linux/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"

/*
 * 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 | KM_LARGE;

	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 | KM_LARGE);
	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(
	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_ihash_t	*ih;
	xfs_inode_t	*ip;
	xfs_inode_t	*iq;
	bhv_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 = 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(&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 & XFS_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,
			  (flags & XFS_IGET_BULKSTAT) ? XFS_IMAP_BULKSTAT : 0);
	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)
		xfs_ilock(ip, lock_flags);

	if ((ip->i_d.di_mode == 0) && !(flags & XFS_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;
			if (ch->ch_list)
				ch->ch_list->chl_prev = chlnew;
			chlnew->chl_next = ch->ch_list;
			chlnew->chl_prev = NULL;
			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.
	 */
	bhv_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;
	bhv_vnode_t	*vp = NULL;
	int		error;

	XFS_STATS_INC(xs_ig_attempts);

retry:
	if ((inode = iget_locked(XFS_MTOVFS(mp)->vfs_super, ino))) {
		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", (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)
{
	bhv_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)
{
	bhv_vnode_t	*vp = XFS_ITOV(ip);
	struct inode	*inode = vn_to_inode(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)
{
	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_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;
		chl = ip->i_chash;
		if (chl->chl_prev)
			chl->chl_prev->chl_next = chl->chl_next;
		else
			ch->ch_list = chl->chl_next;
		if (chl->chl_next)
			chl->chl_next->chl_prev = chl->chl_prev;
		kmem_zone_free(xfs_chashlist_zone, chl);
	} 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(issemalocked(&(ip->i_flock)));
	vsema(&(ip->i_flock));
}