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, 9 insertions, 4 deletions

diff --git a/fs/autofs4/symlink.c b/fs/autofs4/symlink.c
index da0c33481bc0..39e6f0bdf8e3 100644
--- a/fs/autofs4/symlink.c
+++ b/fs/autofs4/symlink.c
@@ -12,10 +12,15 @@
 
 #include "autofs_i.h"
 
-static const char *autofs4_follow_link(struct dentry *dentry, void **cookie)
+static const char *autofs4_get_link(struct dentry *dentry,
+				    struct inode *inode, void **cookie)
 {
-	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
-	struct autofs_info *ino = autofs4_dentry_ino(dentry);
+	struct autofs_sb_info *sbi;
+	struct autofs_info *ino;
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+	sbi = autofs4_sbi(dentry->d_sb);
+	ino = autofs4_dentry_ino(dentry);
 	if (ino && !autofs4_oz_mode(sbi))
 		ino->last_used = jiffies;
 	return d_inode(dentry)->i_private;
@@ -23,5 +28,5 @@ static const char *autofs4_follow_link(struct dentry *dentry, void **cookie)
 
 const struct inode_operations autofs4_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= autofs4_follow_link
+	.get_link	= autofs4_get_link
 };