Merge master.kernel.org:/home/rmk/linux-2.6-mmc

[linux-2.6/mini2440.git] / fs / xfs / xfs_iget.c

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir.h"
#include "xfs_dir2.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dir_sf.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_quota.h"
#include "xfs_utils.h"

/*
 * Initialize the inode hash table for the newly mounted file system.
 * Choose an initial table size based on user specified value, else
 * use a simple algorithm using the maximum number of inodes as an
 * indicator for table size, and clamp it between one and some large
 * number of pages.
 */
void
xfs_ihash_init(xfs_mount_t *mp)
{
        __uint64_t      icount;
        uint            i, flags = KM_SLEEP | KM_MAYFAIL;

        if (!mp->m_ihsize) {
                icount = mp->m_maxicount ? mp->m_maxicount :
                         (mp->m_sb.sb_dblocks << mp->m_sb.sb_inopblog);
                mp->m_ihsize = 1 << max_t(uint, 8,
                                        (xfs_highbit64(icount) + 1) / 2);
                mp->m_ihsize = min_t(uint, mp->m_ihsize,
                                        (64 * NBPP) / sizeof(xfs_ihash_t));
        }

        while (!(mp->m_ihash = (xfs_ihash_t *)kmem_zalloc(mp->m_ihsize *
                                                sizeof(xfs_ihash_t), flags))) {
                if ((mp->m_ihsize >>= 1) <= NBPP)
                        flags = KM_SLEEP;
        }
        for (i = 0; i < mp->m_ihsize; i++) {
                rwlock_init(&(mp->m_ihash[i].ih_lock));
        }
}

/*
 * Free up structures allocated by xfs_ihash_init, at unmount time.
 */
void
xfs_ihash_free(xfs_mount_t *mp)
{
        kmem_free(mp->m_ihash, mp->m_ihsize*sizeof(xfs_ihash_t));
        mp->m_ihash = NULL;
}

/*
 * Initialize the inode cluster hash table for the newly mounted file system.
 * Its size is derived from the ihash table size.
 */
void
xfs_chash_init(xfs_mount_t *mp)
{
        uint    i;

        mp->m_chsize = max_t(uint, 1, mp->m_ihsize /
                         (XFS_INODE_CLUSTER_SIZE(mp) >> mp->m_sb.sb_inodelog));
        mp->m_chsize = min_t(uint, mp->m_chsize, mp->m_ihsize);
        mp->m_chash = (xfs_chash_t *)kmem_zalloc(mp->m_chsize
                                                 * sizeof(xfs_chash_t),
                                                 KM_SLEEP);
        for (i = 0; i < mp->m_chsize; i++) {
                spinlock_init(&mp->m_chash[i].ch_lock,"xfshash");
        }
}

/*
 * Free up structures allocated by xfs_chash_init, at unmount time.
 */
void
xfs_chash_free(xfs_mount_t *mp)
{
        int     i;

        for (i = 0; i < mp->m_chsize; i++) {
                spinlock_destroy(&mp->m_chash[i].ch_lock);
        }

        kmem_free(mp->m_chash, mp->m_chsize*sizeof(xfs_chash_t));
        mp->m_chash = NULL;
}

/*
 * Try to move an inode to the front of its hash list if possible
 * (and if its not there already).  Called right after obtaining
 * the list version number and then dropping the read_lock on the
 * hash list in question (which is done right after looking up the
 * inode in question...).
 */
STATIC void
xfs_ihash_promote(
        xfs_ihash_t     *ih,
        xfs_inode_t     *ip,
        ulong           version)
{
        xfs_inode_t     *iq;

        if ((ip->i_prevp != &ih->ih_next) && write_trylock(&ih->ih_lock)) {
                if (likely(version == ih->ih_version)) {
                        /* remove from list */
                        if ((iq = ip->i_next)) {
                                iq->i_prevp = ip->i_prevp;
                        }
                        *ip->i_prevp = iq;

                        /* insert at list head */
                        iq = ih->ih_next;
                        iq->i_prevp = &ip->i_next;
                        ip->i_next = iq;
                        ip->i_prevp = &ih->ih_next;
                        ih->ih_next = ip;
                }
                write_unlock(&ih->ih_lock);
        }
}

/*
 * Look up an inode by number in the given file system.
 * The inode is looked up in the hash table for the file system
 * represented by the mount point parameter mp.  Each bucket of
 * the hash table is guarded by an individual semaphore.
 *
 * If the inode is found in the hash table, its corresponding vnode
 * is obtained with a call to vn_get().  This call takes care of
 * coordination with the reclamation of the inode and vnode.  Note
 * that the vmap structure is filled in while holding the hash lock.
 * This gives us the state of the inode/vnode when we found it and
 * is used for coordination in vn_get().
 *
 * If it is not in core, read it in from the file system's device and
 * add the inode into the hash table.
 *
 * The inode is locked according to the value of the lock_flags parameter.
 * This flag parameter indicates how and if the inode's IO lock and inode lock
 * should be taken.
 *
 * mp -- the mount point structure for the current file system.  It points
 *       to the inode hash table.
 * tp -- a pointer to the current transaction if there is one.  This is
 *       simply passed through to the xfs_iread() call.
 * ino -- the number of the inode desired.  This is the unique identifier
 *        within the file system for the inode being requested.
 * lock_flags -- flags indicating how to lock the inode.  See the comment
 *               for xfs_ilock() for a list of valid values.
 * bno -- the block number starting the buffer containing the inode,
 *        if known (as by bulkstat), else 0.
 */
STATIC int
xfs_iget_core(
        vnode_t         *vp,
        xfs_mount_t     *mp,
        xfs_trans_t     *tp,
        xfs_ino_t       ino,
        uint            flags,
        uint            lock_flags,
        xfs_inode_t     **ipp,
        xfs_daddr_t     bno)
{
        xfs_ihash_t     *ih;
        xfs_inode_t     *ip;
        xfs_inode_t     *iq;
        vnode_t         *inode_vp;
        ulong           version;
        int             error;
        /* REFERENCED */
        xfs_chash_t     *ch;
        xfs_chashlist_t *chl, *chlnew;
        SPLDECL(s);


        ih = XFS_IHASH(mp, ino);

again:
        read_lock(&ih->ih_lock);

        for (ip = ih->ih_next; ip != NULL; ip = ip->i_next) {
                if (ip->i_ino == ino) {
                        /*
                         * If INEW is set this inode is being set up
                         * we need to pause and try again.
                         */
                        if (ip->i_flags & XFS_INEW) {
                                read_unlock(&ih->ih_lock);
                                delay(1);
                                XFS_STATS_INC(xs_ig_frecycle);

                                goto again;
                        }

                        inode_vp = XFS_ITOV_NULL(ip);
                        if (inode_vp == NULL) {
                                /*
                                 * If IRECLAIM is set this inode is
                                 * on its way out of the system,
                                 * we need to pause and try again.
                                 */
                                if (ip->i_flags & XFS_IRECLAIM) {
                                        read_unlock(&ih->ih_lock);
                                        delay(1);
                                        XFS_STATS_INC(xs_ig_frecycle);

                                        goto again;
                                }

                                vn_trace_exit(vp, "xfs_iget.alloc",
                                        (inst_t *)__return_address);

                                XFS_STATS_INC(xs_ig_found);

                                ip->i_flags &= ~XFS_IRECLAIMABLE;
                                version = ih->ih_version;
                                read_unlock(&ih->ih_lock);
                                xfs_ihash_promote(ih, ip, version);

                                XFS_MOUNT_ILOCK(mp);
                                list_del_init(&ip->i_reclaim);
                                XFS_MOUNT_IUNLOCK(mp);

                                goto finish_inode;

                        } else if (vp != inode_vp) {
                                struct inode *inode = LINVFS_GET_IP(inode_vp);

                                /* The inode is being torn down, pause and
                                 * try again.
                                 */
                                if (inode->i_state & (I_FREEING | I_CLEAR)) {
                                        read_unlock(&ih->ih_lock);
                                        delay(1);
                                        XFS_STATS_INC(xs_ig_frecycle);

                                        goto again;
                                }
/* Chances are the other vnode (the one in the inode) is being torn
 * down right now, and we landed on top of it. Question is, what do
 * we do? Unhook the old inode and hook up the new one?
 */
                                cmn_err(CE_PANIC,
                        "xfs_iget_core: ambiguous vns: vp/0x%p, invp/0x%p",
                                                inode_vp, vp);
                        }

                        /*
                         * Inode cache hit: if ip is not at the front of
                         * its hash chain, move it there now.
                         * Do this with the lock held for update, but
                         * do statistics after releasing the lock.
                         */
                        version = ih->ih_version;
                        read_unlock(&ih->ih_lock);
                        xfs_ihash_promote(ih, ip, version);
                        XFS_STATS_INC(xs_ig_found);

finish_inode:
                        if (ip->i_d.di_mode == 0) {
                                if (!(flags & IGET_CREATE))
                                        return ENOENT;
                                xfs_iocore_inode_reinit(ip);
                        }
        
                        if (lock_flags != 0)
                                xfs_ilock(ip, lock_flags);

                        ip->i_flags &= ~XFS_ISTALE;

                        vn_trace_exit(vp, "xfs_iget.found",
                                                (inst_t *)__return_address);
                        goto return_ip;
                }
        }

        /*
         * Inode cache miss: save the hash chain version stamp and unlock
         * the chain, so we don't deadlock in vn_alloc.
         */
        XFS_STATS_INC(xs_ig_missed);

        version = ih->ih_version;

        read_unlock(&ih->ih_lock);

        /*
         * Read the disk inode attributes into a new inode structure and get
         * a new vnode for it. This should also initialize i_ino and i_mount.
         */
        error = xfs_iread(mp, tp, ino, &ip, bno);
        if (error) {
                return error;
        }

        vn_trace_exit(vp, "xfs_iget.alloc", (inst_t *)__return_address);

        xfs_inode_lock_init(ip, vp);
        xfs_iocore_inode_init(ip);

        if (lock_flags != 0) {
                xfs_ilock(ip, lock_flags);
        }
                
        if ((ip->i_d.di_mode == 0) && !(flags & IGET_CREATE)) {
                xfs_idestroy(ip);
                return ENOENT;
        }

        /*
         * Put ip on its hash chain, unless someone else hashed a duplicate
         * after we released the hash lock.
         */
        write_lock(&ih->ih_lock);

        if (ih->ih_version != version) {
                for (iq = ih->ih_next; iq != NULL; iq = iq->i_next) {
                        if (iq->i_ino == ino) {
                                write_unlock(&ih->ih_lock);
                                xfs_idestroy(ip);

                                XFS_STATS_INC(xs_ig_dup);
                                goto again;
                        }
                }
        }

        /*
         * These values _must_ be set before releasing ihlock!
         */
        ip->i_hash = ih;
        if ((iq = ih->ih_next)) {
                iq->i_prevp = &ip->i_next;
        }
        ip->i_next = iq;
        ip->i_prevp = &ih->ih_next;
        ih->ih_next = ip;
        ip->i_udquot = ip->i_gdquot = NULL;
        ih->ih_version++;
        ip->i_flags |= XFS_INEW;

        write_unlock(&ih->ih_lock);

        /*
         * put ip on its cluster's hash chain
         */
        ASSERT(ip->i_chash == NULL && ip->i_cprev == NULL &&
               ip->i_cnext == NULL);

        chlnew = NULL;
        ch = XFS_CHASH(mp, ip->i_blkno);
 chlredo:
        s = mutex_spinlock(&ch->ch_lock);
        for (chl = ch->ch_list; chl != NULL; chl = chl->chl_next) {
                if (chl->chl_blkno == ip->i_blkno) {

                        /* insert this inode into the doubly-linked list
                         * where chl points */
                        if ((iq = chl->chl_ip)) {
                                ip->i_cprev = iq->i_cprev;
                                iq->i_cprev->i_cnext = ip;
                                iq->i_cprev = ip;
                                ip->i_cnext = iq;
                        } else {
                                ip->i_cnext = ip;
                                ip->i_cprev = ip;
                        }
                        chl->chl_ip = ip;
                        ip->i_chash = chl;
                        break;
                }
        }

        /* no hash list found for this block; add a new hash list */
        if (chl == NULL)  {
                if (chlnew == NULL) {
                        mutex_spinunlock(&ch->ch_lock, s);
                        ASSERT(xfs_chashlist_zone != NULL);
                        chlnew = (xfs_chashlist_t *)
                                        kmem_zone_alloc(xfs_chashlist_zone,
                                                KM_SLEEP);
                        ASSERT(chlnew != NULL);
                        goto chlredo;
                } else {
                        ip->i_cnext = ip;
                        ip->i_cprev = ip;
                        ip->i_chash = chlnew;
                        chlnew->chl_ip = ip;
                        chlnew->chl_blkno = ip->i_blkno;
                        chlnew->chl_next = ch->ch_list;
                        ch->ch_list = chlnew;
                        chlnew = NULL;
                }
        } else {
                if (chlnew != NULL) {
                        kmem_zone_free(xfs_chashlist_zone, chlnew);
                }
        }

        mutex_spinunlock(&ch->ch_lock, s);


        /*
         * Link ip to its mount and thread it on the mount's inode list.
         */
        XFS_MOUNT_ILOCK(mp);
        if ((iq = mp->m_inodes)) {
                ASSERT(iq->i_mprev->i_mnext == iq);
                ip->i_mprev = iq->i_mprev;
                iq->i_mprev->i_mnext = ip;
                iq->i_mprev = ip;
                ip->i_mnext = iq;
        } else {
                ip->i_mnext = ip;
                ip->i_mprev = ip;
        }
        mp->m_inodes = ip;

        XFS_MOUNT_IUNLOCK(mp);

 return_ip:
        ASSERT(ip->i_df.if_ext_max ==
               XFS_IFORK_DSIZE(ip) / sizeof(xfs_bmbt_rec_t));

        ASSERT(((ip->i_d.di_flags & XFS_DIFLAG_REALTIME) != 0) ==
               ((ip->i_iocore.io_flags & XFS_IOCORE_RT) != 0));

        *ipp = ip;

        /*
         * If we have a real type for an on-disk inode, we can set ops(&unlock)
         * now.  If it's a new inode being created, xfs_ialloc will handle it.
         */
        VFS_INIT_VNODE(XFS_MTOVFS(mp), vp, XFS_ITOBHV(ip), 1);

        return 0;
}


/*
 * The 'normal' internal xfs_iget, if needed it will
 * 'allocate', or 'get', the vnode.
 */
int
xfs_iget(
        xfs_mount_t     *mp,
        xfs_trans_t     *tp,
        xfs_ino_t       ino,
        uint            flags,
        uint            lock_flags,
        xfs_inode_t     **ipp,
        xfs_daddr_t     bno)
{
        struct inode    *inode;
        vnode_t         *vp = NULL;
        int             error;

        XFS_STATS_INC(xs_ig_attempts);

retry:
        if ((inode = iget_locked(XFS_MTOVFS(mp)->vfs_super, ino))) {
                bhv_desc_t      *bdp;
                xfs_inode_t     *ip;

                vp = LINVFS_GET_VP(inode);
                if (inode->i_state & I_NEW) {
                        vn_initialize(inode);
                        error = xfs_iget_core(vp, mp, tp, ino, flags,
                                        lock_flags, ipp, bno);
                        if (error) {
                                vn_mark_bad(vp);
                                if (inode->i_state & I_NEW)
                                        unlock_new_inode(inode);
                                iput(inode);
                        }
                } else {
                        /*
                         * If the inode is not fully constructed due to
                         * filehandle mistmatches wait for the inode to go
                         * away and try again.
                         *
                         * iget_locked will call __wait_on_freeing_inode
                         * to wait for the inode to go away.
                         */
                        if (is_bad_inode(inode) ||
                            ((bdp = vn_bhv_lookup(VN_BHV_HEAD(vp),
                                                  &xfs_vnodeops)) == NULL)) {
                                iput(inode);
                                delay(1);
                                goto retry;
                        }

                        ip = XFS_BHVTOI(bdp);
                        if (lock_flags != 0)
                                xfs_ilock(ip, lock_flags);
                        XFS_STATS_INC(xs_ig_found);
                        *ipp = ip;
                        error = 0;
                }
        } else
                error = ENOMEM; /* If we got no inode we are out of memory */

        return error;
}

/*
 * Do the setup for the various locks within the incore inode.
 */
void
xfs_inode_lock_init(
        xfs_inode_t     *ip,
        vnode_t         *vp)
{
        mrlock_init(&ip->i_lock, MRLOCK_ALLOW_EQUAL_PRI|MRLOCK_BARRIER,
                     "xfsino", (long)vp->v_number);
        mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", vp->v_number);
        init_waitqueue_head(&ip->i_ipin_wait);
        atomic_set(&ip->i_pincount, 0);
        init_sema(&ip->i_flock, 1, "xfsfino", vp->v_number);
}

/*
 * Look for the inode corresponding to the given ino in the hash table.
 * If it is there and its i_transp pointer matches tp, return it.
 * Otherwise, return NULL.
 */
xfs_inode_t *
xfs_inode_incore(xfs_mount_t    *mp,
                 xfs_ino_t      ino,
                 xfs_trans_t    *tp)
{
        xfs_ihash_t     *ih;
        xfs_inode_t     *ip;
        ulong           version;

        ih = XFS_IHASH(mp, ino);
        read_lock(&ih->ih_lock);
        for (ip = ih->ih_next; ip != NULL; ip = ip->i_next) {
                if (ip->i_ino == ino) {
                        /*
                         * If we find it and tp matches, return it.
                         * Also move it to the front of the hash list
                         * if we find it and it is not already there.
                         * Otherwise break from the loop and return
                         * NULL.
                         */
                        if (ip->i_transp == tp) {
                                version = ih->ih_version;
                                read_unlock(&ih->ih_lock);
                                xfs_ihash_promote(ih, ip, version);
                                return (ip);
                        }
                        break;
                }
        }
        read_unlock(&ih->ih_lock);
        return (NULL);
}

/*
 * Decrement reference count of an inode structure and unlock it.
 *
 * ip -- the inode being released
 * lock_flags -- this parameter indicates the inode's locks to be
 *       to be released.  See the comment on xfs_iunlock() for a list
 *       of valid values.
 */
void
xfs_iput(xfs_inode_t    *ip,
         uint           lock_flags)
{
        vnode_t *vp = XFS_ITOV(ip);

        vn_trace_entry(vp, "xfs_iput", (inst_t *)__return_address);

        xfs_iunlock(ip, lock_flags);

        VN_RELE(vp);
}

/*
 * Special iput for brand-new inodes that are still locked
 */
void
xfs_iput_new(xfs_inode_t        *ip,
             uint               lock_flags)
{
        vnode_t         *vp = XFS_ITOV(ip);
        struct inode    *inode = LINVFS_GET_IP(vp);

        vn_trace_entry(vp, "xfs_iput_new", (inst_t *)__return_address);

        if ((ip->i_d.di_mode == 0)) {
                ASSERT(!(ip->i_flags & XFS_IRECLAIMABLE));
                vn_mark_bad(vp);
        }
        if (inode->i_state & I_NEW)
                unlock_new_inode(inode);
        if (lock_flags)
                xfs_iunlock(ip, lock_flags);
        VN_RELE(vp);
}


/*
 * This routine embodies the part of the reclaim code that pulls
 * the inode from the inode hash table and the mount structure's
 * inode list.
 * This should only be called from xfs_reclaim().
 */
void
xfs_ireclaim(xfs_inode_t *ip)
{
        vnode_t         *vp;

        /*
         * Remove from old hash list and mount list.
         */
        XFS_STATS_INC(xs_ig_reclaims);

        xfs_iextract(ip);

        /*
         * Here we do a spurious inode lock in order to coordinate with
         * xfs_sync().  This is because xfs_sync() references the inodes
         * in the mount list without taking references on the corresponding
         * vnodes.  We make that OK here by ensuring that we wait until
         * the inode is unlocked in xfs_sync() before we go ahead and
         * free it.  We get both the regular lock and the io lock because
         * the xfs_sync() code may need to drop the regular one but will
         * still hold the io lock.
         */
        xfs_ilock(ip, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL);

        /*
         * Release dquots (and their references) if any. An inode may escape
         * xfs_inactive and get here via vn_alloc->vn_reclaim path.
         */
        XFS_QM_DQDETACH(ip->i_mount, ip);

        /*
         * Pull our behavior descriptor from the vnode chain.
         */
        vp = XFS_ITOV_NULL(ip);
        if (vp) {
                vn_bhv_remove(VN_BHV_HEAD(vp), XFS_ITOBHV(ip));
        }

        /*
         * Free all memory associated with the inode.
         */
        xfs_idestroy(ip);
}

/*
 * This routine removes an about-to-be-destroyed inode from
 * all of the lists in which it is located with the exception
 * of the behavior chain.
 */
void
xfs_iextract(
        xfs_inode_t     *ip)
{
        xfs_ihash_t     *ih;
        xfs_inode_t     *iq;
        xfs_mount_t     *mp;
        xfs_chash_t     *ch;
        xfs_chashlist_t *chl, *chm;
        SPLDECL(s);

        ih = ip->i_hash;
        write_lock(&ih->ih_lock);
        if ((iq = ip->i_next)) {
                iq->i_prevp = ip->i_prevp;
        }
        *ip->i_prevp = iq;
        ih->ih_version++;
        write_unlock(&ih->ih_lock);

        /*
         * Remove from cluster hash list
         *   1) delete the chashlist if this is the last inode on the chashlist
         *   2) unchain from list of inodes
         *   3) point chashlist->chl_ip to 'chl_next' if to this inode.
         */
        mp = ip->i_mount;
        ch = XFS_CHASH(mp, ip->i_blkno);
        s = mutex_spinlock(&ch->ch_lock);

        if (ip->i_cnext == ip) {
                /* Last inode on chashlist */
                ASSERT(ip->i_cnext == ip && ip->i_cprev == ip);
                ASSERT(ip->i_chash != NULL);
                chm=NULL;
                for (chl = ch->ch_list; chl != NULL; chl = chl->chl_next) {
                        if (chl->chl_blkno == ip->i_blkno) {
                                if (chm == NULL) {
                                        /* first item on the list */
                                        ch->ch_list = chl->chl_next;
                                } else {
                                        chm->chl_next = chl->chl_next;
                                }
                                kmem_zone_free(xfs_chashlist_zone, chl);
                                break;
                        } else {
                                ASSERT(chl->chl_ip != ip);
                                chm = chl;
                        }
                }
                ASSERT_ALWAYS(chl != NULL);
       } else {
                /* delete one inode from a non-empty list */
                iq = ip->i_cnext;
                iq->i_cprev = ip->i_cprev;
                ip->i_cprev->i_cnext = iq;
                if (ip->i_chash->chl_ip == ip) {
                        ip->i_chash->chl_ip = iq;
                }
                ip->i_chash = __return_address;
                ip->i_cprev = __return_address;
                ip->i_cnext = __return_address;
        }
        mutex_spinunlock(&ch->ch_lock, s);

        /*
         * Remove from mount's inode list.
         */
        XFS_MOUNT_ILOCK(mp);
        ASSERT((ip->i_mnext != NULL) && (ip->i_mprev != NULL));
        iq = ip->i_mnext;
        iq->i_mprev = ip->i_mprev;
        ip->i_mprev->i_mnext = iq;

        /*
         * Fix up the head pointer if it points to the inode being deleted.
         */
        if (mp->m_inodes == ip) {
                if (ip == iq) {
                        mp->m_inodes = NULL;
                } else {
                        mp->m_inodes = iq;
                }
        }

        /* Deal with the deleted inodes list */
        list_del_init(&ip->i_reclaim);

        mp->m_ireclaims++;
        XFS_MOUNT_IUNLOCK(mp);
}

/*
 * This is a wrapper routine around the xfs_ilock() routine
 * used to centralize some grungy code.  It is used in places
 * that wish to lock the inode solely for reading the extents.
 * The reason these places can't just call xfs_ilock(SHARED)
 * is that the inode lock also guards to bringing in of the
 * extents from disk for a file in b-tree format.  If the inode
 * is in b-tree format, then we need to lock the inode exclusively
 * until the extents are read in.  Locking it exclusively all
 * the time would limit our parallelism unnecessarily, though.
 * What we do instead is check to see if the extents have been
 * read in yet, and only lock the inode exclusively if they
 * have not.
 *
 * The function returns a value which should be given to the
 * corresponding xfs_iunlock_map_shared().  This value is
 * the mode in which the lock was actually taken.
 */
uint
xfs_ilock_map_shared(
        xfs_inode_t     *ip)
{
        uint    lock_mode;

        if ((ip->i_d.di_format == XFS_DINODE_FMT_BTREE) &&
            ((ip->i_df.if_flags & XFS_IFEXTENTS) == 0)) {
                lock_mode = XFS_ILOCK_EXCL;
        } else {
                lock_mode = XFS_ILOCK_SHARED;
        }

        xfs_ilock(ip, lock_mode);

        return lock_mode;
}

/*
 * This is simply the unlock routine to go with xfs_ilock_map_shared().
 * All it does is call xfs_iunlock() with the given lock_mode.
 */
void
xfs_iunlock_map_shared(
        xfs_inode_t     *ip,
        unsigned int    lock_mode)
{
        xfs_iunlock(ip, lock_mode);
}

/*
 * The xfs inode contains 2 locks: a multi-reader lock called the
 * i_iolock and a multi-reader lock called the i_lock.  This routine
 * allows either or both of the locks to be obtained.
 *
 * The 2 locks should always be ordered so that the IO lock is
 * obtained first in order to prevent deadlock.
 *
 * ip -- the inode being locked
 * lock_flags -- this parameter indicates the inode's locks
 *       to be locked.  It can be:
 *              XFS_IOLOCK_SHARED,
 *              XFS_IOLOCK_EXCL,
 *              XFS_ILOCK_SHARED,
 *              XFS_ILOCK_EXCL,
 *              XFS_IOLOCK_SHARED | XFS_ILOCK_SHARED,
 *              XFS_IOLOCK_SHARED | XFS_ILOCK_EXCL,
 *              XFS_IOLOCK_EXCL | XFS_ILOCK_SHARED,
 *              XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL
 */
void
xfs_ilock(xfs_inode_t   *ip,
          uint          lock_flags)
{
        /*
         * You can't set both SHARED and EXCL for the same lock,
         * and only XFS_IOLOCK_SHARED, XFS_IOLOCK_EXCL, XFS_ILOCK_SHARED,
         * and XFS_ILOCK_EXCL are valid values to set in lock_flags.
         */
        ASSERT((lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) !=
               (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
        ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
               (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
        ASSERT((lock_flags & ~XFS_LOCK_MASK) == 0);

        if (lock_flags & XFS_IOLOCK_EXCL) {
                mrupdate(&ip->i_iolock);
        } else if (lock_flags & XFS_IOLOCK_SHARED) {
                mraccess(&ip->i_iolock);
        }
        if (lock_flags & XFS_ILOCK_EXCL) {
                mrupdate(&ip->i_lock);
        } else if (lock_flags & XFS_ILOCK_SHARED) {
                mraccess(&ip->i_lock);
        }
        xfs_ilock_trace(ip, 1, lock_flags, (inst_t *)__return_address);
}

/*
 * This is just like xfs_ilock(), except that the caller
 * is guaranteed not to sleep.  It returns 1 if it gets
 * the requested locks and 0 otherwise.  If the IO lock is
 * obtained but the inode lock cannot be, then the IO lock
 * is dropped before returning.
 *
 * ip -- the inode being locked
 * lock_flags -- this parameter indicates the inode's locks to be
 *       to be locked.  See the comment for xfs_ilock() for a list
 *       of valid values.
 *
 */
int
xfs_ilock_nowait(xfs_inode_t    *ip,
                 uint           lock_flags)
{
        int     iolocked;
        int     ilocked;

        /*
         * You can't set both SHARED and EXCL for the same lock,
         * and only XFS_IOLOCK_SHARED, XFS_IOLOCK_EXCL, XFS_ILOCK_SHARED,
         * and XFS_ILOCK_EXCL are valid values to set in lock_flags.
         */
        ASSERT((lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) !=
               (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
        ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
               (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
        ASSERT((lock_flags & ~XFS_LOCK_MASK) == 0);

        iolocked = 0;
        if (lock_flags & XFS_IOLOCK_EXCL) {
                iolocked = mrtryupdate(&ip->i_iolock);
                if (!iolocked) {
                        return 0;
                }
        } else if (lock_flags & XFS_IOLOCK_SHARED) {
                iolocked = mrtryaccess(&ip->i_iolock);
                if (!iolocked) {
                        return 0;
                }
        }
        if (lock_flags & XFS_ILOCK_EXCL) {
                ilocked = mrtryupdate(&ip->i_lock);
                if (!ilocked) {
                        if (iolocked) {
                                mrunlock(&ip->i_iolock);
                        }
                        return 0;
                }
        } else if (lock_flags & XFS_ILOCK_SHARED) {
                ilocked = mrtryaccess(&ip->i_lock);
                if (!ilocked) {
                        if (iolocked) {
                                mrunlock(&ip->i_iolock);
                        }
                        return 0;
                }
        }
        xfs_ilock_trace(ip, 2, lock_flags, (inst_t *)__return_address);
        return 1;
}

/*
 * xfs_iunlock() is used to drop the inode locks acquired with
 * xfs_ilock() and xfs_ilock_nowait().  The caller must pass
 * in the flags given to xfs_ilock() or xfs_ilock_nowait() so
 * that we know which locks to drop.
 *
 * ip -- the inode being unlocked
 * lock_flags -- this parameter indicates the inode's locks to be
 *       to be unlocked.  See the comment for xfs_ilock() for a list
 *       of valid values for this parameter.
 *
 */
void
xfs_iunlock(xfs_inode_t *ip,
            uint        lock_flags)
{
        /*
         * You can't set both SHARED and EXCL for the same lock,
         * and only XFS_IOLOCK_SHARED, XFS_IOLOCK_EXCL, XFS_ILOCK_SHARED,
         * and XFS_ILOCK_EXCL are valid values to set in lock_flags.
         */
        ASSERT((lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) !=
               (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
        ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
               (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
        ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_IUNLOCK_NONOTIFY)) == 0);
        ASSERT(lock_flags != 0);

        if (lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) {
                ASSERT(!(lock_flags & XFS_IOLOCK_SHARED) ||
                       (ismrlocked(&ip->i_iolock, MR_ACCESS)));
                ASSERT(!(lock_flags & XFS_IOLOCK_EXCL) ||
                       (ismrlocked(&ip->i_iolock, MR_UPDATE)));
                mrunlock(&ip->i_iolock);
        }

        if (lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) {
                ASSERT(!(lock_flags & XFS_ILOCK_SHARED) ||
                       (ismrlocked(&ip->i_lock, MR_ACCESS)));
                ASSERT(!(lock_flags & XFS_ILOCK_EXCL) ||
                       (ismrlocked(&ip->i_lock, MR_UPDATE)));
                mrunlock(&ip->i_lock);

                /*
                 * Let the AIL know that this item has been unlocked in case
                 * it is in the AIL and anyone is waiting on it.  Don't do
                 * this if the caller has asked us not to.
                 */
                if (!(lock_flags & XFS_IUNLOCK_NONOTIFY) &&
                     ip->i_itemp != NULL) {
                        xfs_trans_unlocked_item(ip->i_mount,
                                                (xfs_log_item_t*)(ip->i_itemp));
                }
        }
        xfs_ilock_trace(ip, 3, lock_flags, (inst_t *)__return_address);
}

/*
 * give up write locks.  the i/o lock cannot be held nested
 * if it is being demoted.
 */
void
xfs_ilock_demote(xfs_inode_t    *ip,
                 uint           lock_flags)
{
        ASSERT(lock_flags & (XFS_IOLOCK_EXCL|XFS_ILOCK_EXCL));
        ASSERT((lock_flags & ~(XFS_IOLOCK_EXCL|XFS_ILOCK_EXCL)) == 0);

        if (lock_flags & XFS_ILOCK_EXCL) {
                ASSERT(ismrlocked(&ip->i_lock, MR_UPDATE));
                mrdemote(&ip->i_lock);
        }
        if (lock_flags & XFS_IOLOCK_EXCL) {
                ASSERT(ismrlocked(&ip->i_iolock, MR_UPDATE));
                mrdemote(&ip->i_iolock);
        }
}

/*
 * The following three routines simply manage the i_flock
 * semaphore embedded in the inode.  This semaphore synchronizes
 * processes attempting to flush the in-core inode back to disk.
 */
void
xfs_iflock(xfs_inode_t *ip)
{
        psema(&(ip->i_flock), PINOD|PLTWAIT);
}

int
xfs_iflock_nowait(xfs_inode_t *ip)
{
        return (cpsema(&(ip->i_flock)));
}

void
xfs_ifunlock(xfs_inode_t *ip)
{
        ASSERT(valusema(&(ip->i_flock)) <= 0);
        vsema(&(ip->i_flock));
}