Add option WITNESS_NO_VNODE to suppress printing LORs between VNODE

locks. To support this, VNODE locks are created with the LK_IS_VNODE
flag. This flag is propagated down using the LO_IS_VNODE flag.

Note that WITNESS still records the LOR. Only the printing and the
optional entering into the kernel debugger is bypassed with the
WITNESS_NO_VNODE option.

6 files changed, 19 insertions, 2 deletions

diff --git a/sys/conf/options b/sys/conf/options
index 3b188b3..e0eda69 100644
--- a/sys/conf/options
+++ b/sys/conf/options
@@ -672,6 +672,7 @@ KTR_ENTRIES		opt_global.h
 KTR_VERBOSE		opt_ktr.h
 WITNESS			opt_global.h
 WITNESS_KDB		opt_witness.h
+WITNESS_NO_VNODE	opt_witness.h
 WITNESS_SKIPSPIN	opt_witness.h
 
 # options for ACPI support
diff --git a/sys/kern/kern_lock.c b/sys/kern/kern_lock.c
index 7962ae1..849f583 100644
--- a/sys/kern/kern_lock.c
+++ b/sys/kern/kern_lock.c
@@ -393,6 +393,8 @@ lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
 		iflags |= LO_WITNESS;
 	if (flags & LK_QUIET)
 		iflags |= LO_QUIET;
+	if (flags & LK_IS_VNODE)
+		iflags |= LO_IS_VNODE;
 	iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
 
 	lk->lk_lock = LK_UNLOCKED;
diff --git a/sys/kern/subr_witness.c b/sys/kern/subr_witness.c
index b30bf08..ac7636ae 100644
--- a/sys/kern/subr_witness.c
+++ b/sys/kern/subr_witness.c
@@ -1289,7 +1289,19 @@ witness_checkorder(struct lock_object *lock, int flags, const char *file,
 			w->w_reversed = w1->w_reversed = 1;
 			witness_increment_graph_generation();
 			mtx_unlock_spin(&w_mtx);
-			
+
+#ifdef WITNESS_NO_VNODE
+			/*
+			 * There are known LORs between VNODE locks. They are
+			 * not an indication of a bug. VNODE locks are flagged
+			 * as such (LO_IS_VNODE) and we don't yell if the LOR
+			 * is between 2 VNODE locks.
+			 */
+			if ((lock->lo_flags & LO_IS_VNODE) != 0 &&
+			    (lock1->li_lock->lo_flags & LO_IS_VNODE) != 0)
+				return;
+#endif
+
 			/*
 			 * Ok, yell about it.
 			 */
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index de118f7..d9cbde2 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -1037,7 +1037,7 @@ alloc:
 	 * By default, don't allow shared locks unless filesystems
 	 * opt-in.
 	 */
-	lockinit(vp->v_vnlock, PVFS, tag, VLKTIMEOUT, LK_NOSHARE);
+	lockinit(vp->v_vnlock, PVFS, tag, VLKTIMEOUT, LK_NOSHARE | LK_IS_VNODE);
 	/*
 	 * Initialize bufobj.
 	 */
diff --git a/sys/sys/lock.h b/sys/sys/lock.h
index ab0122d..07651eb 100644
--- a/sys/sys/lock.h
+++ b/sys/sys/lock.h
@@ -79,6 +79,7 @@ struct lock_class {
 #define	LO_SLEEPABLE	0x00100000	/* Lock may be held while sleeping. */
 #define	LO_UPGRADABLE	0x00200000	/* Lock may be upgraded/downgraded. */
 #define	LO_DUPOK	0x00400000	/* Don't check for duplicate acquires */
+#define	LO_IS_VNODE	0x00800000	/* Tell WITNESS about a VNODE lock */
 #define	LO_CLASSMASK	0x0f000000	/* Class index bitmask. */
 #define LO_NOPROFILE    0x10000000      /* Don't profile this lock */
 
diff --git a/sys/sys/lockmgr.h b/sys/sys/lockmgr.h
index 1a2c92c..f525a06 100644
--- a/sys/sys/lockmgr.h
+++ b/sys/sys/lockmgr.h
@@ -146,6 +146,7 @@ _lockmgr_args_rw(struct lock *lk, u_int flags, struct rwlock *ilk,
 #define	LK_NOWITNESS	0x000010
 #define	LK_QUIET	0x000020
 #define	LK_ADAPTIVE	0x000040
+#define	LK_IS_VNODE	0x000080	/* Tell WITNESS about a VNODE lock */
 
 /*
  * Additional attributes to be used in lockmgr().