Date:   Mon, 12 Sep 2016 21:29:15 +0200
From:   Miklos Szeredi <mszeredi@...hat.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 13/17] vfs: remove unused i_op->readlink

This removes the iop->readlink method, which is now completely unused.

Documentation is updated and a note added to "porting".

Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
---
 Documentation/filesystems/Locking |  2 --
 Documentation/filesystems/porting | 15 +++++++++++++++
 Documentation/filesystems/vfs.txt | 25 ++++++++++++-------------
 include/linux/fs.h                |  3 ---
 4 files changed, 27 insertions(+), 18 deletions(-)

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index d30fb2cb5066..1aa8894ef551 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -54,7 +54,6 @@ prototypes:
 			struct inode *, struct dentry *);
 	int (*rename2) (struct inode *, struct dentry *,
 			struct inode *, struct dentry *, unsigned int);
-	int (*readlink) (struct dentry *, char __user *,int);
 	const char *(*get_link) (struct dentry *, struct inode *, void **);
 	void (*truncate) (struct inode *);
 	int (*permission) (struct inode *, int, unsigned int);
@@ -85,7 +84,6 @@ unlink:		yes (both)
 rmdir:		yes (both)	(see below)
 rename:		yes (all)	(see below)
 rename2:	yes (all)	(see below)
-readlink:	no
 get_link:	no
 setattr:	yes
 permission:	no (may not block if called in rcu-walk mode)
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index b1bd05ea66b2..dcd2b77a9f90 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -592,3 +592,18 @@ in your dentry operations instead.
 	work just as well; if it's something more complicated, use dentry->d_parent.
 	Just be careful not to assume that fetching it more than once will yield
 	the same value - in RCU mode it could change under you.
+--
+[mandatory]
+	->readlink() i_op is gone, all of its functionality taken over by
+	->get_link().  If the filesystem set .readlink to generic_readlink,
+	then it doesn't need to do anything besides removing this
+	assignment.
+
+	In the unlikely case that ->get_link() calls nd_jump_link(), then
+	it needs to do that conditionally, only if is_following_link()
+	returns true.  Otherwise it should return the string representation
+	of the symlink, as the old ->readlink() implementation did.
+
+	If the filesystem set .readlink but not .get_link, then it needs to
+	port the readlink implementation to the get_link interface and set
+	IOP_NOFOLLOW in inode->i_opflags to prevent following the symlink.
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 9ace359d6cc5..3914dc728151 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -349,7 +349,6 @@ struct inode_operations {
 			struct inode *, struct dentry *);
 	int (*rename2) (struct inode *, struct dentry *,
 			struct inode *, struct dentry *, unsigned int);
-	int (*readlink) (struct dentry *, char __user *,int);
 	const char *(*get_link) (struct dentry *, struct inode *,
 				 struct delayed_call *);
 	int (*permission) (struct inode *, int);
@@ -430,19 +429,19 @@ 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
+  get_link: called by the VFS to read or 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
-	to traverse (and possibly resets the current position with
-	nd_jump_link()).  If the body won't go away until the inode
-	is gone, nothing else is needed; if it needs to be otherwise
-	pinned, arrange for its release by having get_link(..., ..., done)
-	do set_delayed_call(done, destructor, argument).
-	In that case destructor(argument) will be called once VFS is
-	done with the body you've returned.
+	symbolic links.  This method returns the symlink body (and if
+	is_following_link() is true, then possibly resets the current
+	position with nd_jump_link()).
+
+	If the body won't go away until the inode is gone, nothing else
+	is needed; if it needs to be otherwise pinned, arrange for its
+	release by having get_link(..., ..., done) do
+	set_delayed_call(done, destructor, argument).  In that case
+	destructor(argument) will be called once VFS is done with the
+	body you've returned.
+
 	May be called in RCU mode; that is indicated by NULL dentry
 	argument.  If request can't be handled without leaving RCU mode,
 	have it return ERR_PTR(-ECHILD).
diff --git a/include/linux/fs.h b/include/linux/fs.h
index bcb0bc774cb6..31e940cb7a4f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1722,9 +1722,6 @@ struct inode_operations {
 	const char * (*get_link) (struct dentry *, struct inode *, struct delayed_call *);
 	int (*permission) (struct inode *, int);
 	struct posix_acl * (*get_acl)(struct inode *, int);
-
-	int (*readlink) (struct dentry *, char __user *,int);
-
 	int (*create) (struct inode *,struct dentry *, umode_t, bool);
 	int (*link) (struct dentry *,struct inode *,struct dentry *);
 	int (*unlink) (struct inode *,struct dentry *);
-- 
2.5.5

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