--- src/sys/kern/vfs_bio.c	2005/11/19 17:19:47	1.53
+++ src/sys/kern/vfs_bio.c	2006/04/18 17:12:25	1.53.2.1
@@ -1577,9 +1577,11 @@ gbincore(struct vnode * vp, daddr_t blkn
  *	This is much better then the old way of writing only one buffer at
  *	a time.  Note that we may not be presented with the buffers in the 
  *	correct order, so we search for the cluster in both directions.
+ *
+ *	The buffer is locked on call.
  */
 int
-vfs_bio_awrite(struct buf * bp)
+vfs_bio_awrite(struct buf *bp)
 {
 	int i;
 	int j;
@@ -1638,13 +1640,13 @@ vfs_bio_awrite(struct buf * bp)
 		 * this is a possible cluster write
 		 */
 		if (ncl != 1) {
+			BUF_UNLOCK(bp);
 			nwritten = cluster_wbuild(vp, size, lblkno - j, ncl);
 			crit_exit();
 			return nwritten;
 		}
 	}
 
-	BUF_LOCK(bp, LK_EXCLUSIVE);
 	bremfree(bp);
 	bp->b_flags |= B_ASYNC;
 
@@ -2083,16 +2085,23 @@ flushbufqueues(void)
 			    (bp->b_flags & B_DEFERRED) == 0 &&
 			    (*bioops.io_countdeps)(bp, 0)) {
 				TAILQ_REMOVE(&bufqueues[BQUEUE_DIRTY],
-				    bp, b_freelist);
+					     bp, b_freelist);
 				TAILQ_INSERT_TAIL(&bufqueues[BQUEUE_DIRTY],
-				    bp, b_freelist);
+				    		  bp, b_freelist);
 				bp->b_flags |= B_DEFERRED;
 				bp = TAILQ_FIRST(&bufqueues[BQUEUE_DIRTY]);
 				continue;
 			}
-			vfs_bio_awrite(bp);
-			++r;
-			break;
+
+			/*
+			 * Only write it out if we can successfully lock
+			 * it.
+			 */
+			if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) == 0) {
+				vfs_bio_awrite(bp);
+				++r;
+				break;
+			}
 		}
 		bp = TAILQ_NEXT(bp, b_freelist);
 	}