From 572798e9ab84d07b0da15a60509889c5372d369a Mon Sep 17 00:00:00 2001
From: kib <kib@FreeBSD.org>
Date: Fri, 5 Jan 2007 09:51:14 +0000
Subject: [PATCH] MFC rev. 1.167 of src/sys/dev/md/md.c rev. 1.514, 1.515 of
 src/sys/kern/vfs_bio.c rev. 1.319, 1.320 of src/sys/sys/vnode.h

Resolve two deadlocks that could be caused by busy md device backed by
vnode.
---
 sys/dev/md/md.c    |  9 +++++++++
 sys/kern/vfs_bio.c | 10 +++++++++-
 sys/sys/vnode.h    |  1 +
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/sys/dev/md/md.c b/sys/dev/md/md.c
index 32c4b48e4482..9079a0996fbf 100644
--- a/sys/dev/md/md.c
+++ b/sys/dev/md/md.c
@@ -647,6 +647,8 @@ md_kthread(void *arg)
 	mtx_lock_spin(&sched_lock);
 	sched_prio(curthread, PRIBIO);
 	mtx_unlock_spin(&sched_lock);
+	if (sc->type == MD_VNODE)
+		curthread->td_pflags |= TDP_NORUNNINGBUF;
 
 	for (;;) {
 		mtx_lock(&sc->queue_mtx);
@@ -877,6 +879,7 @@ mdcreate_vnode(struct md_s *sc, struct md_ioctl *mdio, struct thread *td)
 		VFS_UNLOCK_GIANT(vfslocked);
 		return (error ? error : EINVAL);
 	}
+	nd.ni_vp->v_vflag |= VV_MD;
 	VOP_UNLOCK(nd.ni_vp, 0, td);
 
 	if (mdio->md_fwsectors != 0)
@@ -890,6 +893,9 @@ mdcreate_vnode(struct md_s *sc, struct md_ioctl *mdio, struct thread *td)
 
 	error = mdsetcred(sc, td->td_ucred);
 	if (error != 0) {
+		vn_lock(nd.ni_vp, LK_EXCLUSIVE | LK_RETRY, td);
+		nd.ni_vp->v_vflag &= ~VV_MD;
+		VOP_UNLOCK(nd.ni_vp, 0, td);
 		(void)vn_close(nd.ni_vp, flags, td->td_ucred, td);
 		VFS_UNLOCK_GIANT(vfslocked);
 		return (error);
@@ -920,6 +926,9 @@ mddestroy(struct md_s *sc, struct thread *td)
 	mtx_destroy(&sc->queue_mtx);
 	if (sc->vnode != NULL) {
 		vfslocked = VFS_LOCK_GIANT(sc->vnode->v_mount);
+		vn_lock(sc->vnode, LK_EXCLUSIVE | LK_RETRY, td);
+		sc->vnode->v_vflag &= ~VV_MD;
+		VOP_UNLOCK(sc->vnode, 0, td);
 		(void)vn_close(sc->vnode, sc->flags & MD_READONLY ?
 		    FREAD : (FREAD|FWRITE), sc->cred, td);
 		VFS_UNLOCK_GIANT(vfslocked);
diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index 7148da5fad7e..ca4d52be57c1 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -796,6 +796,8 @@ int
 bufwrite(struct buf *bp)
 {
 	int oldflags;
+	struct vnode *vp;
+	int vp_md;
 
 	CTR3(KTR_BUF, "bufwrite(%p) vp %p flags %X", bp, bp->b_vp, bp->b_flags);
 	if (bp->b_flags & B_INVAL) {
@@ -810,6 +812,12 @@ bufwrite(struct buf *bp)
 	KASSERT(!(bp->b_vflags & BV_BKGRDINPROG),
 	    ("FFS background buffer should not get here %p", bp));
 
+	vp = bp->b_vp;
+	if (vp)
+		vp_md = vp->v_vflag & VV_MD;
+	else
+		vp_md = 0;
+
 	/* Mark the buffer clean */
 	bundirty(bp);
 
@@ -847,7 +855,7 @@ bufwrite(struct buf *bp)
 		 * or syncer daemon trying to clean up as that can lead
 		 * to deadlock.
 		 */
-		if ((curthread->td_pflags & TDP_NORUNNINGBUF) == 0)
+		if ((curthread->td_pflags & TDP_NORUNNINGBUF) == 0 && !vp_md)
 			waitrunningbufspace();
 	}
 
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index 553a6dbcb57b..898a47650d70 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -253,6 +253,7 @@ struct xvnode {
 #define	VV_SYSTEM	0x0080	/* vnode being used by kernel */
 #define	VV_PROCDEP	0x0100	/* vnode is process dependent */
 #define	VV_NOKNOTE	0x0200	/* don't activate knotes on this vnode */
+#define	VV_MD		0x0800	/* vnode backs the md device */
 
 /*
  * Vnode attributes.  A field value of VNOVAL represents a field whose value