From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sat, 22 Mar 2008 20:19:49 +0000 (-0400)
Subject: [PATCH] lock exclusively in collect_mounts() and drop_collected_mounts()
X-Git-Tag: v2.6.26-rc1~1097^2~7
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=1a60a280778ff90270fc7390d9ec102f713a5a29;p=linux-2.6-omap-h63xx.git

[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>
---

diff --git a/fs/namespace.c b/fs/namespace.c
index 678f7ce060f..af2fb3707d0 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);
 }