fs: Remove i_cindex from struct inode

The only user of the i_cindex element in the inode structure is used
is by the firewire drivers.  As part of an attempt to slim down the
inode structure to save memory --- since a typical Linux system will
have hundreds of thousands if not millions of inodes cached, a
reduction in the size inode has high leverage.

The firewire driver does not need i_cindex in any fast path, so it's
simple enough to calculate when it is needed, instead of wasting space
in the inode structure.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: krh@redhat.com
Cc: stefanr@s5r6.in-berlin.de
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 13 insertions, 1 deletions

diff --git a/fs/char_dev.c b/fs/char_dev.c
index 38f71222a552..b7c9d5187a75 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -375,7 +375,6 @@ static int chrdev_open(struct inode *inode, struct file *filp)
                 p = inode->i_cdev;
                 if (!p) {
                         inode->i_cdev = p = new;
-                        inode->i_cindex = idx;
                         list_add(&inode->i_devices, &p->list);
                         new = NULL;
                 } else if (!cdev_get(p))
@@ -405,6 +404,18 @@ static int chrdev_open(struct inode *inode, struct file *filp)
         return ret;
 }
 
+int cdev_index(struct inode *inode)
+{
+        int idx;
+        struct kobject *kobj;
+
+        kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
+        if (!kobj)
+                return -1;
+        kobject_put(kobj);
+        return idx;
+}
+
 void cd_forget(struct inode *inode)
 {
         spin_lock(&cdev_lock);
@@ -557,6 +568,7 @@ EXPORT_SYMBOL(cdev_init);
 EXPORT_SYMBOL(cdev_alloc);
 EXPORT_SYMBOL(cdev_del);
 EXPORT_SYMBOL(cdev_add);
+EXPORT_SYMBOL(cdev_index);
 EXPORT_SYMBOL(register_chrdev);
 EXPORT_SYMBOL(unregister_chrdev);
 EXPORT_SYMBOL(directly_mappable_cdev_bdi);