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, 7 insertions, 3 deletions

diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index 2ac99db3750e..6ce5309ecb7b 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -892,9 +892,13 @@ static const struct inode_operations hostfs_dir_iops = {
 	.setattr	= hostfs_setattr,
 };
 
-static const char *hostfs_follow_link(struct dentry *dentry, void **cookie)
+static const char *hostfs_get_link(struct dentry *dentry,
+				   struct inode *inode, void **cookie)
 {
-	char *link = __getname();
+	char *link;
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+	link = __getname();
 	if (link) {
 		char *path = dentry_name(dentry);
 		int err = -ENOMEM;
@@ -922,7 +926,7 @@ static void hostfs_put_link(struct inode *unused, void *cookie)
 
 static const struct inode_operations hostfs_link_iops = {
 	.readlink	= generic_readlink,
-	.follow_link	= hostfs_follow_link,
+	.get_link	= hostfs_get_link,
 	.put_link	= hostfs_put_link,
 };