replace ->follow_link() with new method that could stay in RCU mode

new method: ->get_link(); replacement of ->follow_link().  The differences
are:
	* inode and dentry are passed separately
	* might be called both in RCU and non-RCU mode;
the former is indicated by passing it a NULL dentry.
	* when called that way it isn't allowed to block
and should return ERR_PTR(-ECHILD) if it needs to be called
in non-RCU mode.

It's a flagday change - the old method is gone, all in-tree instances
converted.  Conversion isn't hard; said that, so far very few instances
do not immediately bail out when called in RCU mode.  That'll change
in the next commits.

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

3 files changed, 6 insertions, 6 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index cbc0f4b..4593f416 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -900,7 +900,7 @@ const struct inode_operations cifs_file_inode_ops = {
 
 const struct inode_operations cifs_symlink_inode_ops = {
 	.readlink = generic_readlink,
-	.follow_link = cifs_follow_link,
+	.get_link = cifs_get_link,
 	.put_link = kfree_put_link,
 	.permission = cifs_permission,
 	/* BB add the following two eventually */
diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index c3cc160..6886328 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -120,9 +120,7 @@ extern struct vfsmount *cifs_dfs_d_automount(struct path *path);
 #endif
 
 /* Functions related to symlinks */
-extern const char *cifs_follow_link(struct dentry *direntry, void **cookie);
-extern int cifs_readlink(struct dentry *direntry, char __user *buffer,
-			 int buflen);
+extern const char *cifs_get_link(struct dentry *, struct inode *, void **);
 extern int cifs_symlink(struct inode *inode, struct dentry *direntry,
 			const char *symname);
 extern int	cifs_removexattr(struct dentry *, const char *);
diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index e3548f7..6f2439b5 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -627,9 +627,8 @@ cifs_hl_exit:
 }
 
 const char *
-cifs_follow_link(struct dentry *direntry, void **cookie)
+cifs_get_link(struct dentry *direntry, struct inode *inode, void **cookie)
 {
-	struct inode *inode = d_inode(direntry);
 	int rc = -ENOMEM;
 	unsigned int xid;
 	char *full_path = NULL;
@@ -639,6 +638,9 @@ cifs_follow_link(struct dentry *direntry, void **cookie)
 	struct cifs_tcon *tcon;
 	struct TCP_Server_Info *server;
 
+	if (!direntry)
+		return ERR_PTR(-ECHILD);
+
 	xid = get_xid();
 
 	tlink = cifs_sb_tlink(cifs_sb);