back out vfs change - todd fries has seen afs issues, and I'm suspicious

this can cause other problems.

6 files changed, 105 insertions, 177 deletions

diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index 6c10bb5f269..aa5978fc664 100644
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vfs_cache.c,v 1.23 2007/05/29 17:33:27 beck Exp $	*/
+/*	$OpenBSD: vfs_cache.c,v 1.24 2007/05/30 04:27:42 beck Exp $	*/
 /*	$NetBSD: vfs_cache.c,v 1.13 1996/02/04 02:18:09 christos Exp $	*/
 
 /*
@@ -69,10 +69,8 @@
  * Structures associated with name caching.
  */
 LIST_HEAD(nchashhead, namecache) *nchashtbl;
-TAILQ_HEAD (, namecache) ncneq;
 u_long	nchash;				/* size of hash table - 1 */
 long	numcache;			/* number of cache entries allocated */
-long	numcachehv;			/* number of holding vnodes */
 TAILQ_HEAD(, namecache) nclruhead;		/* LRU chain */
 struct	nchstats nchstats;		/* cache effectiveness statistics */
 
@@ -131,15 +129,10 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
 	ncpp = &nchashtbl[NCHASH(dvp, cnp)];
 	LIST_FOREACH(ncp, ncpp, nc_hash) {
 		if (ncp->nc_dvp == dvp &&
+		    ncp->nc_dvpid == dvp->v_id &&
 		    ncp->nc_nlen == cnp->cn_namelen &&
-		    !memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen)) {
-#ifdef DIAGNOSTIC
-			if (ncp->nc_dvpid != dvp->v_id)
-				panic("ncp->nc_dvpid %x != dvp->v_id %x\n",
-				ncp->nc_dvpid, dvp->v_id);
-#endif
-				break;
-		}
+		    !memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen))
+			break;
 	}
 	if (ncp == NULL) {
 		nchstats.ncs_miss++;
@@ -166,10 +159,8 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
 			goto remove;
 		}
 	} else if (ncp->nc_vpid != ncp->nc_vp->v_id) {
-#ifdef DIAGNOSTIC
-		panic("ncp->vpid %x != ncp->nc_vp->v_id %x\n", ncp->nc_vpid,
-			ncp->nc_vp->v_id);
-#endif
+		nchstats.ncs_falsehits++;
+		goto remove;
 	}
 
 	vp = ncp->nc_vp;
@@ -210,10 +201,8 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
 	 */
 	if (error || vpid != vp->v_id) {
 		if (!error) {
-#ifdef DIAGNOSTIC
-			panic("vpid %x != vp->vid %x\n", vpid, vp->v_id);
 			vput(vp);
-#endif
+			nchstats.ncs_falsehits++;
 		} else
 			nchstats.ncs_badhits++;
 		/*
@@ -247,7 +236,17 @@ remove:
 	 * the cache entry is invalid, or otherwise don't
 	 * want cache entry to exist.
 	 */
-	cache_delete(ncp);
+	TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
+	LIST_REMOVE(ncp, nc_hash);
+	ncp->nc_hash.le_prev = NULL;
+
+	if (ncp->nc_vhash.le_prev != NULL) {
+		LIST_REMOVE(ncp, nc_vhash);
+		ncp->nc_vhash.le_prev = NULL;
+	}
+
+	pool_put(&nch_pool, ncp);
+	numcache--;
 	return (-1);
 }
 
@@ -281,13 +280,12 @@ cache_revlookup(struct vnode *vp, struct vnode **dvpp, char **bpp, char *bufp)
 
 	LIST_FOREACH(ncp, nvcpp, nc_vhash) {
 		if (ncp->nc_vp == vp &&
+		    ncp->nc_vpid == vp->v_id &&
 		    (dvp = ncp->nc_dvp) != NULL &&
 		    /* avoid pesky '.' entries.. */
 		    dvp != vp && ncp->nc_dvpid == dvp->v_id) {
+
 #ifdef DIAGNOSTIC
-			if (ncp->nc_vpid != vp->v_id)
-				panic("ncp->nc_vpid %x != vp->v_id %x\n",
-				ncp->nc_vpid, vp->v_id);
 			if (ncp->nc_nlen == 1 &&
 			    ncp->nc_name[0] == '.')
 				panic("cache_revlookup: found entry for .");
@@ -340,7 +338,6 @@ cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
 	struct namecache *ncp;
 	struct nchashhead *ncpp;
 	struct ncvhashhead *nvcpp;
-	int hold = 0;
 
 	if (!doingcache || cnp->cn_namelen > NCHNAMLEN)
 		return;
@@ -348,13 +345,22 @@ cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
 	/*
 	 * Free the cache slot at head of lru chain.
 	 */
-	while ((numcache >= desiredvnodes) &&
-		((ncp = TAILQ_FIRST(&nclruhead)) != NULL)){
-		cache_delete(ncp);
-	}
-	ncp = pool_get(&nch_pool, PR_WAITOK);
-	bzero((char *)ncp, sizeof *ncp);
-	numcache++;
+	if (numcache < desiredvnodes) {
+		ncp = pool_get(&nch_pool, PR_WAITOK);
+		bzero((char *)ncp, sizeof *ncp);
+		numcache++;
+	} else if ((ncp = TAILQ_FIRST(&nclruhead)) != NULL) {
+		TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
+		if (ncp->nc_hash.le_prev != NULL) {
+			LIST_REMOVE(ncp, nc_hash);
+			ncp->nc_hash.le_prev = NULL;
+		}
+		if (ncp->nc_vhash.le_prev != NULL) {
+			LIST_REMOVE(ncp, nc_vhash);
+			ncp->nc_vhash.le_prev = NULL;
+		}
+	} else
+		return;
 	/* grab the vnode we just found */
 	ncp->nc_vp = vp;
 	if (vp)
@@ -368,15 +374,6 @@ cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
 	ncpp = &nchashtbl[NCHASH(dvp, cnp)];
 	LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
 
-	/* record references to us in various vnodes... */
-	if (LIST_EMPTY(&dvp->v_cache_src)) {
-		hold = 1;
-		numcachehv++;
-	}
-	LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
-	if (vp)
-		TAILQ_INSERT_HEAD(&vp->v_cache_dst, ncp, nc_dst);
-
 	/*
 	 * Create reverse-cache entries (used in getcwd) for
 	 * directories.
@@ -392,8 +389,6 @@ cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
 		nvcpp = &ncvhashtbl[NCVHASH(vp)];
 		LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash);
 	}
-	if (hold)
-		vhold(dvp);
 }
 
 /*
@@ -402,6 +397,7 @@ cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
 void
 nchinit(void)
 {
+
 	TAILQ_INIT(&nclruhead);
 	nchashtbl = hashinit(desiredvnodes, M_CACHE, M_WAITOK, &nchash);
 	ncvhashtbl = hashinit(desiredvnodes/8, M_CACHE, M_WAITOK, &ncvhash);
@@ -409,45 +405,6 @@ nchinit(void)
 	    &pool_allocator_nointr);
 }
 
-void
-cache_delete (struct namecache *ncp)
-{
-	/*
-	 * just make it go away...
-	 */
-	struct vnode *vp = NULL;
-	/* 
-	 * XXX abuse of the queue macro internals is endemic to this
-	 * and needs fixing - for now this is inherited from earlier evil.
-	 */
-	if (ncp->nc_lru.tqe_prev != NULL) {
-		TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
-		ncp->nc_lru.tqe_prev = NULL;
-	}
-	if (ncp->nc_hash.le_prev != NULL) { 
-		LIST_REMOVE(ncp, nc_hash);
-		ncp->nc_hash.le_prev = NULL;
-	}
-	if (ncp->nc_vhash.le_prev != NULL) {
-		LIST_REMOVE(ncp, nc_vhash);
-		ncp->nc_vhash.le_prev = NULL;
-	}
-	LIST_REMOVE(ncp, nc_src);
-	if (LIST_EMPTY(&ncp->nc_dvp->v_cache_src)) {
-		vp = ncp->nc_dvp;
-		numcachehv--;
-	}
-	if (ncp->nc_vp)
-		TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst, ncp, nc_dst);
-	ncp->nc_vp = NULL;
-	ncp->nc_dvp = NULL;
-	pool_put(&nch_pool, ncp);
-	numcache--;
-	if (vp) {
-		vdrop(vp);
-	}
-}
-
 /*
  * Cache flush, a particular vnode; called when a vnode is renamed to
  * hide entries that would now be invalid
@@ -458,12 +415,6 @@ cache_purge(struct vnode *vp)
 	struct namecache *ncp;
 	struct nchashhead *ncpp;
 
-	while (!LIST_EMPTY(&vp->v_cache_src)) {
-		cache_delete(LIST_FIRST(&vp->v_cache_src));
-	}
-	while (!TAILQ_EMPTY(&vp->v_cache_dst)) {
-		cache_delete(TAILQ_FIRST(&vp->v_cache_dst));
-	}
 	vp->v_id = ++nextvnodeid;
 	if (nextvnodeid != 0)
 		return;
@@ -491,6 +442,18 @@ cache_purgevfs(struct mount *mp)
 		if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp)
 			continue;
 		/* free the resources we had */
-		cache_delete(ncp);
+		ncp->nc_vp = NULL;
+		ncp->nc_dvp = NULL;
+		TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
+		if (ncp->nc_hash.le_prev != NULL) {
+			LIST_REMOVE(ncp, nc_hash);
+			ncp->nc_hash.le_prev = NULL;
+		}
+		if (ncp->nc_vhash.le_prev != NULL) {
+			LIST_REMOVE(ncp, nc_vhash);
+			ncp->nc_vhash.le_prev = NULL;
+		}
+		pool_put(&nch_pool, ncp);
+		numcache--;
 	}
 }
diff --git a/sys/kern/vfs_getcwd.c b/sys/kern/vfs_getcwd.c
index d05b3ba609b..99c52dfe584 100644
--- a/sys/kern/vfs_getcwd.c
+++ b/sys/kern/vfs_getcwd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: vfs_getcwd.c,v 1.10 2007/05/29 05:28:53 beck Exp $ */
+/* $OpenBSD: vfs_getcwd.c,v 1.11 2007/05/30 04:27:42 beck Exp $ */
 /* $NetBSD: vfs_getcwd.c,v 1.3.2.3 1999/07/11 10:24:09 sommerfeld Exp $ */
 
 /*
@@ -239,17 +239,17 @@ vfs_getcwd_getcache(struct vnode **lvpp, struct vnode **uvpp, char **bpp,
 	if (error)
 		*uvpp = NULL;
 
-
-#ifdef DIAGNOSTIC
-	/* XXX should not happen with vhold/vdrop in cache layer now. */
-	if (vpid != uvp->v_id)
-		panic("vpid %d != uvp->v_id %d\n");
-#endif
-	if (error) {
+	/*
+	 * Verify that vget() succeeded, and check that vnode capability
+	 * didn't change while we were waiting for the lock.
+	 */
+	if (error || (vpid != uvp->v_id)) {
 		/*
 		 * Try to get our lock back. If that works, tell the caller to
 		 * try things the hard way, otherwise give up.
 		 */
+		if (!error)
+			vput(uvp);
 
 		*uvpp = NULL;
 		
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 0a5ce5265dd..0aec0ef126d 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vfs_subr.c,v 1.150 2007/05/29 05:28:54 beck Exp $	*/
+/*	$OpenBSD: vfs_subr.c,v 1.151 2007/05/30 04:27:42 beck Exp $	*/
 /*	$NetBSD: vfs_subr.c,v 1.53 1996/04/22 01:39:13 christos Exp $	*/
 
 /*
@@ -339,50 +339,47 @@ getnewvnode(enum vtagtype tag, struct mount *mp, int (**vops)(void *),
 {
 	struct proc *p = curproc;
 	struct freelst *listhd;
+	static int toggle;
 	struct vnode *vp;
 	int s;
 
 	/*
-	 * Allocate a new vnode if we have less than the desired
-	 * number allocated, otherwise, recycle one. Generally we only
+	 * We must choose whether to allocate a new vnode or recycle an
+	 * existing one. The criterion for allocating a new one is that
+	 * the total number of vnodes is less than the number desired or
+	 * there are no vnodes on either free list. Generally we only
 	 * want to recycle vnodes that have no buffers associated with
-	 * them, so we look first on the vnode_free_list. If it is
-	 * empty, we next consider vnodes with referencing buffers on
-	 * the vnode_hold_list. We are reticent to recycle vnodes from
-	 * the vnode_hold_list because we will lose the identity of
-	 * all its referencing buffers.
+	 * them, so we look first on the vnode_free_list. If it is empty,
+	 * we next consider vnodes with referencing buffers on the
+	 * vnode_hold_list. The toggle ensures that half the time we
+	 * will use a buffer from the vnode_hold_list, and half the time
+	 * we will allocate a new one unless the list has grown to twice
+	 * the desired size. We are reticent to recycle vnodes from the
+	 * vnode_hold_list because we will lose the identity of all its
+	 * referencing buffers.
 	 */
-	simple_lock(&vnode_free_list_slock);
+	toggle ^= 1;
+	if (numvnodes > 2 * desiredvnodes)
+		toggle = 0;
+
 	s = splbio();
-	if (numvnodes < desiredvnodes) {
+	if ((numvnodes < desiredvnodes) ||
+	    ((TAILQ_FIRST(listhd = &vnode_free_list) == NULL) &&
+	    ((TAILQ_FIRST(listhd = &vnode_hold_list) == NULL) || toggle))) {
 		splx(s);
 		vp = pool_get(&vnode_pool, PR_WAITOK);
 		bzero((char *)vp, sizeof *vp);
-		LIST_INIT(&vp->v_cache_src);
-		TAILQ_INIT(&vp->v_cache_dst);
 		numvnodes++;
 	} else {
-		for (vp = TAILQ_FIRST(listhd = &vnode_free_list); vp != NULLVP;
+		for (vp = TAILQ_FIRST(listhd); vp != NULLVP;
 		    vp = TAILQ_NEXT(vp, v_freelist)) {
 			if (VOP_ISLOCKED(vp) == 0)
 				break;
 		}
-		/* 
-		 * There is nothing on the free list, so we have to try to
-		 * recycle one off the hold list
-		 */
-		if (vp == NULL) {
-			for (vp = TAILQ_FIRST(listhd = &vnode_hold_list);
-			    vp != NULLVP;
-			    vp = TAILQ_NEXT(vp, v_freelist)) {
-				if ((VOP_ISLOCKED(vp) == 0) && (vp->v_holdcnt == 0))
-					break;
-			}
-		}
 		/*
-		 * We have made a pass through both the free and hold list
-		 * and not encountered an unlocked entry. So this is close
-		 * enough to being empty.
+		 * Unless this is a bad time of the month, at most
+		 * the first NCPUS items on the free list are
+		 * locked, so this is close enough to being empty.
 		 */
 		if (vp == NULL) {
 			splx(s);
@@ -396,11 +393,6 @@ getnewvnode(enum vtagtype tag, struct mount *mp, int (**vops)(void *),
 			vprint("free vnode", vp);
 			panic("free vnode isn't");
 		}
-
-		if (vp->v_holdcnt) {
-			vprint("held vnode", vp);
-			panic("unheld vnode being held!");
-		}
 #endif
 
 		TAILQ_REMOVE(listhd, vp, v_freelist);
@@ -766,7 +758,7 @@ vrele(struct vnode *vp)
 void vhold(struct vnode *vp);
 
 /*
- * declare interest in a vnode.
+ * Page or buffer structure gets a reference.
  */
 void
 vhold(struct vnode *vp)
@@ -783,27 +775,6 @@ vhold(struct vnode *vp)
 	vp->v_holdcnt++;
 }
 
-void vdrop(struct vnode *vp);
-
-/*
- * lose interest in a vnode
- */
-void
-vdrop(struct vnode *vp)
-{
-	vp->v_holdcnt--;
-
-	/*
-	 * If it is on the holdlist and the hold count drops to
-	 * zero, move it to the free list.
-	 */
-	if ((vp->v_bioflag & VBIOONFREELIST) &&
-	    vp->v_holdcnt == 0 && vp->v_usecount == 0) {
-		TAILQ_REMOVE(&vnode_hold_list, vp, v_freelist);
-		TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_freelist);
-	}
-}
-
 /*
  * Remove any vnodes in the vnode table belonging to mount point mp.
  *
@@ -2022,7 +1993,17 @@ brelvp(struct buf *bp)
 	if (vp->v_holdcnt == 0)
 		panic("brelvp: holdcnt");
 #endif
-	vdrop(vp);
+	vp->v_holdcnt--;
+
+	/*
+	 * If it is on the holdlist and the hold count drops to
+	 * zero, move it to the free list.
+	 */
+	if ((vp->v_bioflag & VBIOONFREELIST) &&
+	    vp->v_holdcnt == 0 && vp->v_usecount == 0) {
+		TAILQ_REMOVE(&vnode_hold_list, vp, v_freelist);
+		TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_freelist);
+	}
 }
 
 /*
diff --git a/sys/sys/namei.h b/sys/sys/namei.h
index 2cbdfff7538..83cf2ff28b8 100644
--- a/sys/sys/namei.h
+++ b/sys/sys/namei.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: namei.h,v 1.17 2007/05/29 05:28:54 beck Exp $	*/
+/*	$OpenBSD: namei.h,v 1.18 2007/05/30 04:27:43 beck Exp $	*/
 /*	$NetBSD: namei.h,v 1.11 1996/02/09 18:25:20 christos Exp $	*/
 
 /*
@@ -161,8 +161,6 @@ struct	namecache {
 	LIST_ENTRY(namecache) nc_hash;	/* hash chain */
 	LIST_ENTRY(namecache) nc_vhash;	/* (reverse) directory hash chain */
 	TAILQ_ENTRY(namecache) nc_lru;	/* LRU chain */
-	LIST_ENTRY(namecache) nc_src;	/* source vnodes */
-	TAILQ_ENTRY(namecache) nc_dst;	/* destination vnodes */
 	struct	vnode *nc_dvp;		/* vnode of parent of name */
 	u_long	nc_dvpid;		/* capability number of nc_dvp */
 	struct	vnode *nc_vp;		/* vnode the name refers to */
@@ -177,7 +175,6 @@ int	namei(struct nameidata *ndp);
 int	lookup(struct nameidata *ndp);
 int	relookup(struct vnode *dvp, struct vnode **vpp,
 		      struct componentname *cnp);
-void cache_delete(struct namecache *);
 void cache_purge(struct vnode *);
 int cache_lookup(struct vnode *, struct vnode **, struct componentname *);
 void cache_enter(struct vnode *, struct vnode *, struct componentname *);
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index 37d0654dd4b..bccd2357db3 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vnode.h,v 1.84 2007/05/29 16:25:07 thib Exp $	*/
+/*	$OpenBSD: vnode.h,v 1.85 2007/05/30 04:27:43 beck Exp $	*/
 /*	$NetBSD: vnode.h,v 1.38 1996/02/29 20:59:05 cgd Exp $	*/
 
 /*
@@ -91,8 +91,6 @@ struct vnode {
 	u_int   v_bioflag;
 	u_int   v_holdcnt;			/* buffer references */
 	u_int   v_id;				/* capability identifier */
-	LIST_HEAD(, namecache) v_cache_src;	/* cache entries from us */
-	TAILQ_HEAD(, namecache) v_cache_dst;	/* cache entries to us */
 	struct	mount *v_mount;			/* ptr to vfs we are in */
 	TAILQ_ENTRY(vnode) v_freelist;		/* vnode freelist */
 	LIST_ENTRY(vnode) v_mntvnodes;		/* vnodes for mount point */
@@ -407,8 +405,6 @@ void	vntblinit(void);
 int	vwaitforio(struct vnode *, int, char *, int);
 void	vwakeup(struct vnode *);
 void	vput(struct vnode *);
-void	vhold(struct vnode *);
-void	vdrop(struct vnode *);
 int	vrecycle(struct vnode *, struct proc *);
 void	vrele(struct vnode *);
 void	vref(struct vnode *);
diff --git a/sys/xfs/xfs_node-bsd.c b/sys/xfs/xfs_node-bsd.c
index 0ceea050e63..56e4f2d3638 100644
--- a/sys/xfs/xfs_node-bsd.c
+++ b/sys/xfs/xfs_node-bsd.c
@@ -420,8 +420,6 @@ static struct long_entry tbl;
 static void
 tbl_clear (void)
 {
-    vdrop(tbl.vp);
-    vdrop(tbl.dvp);  
     tbl.dvp = tbl.vp = NULL;
     tbl.name[0] = '\0';
     tbl.len = 0;
@@ -435,8 +433,6 @@ tbl_clear (void)
 static void
 tbl_enter (size_t len, const char *name, struct vnode *dvp, struct vnode *vp)
 {
-    vhold(vp);
-    vhold(dvp);  
     tbl.len = len;
     bcopy(name, tbl.name, len);
     tbl.dvp = dvp;
@@ -457,15 +453,10 @@ tbl_lookup (struct componentname *cnp,
 {
     if (tbl.dvp == dvp
 	&& tbl.len == cnp->cn_namelen
-	&& strncmp(tbl.name, cnp->cn_nameptr, tbl.len) == 0) {
-#ifdef DIAGNOSTIC
-	if (tbl.vpid != tbl.vp->v_id)
-		panic("tbl.vpid %x != tbl.vp->v_id %x", tbl.vpid,
-		    tbl.vp->v_id);
-	if (tbl.dvpid != tbl.dvp->v_id)
-		panic("tbl.dvpid %x != tbl.dvp->v_id %x", tbl.dvpid,
-		    tbl.dvp->v_id);
-#endif
+	&& strncmp(tbl.name, cnp->cn_nameptr, tbl.len) == 0
+	&& tbl.dvpid == tbl.dvp->v_id
+	&& tbl.vpid == tbl.vp->v_id) {
+
 	*res = tbl.vp;
 	return -1;
     } else
@@ -676,10 +667,10 @@ xfs_dnlc_lock(struct vnode *dvp,
 	xfs_vfs_writelock(dvp, xfs_cnp_to_proc(cnp));
 #endif
 
-#ifdef DIAGNOSTIC
-	if (dvp->v_id != vpid)
-		panic("dvp->v_id %x != vpid %x", dvp->v_id, vpid);
-#endif	
+	if (error == 0 && dvp->v_id != vpid) {
+	    vput(*res);
+	    return 0;
+	}
     } else {
 #ifdef HAVE_FREEBSD_THREAD
 	error = xfs_do_vget(*res, LK_EXCLUSIVE, xfs_cnp_to_thread(cnp));