[PATCH] lock exclusively in collect_mounts() and drop_collected_mounts()

Taking namespace_sem shared there isn't worth the trouble, especially with
vfsmount ID allocation about to be added.  That way we know that umount_tree(),
copy_tree() and clone_mnt() are _always_ serialized by namespace_sem.
umount_tree() still needs vfsmount_lock (it manipulates hash chains, among
other things), but that's a separate story.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 4 insertions, 4 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 678f7ce060f2..af2fb3707d0a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1091,20 +1091,20 @@ Enomem:
 struct vfsmount *collect_mounts(struct vfsmount *mnt, struct dentry *dentry)
 {
         struct vfsmount *tree;
-        down_read(&namespace_sem);
+        down_write(&namespace_sem);
         tree = copy_tree(mnt, dentry, CL_COPY_ALL | CL_PRIVATE);
-        up_read(&namespace_sem);
+        up_write(&namespace_sem);
         return tree;
 }
 
 void drop_collected_mounts(struct vfsmount *mnt)
 {
         LIST_HEAD(umount_list);
-        down_read(&namespace_sem);
+        down_write(&namespace_sem);
         spin_lock(&vfsmount_lock);
         umount_tree(mnt, 0, &umount_list);
         spin_unlock(&vfsmount_lock);
-        up_read(&namespace_sem);
+        up_write(&namespace_sem);
         release_mounts(&umount_list);
 }