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>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index e3548f73bdea..6f2439b508b5 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);