sysfs, kernfs: make inode number ida per kernfs_root

kernfs is being updated to allow multiple sysfs_dirent hierarchies so
that it can also be used by other users.  Currently, inode number is
allocated using a global ida, sysfs_ino_ida; however, inos for
different hierarchies should be handled separately.

This patch makes ino allocation per kernfs_root.  sysfs_ino_ida is
replaced by kernfs_root->ino_ida and sysfs_new_dirent() is updated to
take @root and allocate ino from it.  ida_simple_get/remove() are used
instead of sysfs_ino_lock and sysfs_alloc/free_ino().

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
index af3570b..004c164 100644
--- a/fs/kernfs/symlink.c
+++ b/fs/kernfs/symlink.c
@@ -30,7 +30,8 @@
 	struct sysfs_addrm_cxt acxt;
 	int error;
 
-	sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
+	sd = sysfs_new_dirent(kernfs_root(parent), name, S_IFLNK|S_IRWXUGO,
+			      SYSFS_KOBJ_LINK);
 	if (!sd)
 		return ERR_PTR(-ENOMEM);