4 files changed, 23 insertions, 6 deletions

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index bdd025ceb763..95280079c0b3 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -596,3 +596,7 @@ in your dentry operations instead.
 [mandatory]
         ->rename() has an added flags argument.  Any flags not handled by the
         filesystem should result in EINVAL being returned.
+--
+[recommended]
+        ->readlink is optional for symlinks.  Don't set, unless filesystem needs
+        to fake something for readlink(2).
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index b5039a00caaf..038241123ca5 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -451,9 +451,6 @@ otherwise noted.
         exist; this is checked by the VFS.  Unlike plain rename,
         source and target may be of different type.
 
-  readlink: called by the readlink(2) system call. Only required if
-        you want to support reading symbolic links
-
   get_link: called by the VFS to follow a symbolic link to the
         inode it points to.  Only required if you want to support
         symbolic links.  This method returns the symlink body
@@ -468,6 +465,12 @@ otherwise noted.
         argument.  If request can't be handled without leaving RCU mode,
         have it return ERR_PTR(-ECHILD).
 
+  readlink: this is now just an override for use by readlink(2) for the
+        cases when ->get_link uses nd_jump_link() or object is not in
+        fact a symlink.  Normally filesystems should only implement
+        ->get_link for symlinks and readlink(2) will automatically use
+        that.
+
   permission: called by the VFS to check for access rights on a POSIX-like
         filesystem.
 
diff --git a/fs/namei.c b/fs/namei.c
index 12a4159de72a..b87465d67c60 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4682,10 +4682,19 @@ int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 {
         struct inode *inode = d_inode(dentry);
 
-        if (!inode->i_op->readlink)
-                return -EINVAL;
+        if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {
+                if (unlikely(inode->i_op->readlink))
+                        return inode->i_op->readlink(dentry, buffer, buflen);
+
+                if (!d_is_symlink(dentry))
+                        return -EINVAL;
+
+                spin_lock(&inode->i_lock);
+                inode->i_opflags |= IOP_DEFAULT_READLINK;
+                spin_unlock(&inode->i_lock);
+        }
 
-        return inode->i_op->readlink(dentry, buffer, buflen);
+        return generic_readlink(dentry, buffer, buflen);
 }
 EXPORT_SYMBOL(vfs_readlink);
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index eba20d1c068d..f6c206eae6ac 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -595,6 +595,7 @@ is_uncached_acl(struct posix_acl *acl)
 #define IOP_LOOKUP      0x0002
 #define IOP_NOFOLLOW    0x0004
 #define IOP_XATTR       0x0008
+#define IOP_DEFAULT_READLINK    0x0010
 
 /*
  * Keep mostly read-only and often accessed (especially for