- Solve a problem where a vput could be called on an outgoing directory

   without Giant held.  Do this by tracking the vfslocked state for
   the directory seperate from the child.  This is only important
   in the case where we cross a mountpoint.

Sponsored by:	Isilon Systems, Inc.
MFC After:	3 days

1 files changed, 13 insertions, 5 deletions

diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
index 8ad90bb..42327ca 100644
--- a/sys/kern/vfs_lookup.c
+++ b/sys/kern/vfs_lookup.c
@@ -60,7 +60,7 @@ __FBSDID("$FreeBSD$");
 
 #include <vm/uma.h>
 
-#define NAMEI_DIAGNOSTIC 1
+#define	NAMEI_DIAGNOSTIC 1
 #undef NAMEI_DIAGNOSTIC
 
 /*
@@ -352,11 +352,13 @@ lookup(ndp)
 	struct thread *td = cnp->cn_thread;
 	int vfslocked;
 	int tvfslocked;
+	int dvfslocked;
 
 	/*
 	 * Setup: break out flag bits into variables.
 	 */
 	vfslocked = (ndp->ni_cnd.cn_flags & GIANTHELD) != 0;
+	dvfslocked = 0;
 	ndp->ni_cnd.cn_flags &= ~GIANTHELD;
 	wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
 	KASSERT(cnp->cn_nameiop == LOOKUP || wantparent,
@@ -623,9 +625,8 @@ unionlookup:
 		if (vfs_busy(mp, 0, 0, td))
 			continue;
 		vput(dp);
-		tvfslocked = VFS_LOCK_GIANT(mp);
-		VFS_UNLOCK_GIANT(vfslocked);
-		vfslocked = tvfslocked;
+		dvfslocked = vfslocked;
+		vfslocked = VFS_LOCK_GIANT(mp);
 		VOP_UNLOCK(ndp->ni_dvp, 0, td);
 		error = VFS_ROOT(mp, cnp->cn_lkflags, &tdp, td);
 		VOP_LOCK(ndp->ni_dvp, cnp->cn_lkflags | LK_RETRY, td);
@@ -687,6 +688,8 @@ nextname:
 			vput(ndp->ni_dvp);
 		else
 			vrele(ndp->ni_dvp);
+		VFS_UNLOCK_GIANT(dvfslocked);
+		dvfslocked = 0;
 		goto dirloop;
 	}
 	/*
@@ -706,13 +709,17 @@ nextname:
 			vput(ndp->ni_dvp);
 		else
 			vrele(ndp->ni_dvp);
+		VFS_UNLOCK_GIANT(dvfslocked);
+		dvfslocked = 0;
 	} else if ((cnp->cn_flags & LOCKPARENT) == 0 && ndp->ni_dvp != dp)
 		VOP_UNLOCK(ndp->ni_dvp, 0, td);
 
 	if ((cnp->cn_flags & LOCKLEAF) == 0)
 		VOP_UNLOCK(dp, 0, td);
 success:
-	if (vfslocked)
+	if (vfslocked && dvfslocked)
+		VFS_UNLOCK_GIANT(dvfslocked);	/* Only need one */
+	if (vfslocked || dvfslocked)
 		ndp->ni_cnd.cn_flags |= GIANTHELD;
 	return (0);
 
@@ -725,6 +732,7 @@ bad:
 	if (!dpunlocked)
 		vput(dp);
 	VFS_UNLOCK_GIANT(vfslocked);
+	VFS_UNLOCK_GIANT(dvfslocked);
 	ndp->ni_cnd.cn_flags &= ~GIANTHELD;
 	ndp->ni_vp = NULL;
 	return (error);