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, 2 deletions

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 245268a0cdf0..f638fd58b5b3 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -414,13 +414,17 @@ xfs_vn_rename(
  * uio is kmalloced for this reason...
  */
 STATIC const char *
-xfs_vn_follow_link(
+xfs_vn_get_link(
         struct dentry           *dentry,
+        struct inode            *inode,
         void                    **cookie)
 {
         char                    *link;
         int                     error = -ENOMEM;
 
+        if (!dentry)
+                return ERR_PTR(-ECHILD);
+
         link = kmalloc(MAXPATHLEN+1, GFP_KERNEL);
         if (!link)
                 goto out_err;
@@ -1172,7 +1176,7 @@ static const struct inode_operations xfs_dir_ci_inode_operations = {
 
 static const struct inode_operations xfs_symlink_inode_operations = {
         .readlink               = generic_readlink,
-        .follow_link            = xfs_vn_follow_link,
+        .get_link               = xfs_vn_get_link,
         .put_link               = kfree_put_link,
         .getattr                = xfs_vn_getattr,
         .setattr                = xfs_vn_setattr,