Combined all patches. you may have reservations about patches 4,5.

gistfile1.txt

From dad83af033474363bbf4ce519adaab7190eceea5 Mon Sep 17 00:00:00 2001
From: coypu <coypu@sdf.org>
Date: Mon, 16 May 2016 18:24:56 +0300
Subject: [PATCH 1/6] Get rid of UFS_WAPBL_BEGIN1/END1

ufs makeinode no longer releases dvp, so incrementing the
usecount for wapbl is unnecessary.
---
 sys/ufs/ufs/ufs_vnops.c | 16 ++++++++--------
 sys/ufs/ufs/ufs_wapbl.h |  5 -----
 2 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/sys/ufs/ufs/ufs_vnops.c b/sys/ufs/ufs/ufs_vnops.c
index 8f0edc1..41154f5 100644
--- a/sys/ufs/ufs/ufs_vnops.c
+++ b/sys/ufs/ufs/ufs_vnops.c
@@ -151,7 +151,7 @@ ufs_create(void *v)
 	UFS_CHECK_CRAPCOUNTER(VTOI(dvp));
 
 	/*
-	 * UFS_WAPBL_BEGIN1(dvp->v_mount, dvp) performed by successful
+	 * UFS_WAPBL_BEGIN(dvp->v_mount) performed by successful
 	 * ufs_makeinode
 	 */
 	fstrans_start(dvp->v_mount, FSTRANS_SHARED);
@@ -160,7 +160,7 @@ ufs_create(void *v)
 		fstrans_done(dvp->v_mount);
 		return (error);
 	}
-	UFS_WAPBL_END1(dvp->v_mount, dvp);
+	UFS_WAPBL_END(dvp->v_mount);
 	fstrans_done(dvp->v_mount);
 	VN_KNOTE(dvp, NOTE_WRITE);
 	VOP_UNLOCK(*ap->a_vpp);
@@ -194,7 +194,7 @@ ufs_mknod(void *v)
 	UFS_CHECK_CRAPCOUNTER(VTOI(ap->a_dvp));
 
 	/*
-	 * UFS_WAPBL_BEGIN1(dvp->v_mount, dvp) performed by successful
+	 * UFS_WAPBL_BEGIN(dvp->v_mount) performed by successful
 	 * ufs_makeinode
 	 */
 	fstrans_start(ap->a_dvp->v_mount, FSTRANS_SHARED);
@@ -204,7 +204,7 @@ ufs_mknod(void *v)
 	ip = VTOI(*vpp);
 	ip->i_flag |= IN_ACCESS | IN_CHANGE | IN_UPDATE;
 	UFS_WAPBL_UPDATE(*vpp, NULL, NULL, 0);
-	UFS_WAPBL_END1(ap->a_dvp->v_mount, ap->a_dvp);
+	UFS_WAPBL_END(ap->a_dvp->v_mount);
 	VOP_UNLOCK(*vpp);
 out:
 	fstrans_done(ap->a_dvp->v_mount);
@@ -1200,7 +1200,7 @@ ufs_symlink(void *v)
 	UFS_CHECK_CRAPCOUNTER(VTOI(ap->a_dvp));
 
 	/*
-	 * UFS_WAPBL_BEGIN1(dvp->v_mount, dvp) performed by successful
+	 * UFS_WAPBL_BEGIN(dvp->v_mount) performed by successful
 	 * ufs_makeinode
 	 */
 	fstrans_start(ap->a_dvp->v_mount, FSTRANS_SHARED);
@@ -1232,7 +1232,7 @@ ufs_symlink(void *v)
 		error = ufs_bufio(UIO_WRITE, vp, ap->a_target, len, (off_t)0,
 		    IO_NODELOCKED | IO_JOURNALLOCKED, ap->a_cnp->cn_cred, NULL,
 		    NULL);
-	UFS_WAPBL_END1(ap->a_dvp->v_mount, ap->a_dvp);
+	UFS_WAPBL_END(ap->a_dvp->v_mount);
 	VOP_UNLOCK(vp);
 	if (error)
 		vrele(vp);
@@ -1784,7 +1784,7 @@ ufs_makeinode(struct vattr *vap, struct vnode *dvp,
 	}
 	*vpp = tvp;
 	ip = VTOI(tvp);
-	error = UFS_WAPBL_BEGIN1(dvp->v_mount, dvp);
+	error = UFS_WAPBL_BEGIN(dvp->v_mount);
 	if (error) {
 		vput(tvp);
 		return (error);
@@ -1832,7 +1832,7 @@ ufs_makeinode(struct vattr *vap, struct vnode *dvp,
 	DIP_ASSIGN(ip, nlink, 0);
 	ip->i_flag |= IN_CHANGE;
 	UFS_WAPBL_UPDATE(tvp, NULL, NULL, 0);
-	UFS_WAPBL_END1(dvp->v_mount, dvp);
+	UFS_WAPBL_END(dvp->v_mount);
 	vput(tvp);
 	return (error);
 }
diff --git a/sys/ufs/ufs/ufs_wapbl.h b/sys/ufs/ufs/ufs_wapbl.h
index 1eab045..b8386cf 100644
--- a/sys/ufs/ufs/ufs_wapbl.h
+++ b/sys/ufs/ufs/ufs_wapbl.h
@@ -134,10 +134,7 @@ ufs_wapbl_end2(struct mount *mp, struct vnode *vp1, struct vnode *vp2)
 
 #define	UFS_WAPBL_BEGIN(mp)						\
 	ufs_wapbl_begin2(mp, NULL, NULL, __FUNCTION__, __LINE__)
-#define	UFS_WAPBL_BEGIN1(mp, v1)					\
-	ufs_wapbl_begin2(mp, v1, NULL, __FUNCTION__, __LINE__)
 #define	UFS_WAPBL_END(mp)	ufs_wapbl_end2(mp, NULL, NULL)
-#define	UFS_WAPBL_END1(mp, v1)	ufs_wapbl_end2(mp, v1, NULL)
 
 #define	UFS_WAPBL_UPDATE(vp, access, modify, flags)			\
 	if ((vp)->v_mount->mnt_wapbl) {					\
@@ -164,9 +161,7 @@ ufs_wapbl_end2(struct mount *mp, struct vnode *vp1, struct vnode *vp2)
 
 #else /* ! WAPBL */
 #define	UFS_WAPBL_BEGIN(mp) (__USE(mp), 0)
-#define	UFS_WAPBL_BEGIN1(mp, v1) 0
 #define	UFS_WAPBL_END(mp)	do { } while (0)
-#define	UFS_WAPBL_END1(mp, v1)
 #define	UFS_WAPBL_UPDATE(vp, access, modify, flags)	do { } while (0)
 #define	UFS_WAPBL_JLOCK_ASSERT(mp)
 #define	UFS_WAPBL_JUNLOCK_ASSERT(mp)
-- 
2.8.1

From 74a1a890f69351e9406ec53cde41f6cea882dc44 Mon Sep 17 00:00:00 2001
From: coypu <coypu@sdf.org>
Date: Mon, 16 May 2016 20:00:46 +0300
Subject: [PATCH 2/6] Simplify ufs_wapbl_begin2/end2, drop 2 suffix

We are no longer calling UFS_WAPBL_BEGIN/END with vnodes (we are giving
NULL as a parameter in all cases), so we can get rid of this input
parameter and the relevant check.
---
 sys/ufs/ufs/ufs_wapbl.h | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/sys/ufs/ufs/ufs_wapbl.h b/sys/ufs/ufs/ufs_wapbl.h
index b8386cf..05f41a7 100644
--- a/sys/ufs/ufs/ufs_wapbl.h
+++ b/sys/ufs/ufs/ufs_wapbl.h
@@ -95,16 +95,10 @@ void	ufs_wapbl_verify_inodes(struct mount *, const char *);
 #endif
 
 static __inline int
-ufs_wapbl_begin2(struct mount *mp, struct vnode *vp1, struct vnode *vp2,
-		 const char *file, int line)
+ufs_wapbl_begin(struct mount *mp, const char *file, int line)
 {
 	if (mp->mnt_wapbl) {
 		int error;
-
-		if (vp1)
-			vref(vp1);
-		if (vp2)
-			vref(vp2);
 		error = wapbl_begin(mp->mnt_wapbl, file, line);
 		if (error)
 			return error;
@@ -117,7 +111,7 @@ ufs_wapbl_begin2(struct mount *mp, struct vnode *vp1, struct vnode *vp2,
 }
 
 static __inline void
-ufs_wapbl_end2(struct mount *mp, struct vnode *vp1, struct vnode *vp2)
+ufs_wapbl_end(struct mount *mp)
 {
 	if (mp->mnt_wapbl) {
 #ifdef WAPBL_DEBUG_INODES
@@ -125,16 +119,12 @@ ufs_wapbl_end2(struct mount *mp, struct vnode *vp1, struct vnode *vp2)
 			ufs_wapbl_verify_inodes(mp, "wapbl_end");
 #endif
 		wapbl_end(mp->mnt_wapbl);
-		if (vp2)
-			vrele(vp2);
-		if (vp1)
-			vrele(vp1);
 	}
 }
 
 #define	UFS_WAPBL_BEGIN(mp)						\
-	ufs_wapbl_begin2(mp, NULL, NULL, __FUNCTION__, __LINE__)
-#define	UFS_WAPBL_END(mp)	ufs_wapbl_end2(mp, NULL, NULL)
+	ufs_wapbl_begin(mp, __FUNCTION__, __LINE__)
+#define	UFS_WAPBL_END(mp) ufs_wapbl_end(mp)
 
 #define	UFS_WAPBL_UPDATE(vp, access, modify, flags)			\
 	if ((vp)->v_mount->mnt_wapbl) {					\
-- 
2.8.1

From 114d0dce93611f4c8e8b78f38596e23cce089813 Mon Sep 17 00:00:00 2001
From: coypu <coypu@sdf.org>
Date: Mon, 16 May 2016 20:15:29 +0300
Subject: [PATCH 3/6] While here, replace GCC __FUNCTION__ by C99 __func__

---
 sys/ufs/ufs/ufs_wapbl.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/ufs/ufs/ufs_wapbl.h b/sys/ufs/ufs/ufs_wapbl.h
index 05f41a7..c997e3c 100644
--- a/sys/ufs/ufs/ufs_wapbl.h
+++ b/sys/ufs/ufs/ufs_wapbl.h
@@ -123,7 +123,7 @@ ufs_wapbl_end(struct mount *mp)
 }
 
 #define	UFS_WAPBL_BEGIN(mp)						\
-	ufs_wapbl_begin(mp, __FUNCTION__, __LINE__)
+	ufs_wapbl_begin(mp, __func__, __LINE__)
 #define	UFS_WAPBL_END(mp) ufs_wapbl_end(mp)
 
 #define	UFS_WAPBL_UPDATE(vp, access, modify, flags)			\
-- 
2.8.1

From 0041cdff0fb74cdde7f59186ef1229c1579eee26 Mon Sep 17 00:00:00 2001
From: coypu <coypu@sdf.org>
Date: Thu, 19 May 2016 02:32:42 +0300
Subject: [PATCH 4/6] Replace deprecated disabled code by comment

describing what it intends to do, and why it won't work yet
---
 sys/kern/vfs_wapbl.c | 34 ++++------------------------------
 1 file changed, 4 insertions(+), 30 deletions(-)

diff --git a/sys/kern/vfs_wapbl.c b/sys/kern/vfs_wapbl.c
index e63f228..41797f0 100644
--- a/sys/kern/vfs_wapbl.c
+++ b/sys/kern/vfs_wapbl.c
@@ -1431,44 +1431,18 @@ wapbl_biodone(struct buf *bp)
 #endif
 
 	if (bp->b_error) {
-#ifdef notyet /* Can't currently handle possible dirty buffer reuse */
 		/*
-		 * XXXpooka: interfaces not fully updated
-		 * Note: this was not enabled in the original patch
-		 * against netbsd4 either.  I don't know if comment
-		 * above is true or not.
+		 * If an error occurs, it would be nice to leave the buffer
+		 * as a delayed write on the LRU queue so that we can retry
+		 * it later. But buffercache(9) can't handle dirty buffer
+		 * reuse, so just mark the log permanently errored out.
 		 */
-
-		/*
-		 * If an error occurs, report the error and leave the
-		 * buffer as a delayed write on the LRU queue.
-		 * restarting the write would likely result in
-		 * an error spinloop, so let it be done harmlessly
-		 * by the syncer.
-		 */
-		bp->b_flags &= ~(B_DONE);
-		simple_unlock(&bp->b_interlock);
-
-		if (we->we_error == 0) {
-			mutex_enter(&wl->wl_mtx);
-			wl->wl_error_count++;
-			mutex_exit(&wl->wl_mtx);
-			cv_broadcast(&wl->wl_reclaimable_cv);
-		}
-		we->we_error = bp->b_error;
-		bp->b_error = 0;
-		brelse(bp);
-		return;
-#else
-		/* For now, just mark the log permanently errored out */
-
 		mutex_enter(&wl->wl_mtx);
 		if (wl->wl_error_count == 0) {
 			wl->wl_error_count++;
 			cv_broadcast(&wl->wl_reclaimable_cv);
 		}
 		mutex_exit(&wl->wl_mtx);
-#endif
 	}
 
 	/*
-- 
2.8.1

From a8e74e2c021cd13743b952037342b54d36a1d59f Mon Sep 17 00:00:00 2001
From: coypu <coypu@sdf.org>
Date: Thu, 19 May 2016 03:01:28 +0300
Subject: [PATCH 5/6] Simplify buffer error handling case.

Don't bother advancing the log when errors occur.
---
 sys/kern/vfs_wapbl.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/sys/kern/vfs_wapbl.c b/sys/kern/vfs_wapbl.c
index 41797f0..e983fb6 100644
--- a/sys/kern/vfs_wapbl.c
+++ b/sys/kern/vfs_wapbl.c
@@ -1323,9 +1323,10 @@ wapbl_truncate(struct wapbl *wl, size_t minfree)
 		return 0;
 	}
 	minfree -= avail;
-	while ((wl->wl_error_count == 0) &&
-	    (wl->wl_reclaimable_bytes < minfree)) {
-        	WAPBL_PRINTF(WAPBL_PRINT_TRUNCATE,
+	while (wl->wl_reclaimable_bytes < minfree) {
+		if (wl->wl_error_count != 0)
+			break;
+		WAPBL_PRINTF(WAPBL_PRINT_TRUNCATE,
                    ("wapbl_truncate: sleeping on %p wl=%p bytes=%zd "
 		    "minfree=%zd\n",
                     &wl->wl_reclaimable_bytes, wl, wl->wl_reclaimable_bytes,
@@ -1333,11 +1334,12 @@ wapbl_truncate(struct wapbl *wl, size_t minfree)
 
 		cv_wait(&wl->wl_reclaimable_cv, &wl->wl_mtx);
 	}
-	if (wl->wl_reclaimable_bytes < minfree) {
+	if (wl->wl_error_count != 0) {
 		KASSERT(wl->wl_error_count);
 		/* XXX maybe get actual error from buffer instead someday? */
-		error = EIO;
+		return EIO;
 	}
+
 	head = wl->wl_head;
 	tail = wl->wl_tail;
 	delta = wl->wl_reclaimable_bytes;
@@ -1356,9 +1358,6 @@ wapbl_truncate(struct wapbl *wl, size_t minfree)
 		wapbl_space_used(wl->wl_circ_size, head, tail));
 	mutex_exit(&wl->wl_mtx);
 
-	if (error)
-		return error;
-
 	/*
 	 * This is where head, tail and delta are unprotected
 	 * from races against itself or flush.  This is ok since
-- 
2.8.1

From 9c0391939070065963917ef56530a6bd3e61adad Mon Sep 17 00:00:00 2001
From: coypu <coypu@sdf.org>
Date: Thu, 19 May 2016 06:56:33 +0300
Subject: [PATCH 6/6] Enable somewhat excessive diagnostic asserts

They do not trigger panics.
---
 sys/kern/vfs_wapbl.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/sys/kern/vfs_wapbl.c b/sys/kern/vfs_wapbl.c
index e983fb6..7512df3 100644
--- a/sys/kern/vfs_wapbl.c
+++ b/sys/kern/vfs_wapbl.c
@@ -1418,7 +1418,6 @@ wapbl_biodone(struct buf *bp)
 		return;
 	}
 
-#ifdef ohbother
 	KDASSERT(bp->b_oflags & BO_DONE);
 	KDASSERT(!(bp->b_oflags & BO_DELWRI));
 	KDASSERT(bp->b_flags & B_ASYNC);
@@ -1427,7 +1426,6 @@ wapbl_biodone(struct buf *bp)
 	KDASSERT(!(bp->b_flags & B_READ));
 	KDASSERT(!(bp->b_cflags & BC_INVAL));
 	KDASSERT(!(bp->b_cflags & BC_NOCACHE));
-#endif
 
 	if (bp->b_error) {
 		/*
-- 
2.8.1