- Add an interlock argument to BUF_LOCK and BUF_TIMELOCK.

 - Remove the buftimelock mutex and acquire the buf's interlock to protect
   these fields instead.
 - Hold the vnode interlock while locking bufs on the clean/dirty queues.
   This reduces some cases from one BUF_LOCK with a LK_NOWAIT and another
   BUF_LOCK with a LK_TIMEFAIL to a single lock.

Reviewed by:	arch, mckusick

2 files changed, 13 insertions, 11 deletions

diff --git a/sys/sys/buf.h b/sys/sys/buf.h
index ac60adf..94c23cc 100644
--- a/sys/sys/buf.h
+++ b/sys/sys/buf.h
@@ -273,7 +273,6 @@ struct buf {
 /*
  * Buffer locking
  */
-extern struct mtx buftimelock;		/* Interlock on setting prio and timo */
 extern const char *buf_wmesg;		/* Default buffer lock message */
 #define BUF_WMESG "bufwait"
 #include <sys/proc.h>			/* XXX for curthread */
@@ -288,37 +287,39 @@ extern const char *buf_wmesg;		/* Default buffer lock message */
  *
  * Get a lock sleeping non-interruptably until it becomes available.
  */
-static __inline int BUF_LOCK(struct buf *, int);
+static __inline int BUF_LOCK(struct buf *, int, struct mtx *);
 static __inline int
-BUF_LOCK(struct buf *bp, int locktype)
+BUF_LOCK(struct buf *bp, int locktype, struct mtx *interlock)
 {
 	int s, ret;
 
 	s = splbio();
-	mtx_lock(&buftimelock);
-	locktype |= LK_INTERLOCK;
+	mtx_lock(bp->b_lock.lk_interlock);
+	locktype |= LK_INTERNAL;
 	bp->b_lock.lk_wmesg = buf_wmesg;
 	bp->b_lock.lk_prio = PRIBIO + 4;
-	ret = lockmgr(&(bp)->b_lock, locktype, &buftimelock, curthread);
+	ret = lockmgr(&(bp)->b_lock, locktype, interlock, curthread);
 	splx(s);
 	return ret;
 }
 /*
  * Get a lock sleeping with specified interruptably and timeout.
  */
-static __inline int BUF_TIMELOCK(struct buf *, int, char *, int, int);
+static __inline int BUF_TIMELOCK(struct buf *, int, struct mtx *,
+    char *, int, int);
 static __inline int
-BUF_TIMELOCK(struct buf *bp, int locktype, char *wmesg, int catch, int timo)
+BUF_TIMELOCK(struct buf *bp, int locktype, struct mtx *interlock,
+    char *wmesg, int catch, int timo)
 {
 	int s, ret;
 
 	s = splbio();
-	mtx_lock(&buftimelock);
-	locktype |= LK_INTERLOCK | LK_TIMELOCK;
+	mtx_lock(bp->b_lock.lk_interlock);
+	locktype |= LK_INTERNAL | LK_TIMELOCK;
 	bp->b_lock.lk_wmesg = wmesg;
 	bp->b_lock.lk_prio = (PRIBIO + 4) | catch;
 	bp->b_lock.lk_timo = timo;
-	ret = lockmgr(&(bp)->b_lock, (locktype), &buftimelock, curthread);
+	ret = lockmgr(&(bp)->b_lock, (locktype), interlock, curthread);
 	splx(s);
 	return ret;
 }
diff --git a/sys/sys/lockmgr.h b/sys/sys/lockmgr.h
index a186614..26226cd 100644
--- a/sys/sys/lockmgr.h
+++ b/sys/sys/lockmgr.h
@@ -149,6 +149,7 @@ struct lock {
 				    */
 #define LK_RETRY	0x00020000 /* vn_lock: retry until locked */
 #define	LK_THISLAYER	0x00040000 /* vn_lock: lock/unlock only current layer */
+#define	LK_INTERNAL	0x00080000/* The internal lock is already held */
 
 /*
  * Internal state flags corresponding to lk_sharecount, and lk_waitcount