[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>

2 files changed, 2 insertions, 2 deletions

diff --git a/drivers/usb/host/isp116x-hcd.c b/drivers/usb/host/isp116x-hcd.c
index 5147ed4a6662..8c6b38a0b5bb 100644
--- a/drivers/usb/host/isp116x-hcd.c
+++ b/drivers/usb/host/isp116x-hcd.c
@@ -1204,7 +1204,7 @@ static int isp116x_show_dbg(struct seq_file *s, void *unused)
 
 static int isp116x_open_seq(struct inode *inode, struct file *file)
 {
-        return single_open(file, isp116x_show_dbg, inode->u.generic_ip);
+        return single_open(file, isp116x_show_dbg, inode->i_private);
 }
 
 static struct file_operations isp116x_debug_fops = {
diff --git a/drivers/usb/host/uhci-debug.c b/drivers/usb/host/uhci-debug.c
index dc286a48cafd..d1372cb27f33 100644
--- a/drivers/usb/host/uhci-debug.c
+++ b/drivers/usb/host/uhci-debug.c
@@ -428,7 +428,7 @@ struct uhci_debug {
 
 static int uhci_debug_open(struct inode *inode, struct file *file)
 {
-        struct uhci_hcd *uhci = inode->u.generic_ip;
+        struct uhci_hcd *uhci = inode->i_private;
         struct uhci_debug *up;
         int ret = -ENOMEM;
         unsigned long flags;