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D37458.id113395.diff
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diff --git a/sys/fs/nullfs/null_vfsops.c b/sys/fs/nullfs/null_vfsops.c
--- a/sys/fs/nullfs/null_vfsops.c
+++ b/sys/fs/nullfs/null_vfsops.c
@@ -201,6 +201,12 @@
&xmp->notify_node);
}
+ if (lowerrootvp == mp->mnt_vnodecovered) {
+ vn_lock(lowerrootvp, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
+ lowerrootvp->v_vflag |= VV_CROSSLOCK;
+ VOP_UNLOCK(lowerrootvp);
+ }
+
MNT_ILOCK(mp);
if ((xmp->nullm_flags & NULLM_CACHE) != 0) {
mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag &
@@ -261,6 +267,11 @@
vfs_unregister_for_notification(mntdata->nullm_vfs,
&mntdata->notify_node);
}
+ if (mntdata->nullm_lowerrootvp == mp->mnt_vnodecovered) {
+ vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
+ mp->mnt_vnodecovered->v_vflag &= ~VV_CROSSLOCK;
+ VOP_UNLOCK(mp->mnt_vnodecovered);
+ }
vfs_unregister_upper(mntdata->nullm_vfs, &mntdata->upper_node);
vrele(mntdata->nullm_lowerrootvp);
mp->mnt_data = NULL;
diff --git a/sys/fs/unionfs/union_vfsops.c b/sys/fs/unionfs/union_vfsops.c
--- a/sys/fs/unionfs/union_vfsops.c
+++ b/sys/fs/unionfs/union_vfsops.c
@@ -329,7 +329,7 @@
* order unionfs currently requires.
*/
if (!below) {
- vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY);
+ vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
mp->mnt_vnodecovered->v_vflag |= VV_CROSSLOCK;
VOP_UNLOCK(mp->mnt_vnodecovered);
}
@@ -386,7 +386,7 @@
if (error)
return (error);
- vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY);
+ vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
mp->mnt_vnodecovered->v_vflag &= ~VV_CROSSLOCK;
VOP_UNLOCK(mp->mnt_vnodecovered);
vfs_unregister_upper(ump->um_lowervp->v_mount, &ump->um_lower_link);
diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
--- a/sys/kern/vfs_lookup.c
+++ b/sys/kern/vfs_lookup.c
@@ -1265,14 +1265,28 @@
crosslock = (dp->v_vflag & VV_CROSSLOCK) != 0;
crosslkflags = compute_cn_lkflags(mp, cnp->cn_lkflags,
cnp->cn_flags);
- if (__predict_false(crosslock) &&
- (crosslkflags & LK_EXCLUSIVE) != 0 &&
- VOP_ISLOCKED(dp) != LK_EXCLUSIVE) {
- vn_lock(dp, LK_UPGRADE | LK_RETRY);
- if (VN_IS_DOOMED(dp)) {
- error = ENOENT;
- goto bad2;
- }
+ if (__predict_false(crosslock)) {
+ /*
+ * We are going to be holding the vnode lock, which
+ * in this case is shared by the root vnode of the
+ * filesystem mounted at mp, across the call to
+ * VFS_ROOT(). Make the situation clear to the
+ * filesystem by passing LK_CANRECURSE if the
+ * lock is held exclusive, or by clearinng
+ * LK_NODDLKTREAT to allow recursion on the shared
+ * lock in the presence of an exclusive waiter.
+ */
+ if (VOP_ISLOCKED(dp) == LK_EXCLUSIVE) {
+ crosslkflags &= ~LK_SHARED;
+ crosslkflags |= (LK_EXCLUSIVE | LK_CANRECURSE);
+ } else if ((crosslkflags & LK_EXCLUSIVE) != 0) {
+ vn_lock(dp, LK_UPGRADE | LK_RETRY);
+ if (VN_IS_DOOMED(dp)) {
+ error = ENOENT;
+ goto bad2;
+ }
+ } else
+ crosslkflags &= ~LK_NODDLKTREAT;
}
if (vfs_busy(mp, 0) != 0)
continue;

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