- Complete part of the unfinished bufobj work by consistently using

   BO_LOCK/UNLOCK/MTX when manipulating the bufobj.
 - Create a new lock in the bufobj to lock bufobj fields independently.
   This leaves the vnode interlock as an 'identity' lock while the bufobj
   is an io lock.  The bufobj lock is ordered before the vnode interlock
   and also before the mnt ilock.
 - Exploit this new lock order to simplify softdep_check_suspend().
 - A few sync related functions are marked with a new XXX to note that
   we may not properly interlock against a non-zero bv_cnt when
   attempting to sync all vnodes on a mountlist.  I do not believe this
   race is important.  If I'm wrong this will make these locations easier
   to find.

Reviewed by:	kib (earlier diff)
Tested by:	kris, pho (earlier diff)

1 files changed, 14 insertions, 12 deletions

diff --git a/sys/ufs/ffs/ffs_vnops.c b/sys/ufs/ffs/ffs_vnops.c
index 7968662..dca262c 100644
--- a/sys/ufs/ffs/ffs_vnops.c
+++ b/sys/ufs/ffs/ffs_vnops.c
@@ -195,6 +195,7 @@ int
 ffs_syncvnode(struct vnode *vp, int waitfor)
 {
 	struct inode *ip = VTOI(vp);
+	struct bufobj *bo;
 	struct buf *bp;
 	struct buf *nbp;
 	int s, error, wait, passes, skipmeta;
@@ -202,6 +203,7 @@ ffs_syncvnode(struct vnode *vp, int waitfor)
 
 	wait = (waitfor == MNT_WAIT);
 	lbn = lblkno(ip->i_fs, (ip->i_size + ip->i_fs->fs_bsize - 1));
+	bo = &vp->v_bufobj;
 
 	/*
 	 * Flush all dirty buffers associated with a vnode.
@@ -211,11 +213,11 @@ ffs_syncvnode(struct vnode *vp, int waitfor)
 	if (wait)
 		skipmeta = 1;
 	s = splbio();
-	VI_LOCK(vp);
+	BO_LOCK(bo);
 loop:
-	TAILQ_FOREACH(bp, &vp->v_bufobj.bo_dirty.bv_hd, b_bobufs)
+	TAILQ_FOREACH(bp, &bo->bo_dirty.bv_hd, b_bobufs)
 		bp->b_vflags &= ~BV_SCANNED;
-	TAILQ_FOREACH_SAFE(bp, &vp->v_bufobj.bo_dirty.bv_hd, b_bobufs, nbp) {
+	TAILQ_FOREACH_SAFE(bp, &bo->bo_dirty.bv_hd, b_bobufs, nbp) {
 		/*
 		 * Reasons to skip this buffer: it has already been considered
 		 * on this pass, this pass is the first time through on a
@@ -231,13 +233,13 @@ loop:
 			continue;
 		if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL))
 			continue;
-		VI_UNLOCK(vp);
+		BO_UNLOCK(bo);
 		if (!wait && !LIST_EMPTY(&bp->b_dep) &&
 		    (bp->b_flags & B_DEFERRED) == 0 &&
 		    buf_countdeps(bp, 0)) {
 			bp->b_flags |= B_DEFERRED;
 			BUF_UNLOCK(bp);
-			VI_LOCK(vp);
+			BO_LOCK(bo);
 			continue;
 		}
 		if ((bp->b_flags & B_DELWRI) == 0)
@@ -286,8 +288,8 @@ loop:
 		 * Since we may have slept during the I/O, we need
 		 * to start from a known point.
 		 */
-		VI_LOCK(vp);
-		nbp = TAILQ_FIRST(&vp->v_bufobj.bo_dirty.bv_hd);
+		BO_LOCK(bo);
+		nbp = TAILQ_FIRST(&bo->bo_dirty.bv_hd);
 	}
 	/*
 	 * If we were asked to do this synchronously, then go back for
@@ -299,8 +301,8 @@ loop:
 	}
 
 	if (wait) {
-		bufobj_wwait(&vp->v_bufobj, 3, 0);
-		VI_UNLOCK(vp);
+		bufobj_wwait(bo, 3, 0);
+		BO_UNLOCK(bo);
 
 		/*
 		 * Ensure that any filesystem metatdata associated
@@ -311,8 +313,8 @@ loop:
 			return (error);
 		s = splbio();
 
-		VI_LOCK(vp);
-		if (vp->v_bufobj.bo_dirty.bv_cnt > 0) {
+		BO_LOCK(bo);
+		if (bo->bo_dirty.bv_cnt > 0) {
 			/*
 			 * Block devices associated with filesystems may
 			 * have new I/O requests posted for them even if
@@ -331,7 +333,7 @@ loop:
 #endif
 		}
 	}
-	VI_UNLOCK(vp);
+	BO_UNLOCK(bo);
 	splx(s);
 	return (ffs_update(vp, wait));
 }