Merge git://git.kernel.org/pub/scm/linux/kernel/git/sam/x86

[linux-2.6/verdex.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_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_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"

/*
 * Look up an inode by number in the given file system.
 * The inode is looked up in the cache held in each AG.
 * If the inode is found in the cache, attach it to the provided
 * vnode.
 *
 * If it is not in core, read it in from the file system's device,
 * add it to the cache and attach the provided vnode.
 *
 * 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(
        bhv_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_inode_t     *ip;
        xfs_inode_t     *iq;
        bhv_vnode_t     *inode_vp;
        int             error;
        xfs_icluster_t  *icl, *new_icl = NULL;
        unsigned long   first_index, mask;
        xfs_perag_t     *pag;
        xfs_agino_t     agino;

        /* the radix tree exists only in inode capable AGs */
        if (XFS_INO_TO_AGNO(mp, ino) >= mp->m_maxagi)
                return EINVAL;

        /* get the perag structure and ensure that it's inode capable */
        pag = xfs_get_perag(mp, ino);
        if (!pag->pagi_inodeok)
                return EINVAL;
        ASSERT(pag->pag_ici_init);
        agino = XFS_INO_TO_AGINO(mp, ino);

again:
        read_lock(&pag->pag_ici_lock);
        ip = radix_tree_lookup(&pag->pag_ici_root, agino);

        if (ip != NULL) {
                /*
                 * If INEW is set this inode is being set up
                 * we need to pause and try again.
                 */
                if (xfs_iflags_test(ip, XFS_INEW)) {
                        read_unlock(&pag->pag_ici_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 (xfs_iflags_test(ip, XFS_IRECLAIM)) {
                                read_unlock(&pag->pag_ici_lock);
                                delay(1);
                                XFS_STATS_INC(xs_ig_frecycle);

                                goto again;
                        }
                        ASSERT(xfs_iflags_test(ip, XFS_IRECLAIMABLE));

                        /*
                         * If lookup is racing with unlink, then we
                         * should return an error immediately so we
                         * don't remove it from the reclaim list and
                         * potentially leak the inode.
                         */
                        if ((ip->i_d.di_mode == 0) &&
                            !(flags & XFS_IGET_CREATE)) {
                                read_unlock(&pag->pag_ici_lock);
                                xfs_put_perag(mp, pag);
                                return ENOENT;
                        }

                        /*
                         * There may be transactions sitting in the
                         * incore log buffers or being flushed to disk
                         * at this time.  We can't clear the
                         * XFS_IRECLAIMABLE flag until these
                         * transactions have hit the disk, otherwise we
                         * will void the guarantee the flag provides
                         * xfs_iunpin()
                         */
                        if (xfs_ipincount(ip)) {
                                read_unlock(&pag->pag_ici_lock);
                                xfs_log_force(mp, 0,
                                        XFS_LOG_FORCE|XFS_LOG_SYNC);
                                XFS_STATS_INC(xs_ig_frecycle);
                                goto again;
                        }

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

                        XFS_STATS_INC(xs_ig_found);

                        xfs_iflags_clear(ip, XFS_IRECLAIMABLE);
                        read_unlock(&pag->pag_ici_lock);

                        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 = vn_to_inode(inode_vp);

                        /* The inode is being torn down, pause and
                         * try again.
                         */
                        if (inode->i_state & (I_FREEING | I_CLEAR)) {
                                read_unlock(&pag->pag_ici_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
                 */
                read_unlock(&pag->pag_ici_lock);
                XFS_STATS_INC(xs_ig_found);

finish_inode:
                if (ip->i_d.di_mode == 0) {
                        if (!(flags & XFS_IGET_CREATE)) {
                                xfs_put_perag(mp, pag);
                                return ENOENT;
                        }
                        xfs_iocore_inode_reinit(ip);
                }

                if (lock_flags != 0)
                        xfs_ilock(ip, lock_flags);

                xfs_iflags_clear(ip, XFS_ISTALE);
                vn_trace_exit(ip, "xfs_iget.found",
                                        (inst_t *)__return_address);
                goto return_ip;
        }

        /*
         * Inode cache miss
         */
        read_unlock(&pag->pag_ici_lock);
        XFS_STATS_INC(xs_ig_missed);

        /*
         * 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,
                          (flags & XFS_IGET_BULKSTAT) ? XFS_IMAP_BULKSTAT : 0);
        if (error) {
                xfs_put_perag(mp, pag);
                return error;
        }

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

        xfs_inode_lock_init(ip, vp);
        xfs_iocore_inode_init(ip);
        if (lock_flags)
                xfs_ilock(ip, lock_flags);

        if ((ip->i_d.di_mode == 0) && !(flags & XFS_IGET_CREATE)) {
                xfs_idestroy(ip);
                xfs_put_perag(mp, pag);
                return ENOENT;
        }

        /*
         * This is a bit messy - we preallocate everything we _might_
         * need before we pick up the ici lock. That way we don't have to
         * juggle locks and go all the way back to the start.
         */
        new_icl = kmem_zone_alloc(xfs_icluster_zone, KM_SLEEP);
        if (radix_tree_preload(GFP_KERNEL)) {
                delay(1);
                goto again;
        }
        mask = ~(((XFS_INODE_CLUSTER_SIZE(mp) >> mp->m_sb.sb_inodelog)) - 1);
        first_index = agino & mask;
        write_lock(&pag->pag_ici_lock);

        /*
         * Find the cluster if it exists
         */
        icl = NULL;
        if (radix_tree_gang_lookup(&pag->pag_ici_root, (void**)&iq,
                                                        first_index, 1)) {
                if ((iq->i_ino & mask) == first_index)
                        icl = iq->i_cluster;
        }

        /*
         * insert the new inode
         */
        error = radix_tree_insert(&pag->pag_ici_root, agino, ip);
        if (unlikely(error)) {
                BUG_ON(error != -EEXIST);
                write_unlock(&pag->pag_ici_lock);
                radix_tree_preload_end();
                xfs_idestroy(ip);
                XFS_STATS_INC(xs_ig_dup);
                goto again;
        }

        /*
         * These values _must_ be set before releasing ihlock!
         */
        ip->i_udquot = ip->i_gdquot = NULL;
        xfs_iflags_set(ip, XFS_INEW);

        ASSERT(ip->i_cluster == NULL);

        if (!icl) {
                spin_lock_init(&new_icl->icl_lock);
                INIT_HLIST_HEAD(&new_icl->icl_inodes);
                icl = new_icl;
                new_icl = NULL;
        } else {
                ASSERT(!hlist_empty(&icl->icl_inodes));
        }
        spin_lock(&icl->icl_lock);
        hlist_add_head(&ip->i_cnode, &icl->icl_inodes);
        ip->i_cluster = icl;
        spin_unlock(&icl->icl_lock);

        write_unlock(&pag->pag_ici_lock);
        radix_tree_preload_end();
        if (new_icl)
                kmem_zone_free(xfs_icluster_zone, new_icl);

        /*
         * 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);
        xfs_put_perag(mp, pag);

 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));

        xfs_iflags_set(ip, XFS_IMODIFIED);
        *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.
         */
        xfs_initialize_vnode(mp, vp, ip);
        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;
        bhv_vnode_t     *vp = NULL;
        int             error;

        XFS_STATS_INC(xs_ig_attempts);

retry:
        inode = iget_locked(mp->m_super, ino);
        if (inode) {
                xfs_inode_t     *ip;

                vp = vn_from_inode(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 mismatches 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) ||
                            ((ip = xfs_vtoi(vp)) == NULL)) {
                                iput(inode);
                                delay(1);
                                goto retry;
                        }

                        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,
        bhv_vnode_t     *vp)
{
        mrlock_init(&ip->i_lock, MRLOCK_ALLOW_EQUAL_PRI|MRLOCK_BARRIER,
                     "xfsino", ip->i_ino);
        mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);
        init_waitqueue_head(&ip->i_ipin_wait);
        atomic_set(&ip->i_pincount, 0);
        initnsema(&ip->i_flock, 1, "xfsfino");
}

/*
 * 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_inode_t     *ip;
        xfs_perag_t     *pag;

        pag = xfs_get_perag(mp, ino);
        read_lock(&pag->pag_ici_lock);
        ip = radix_tree_lookup(&pag->pag_ici_root, XFS_INO_TO_AGINO(mp, ino));
        read_unlock(&pag->pag_ici_lock);
        xfs_put_perag(mp, pag);

        /* the returned inode must match the transaction */
        if (ip && (ip->i_transp != tp))
                return NULL;
        return ip;
}

/*
 * 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)
{
        bhv_vnode_t     *vp = XFS_ITOV(ip);

        vn_trace_entry(ip, "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)
{
        bhv_vnode_t     *vp = XFS_ITOV(ip);
        struct inode    *inode = vn_to_inode(vp);

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

        if ((ip->i_d.di_mode == 0)) {
                ASSERT(!xfs_iflags_test(ip, 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)
{
        bhv_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_to_inode(vp)->i_private = NULL;
                ip->i_vnode = NULL;
        }

        /*
         * Free all memory associated with the inode.
         */
        xfs_iunlock(ip, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL);
        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_mount_t     *mp = ip->i_mount;
        xfs_perag_t     *pag = xfs_get_perag(mp, ip->i_ino);
        xfs_inode_t     *iq;

        write_lock(&pag->pag_ici_lock);
        radix_tree_delete(&pag->pag_ici_root, XFS_INO_TO_AGINO(mp, ip->i_ino));
        write_unlock(&pag->pag_ici_lock);
        xfs_put_perag(mp, pag);

        /*
         * Remove from cluster list
         */
        mp = ip->i_mount;
        spin_lock(&ip->i_cluster->icl_lock);
        hlist_del(&ip->i_cnode);
        spin_unlock(&ip->i_cluster->icl_lock);

        /* was last inode in cluster? */
        if (hlist_empty(&ip->i_cluster->icl_inodes))
                kmem_zone_free(xfs_icluster_zone, ip->i_cluster);

        /*
         * 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 | XFS_LOCK_DEP_MASK)) == 0);

        if (lock_flags & XFS_IOLOCK_EXCL) {
                mrupdate_nested(&ip->i_iolock, XFS_IOLOCK_DEP(lock_flags));
        } else if (lock_flags & XFS_IOLOCK_SHARED) {
                mraccess_nested(&ip->i_iolock, XFS_IOLOCK_DEP(lock_flags));
        }
        if (lock_flags & XFS_ILOCK_EXCL) {
                mrupdate_nested(&ip->i_lock, XFS_ILOCK_DEP(lock_flags));
        } else if (lock_flags & XFS_ILOCK_SHARED) {
                mraccess_nested(&ip->i_lock, XFS_ILOCK_DEP(lock_flags));
        }
        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 | XFS_LOCK_DEP_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 |
                        XFS_LOCK_DEP_MASK)) == 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(issemalocked(&(ip->i_flock)));
        vsema(&(ip->i_flock));
}