namei: move clearing LOOKUP_RCU towards rcu_read_unlock()

try_to_unlazy()/try_to_unlazy_next() drop LOOKUP_RCU in the
very beginning and do rcu_read_unlock() only at the very end.
However, nothing done in between even looks at the flag in
question; might as well clear it at the same time we unlock.

Note that try_to_unlazy_next() used to call legitimize_mnt(),
which might drop/regain rcu_read_lock() in some cases.  This
is no longer true, so we really have rcu_read_lock() held
all along until the end.

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

diff --git a/fs/namei.c b/fs/namei.c
index e864d5b9eeac192fcba1d132c87e9e9a9aab05c7..4b7a2147c2070a86d73e8e4c3b06ee23b4760997 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -665,6 +665,12 @@ static void drop_links(struct nameidata *nd)
        }
 }
 
+static void leave_rcu(struct nameidata *nd)
+{
+       nd->flags &= ~LOOKUP_RCU;
+       rcu_read_unlock();
+}
+
 static void terminate_walk(struct nameidata *nd)
 {
        drop_links(nd);
@@ -678,8 +684,7 @@ static void terminate_walk(struct nameidata *nd)
                        nd->state &= ~ND_ROOT_GRABBED;
                }
        } else {
-               nd->flags &= ~LOOKUP_RCU;
-               rcu_read_unlock();
+               leave_rcu(nd);
        }
        nd->depth = 0;
        nd->path.mnt = NULL;
@@ -765,14 +770,13 @@ static bool try_to_unlazy(struct nameidata *nd)
 
        BUG_ON(!(nd->flags & LOOKUP_RCU));
 
-       nd->flags &= ~LOOKUP_RCU;
        if (unlikely(!legitimize_links(nd)))
                goto out1;
        if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
                goto out;
        if (unlikely(!legitimize_root(nd)))
                goto out;
-       rcu_read_unlock();
+       leave_rcu(nd);
        BUG_ON(nd->inode != parent->d_inode);
        return true;
 
@@ -780,7 +784,7 @@ out1:
        nd->path.mnt = NULL;
        nd->path.dentry = NULL;
 out:
-       rcu_read_unlock();
+       leave_rcu(nd);
        return false;
 }
 
@@ -802,7 +806,6 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsi
        int res;
        BUG_ON(!(nd->flags & LOOKUP_RCU));
 
-       nd->flags &= ~LOOKUP_RCU;
        if (unlikely(!legitimize_links(nd)))
                goto out2;
        res = __legitimize_mnt(nd->path.mnt, nd->m_seq);
@@ -831,7 +834,7 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsi
         */
        if (unlikely(!legitimize_root(nd)))
                goto out_dput;
-       rcu_read_unlock();
+       leave_rcu(nd);
        return true;
 
 out2:
@@ -839,10 +842,10 @@ out2:
 out1:
        nd->path.dentry = NULL;
 out:
-       rcu_read_unlock();
+       leave_rcu(nd);
        return false;
 out_dput:
-       rcu_read_unlock();
+       leave_rcu(nd);
        dput(dentry);
        return false;
 }