split __follow_mount_rcu() into normal and .. cases

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

diff --git a/fs/namei.c b/fs/namei.c
index 2358b326b2211ef93b912e7a43062763de8999a9..da9c26578663bba550e8e2699016132602412d91 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -919,12 +919,11 @@ static inline bool managed_dentry_might_block(struct dentry *dentry)
 }
 
 /*
- * Skip to top of mountpoint pile in rcuwalk mode.  We abort the rcu-walk if we
- * meet a managed dentry and we're not walking to "..".  True is returned to
- * continue, false to abort.
+ * Try to skip to top of mountpoint pile in rcuwalk mode.  Fail if
+ * we meet a managed dentry that would need blocking.
  */
 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
-                              struct inode **inode, bool reverse_transit)
+                              struct inode **inode)
 {
        for (;;) {
                struct vfsmount *mounted;
@@ -933,8 +932,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
                 * that wants to block transit.
                 */
                *inode = path->dentry->d_inode;
-               if (!reverse_transit &&
-                    unlikely(managed_dentry_might_block(path->dentry)))
+               if (unlikely(managed_dentry_might_block(path->dentry)))
                        return false;
 
                if (!d_mountpoint(path->dentry))
@@ -949,10 +947,29 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
        }
 
        if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
-               return reverse_transit;
+               return false;
        return true;
 }
 
+static void follow_mount_rcu(struct nameidata *nd, struct path *path,
+                              struct inode **inode)
+{
+       for (;;) {
+               struct vfsmount *mounted;
+               *inode = path->dentry->d_inode;
+
+               if (!d_mountpoint(path->dentry))
+                       break;
+
+               mounted = __lookup_mnt(path->mnt, path->dentry, 1);
+               if (!mounted)
+                       break;
+               path->mnt = mounted;
+               path->dentry = mounted->mnt_root;
+               nd->seq = read_seqcount_begin(&path->dentry->d_seq);
+       }
+}
+
 static int follow_dotdot_rcu(struct nameidata *nd)
 {
        struct inode *inode = nd->inode;
@@ -982,7 +999,7 @@ static int follow_dotdot_rcu(struct nameidata *nd)
                nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
                inode = nd->path.dentry->d_inode;
        }
-       __follow_mount_rcu(nd, &nd->path, &inode, true);
+       follow_mount_rcu(nd, &nd->path, &inode);
        nd->inode = inode;
        return 0;
 
@@ -1157,7 +1174,7 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
                }
                path->mnt = mnt;
                path->dentry = dentry;
-               if (likely(__follow_mount_rcu(nd, path, inode, false)))
+               if (likely(__follow_mount_rcu(nd, path, inode)))
                        return 0;
 unlazy:
                if (unlazy_walk(nd, dentry))