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, 8 insertions, 3 deletions

diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c
index ec5c8325b503..b91c01ebb688 100644
--- a/fs/configfs/symlink.c
+++ b/fs/configfs/symlink.c
@@ -279,11 +279,16 @@ static int configfs_getlink(struct dentry *dentry, char * path)
 
 }
 
-static const char *configfs_follow_link(struct dentry *dentry, void **cookie)
+static const char *configfs_get_link(struct dentry *dentry,
+                                     struct inode *inode, void **cookie)
 {
-        unsigned long page = get_zeroed_page(GFP_KERNEL);
+        unsigned long page;
         int error;
 
+        if (!dentry)
+                return ERR_PTR(-ECHILD);
+
+        page = get_zeroed_page(GFP_KERNEL);
         if (!page)
                 return ERR_PTR(-ENOMEM);
 
@@ -297,7 +302,7 @@ static const char *configfs_follow_link(struct dentry *dentry, void **cookie)
 }
 
 const struct inode_operations configfs_symlink_inode_operations = {
-        .follow_link = configfs_follow_link,
+        .get_link = configfs_get_link,
         .readlink = generic_readlink,
         .put_link = free_page_put_link,
         .setattr = configfs_setattr,