split __follow_mount_rcu() into normal and .. cases

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

1 files changed, 26 insertions, 9 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 2358b326b221..da9c26578663 100644
--- 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))