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, 6 insertions, 3 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 5e2e08712d3b..148e8ef7c541 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1365,14 +1365,17 @@ static int fuse_readdir(struct file *file, struct dir_context *ctx)
         return err;
 }
 
-static const char *fuse_follow_link(struct dentry *dentry, void **cookie)
+static const char *fuse_get_link(struct dentry *dentry,
+                                 struct inode *inode, void **cookie)
 {
-        struct inode *inode = d_inode(dentry);
         struct fuse_conn *fc = get_fuse_conn(inode);
         FUSE_ARGS(args);
         char *link;
         ssize_t ret;
 
+        if (!dentry)
+                return ERR_PTR(-ECHILD);
+
         link = (char *) __get_free_page(GFP_KERNEL);
         if (!link)
                 return ERR_PTR(-ENOMEM);
@@ -1909,7 +1912,7 @@ static const struct inode_operations fuse_common_inode_operations = {
 
 static const struct inode_operations fuse_symlink_inode_operations = {
         .setattr        = fuse_setattr,
-        .follow_link    = fuse_follow_link,
+        .get_link       = fuse_get_link,
         .put_link       = free_page_put_link,
         .readlink       = generic_readlink,
         .getattr        = fuse_getattr,