[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, 2 insertions, 2 deletions

diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index f7aef5b..5bf06a1 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -177,7 +177,7 @@ int devpts_pty_new(struct tty_struct *tty)
 	inode->i_gid = config.setgid ? config.gid : current->fsgid;
 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 	init_special_inode(inode, S_IFCHR|config.mode, device);
-	inode->u.generic_ip = tty;
+	inode->i_private = tty;
 
 	dentry = get_node(number);
 	if (!IS_ERR(dentry) && !dentry->d_inode)
@@ -196,7 +196,7 @@ struct tty_struct *devpts_get_tty(int number)
 	tty = NULL;
 	if (!IS_ERR(dentry)) {
 		if (dentry->d_inode)
-			tty = dentry->d_inode->u.generic_ip;
+			tty = dentry->d_inode->i_private;
 		dput(dentry);
 	}