PERFORCE change 94124 for review

[John Baldwin]

http://perforce.freebsd.org/chv.cgi?CH=94124

Change 94124 by jhb at jhb_slimer on 2006/03/27 19:29:53

	- Conditionalize Giant for VFS operations.
	- Use the right msleep wait channel to avoid possible panics due to
	  races with kldunload when tearing down the kthread and use the
	  queue mutex to protect writes to the flags member of the softc once
	  a md device is created.

Affected files ...

.. //depot/projects/smpng/sys/dev/md/md.c#75 edit

Differences ...

==== //depot/projects/smpng/sys/dev/md/md.c#75 (text+ko) ====

@@ -88,7 +88,8 @@
 
 #define MD_MODVER 1
 
-#define MD_SHUTDOWN 0x10000	/* Tell worker thread to terminate. */
+#define MD_SHUTDOWN	0x10000		/* Tell worker thread to terminate. */
+#define	MD_EXITING	0x20000		/* Worker thread is exiting. */
 
 #ifndef MD_NSECT
 #define MD_NSECT (10000 * 2)
@@ -485,12 +486,11 @@
 static int
 mdstart_vnode(struct md_s *sc, struct bio *bp)
 {
-	int error;
+	int error, vfslocked;
 	struct uio auio;
 	struct iovec aiov;
 	struct mount *mp;
 
-	mtx_assert(&Giant, MA_OWNED);
 	/*
 	 * VNODE I/O
 	 *
@@ -519,6 +519,7 @@
 	 * When reading set IO_DIRECT to try to avoid double-caching
 	 * the data.  When writing IO_DIRECT is not optimal.
 	 */
+	vfslocked = VFS_LOCK_GIANT(sc->vnode->v_mount);
 	if (bp->bio_cmd == BIO_READ) {
 		vn_lock(sc->vnode, LK_EXCLUSIVE | LK_RETRY, curthread);
 		error = VOP_READ(sc->vnode, &auio, IO_DIRECT, sc->cred);
@@ -531,6 +532,7 @@
 		VOP_UNLOCK(sc->vnode, 0, curthread);
 		vn_finished_write(mp);
 	}
+	VFS_UNLOCK_GIANT(vfslocked);
 	bp->bio_resid = auio.uio_resid;
 	return (error);
 }
@@ -641,35 +643,20 @@
 {
 	struct md_s *sc;
 	struct bio *bp;
-	int error, hasgiant;
+	int error;
 
 	sc = arg;
 	mtx_lock_spin(&sched_lock);
 	sched_prio(curthread, PRIBIO);
 	mtx_unlock_spin(&sched_lock);
 
-	switch (sc->type) {
-	case MD_VNODE:
-		mtx_lock(&Giant);
-		hasgiant = 1;
-		break;
-	case MD_MALLOC:
-	case MD_PRELOAD:
-	case MD_SWAP:
-	default:
-		hasgiant = 0;
-		break;
-	}
-	
 	for (;;) {
+		mtx_lock(&sc->queue_mtx);
 		if (sc->flags & MD_SHUTDOWN) {
-			sc->procp = NULL;
-			wakeup(&sc->procp);
-			if (hasgiant)
-				mtx_unlock(&Giant);
+			sc->flags |= MD_EXITING;
+			mtx_unlock_spin(&sc->queue_mtx);
 			kthread_exit(0);
 		}
-		mtx_lock(&sc->queue_mtx);
 		bp = bioq_takefirst(&sc->bio_queue);
 		if (!bp) {
 			msleep(sc, &sc->queue_mtx, PRIBIO | PDROP, "mdwait", 0);
@@ -867,7 +854,7 @@
 {
 	struct vattr vattr;
 	struct nameidata nd;
-	int error, flags;
+	int error, flags, vfslocked;
 
 	error = copyinstr(mdio->md_file, sc->file, sizeof(sc->file), NULL);
 	if (error != 0)
@@ -879,15 +866,17 @@
 	 */
 	if ((mdio->md_options & MD_READONLY) != 0)
 		flags &= ~FWRITE;
-	NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, sc->file, td);
+	NDINIT(&nd, LOOKUP, FOLLOW | MPSAFE, UIO_SYSSPACE, sc->file, td);
 	error = vn_open(&nd, &flags, 0, -1);
 	if (error != 0)
 		return (error);
+	vfslocked = NDHASGIANT(&nd);
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	if (nd.ni_vp->v_type != VREG ||
 	    (error = VOP_GETATTR(nd.ni_vp, &vattr, td->td_ucred, td))) {
 		VOP_UNLOCK(nd.ni_vp, 0, td);
 		(void)vn_close(nd.ni_vp, flags, td->td_ucred, td);
+		VFS_UNLOCK_GIANT(vfslocked);
 		return (error ? error : EINVAL);
 	}
 	VOP_UNLOCK(nd.ni_vp, 0, td);
@@ -904,15 +893,17 @@
 	error = mdsetcred(sc, td->td_ucred);
 	if (error != 0) {
 		(void)vn_close(nd.ni_vp, flags, td->td_ucred, td);
+		VFS_UNLOCK_GIANT(vfslocked);
 		return (error);
 	}
+	VFS_UNLOCK_GIANT(vfslocked);
 	return (0);
 }
 
 static int
 mddestroy(struct md_s *sc, struct thread *td)
 {
-
+	int vfslocked;
 
 	if (sc->gp) {
 		sc->gp->softc = NULL;
@@ -922,16 +913,18 @@
 		sc->gp = NULL;
 		sc->pp = NULL;
 	}
+	mtx_lock(&sc->queue_mtx);
 	sc->flags |= MD_SHUTDOWN;
 	wakeup(sc);
-	while (sc->procp != NULL)
-		tsleep(&sc->procp, PRIBIO, "mddestroy", hz / 10);
+	while (!(sc->flags & MD_EXITING))
+		msleep(sc->procp, &sc->queue_mtx, PRIBIO, "mddestroy", hz / 10);
+	mtx_unlock(&sc->queue_mtx);
 	mtx_destroy(&sc->queue_mtx);
 	if (sc->vnode != NULL) {
-		mtx_lock(&Giant);
+		vfslocked = VFS_LOCK_GIANT(sc->vnode->v_mount);
 		(void)vn_close(sc->vnode, sc->flags & MD_READONLY ?
 		    FREAD : (FREAD|FWRITE), sc->cred, td);
-		mtx_unlock(&Giant);
+		VFS_UNLOCK_GIANT(vfslocked);
 	}
 	if (sc->cred != NULL)
 		crfree(sc->cred);