[PATCH] inode_diet: Replace inode.u.generic_ip with inode.i_private

The following patches reduce the size of the VFS inode structure by 28 bytes
on a UP x86.  (It would be more on an x86_64 system).  This is a 10% reduction
in the inode size on a UP kernel that is configured in a production mode
(i.e., with no spinlock or other debugging functions enabled; if you want to
save memory taken up by in-core inodes, the first thing you should do is
disable the debugging options; they are responsible for a huge amount of bloat
in the VFS inode structure).

This patch:

The filesystem or device-specific pointer in the inode is inside a union,
which is pretty pointless given that all 30+ users of this field have been
using the void pointer.  Get rid of the union and rename it to i_private, with
a comment to explain who is allowed to use the void pointer.  This is just a
cleanup, but it allows us to reuse the union 'u' for something something where
the union will actually be used.

[judith@osdl.org: powerpc build fix]
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Judith Lebzelter <judith@osdl.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
index 3bdc5e3ba234..ffaa8c1afad8 100644
--- a/drivers/usb/gadget/inode.c
+++ b/drivers/usb/gadget/inode.c
@@ -844,7 +844,7 @@ fail1:
 static int
 ep_open (struct inode *inode, struct file *fd)
 {
-        struct ep_data          *data = inode->u.generic_ip;
+        struct ep_data          *data = inode->i_private;
         int                     value = -EBUSY;
 
         if (down_interruptible (&data->lock) != 0)
@@ -1909,7 +1909,7 @@ fail:
 static int
 dev_open (struct inode *inode, struct file *fd)
 {
-        struct dev_data         *dev = inode->u.generic_ip;
+        struct dev_data         *dev = inode->i_private;
         int                     value = -EBUSY;
 
         if (dev->state == STATE_DEV_DISABLED) {
@@ -1970,7 +1970,7 @@ gadgetfs_make_inode (struct super_block *sb,
                 inode->i_blocks = 0;
                 inode->i_atime = inode->i_mtime = inode->i_ctime
                                 = CURRENT_TIME;
-                inode->u.generic_ip = data;
+                inode->i_private = data;
                 inode->i_fop = fops;
         }
         return inode;