_to_cpu(iagp->inosmap[sword]);
                        extsmap = le32_to_cpu(iagp->extsmap[sword]);
                }
        }
        /* unlock imap inode */
        IREAD_UNLOCK(ipimap);

        /* nothing doing in this iag, so release it. */
        release_metapage(mp);

      tryag:
        /*
         * try to allocate anywhere within the same AG as the parent inode.
         */
        rc = diAllocAG(imap, agno, dir, ip);

        AG_UNLOCK(imap, agno);

        if (rc != -ENOSPC)
                return (rc);

        /*
         * try to allocate in any AG.
         */
        return (diAllocAny(imap, agno, dir, ip));
}


/*
 * NAME:        diAllocAG(imap,agno,dir,ip)
 *
 * FUNCTION:    allocate a disk inode from the allocation group.
 *
 *              this routine first determines if a new extent of free
 *              inodes should be added for the allocation group, with
 *              the current request satisfied from this extent. if this
 *              is the case, an attempt will be made to do just that.  if
 *              this attempt fails or it has been determined that a new
 *              extent should not be added, an attempt is made to satisfy
 *              the request by allocating an existing (backed) free inode
 *              from the allocation group.
 *
 * PRE CONDITION: Already have the AG lock for this AG.
 *
 * PARAMETERS:
 *      imap    - pointer to inode map control structure.
 *      agno    - allocation group to allocate from.
 *      dir     - 'true' if the new disk inode is for a directory.
 *      ip      - pointer to the new inode to be filled in on successful return
 *                with the disk inode number allocated, its extent address
 *                and the start of the ag.
 *
 * RETURN VALUES:
 *      0       - success.
 *      -ENOSPC - insufficient disk resources.
 *      -EIO    - i/o error.
 */
static int
diAllocAG(struct inomap * imap, int agno, bool dir, struct inode *ip)
{
        int rc, addext, numfree, numinos;

        /* get the number of free and the number of backed disk
         * inodes currently within the ag.
         */
        numfree = imap->im_agctl[agno].numfree;
        numinos = imap->im_agctl[agno].numinos;

        if (numfree > numinos) {
                jfs_error(ip->i_sb, "diAllocAG: numfree > numinos");
                return -EIO;
        }

        /* determine if we should allocate a new extent of free inodes
         * within the ag: for directory inodes, add a new extent
         * if there are a small number of free inodes or number of free
         * inodes is a small percentage of the number of backed inodes.
         */
        if (dir)
                addext = (numfree < 64 ||
                          (numfree < 256
                           && ((numfree * 100) / numinos) <= 20));
        else
                addext = (numfree == 0);

        /*
         * try to allocate a new extent of free inodes.
         */
        if (addext) {
                /* if free space is not avaliable for this new extent, try
                 * below to allocate a free and existing (already backed)
                 * inode from the ag.
                 */
                if ((rc = diAllocExt(imap, agno, ip)) != -ENOSPC)
                        return (rc);
        }

        /*
         * try to allocate an existing free inode from the ag.
         */
        return (diAllocIno(imap, agno, ip));
}


/*
 * NAME:        diAllocAny(imap,agno,dir,iap)
 *
 * FUNCTION:    allocate a disk inode from any other allocation group.
 *
 *              this routine is called when an allocation attempt within
 *              the primary allocation group has failed. if attempts to
 *              allocate an inode from any allocation group other than the
 *              specified primary group.
 *
 * PARAMETERS:
 *      imap    - pointer to inode map control structure.
 *      agno    - primary allocation group (to avoid).
 *      dir     - 'true' if the new disk inode is for a directory.
 *      ip      - pointer to a new inode to be filled in on successful return
 *                with the disk inode number allocated, its extent address
 *                and the start of the ag.
 *
 * RETURN VALUES:
 *      0       - success.
 *      -ENOSPC - insufficient disk resources.
 *      -EIO    - i/o error.
 */
static int
diAllocAny(struct inomap * imap, int agno, bool dir, struct inode *ip)
{
        int ag, rc;
        int maxag = JFS_SBI(imap->im_ipimap->i_sb)->bmap->db_maxag;


        /* try to allocate from the ags following agno up to
         * the maximum ag number.
         */
        for (ag = agno + 1; ag <= maxag; ag++) {
                AG_LOCK(imap, ag);

                rc = diAllocAG(imap, ag, dir, ip);

                AG_UNLOCK(imap, ag);

                if (rc != -ENOSPC)
                        return (rc);
        }

        /* try to allocate from the ags in front of agno.
         */
        for (ag = 0; ag < agno; ag++) {
                AG_LOCK(imap, ag);

                rc = diAllocAG(imap, ag, dir, ip);

                AG_UNLOCK(imap, ag);

                if (rc != -ENOSPC)
                        return (rc);
        }

        /* no free disk inodes.
         */
        return -ENOSPC;
}


/*
 * NAME:        diAllocIno(imap,agno,ip)
 *
 * FUNCTION:    allocate a disk inode from the allocation group's free
 *              inode list, returning an error if this free list is
 *              empty (i.e. no iags on the list).
 *
 *              allocation occurs from the first iag on the list using
 *              the iag's free inode summary map to find the leftmost
 *              free inode in the iag.
 *
 * PRE CONDITION: Already have AG lock for this AG.
 *
 * PARAMETERS:
 *      imap    - pointer to inode map control structure.
 *      agno    - allocation group.
 *      ip      - pointer to new inode to be filled in on successful return
 *                with the disk inode number allocated, its extent address
 *                and the start of the ag.
 *
 * RETURN VALUES:
 *      0       - success.
 *      -ENOSPC - insufficient disk resources.
 *      -EIO    - i/o error.
 */
static int diAllocIno(struct inomap * imap, int agno, struct inode *ip)
{
        int iagno, ino, rc, rem, extno, sword;
        struct metapage *mp;
        struct iag *iagp;

        /* check if there are iags on the ag's free inode list.
         */
        if ((iagno = imap->im_agctl[agno].inofree) < 0)
                return -ENOSPC;

        /* obtain read lock on imap inode */
        IREAD_LOCK(imap->im_ipimap, RDWRLOCK_IMAP);

        /* read the iag at the head of the list.
         */
        if ((rc = diIAGRead(imap, iagno, &mp))) {
                IREAD_UNLOCK(imap->im_ipimap);
                return (rc);
        }
        iagp = (struct iag *) mp->data;

        /* better be free inodes in this iag if it is on the
         * list.
         */
        if (!iagp->nfreeinos) {
                IREAD_UNLOCK(imap->im_ipimap);
                release_metapage(mp);
                jfs_error(ip->i_sb,
                          "diAllocIno: nfreeinos = 0, but iag on freelist");
                return -EIO;
        }

        /* scan the free inode summary map to find an extent
         * with free inodes.
         */
        for (sword = 0;; sword++) {
                if (sword >= SMAPSZ) {
                        IREAD_UNLOCK(imap->im_ipimap);
                        release_metapage(mp);
                        jfs_error(ip->i_sb,
                                  "diAllocIno: free inode not found in summary map");
                        return -EIO;
                }

                if (~iagp->inosmap[sword])
                        break;
        }

        /* found a extent with free inodes. determine
         * the extent number.
         */
        rem = diFindFree(le32_to_cpu(iagp->inosmap[sword]), 0);
        if (rem >= EXTSPERSUM) {
                IREAD_UNLOCK(imap->im_ipimap);
                release_metapage(mp);
                jfs_error(ip->i_sb, "diAllocIno: no free extent found");
                return -EIO;
        }
        extno = (sword << L2EXTSPERSUM) + rem;

        /* find the first free inode in the extent.
         */
        rem = diFindFree(le32_to_cpu(iagp->wmap[extno]), 0);
        if (rem >= INOSPEREXT) {
                IREAD_UNLOCK(imap->im_ipimap);
                release_metapage(mp);
                jfs_error(ip->i_sb, "diAllocIno: free inode not found");
                return -EIO;
        }

        /* compute the inode number within the iag.
         */
        ino = (extno << L2INOSPEREXT) + rem;

        /* allocate the inode.
         */
        rc = diAllocBit(imap, iagp, ino);
        IREAD_UNLOCK(imap->im_ipimap);
        if (rc) {
                release_metapage(mp);
                return (rc);
        }

        /* set the results of the allocation and write the iag.
         */
        diInitInode(ip, iagno, ino, extno, iagp);
        write_metapage(mp);

        return (0);
}


/*
 * NAME:        diAllocExt(imap,agno,ip)
 *
 * FUNCTION:    add a new extent of free inodes to an iag, allocating
 *              an inode from this extent to satisfy the current allocation
 *              request.
 *
 *              this routine first tries to find an existing iag with free
 *              extents through the ag free extent list.  if list is not
 *              empty, the head of the list will be selected as the home
 *              of the new extent of free inodes.  otherwise (the list is
 *              empty), a new iag will be allocated for the ag to contain
 *              the extent.
 *
 *              once an iag has been selected, the free extent summary map
 *              is used to locate a free extent within the iag and diNewExt()
 *              is called to initialize the extent, with initialization
 *              including the allocation of the first inode of the extent
 *              for the purpose of satisfying this request.
 *
 * PARAMETERS:
 *      imap    - pointer to inode map control structure.
 *      agno    - allocation group number.
 *      ip      - pointer to new inode to be filled in on successful return
 *                with the disk inode number allocated, its extent address
 *                and the start of the ag.
 *
 * RETURN VALUES:
 *      0       - success.
 *      -ENOSPC - insufficient disk resources.
 *      -EIO    - i/o error.
 */
static int diAllocExt(struct inomap * imap, int agno, struct inode *ip)
{
        int rem, iagno, sword, extno, rc;
        struct metapage *mp;
        struct iag *iagp;

        /* check if the ag has any iags with free extents.  if not,
         * allocate a new iag for the ag.
         */
        if ((iagno = imap->im_agctl[agno].extfree) < 0) {
                /* If successful, diNewIAG will obtain the read lock on the
                 * imap inode.
                 */
                if ((rc = diNewIAG(imap, &iagno, agno, &mp))) {
                        return (rc);
                }
                iagp = (struct iag *) mp->data;

                /* set the ag number if this a brand new iag
                 */
                iagp->agstart =
                    cpu_to_le64(AGTOBLK(agno, imap->im_ipimap));
        } else {
                /* read the iag.
                 */
                IREAD_LOCK(imap->im_ipimap, RDWRLOCK_IMAP);
                if ((rc = diIAGRead(imap, iagno, &mp))) {
                        IREAD_UNLOCK(imap->im_ipimap);
                        jfs_error(ip->i_sb, "diAllocExt: error reading iag");
                        return rc;
                }
                iagp = (struct iag *) mp->data;
        }

        /* using the free extent summary map, find a free extent.
         */
        for (sword = 0;; sword++) {
                if (sword >= SMAPSZ) {
                        release_metapage(mp);
                        IREAD_UNLOCK(imap->im_ipimap);
                        jfs_error(ip->i_sb,
                                  "diAllocExt: free ext summary map not found");
                        return -EIO;
                }
                if (~iagp->extsmap[sword])
                        break;
        }

        /* determine the extent number of the free extent.
         */
        rem = diFindFree(le32_to_cpu(iagp->extsmap[sword]), 0);
        if (rem >= EXTSPERSUM) {
                release_metapage(mp);
                IREAD_UNLOCK(imap->im_ipimap);
                jfs_error(ip->i_sb, "diAllocExt: free extent not found");
                return -EIO;
        }
        extno = (sword << L2EXTSPERSUM) + rem;

        /* initialize the new extent.
         */
        rc = diNewExt(imap, iagp, extno);
        IREAD_UNLOCK(imap->im_ipimap);
        if (rc) {
                /* something bad happened.  if a new iag was allocated,
                 * place it back on the inode map's iag free list, and
                 * clear the ag number information.
                 */
                if (iagp->nfreeexts == cpu_to_le32(EXTSPERIAG)) {
                        IAGFREE_LOCK(imap);
                        iagp->iagfree = cpu_to_le32(imap->im_freeiag);
                        imap->im_freeiag = iagno;
                        IAGFREE_UNLOCK(imap);
                }
                write_metapage(mp);
                return (rc);
        }

        /* set the results of the allocation and write the iag.
         */
        diInitInode(ip, iagno, extno << L2INOSPEREXT, extno, iagp);

        write_metapage(mp);

        return (0);
}

/*
 * NAME:        diAllocBit(imap,iagp,ino)
 *
 * FUNCTION:    allocate a backed inode from an iag.
 *
 *              this routine performs the mechanics of allocating a
 *              specified inode from a backed extent.
 *
 *              if the inode to be allocated represents the last free
 *              inode within the iag, the iag will be removed from the
 *              ag free inode list.
 *
 *              a careful update approach is used to provide consistency
 *              in the face of updates to multiple buffers.  under this
 *              approach, all required buffers are obtained before making
 *              any updates and are held all are updates are complete.
 *
 * PRE CONDITION: Already have buffer lock on iagp.  Already have AG lock on
 *      this AG.  Must have read lock on imap inode.
 *
 * PARAMETERS:
 *      imap    - pointer to inode map control structure.
 *      iagp    - pointer to iag.
 *      ino     - inode number to be allocated within the iag.
 *
 * RETURN VALUES:
 *      0       - success.
 *      -ENOSPC - insufficient disk resources.
 *      -EIO    - i/o error.
 */
static int diAllocBit(struct inomap * imap, struct iag * iagp, int ino)
{
        int extno, bitno, agno, sword, rc;
        struct metapage *amp = NULL, *bmp = NULL;
        struct iag *aiagp = NULL, *biagp = NULL;
        u32 mask;

        /* check if this is the last free inode within the iag.
         * if so, it will have to be removed from the ag free
         * inode list, so get the iags preceeding and following
         * it on the list.
         */
        if (iagp->nfreeinos == cpu_to_le32(1)) {
                if ((int) le32_to_cpu(iagp->inofreefwd) >= 0) {
                        if ((rc =
                             diIAGRead(imap, le32_to_cpu(iagp->inofreefwd),
                                       &amp)))
                                return (rc);
                        aiagp = (struct iag *) amp->data;
                }

                if ((int) le32_to_cpu(iagp->inofreeback) >= 0) {
                        if ((rc =
                             diIAGRead(imap,
                                       le32_to_cpu(iagp->inofreeback),
                                       &bmp))) {
                                if (amp)
                                        release_metapage(amp);
                                return (rc);
                        }
                        biagp = (struct iag *) bmp->data;
                }
        }

        /* get the ag number, extent number, inode number within
         * the extent.
         */
        agno = BLKTOAG(le64_to_cpu(iagp->agstart), JFS_SBI(imap->im_ipimap->i_sb));
        extno = ino >> L2INOSPEREXT;
        bitno = ino & (INOSPEREXT - 1);

        /* compute the mask for setting the map.
         */
        mask = HIGHORDER >> bitno;

        /* the inode should be free and backed.
         */
        if (((le32_to_cpu(iagp->pmap[extno]) & mask) != 0) ||
            ((le32_to_cpu(iagp->wmap[extno]) & mask) != 0) ||
            (addressPXD(&iagp->inoext[extno]) == 0)) {
                if (amp)
                        release_metapage(amp);
                if (bmp)
                        release_metapage(bmp);

                jfs_error(imap->im_ipimap->i_sb,
                          "diAllocBit: iag inconsistent");
                return -EIO;
        }

        /* mark the inode as allocated in the working map.
         */
        iagp->wmap[extno] |= cpu_to_le32(mask);

        /* check if all inodes within the extent are now
         * allocated.  if so, update the free inode summary
         * map to reflect this.
         */
        if (iagp->wmap[extno] == cpu_to_le32(ONES)) {
                sword = extno >> L2EXTSPERSUM;
                bitno = extno & (EXTSPERSUM - 1);
                iagp->inosmap[sword] |= cpu_to_le32(HIGHORDER >> bitno);
        }

        /* if this was the last free inode in the iag, remove the
         * iag from the ag free inode list.
         */
        if (iagp->nfreeinos == cpu_to_le32(1)) {
                if (amp) {
                        aiagp->inofreeback = iagp->inofreeback;
                        write_metapage(amp);
                }

                if (bmp) {
                        biagp->inofreefwd = iagp->inofreefwd;
                        write_metapage(bmp);
                } else {
                        imap->im_agctl[agno].inofree =
                            le32_to_cpu(iagp->inofreefwd);
                }
                iagp->inofreefwd = iagp->inofreeback = cpu_to_le32(-1);
        }

        /* update the free inode count at the iag, ag, inode
         * map levels.
         */
        iagp->nfreeinos = cpu_to_le32(le32_to_cpu(iagp->nfreeinos) - 1);
        imap->im_agctl[agno].numfree -= 1;
        atomic_dec(&imap->im_numfree);

        return (0);
}


/*
 * NAME:        diNewExt(imap,iagp,extno)
 *
 * FUNCTION:    initialize a new extent of inodes for an iag, allocating
 *              the first inode of the extent for use for the current
 *              allocation request.
 *
 *              disk resources are allocated for the new extent of inodes
 *              and the inodes themselves are initialized to reflect their
 *              existence within the extent (i.e. their inode numbers and
 *              inode extent addresses are set) and their initial state
 *              (mode and link count are set to zero).
 *
 *              if the iag is new, it is not yet on an ag extent free list
 *              but will now be placed on this list.
 *
 *              if the allocation of the new extent causes the iag to
 *              have no free extent, the iag will be removed from the
 *              ag extent free list.
 *
 *              if the iag has no free backed inodes, it will be placed
 *              on the ag free inode list, since the addition of the new
 *              extent will now cause it to have free inodes.
 *
 *              a careful update approach is used to provide consistency
 *              (i.e. list consistency) in the face of updates to multiple
 *              buffers.  under this approach, all required buffers are
 *              obtained before making any updates and are held until all
 *              updates are complete.
 *
 * PRE CONDITION: Already have buffer lock on iagp.  Already have AG lock on
 *      this AG.  Must have read lock on imap inode.
 *
 * PARAMETERS:
 *      imap    - pointer to inode map control structure.
 *      iagp    - pointer to iag.
 *      extno   - extent number.
 *
 * RETURN VALUES:
 *      0       - success.
 *      -ENOSPC - insufficient disk resources.
 *      -EIO    - i/o error.
 */
static int diNewExt(struct inomap * imap, struct iag * iagp, int extno)
{
        int agno, iagno, fwd, back, freei = 0, sword, rc;
        struct iag *aiagp = NULL, *biagp = NULL, *ciagp = NULL;
        struct metapage *amp, *bmp, *cmp, *dmp;
        struct inode *ipimap;
        s64 blkno, hint;
        int i, j;
        u32 mask;
        ino_t ino;
        struct dinode *dp;
        struct jfs_sb_info *sbi;

        /* better have free extents.
         */
        if (!iagp->nfreeexts) {
                jfs_error(imap->im_ipimap->i_sb, "diNewExt: no free extents");
                return -EIO;
        }

        /* get the inode map inode.
         */
        ipimap = imap->im_ipimap;
        sbi = JFS_SBI(ipimap->i_sb);

        amp = bmp = cmp = NULL;

        /* get the ag and iag numbers for this iag.
         */
        agno = BLKTOAG(le64_to_cpu(iagp->agstart), sbi);
        iagno = le32_to_cpu(iagp->iagnum);

        /* check if this is the last free extent within the
         * iag.  if so, the iag must be removed from the ag
         * free extent list, so get the iags preceeding and
         * following the iag on this list.
         */
        if (iagp->nfreeexts == cpu_to_le32(1)) {
                if ((fwd = le32_to_cpu(iagp->extfreefwd)) >= 0) {
                        if ((rc = diIAGRead(imap, fwd, &amp)))
                                return (rc);
                        aiagp = (struct iag *) amp->data;
                }

                if ((back = le32_to_cpu(iagp->extfreeback)) >= 0) {
                        if ((rc = diIAGRead(imap, back, &bmp)))
                                goto error_out;
                        biagp = (struct iag *) bmp->data;
                }
        } else {
                /* the iag has free extents.  if all extents are free
                 * (as is the case for a newly allocated iag), the iag
                 * must be added to the ag free extent list, so get
                 * the iag at the head of the list in preparation for
                 * adding this iag to this list.
                 */
                fwd = back = -1;
                if (iagp->nfreeexts == cpu_to_le32(EXTSPERIAG)) {
                        if ((fwd = imap->im_agctl[agno].extfree) >= 0) {
                                if ((rc = diIAGRead(imap, fwd, &amp)))
                                        goto error_out;
                                aiagp = (struct iag *) amp->data;
                        }
                }
        }

        /* check if the iag has no free inodes.  if so, the iag
         * will have to be added to the ag free inode list, so get
         * the iag at the head of the list in preparation for
         * adding this iag to this list.  in doing this, we must
         * check if we already have the iag at the head of
         * the list in hand.
         */
        if (iagp->nfreeinos == 0) {
                freei = imap->im_agctl[agno].inofree;

                if (freei >= 0) {
                        if (freei == fwd) {
                                ciagp = aiagp;
                        } else if (freei == back) {
                                ciagp = biagp;
                        } else {
                                if ((rc = diIAGRead(imap, freei, &cmp)))
                                        goto error_out;
                                ciagp = (struct iag *) cmp->data;
                        }
                        if (ciagp == NULL) {
                                jfs_error(imap->im_ipimap->i_sb,
                                          "diNewExt: ciagp == NULL");
                                rc = -EIO;
                                goto error_out;
                        }
                }
        }

        /* allocate disk space for the inode extent.
         */
        if ((extno == 0) || (addressPXD(&iagp->inoext[extno - 1]) == 0))
                hint = ((s64) agno << sbi->bmap->db_agl2size) - 1;
        else
                hint = addressPXD(&iagp->inoext[extno - 1]) +
                    lengthPXD(&iagp->inoext[extno - 1]) - 1;

        if ((rc = dbAlloc(ipimap, hint, (s64) imap->im_nbperiext, &blkno)))
                goto error_out;

        /* compute the inode number of the first inode within the
         * extent.
         */
        ino = (iagno << L2INOSPERIAG) + (extno << L2INOSPEREXT);

        /* initialize the inodes within the newly allocated extent a
         * page at a time.
         */
        for (i = 0; i < imap->im_nbperiext; i += sbi->nbperpage) {
                /* get a buffer for this page of disk inodes.
                 */
                dmp = get_metapage(ipimap, blkno + i, PSIZE, 1);
                if (dmp == NULL) {
                        rc = -EIO;
                        goto error_out;
                }
                dp = (struct dinode *) dmp->data;

                /* initialize the inode number, mode, link count and
                 * inode extent address.
                 */
                for (j = 0; j < INOSPERPAGE; j++, dp++, ino++) {
                        dp->di_inostamp = cpu_to_le32(sbi->inostamp);
                        dp->di_number = cpu_to_le32(ino);
                        dp->di_fileset = cpu_to_le32(FILESYSTEM_I);
                        dp->di_mode = 0;
                        dp->di_nlink = 0;
                        PXDaddress(&(dp->di_ixpxd), blkno);
                        PXDlength(&(dp->di_ixpxd), imap->im_nbperiext);
                }
                write_metapage(dmp);
        }

        /* if this is the last free extent within the iag, remove the
         * iag from the ag free extent list.
         */
        if (iagp->nfreeexts == cpu_to_le32(1)) {
                if (fwd >= 0)
                        aiagp->extfreeback = iagp->extfreeback;

                if (back >= 0)
                        biagp->extfreefwd = iagp->extfreefwd;
                else
                        imap->im_agctl[agno].extfree =
                            le32_to_cpu(iagp->extfreefwd);

                iagp->extfreefwd = iagp->extfreeback = cpu_to_le32(-1);
        } else {
                /* if the iag has all free extents (newly allocated iag),
                 * add the iag to the ag free extent list.
                 */
                if (iagp->nfreeexts == cpu_to_le32(EXTSPERIAG)) {
                        if (fwd >= 0)
                                aiagp->extfreeback = cpu_to_le32(iagno);

                        iagp->extfreefwd = cpu_to_le32(fwd);
                        iagp->extfreeback = cpu_to_le32(-1);
                        imap->im_agctl[agno].extfree = iagno;
                }
        }

        /* if the iag has no free inodes, add the iag to the
         * ag free inode list.
         */
        if (iagp->nfreeinos == 0) {
                if (freei >= 0)
                        ciagp->inofreeback = cpu_to_le32(iagno);

                iagp->inofreefwd =
                    cpu_to_le32(imap->im_agctl[agno].inofree);
                iagp->inofreeback = cpu_to_le32(-1);
                imap->im_agctl[agno].inofree = iagno;
        }

        /* initialize the extent descriptor of the extent. */
        PXDlength(&iagp->inoext[extno], imap->im_nbperiext);
        PXDaddress(&iagp->inoext[extno], blkno);

        /* initialize the working and persistent map of the extent.
         * the working map will be initialized such that
         * it indicates the first inode of the extent is allocated.
         */
        iagp->wmap[extno] = cpu_to_le32(HIGHORDER);
        iagp->pmap[extno] = 0;

        /* update the free inode and free extent summary maps
         * for the extent to indicate the extent has free inodes
         * and no longer represents a free extent.
         */
        sword = extno >> L2EXTSPERSUM;
        mask = HIGHORDER >> (extno & (EXTSPERSUM - 1));
        iagp->extsmap[sword] |= cpu_to_le32(mask);
        iagp->inosmap[sword] &= cpu_to_le32(~mask);

        /* update the free inode and free extent counts for the
         * iag.
         */
        iagp->nfreeinos = cpu_to_le32(le32_to_cpu(iagp->nfreeinos) +
                                      (INOSPEREXT - 1));
        iagp->nfreeexts = cpu_to_le32(le32_to_cpu(iagp->nfreeexts) - 1);

        /* update the free and backed inode counts for the ag.
         */
        imap->im_agctl[agno].numfree += (INOSPEREXT - 1);
        imap->im_agctl[agno].numinos += INOSPEREXT;

        /* update the free and backed inode counts for the inode map.
         */
        atomic_add(INOSPEREXT - 1, &imap->im_numfree);
        atomic_add(INOSPEREXT, &imap->im_numinos);

        /* write the iags.
         */
        if (amp)
                write_metapage(amp);
        if (bmp)
                write_metapage(bmp);
        if (cmp)
                write_metapage(cmp);

        return (0);

      error_out:

        /* release the iags.
         */
        if (amp)
                release_metapage(amp);
        if (bmp)
                release_metapage(bmp);
        if (cmp)
                release_metapage(cmp);

        return (rc);
}


/*
 * NAME:        diNewIAG(imap,iagnop,agno)
 *
 * FUNCTION:    allocate a new iag for an allocation group.
 *
 *              first tries to allocate the iag from the inode map
 *              iagfree list:
 *              if the list has free iags, the head of the list is removed
 *              and returned to satisfy the request.
 *              if the inode map's iag free list is empty, the inode map
 *              is extended to hold a new iag. this new iag is initialized
 *              and returned to satisfy the request.
 *
 * PARAMETERS:
 *      imap    - pointer to inode map control structure.
 *      iagnop  - pointer to an iag number set with the number of the
 *                newly allocated iag upon successful return.
 *      agno    - allocation group number.
 *      bpp     - Buffer pointer to be filled in with new IAG's buffer
 *
 * RETURN VALUES:
 *      0       - success.
 *      -ENOSPC - insufficient disk resources.
 *      -EIO    - i/o error.
 *
 * serialization:
 *      AG lock held on entry/exit;
 *      write lock on the map is held inside;
 *      read lock on the map is held on successful completion;
 *
 * note: new iag transaction:
 * . synchronously write iag;
 * . write log of xtree and inode of imap;
 * . commit;
 * . synchronous write of xtree (right to left, bottom to top);
 * . at start of logredo(): init in-memory imap with one additional iag page;
 * . at end of logredo(): re-read imap inode to determine
 *   new imap size;
 */
static int
diNewIAG(struct inomap * imap, int *iagnop, int agno, struct metapage ** mpp)
{
        int rc;
        int iagno, i, xlen;
        struct inode *ipimap;
        struct super_block *sb;
        struct jfs_sb_info *sbi;
        struct metapage *mp;
        struct iag *iagp;
        s64 xaddr = 0;
        s64 blkno;
        tid_t tid;
        struct inode *iplist[1];

        /* pick up pointers to the inode map and mount inodes */
        ipimap = imap->im_ipimap;
        sb = ipimap->i_sb;
        sbi = JFS_SBI(sb);

        /* acquire the free iag lock */
        IAGFREE_LOCK(imap);

        /* if there are any iags on the inode map free iag list,
         * allocate the iag from the head of the list.
         */
        if (imap->im_freeiag >= 0) {
                /* pick up the iag number at the head of the list */
                iagno = imap->im_freeiag;

                /* determine the logical block number of the iag */
                blkno = IAGTOLBLK(iagno, sbi->l2nbperpage);
        } else {
                /* no free iags. the inode map will have to be extented
                 * to include a new iag.
                 */

                /* acquire inode map lock */
                IWRITE_LOCK(ipimap, RDWRLOCK_IMAP);

                if (ipimap->i_size >> L2PSIZE != imap->im_nextiag + 1) {
                        IWRITE_UNLOCK(ipimap);
                        IAGFREE_UNLOCK(imap);
                        jfs_error(imap->im_ipimap->i_sb,
                                  "diNewIAG: ipimap->i_size is wrong");
                        return -EIO;
                }


                /* get the next avaliable iag number */
                iagno = imap->im_nextiag;

                /* make sure that we have not exceeded the maximum inode
                 * number limit.
                 */
                if (iagno > (MAXIAGS - 1)) {
                        /* release the inode map lock */
                        IWRITE_UNLOCK(ipimap);

                        rc = -ENOSPC;
                        goto out;
                }

                /*
                 * synchronously append new iag page.
                 */
                /* determine the logical address of iag page to append */
                blkno = IAGTOLBLK(iagno, sbi->l2nbperpage);

                /* Allocate extent for new iag page */
                xlen = sbi->nbperpage;
                if ((rc = dbAlloc(ipimap, 0, (s64) xlen, &xaddr))) {
                        /* release the inode map lock */
                        IWRITE_UNLOCK(ipimap);

                        goto out;
                }

                /*
                 * start transaction of update of the inode map
                 * addressing structure pointing to the new iag page;
                 */
                tid = txBegin(sb, COMMIT_FORCE);
                mutex_lock(&JFS_IP(ipimap)->commit_mutex);

                /* update the inode map addressing structure to point to it */
                if ((rc =
                     xtInsert(tid, ipimap, 0, blkno, xlen, &xaddr, 0))) {
                        txEnd(tid);
                        mutex_unlock(&JFS_IP(ipimap)->commit_mutex);
                        /* Free the blocks allocated for the iag since it was
                         * not successfully added to the inode map
                         */
                        dbFree(ipimap, xaddr, (s64) xlen);

                        /* release the inode map lock */
                        IWRITE_UNLOCK(ipimap);

                        goto out;
                }

                /* update the inode map's inode to reflect the extension */
                ipimap->i_size += PSIZE;
                inode_add_bytes(ipimap, PSIZE);

                /* assign a buffer for the page */
                mp = get_metapage(ipimap, blkno, PSIZE, 0);
                if (!mp) {
                        /*
                         * This is very unlikely since we just created the
                         * extent, but let's try to handle it correctly
                         */
                        xtTruncate(tid, ipimap, ipimap->i_size - PSIZE,
                                   COMMIT_PWMAP);

                        txAbort(tid, 0);
                        txEnd(tid);

                        /* release the inode map lock */
                        IWRITE_UNLOCK(ipimap);

                        rc = -EIO;
                        goto out;
                }
                iagp = (struct iag *) mp->data;

                /* init the iag */
                memset(iagp, 0, sizeof(struct iag));
                iagp->iagnum = cpu_to_le32(iagno);
                iagp->inofreefwd = iagp->inofreeback = cpu_to_le32(-1);
                iagp->extfreefwd = iagp->extfreeback = cpu_to_le32(-1);
                iagp->iagfree = cpu_to_le32(-1);
                iagp->nfreeinos = 0;
                iagp->nfreeexts = cpu_to_le32(EXTSPERIAG);

                /* initialize the free inode summary map (free extent
                 * summary map initialization handled by bzero).
                 */
                for (i = 0; i < SMAPSZ; i++)
                        iagp->inosmap[i] = cpu_to_le32(ONES);

                /*
                 * Write and sync the metapage
                 */
                flush_metapage(mp);

                /*
                 * txCommit(COMMIT_FORCE) will synchronously write address
                 * index pages and inode after commit in careful update order
                 * of address index pages (right to left, bottom up);
                 */
                iplist[0] = ipimap;
                rc = txCommit(tid, 1, &iplist[0], COMMIT_FORCE);

                txEnd(tid);
                mutex_unlock(&JFS_IP(ipimap)->commit_mutex);

                duplicateIXtree(sb, blkno, xlen, &xaddr);

                /* update the next avaliable iag number */
                imap->im_nextiag += 1;

                /* Add the iag to the iag free list so we don't lose the iag
                 * if a failure happens now.
                 */
                imap->im_freeiag = iagno;

                /* Until we have logredo working, we want the imap inode &
                 * control page to be up to date.
                 */
                diSync(ipimap);

                /* release the inode map lock */
                IWRITE_UNLOCK(ipimap);
        }

        /* obtain read lock on map */
        IREAD_LOCK(ipimap, RDWRLOCK_IMAP);

        /* read the iag */
        if ((rc = diIAGRead(imap, iagno, &mp))) {
                IREAD_UNLOCK(ipimap);
                rc = -EIO;
                goto out;
        }
        iagp = (struct iag *) mp->data;

        /* remove the iag from the iag free list */
        imap->im_freeiag = le32_to_cpu(iagp->iagfree);
        iagp->iagfree = cpu_to_le32(-1);

        /* set the return iag number and buffer pointer */
        *iagnop = iagno;
        *mpp = mp;

      out:
        /* release the iag free lock */
        IAGFREE_UNLOCK(imap);

        return (rc);
}

/*
 * NAME:        diIAGRead()
 *
 * FUNCTION:    get the buffer for the specified iag within a fileset
 *              or aggregate inode map.
 *
 * PARAMETERS:
 *      imap    - pointer to inode map control structure.
 *      iagno   - iag number.
 *      bpp     - point to buffer pointer to be filled in on successful
 *                exit.
 *
 * SERIALIZATION:
 *      must have read lock on imap inode
 *      (When called by diExtendFS, the filesystem is quiesced, therefore
 *       the read lock is unnecessary.)
 *
 * RETURN VALUES:
 *      0       - success.
 *      -EIO    - i/o error.
 */
static int diIAGRead(struct inomap * imap, int iagno, struct metapage ** mpp)
{
        struct inode *ipimap = imap->im_ipimap;
        s64 blkno;

        /* compute the logical block number of the iag. */
        blkno = IAGTOLBLK(iagno, JFS_SBI(ipimap->i_sb)->l2nbperpage);

        /* read the iag. */
        *mpp = read_metapage(ipimap, blkno, PSIZE, 0);
        if (*mpp == NULL) {
                return -EIO;
        }

        return (0);
}

/*
 * NAME:        diFindFree()
 *
 * FUNCTION:    find the first free bit in a word starting at
 *              the specified bit position.
 *
 * PARAMETERS:
 *      word    - word to be examined.
 *      start   - starting bit position.
 *
 * RETURN VALUES:
 *      bit position of first free bit in the word or 32 if
 *      no free bits were found.
 */
static int diFindFree(u32 word, int start)
{
        int bitno;
        assert(start < 32);
        /* scan the word for the first free bit. */
        for (word <<= start, bitno = start; bitno < 32;
             bitno++, word <<= 1) {
                if ((word & HIGHORDER) == 0)
                        break;
        }
        return (bitno);
}

/*
 * NAME:        diUpdatePMap()
 *
 * FUNCTION: Update the persistent map in an IAG for the allocation or
 *      freeing of the specified inode.
 *
 * PRE CONDITIONS: Working map has already been updated for allocate.
 *
 * PARAMETERS:
 *      ipimap  - Incore inode map inode
 *      inum    - Number of inode to mark in permanent map
 *      is_free - If 'true' indicates inode should be marked freed, otherwise
 *                indicates inode should be marked allocated.
 *
 * RETURN VALUES:
 *              0 for success
 */
int
diUpdatePMap(struct inode *ipimap,
             unsigned long inum, bool is_free, struct tblock * tblk)
{
        int rc;
        struct iag *iagp;
        struct metapage *mp;
        int iagno, ino, extno, bitno;
        struct inomap *imap;
        u32 mask;
        struct jfs_log *log;
        int lsn, difft, diffp;
        unsigned long flags;

        imap = JFS_IP(ipimap)->i_imap;
        /* get the iag number containing the inode */
        iagno = INOTOIAG(inum);
        /* make sure that the iag is contained within the map */
        if (iagno >= imap->im_nextiag) {
                jfs_error(ipimap->i_sb,
                          "diUpdatePMap: the iag is outside the map");
                return -EIO;
        }
        /* read the iag */
        IREAD_LOCK(ipimap, RDWRLOCK_IMAP);
        rc = diIAGRead(imap, iagno, &mp);
        IREAD_UNLOCK(ipimap);
        if (rc)
                return (rc);
        metapage_wait_for_io(mp);
        iagp = (struct iag *) mp->data;
        /* get the inode number and extent number of the inode within
         * the iag and the inode number within the extent.
         */
        ino = inum & (INOSPERIAG - 1);
        extno = ino >> L2INOSPEREXT;
        bitno = ino & (INOSPEREXT - 1);
        mask = HIGHORDER >> bitno;
        /*
         * mark the inode free in persistent map:
         */
        if (is_free) {
                /* The inode should have been allocated both in working
                 * map and in persistent map;
                 * the inode will be freed from working map at the release
                 * of last reference release;
                 */
                if (!(le32_to_cpu(iagp->wmap[extno]) & mask)) {
                        jfs_error(ipimap->i_sb,
                                  "diUpdatePMap: inode %ld not marked as "
                                  "allocated in wmap!", inum);
                }
                if (!(le32_to_cpu(iagp->pmap[extno]) & mask)) {
                        jfs_error(ipimap->i_sb,
                                  "diUpdatePMap: inode %ld not marked as "
                                  "allocated in pmap!", inum);
                }
                /* update the bitmap for the extent of the freed inode */
                iagp->pmap[extno] &= cpu_to_le32(~mask);
        }
        /*
         * mark the inode allocated in persistent map:
         */
        else {
                /* The inode should be already allocated in the working map
                 * and should be free in persistent map;
                 */
                if (!(le32_to_cpu(iagp->wmap[extno]) & mask)) {
                        release_metapage(mp);
                        jfs_error(ipimap->i_sb,
                                  "diUpdatePMap: the inode is not allocated in "
                                  "the working map");
                        return -EIO;
                }
                if ((le32_to_cpu(iagp->pmap[extno]) & mask) != 0) {
                        release_metapage(mp);
                        jfs_error(ipimap->i_sb,
                                  "diUpdatePMap: the inode is not free in the "
                                  "persistent map");
                        return -EIO;
                }
                /* update the bitmap for the extent of the allocated inode */
                iagp->pmap[extno] |= cpu_to_le32(mask);
        }
        /*
         * update iag lsn
         */
        lsn = tblk->lsn;
        log = JFS_SBI(tblk->sb)->log;
        LOGSYNC_LOCK(log, flags);
        if (mp->lsn != 0) {
                /* inherit older/smaller lsn */
                logdiff(difft, lsn, log);
                logdiff(diffp, mp->lsn, log);
                if (difft < diffp) {
                        mp->lsn = lsn;
                        /* move mp after tblock in logsync list */
                        list_move(&mp->synclist, &tblk->synclist);
                }
                /* inherit younger/larger clsn */
                assert(mp->clsn);
                logdiff(difft, tblk->clsn, log);
                logdiff(diffp, mp->clsn, log);
                if (difft > diffp)
                        mp->clsn = tblk->clsn;
        } else {
                mp->log = log;
                mp->lsn = lsn;
                /* insert mp after tblock in logsync list */
                log->count++;
                list_add(&mp->synclist, &tblk->synclist);
                mp->clsn = tblk->clsn;
        }
        LOGSYNC_UNLOCK(log, flags);
        write_metapage(mp);
        return (0);
}

/*
 *      diExtendFS()
 *
 * function: update imap for extendfs();
 *
 * note: AG size has been increased s.t. each k old contiguous AGs are
 * coalesced into a new AG;
 */
int diExtendFS(struct inode *ipimap, struct inode *ipbmap)
{
        int rc, rcx = 0;
        struct inomap *imap = JFS_IP(ipimap)->i_imap;
        struct iag *iagp = NULL, *hiagp = NULL;
        struct bmap *mp = JFS_SBI(ipbmap->i_sb)->bmap;
        struct metapage *bp, *hbp;
        int i, n, head;
        int numinos, xnuminos = 0, xnumfree = 0;
        s64 agstart;

        jfs_info("diExtendFS: nextiag:%d numinos:%d numfree:%d",
                   imap->im_nextiag, atomic_read(&imap->im_numinos),
                   atomic_read(&imap->im_numfree));

        /*
         *      reconstruct imap
         *
         * coalesce contiguous k (newAGSize/oldAGSize) AGs;
         * i.e., (AGi, ..., AGj) where i = k*n and j = k*(n+1) - 1 to AGn;
         * note: new AG size = old AG size * (2**x).
         */

        /* init per AG control information im_agctl[] */
        for (i = 0; i < MAXAG; i++) {
                imap->im_agctl[i].inofree = -1;
                imap->im_agctl[i].extfree = -1;
                imap->im_agctl[i].numinos = 0;  /* number of backed inodes */
                imap->im_agctl[i].numfree = 0;  /* number of free backed inodes */
        }

        /*
         *      process each iag page of the map.
         *
         * rebuild AG Free Inode List, AG Free Inode Extent List;
         */
        for (i = 0; i < imap->im_nextiag; i++) {
                if ((rc = diIAGRead(imap, i, &bp))) {
                        rcx = rc;
                        continue;
                }
                iagp = (struct iag *) bp->data;
                if (le32_to_cpu(iagp->iagnum) != i) {
                        release_metapage(bp);
                        jfs_error(ipimap->i_sb,
                                  "diExtendFs: unexpected value of iagnum");
                        return -EIO;
                }

                /* leave free iag in the free iag list */
                if (iagp->nfreeexts == cpu_to_le32(EXTSPERIAG)) {
                        release_metapage(bp);
                        continue;
                }

                /* agstart that computes to the same ag is treated as same; */
                agstart = le64_to_cpu(iagp->agstart);
                /* iagp->agstart = agstart & ~(mp->db_agsize - 1); */
                n = agstart >> mp->db_agl2size;

                /* compute backed inodes */
                numinos = (EXTSPERIAG - le32_to_cpu(iagp->nfreeexts))
                    << L2INOSPEREXT;
                if (numinos > 0) {
                        /* merge AG backed inodes */
                        imap->im_agctl[n].numinos += numinos;
                        xnuminos += numinos;
                }

                /* if any backed free inodes, insert at AG free inode list */
                if ((int) le32_to_cpu(iagp->nfreeinos) > 0) {
                        if ((head = imap->im_agctl[n].inofree) == -1) {
                                iagp->inofreefwd = cpu_to_le32(-1);
                                iagp->inofreeback = cpu_to_le32(-1);
                        } else {
                                if ((rc = diIAGRead(imap, head, &hbp))) {
                                        rcx = rc;
                                        goto nextiag;
                                }
                                hiagp = (struct iag *) hbp->data;
                                hiagp->inofreeback = iagp->iagnum;
                                iagp->inofreefwd = cpu_to_le32(head);
                                iagp->inofreeback = cpu_to_le32(-1);
                                write_metapage(hbp);
                        }

                        imap->im_agctl[n].inofree =
                            le32_to_cpu(iagp->iagnum);

                        /* merge AG backed free inodes */
                        imap->im_agctl[n].numfree +=
                            le32_to_cpu(iagp->nfreeinos);
                        xnumfree += le32_to_cpu(iagp->nfreeinos);
                }

                /* if any free extents, insert at AG free extent list */
                if (le32_to_cpu(iagp->nfreeexts) > 0) {
                        if ((head = imap->im_agctl[n].extfree) == -1) {
                                iagp->extfreefwd = cpu_to_le32(-1);
                                iagp->extfreeback = cpu_to_le32(-1);
                        } else {
                                if ((rc = diIAGRead(imap, head, &hbp))) {
                                        rcx = rc;
                                        goto nextiag;
                                }
                                hiagp = (struct iag *) hbp->data;
                                hiagp->extfreeback = iagp->iagnum;
                                iagp->extfreefwd = cpu_to_le32(head);
                                iagp->extfreeback = cpu_to_le32(-1);
                                write_metapage(hbp);
                        }

                        imap->im_agctl[n].extfree =
                            le32_to_cpu(iagp->iagnum);
                }

              nextiag:
                write_metapage(bp);
        }

        if (xnuminos != atomic_read(&imap->im_numinos) ||
            xnumfree != atomic_read(&imap->im_numfree)) {
                jfs_error(ipimap->i_sb,
                          "diExtendFs: numinos or numfree incorrect");
                return -EIO;
        }

        return rcx;
}