Index: sys/nfs/nfs_bio.c
===================================================================
RCS file: /home/netbsd/src/sys/nfs/nfs_bio.c,v
retrieving revision 1.193
diff -p -u -r1.193 nfs_bio.c
--- sys/nfs/nfs_bio.c	15 Jan 2020 17:55:44 -0000	1.193
+++ sys/nfs/nfs_bio.c	20 Feb 2020 07:13:56 -0000
@@ -1,4 +1,4 @@
-/*	$NetBSD: nfs_bio.c,v 1.193 2020/01/15 17:55:44 ad Exp $	*/
+/*	$NetBSD: nfs_bio.c,v 1.188.2.1 2011/11/02 21:53:59 yamt Exp $	*/
 
 /*
  * Copyright (c) 1989, 1993
@@ -1057,6 +1057,8 @@ again:
 					nfs_merge_commit_ranges(vp);
 				} else {
 					nfs_add_committed_range(vp, off, cnt);
+					nfs_del_tobecommitted_range(vp, off,
+					    cnt);
 				}
 			}
 		} else {
@@ -1098,6 +1100,7 @@ again:
 		 */
 		mutex_enter(&np->n_commitlock);
 		nfs_add_tobecommitted_range(vp, off, cnt);
+		nfs_del_committed_range(vp, off, cnt);
 		/*
 		 * if there can be too many uncommitted pages, commit them now.
 		 */
@@ -1133,7 +1136,7 @@ again:
 		 * pages are now on stable storage.
 		 */
 		mutex_enter(&np->n_commitlock);
-		nfs_del_committed_range(vp, off, cnt);
+		nfs_del_tobecommitted_range(vp, off, cnt);
 		mutex_exit(&np->n_commitlock);
 		mutex_enter(uobj->vmobjlock);
 		for (i = 0; i < npages; i++) {
Index: sys/nfs/nfs_subs.c
===================================================================
RCS file: /home/netbsd/src/sys/nfs/nfs_subs.c,v
retrieving revision 1.236
diff -p -u -r1.236 nfs_subs.c
--- sys/nfs/nfs_subs.c	15 Dec 2019 21:11:34 -0000	1.236
+++ sys/nfs/nfs_subs.c	20 Feb 2020 07:15:31 -0000
@@ -1,4 +1,4 @@
-/*	$NetBSD: nfs_subs.c,v 1.236 2019/12/15 21:11:34 ad Exp $	*/
+/*	$NetBSD: nfs_subs.c,v 1.221.2.1 2011/11/02 21:53:59 yamt Exp $	*/
 
 /*
  * Copyright (c) 1989, 1993
@@ -1760,8 +1760,6 @@ nfs_clearcommit_selector(void *cl, struc
 	np = VTONFS(vp);
 	if (vp->v_type != VREG || vp->v_mount != c->mp || np == NULL)
 		return false;
-	np->n_pushlo = np->n_pushhi = np->n_pushedlo =
-	    np->n_pushedhi = 0;
 	np->n_commitflags &=
 	    ~(NFS_COMMIT_PUSH_VALID | NFS_COMMIT_PUSHED_VALID);
 	uvm_page_array_init(&a);
@@ -1809,19 +1807,7 @@ nfs_merge_commit_ranges(struct vnode *vp
 	struct nfsnode *np = VTONFS(vp);
 
 	KASSERT(np->n_commitflags & NFS_COMMIT_PUSH_VALID);
-
-	if (!(np->n_commitflags & NFS_COMMIT_PUSHED_VALID)) {
-		np->n_pushedlo = np->n_pushlo;
-		np->n_pushedhi = np->n_pushhi;
-		np->n_commitflags |= NFS_COMMIT_PUSHED_VALID;
-	} else {
-		if (np->n_pushlo < np->n_pushedlo)
-			np->n_pushedlo = np->n_pushlo;
-		if (np->n_pushhi > np->n_pushedhi)
-			np->n_pushedhi = np->n_pushhi;
-	}
-
-	np->n_pushlo = np->n_pushhi = 0;
+	nfs_add_committed_range(vp, np->n_pushlo, np->n_pushhi - np->n_pushlo);
 	np->n_commitflags &= ~NFS_COMMIT_PUSH_VALID;
 
 #ifdef NFS_DEBUG_COMMIT
@@ -1872,11 +1858,15 @@ nfs_add_committed_range(struct vnode *vp
 		np->n_pushedhi = hi;
 		np->n_commitflags |= NFS_COMMIT_PUSHED_VALID;
 	} else {
-		if (hi > np->n_pushedhi)
+		/*
+		 * note that it's unsafe to add more than requested.
+		 */
+		if (hi > np->n_pushedhi && lo <= np->n_pushedhi)
 			np->n_pushedhi = hi;
-		if (lo < np->n_pushedlo)
+		if (lo < np->n_pushedlo && hi >= np->n_pushedlo)
 			np->n_pushedlo = lo;
 	}
+	KASSERT(np->n_pushedhi >= np->n_pushedlo);
 #ifdef NFS_DEBUG_COMMIT
 	printf("add: committed: %u - %u\n", (unsigned)np->n_pushedlo,
 	    (unsigned)np->n_pushedhi);
@@ -1912,6 +1902,9 @@ nfs_del_committed_range(struct vnode *vp
 		else
 			np->n_pushedlo = hi;
 	}
+	if (np->n_pushedhi <= np->n_pushedlo) {
+		np->n_commitflags &= ~NFS_COMMIT_PUSHED_VALID;
+	}
 #ifdef NFS_DEBUG_COMMIT
 	printf("del: committed: %u - %u\n", (unsigned)np->n_pushedlo,
 	    (unsigned)np->n_pushedhi);
@@ -1937,6 +1930,7 @@ nfs_add_tobecommitted_range(struct vnode
 		if (hi > np->n_pushhi)
 			np->n_pushhi = hi;
 	}
+	KASSERT(np->n_pushhi >= np->n_pushlo);
 #ifdef NFS_DEBUG_COMMIT
 	printf("add: tobecommitted: %u - %u\n", (unsigned)np->n_pushlo,
 	    (unsigned)np->n_pushhi);
@@ -1964,6 +1958,10 @@ nfs_del_tobecommitted_range(struct vnode
 		np->n_pushhi = lo;
 	else {
 		/*
+		 * following can cause a lot of small (eg. 64KB) commit rpcs.
+		 */
+#if 0
+		/*
 		 * XXX There's only one range. If the deleted range
 		 * is in the middle, pick the largest of the
 		 * contiguous ranges that it leaves.
@@ -1972,6 +1970,10 @@ nfs_del_tobecommitted_range(struct vnode
 			np->n_pushhi = lo;
 		else
 			np->n_pushlo = hi;
+#endif
+	}
+	if (np->n_pushhi <= np->n_pushlo) {
+		np->n_commitflags &= ~NFS_COMMIT_PUSH_VALID;
 	}
 #ifdef NFS_DEBUG_COMMIT
 	printf("del: tobecommitted: %u - %u\n", (unsigned)np->n_pushlo,