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, 3 deletions

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index bd95b9fdebb0..10360b268794 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -393,9 +393,10 @@ static const struct file_operations proc_reg_file_ops_no_compat = {
 };
 #endif
 
-static const char *proc_follow_link(struct dentry *dentry, void **cookie)
+static const char *proc_get_link(struct dentry *dentry,
+                                 struct inode *inode, void **cookie)
 {
-        struct proc_dir_entry *pde = PDE(d_inode(dentry));
+        struct proc_dir_entry *pde = PDE(inode);
         if (unlikely(!use_pde(pde)))
                 return ERR_PTR(-EINVAL);
         *cookie = pde;
@@ -409,7 +410,7 @@ static void proc_put_link(struct inode *unused, void *p)
 
 const struct inode_operations proc_link_inode_operations = {
         .readlink       = generic_readlink,
-        .follow_link    = proc_follow_link,
+        .get_link       = proc_get_link,
         .put_link       = proc_put_link,
 };