diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -400,12 +400,6 @@
  */
 uma_zone_t buf_zone;
 
-/*
- * Single global constant for BUF_WMESG, to avoid getting multiple references.
- * buf_wmesg is referred from macros.
- */
-const char *buf_wmesg = BUF_WMESG;
-
 static int
 sysctl_runningspace(SYSCTL_HANDLER_ARGS)
 {
@@ -1184,6 +1178,12 @@
 	return (v);
 }
 
+/*
+ * Single global constant for BUF_WMESG, to avoid getting multiple
+ * references.
+ */
+static const char buf_wmesg[] = "bufwait";
+
 /* Initialize the buffer subsystem.  Called before use of any buffers. */
 void
 bufinit(void)
@@ -1214,7 +1214,7 @@
 		bp->b_xflags = 0;
 		bp->b_data = bp->b_kvabase = unmapped_buf;
 		LIST_INIT(&bp->b_dep);
-		BUF_LOCKINIT(bp);
+		BUF_LOCKINIT(bp, buf_wmesg);
 		bq_insert(&bqempty, bp, false);
 	}
 
@@ -1718,7 +1718,7 @@
 	if (freebufs == bd->bd_lofreebuffers)
 		bufspace_daemon_wakeup(bd);
 
-	error = BUF_LOCK(bp, LK_EXCLUSIVE, NULL);
+	error = BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL);
 	KASSERT(error == 0, ("%s: BUF_LOCK on free buf %p: %d.", __func__, bp,
 	    error));
 	(void)error;
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -5059,10 +5059,7 @@
 	 */
 	if (vfs_busy(mp, MBF_NOWAIT) != 0)
 		return (0);
-	if (vn_start_write(NULL, &mp, V_NOWAIT) != 0) {
-		vfs_unbusy(mp);
-		return (0);
-	}
+	VOP_UNLOCK(syncvp);
 	save = curthread_pflags_set(TDP_SYNCIO);
 	/*
 	 * The filesystem at hand may be idle with free vnodes stored in the
@@ -5071,7 +5068,7 @@
 	vfs_periodic(mp, MNT_NOWAIT);
 	error = VFS_SYNC(mp, MNT_LAZY);
 	curthread_pflags_restore(save);
-	vn_finished_write(mp);
+	vn_lock(syncvp, LK_EXCLUSIVE | LK_RETRY);
 	vfs_unbusy(mp);
 	return (error);
 }
diff --git a/sys/sys/buf.h b/sys/sys/buf.h
--- a/sys/sys/buf.h
+++ b/sys/sys/buf.h
@@ -292,16 +292,14 @@
 /*
  * Buffer locking
  */
-extern const char *buf_wmesg;		/* Default buffer lock message */
-#define BUF_WMESG "bufwait"
 #include <sys/proc.h>			/* XXX for curthread */
 #include <sys/mutex.h>
 
 /*
  * Initialize a lock.
  */
-#define BUF_LOCKINIT(bp)						\
-	lockinit(&(bp)->b_lock, PRIBIO + 4, buf_wmesg, 0, LK_NEW)
+#define BUF_LOCKINIT(bp, wmesg)						\
+	lockinit(&(bp)->b_lock, PRIBIO + 4, wmesg, 0, LK_NEW)
 /*
  *
  * Get a lock sleeping non-interruptably until it becomes available.
diff --git a/sys/ufs/ffs/ffs_inode.c b/sys/ufs/ffs/ffs_inode.c
--- a/sys/ufs/ffs/ffs_inode.c
+++ b/sys/ufs/ffs/ffs_inode.c
@@ -179,7 +179,7 @@
 		pause("ffsupd", 1);
 		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 		vrele(vp);
-		if (VN_IS_DOOMED(vp))
+		if (!IS_UFS(vp))
 			return (ENOENT);
 
 		/*
diff --git a/sys/ufs/ffs/ffs_snapshot.c b/sys/ufs/ffs/ffs_snapshot.c
--- a/sys/ufs/ffs/ffs_snapshot.c
+++ b/sys/ufs/ffs/ffs_snapshot.c
@@ -1809,9 +1809,15 @@
 		VI_UNLOCK(devvp);
 		return (0);
 	}
+
+	/*
+	 * Use LK_SLEEPFAIL because sn might be freed under us while
+	 * both devvp interlock and snaplk are not owned.
+	 */
 	if (lockmgr(&sn->sn_lock, LK_INTERLOCK | LK_EXCLUSIVE | LK_SLEEPFAIL,
 	    VI_MTX(devvp)) != 0)
 		goto retry;
+
 	TAILQ_FOREACH(ip, &sn->sn_head, i_nextsnap) {
 		vp = ITOV(ip);
 		if (DOINGSOFTDEP(vp))
diff --git a/sys/ufs/ffs/ffs_softdep.c b/sys/ufs/ffs/ffs_softdep.c
--- a/sys/ufs/ffs/ffs_softdep.c
+++ b/sys/ufs/ffs/ffs_softdep.c
@@ -13772,7 +13772,7 @@
 		vholdl(vp);
 		vn_lock(vp, LK_EXCLUSIVE | LK_INTERLOCK | LK_RETRY);
 		VI_LOCK(vp);
-		if (vp->v_data != NULL && vp->v_usecount == 0) {
+		if (IS_UFS(vp) && vp->v_usecount == 0) {
 			while ((vp->v_iflag & VI_OWEINACT) != 0) {
 				error = vinactive(vp);
 				if (error != 0 && error != ERELOOKUP)
diff --git a/sys/ufs/ffs/ffs_vnops.c b/sys/ufs/ffs/ffs_vnops.c
--- a/sys/ufs/ffs/ffs_vnops.c
+++ b/sys/ufs/ffs/ffs_vnops.c
@@ -2066,7 +2066,7 @@
 	 *    and respond to dead vnodes by returning ESTALE.
 	 */
 	VOP_LOCK(vp, vp_locked | LK_RETRY);
-	if (!VN_IS_DOOMED(vp))
+	if (IS_UFS(vp))
 		return (0);
 
 	/*
diff --git a/sys/ufs/ufs/inode.h b/sys/ufs/ufs/inode.h
--- a/sys/ufs/ufs/inode.h
+++ b/sys/ufs/ufs/inode.h
@@ -247,6 +247,7 @@
 	} while (0)
 
 #define	IS_SNAPSHOT(ip)		((ip)->i_flags & SF_SNAPSHOT)
+#define	IS_UFS(vp)		((vp)->v_data != NULL)
 
 /*
  * Structure used to pass around logical block paths generated by
diff --git a/sys/ufs/ufs/ufs_bmap.c b/sys/ufs/ufs/ufs_bmap.c
--- a/sys/ufs/ufs/ufs_bmap.c
+++ b/sys/ufs/ufs/ufs_bmap.c
@@ -217,14 +217,12 @@
 		 * return a request for a zeroed out buffer if attempts
 		 * are made to read a BLK_NOCOPY or BLK_SNAP block.
 		 */
-		if ((ip->i_flags & SF_SNAPSHOT) && DIP(ip, i_db[bn]) > 0 &&
+		if (IS_SNAPSHOT(ip) && DIP(ip, i_db[bn]) > 0 &&
 		    DIP(ip, i_db[bn]) < ump->um_seqinc) {
 			*bnp = -1;
 		} else if (*bnp == 0) {
-			if (ip->i_flags & SF_SNAPSHOT)
-				*bnp = blkptrtodb(ump, bn * ump->um_seqinc);
-			else
-				*bnp = -1;
+			*bnp = IS_SNAPSHOT(ip) ? blkptrtodb(ump,
+			    bn * ump->um_seqinc) : -1;
 		} else if (runp) {
 			ufs2_daddr_t bnb = bn;
 			for (++bn; bn < UFS_NDADDR && *runp < maxrun &&
@@ -320,13 +318,13 @@
 	 * return a request for a zeroed out buffer if attempts are made
 	 * to read a BLK_NOCOPY or BLK_SNAP block.
 	 */
-	if ((ip->i_flags & SF_SNAPSHOT) && daddr > 0 && daddr < ump->um_seqinc){
+	if (IS_SNAPSHOT(ip) && daddr > 0 && daddr < ump->um_seqinc){
 		*bnp = -1;
 		return (0);
 	}
 	*bnp = blkptrtodb(ump, daddr);
 	if (*bnp == 0) {
-		if (ip->i_flags & SF_SNAPSHOT)
+		if (IS_SNAPSHOT(ip))
 			*bnp = blkptrtodb(ump, bn * ump->um_seqinc);
 		else
 			*bnp = -1;
@@ -367,7 +365,7 @@
 	mp = vp->v_mount;
 	ump = VFSTOUFS(mp);
 
-	if (vp->v_type != VREG || (ip->i_flags & SF_SNAPSHOT) != 0)
+	if (vp->v_type != VREG || IS_SNAPSHOT(ip))
 		return (EINVAL);
 	if (*offp < 0 || *offp >= ip->i_size)
 		return (ENXIO);
diff --git a/sys/ufs/ufs/ufs_lookup.c b/sys/ufs/ufs/ufs_lookup.c
--- a/sys/ufs/ufs/ufs_lookup.c
+++ b/sys/ufs/ufs/ufs_lookup.c
@@ -1245,8 +1245,7 @@
 	 * drop its snapshot reference so that it will be reclaimed
 	 * when last open reference goes away.
 	 */
-	if (ip != NULL && (ip->i_flags & SF_SNAPSHOT) != 0 &&
-	    ip->i_effnlink == 0)
+	if (ip != NULL && IS_SNAPSHOT(ip) && ip->i_effnlink == 0)
 		UFS_SNAPGONE(ip);
 	return (error);
 }
@@ -1320,7 +1319,7 @@
 	 * drop its snapshot reference so that it will be reclaimed
 	 * when last open reference goes away.
 	 */
-	if ((oip->i_flags & SF_SNAPSHOT) != 0 && oip->i_effnlink == 0)
+	if (IS_SNAPSHOT(oip) && oip->i_effnlink == 0)
 		UFS_SNAPGONE(oip);
 	return (error);
 }
diff --git a/sys/ufs/ufs/ufs_vnops.c b/sys/ufs/ufs/ufs_vnops.c
--- a/sys/ufs/ufs/ufs_vnops.c
+++ b/sys/ufs/ufs/ufs_vnops.c
@@ -702,7 +702,7 @@
 			 */
 			if (vp->v_mount->mnt_flag & MNT_RDONLY)
 				return (EROFS);
-			if ((ip->i_flags & SF_SNAPSHOT) != 0)
+			if (IS_SNAPSHOT(ip))
 				return (EPERM);
 			break;
 		default:
@@ -726,7 +726,7 @@
 	    vap->va_birthtime.tv_sec != VNOVAL) {
 		if (vp->v_mount->mnt_flag & MNT_RDONLY)
 			return (EROFS);
-		if ((ip->i_flags & SF_SNAPSHOT) != 0)
+		if (IS_SNAPSHOT(ip))
 			return (EPERM);
 		error = vn_utimes_perm(vp, vap, cred, td);
 		if (error != 0)
@@ -754,8 +754,8 @@
 	if (vap->va_mode != (mode_t)VNOVAL) {
 		if (vp->v_mount->mnt_flag & MNT_RDONLY)
 			return (EROFS);
-		if ((ip->i_flags & SF_SNAPSHOT) != 0 && (vap->va_mode &
-		   (S_IXUSR | S_IWUSR | S_IXGRP | S_IWGRP | S_IXOTH | S_IWOTH)))
+		if (IS_SNAPSHOT(ip) && (vap->va_mode & (S_IXUSR | S_IWUSR |
+		    S_IXGRP | S_IWGRP | S_IXOTH | S_IWOTH)) != 0)
 			return (EPERM);
 		error = ufs_chmod(vp, (int)vap->va_mode, cred, td);
 	}
@@ -1022,7 +1022,7 @@
 	error = ufs_dirremove(dvp, ip, ap->a_cnp->cn_flags, 0);
 	if (ip->i_nlink <= 0)
 		vp->v_vflag |= VV_NOSYNC;
-	if ((ip->i_flags & SF_SNAPSHOT) != 0) {
+	if (IS_SNAPSHOT(ip)) {
 		/*
 		 * Avoid deadlock where another thread is trying to
 		 * update the inodeblock for dvp and is waiting on
diff --git a/sys/vm/vm_pager.c b/sys/vm/vm_pager.c
--- a/sys/vm/vm_pager.c
+++ b/sys/vm/vm_pager.c
@@ -489,6 +489,8 @@
 	BUF_UNLOCK(bp);
 }
 
+static const char pbuf_wmesg[] = "pbufwait";
+
 static int
 pbuf_init(void *mem, int size, int flags)
 {
@@ -498,7 +500,7 @@
 	if (bp->b_kvabase == NULL)
 		return (ENOMEM);
 	bp->b_kvasize = ptoa(PBUF_PAGES);
-	BUF_LOCKINIT(bp);
+	BUF_LOCKINIT(bp, pbuf_wmesg);
 	LIST_INIT(&bp->b_dep);
 	bp->b_rcred = bp->b_wcred = NOCRED;
 	bp->b_xflags = 0;