[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/fs/fuse/control.c b/fs/fuse/control.c
index 46fe60b2da23..79ec1f23d4d2 100644
--- a/fs/fuse/control.c
+++ b/fs/fuse/control.c
@@ -23,7 +23,7 @@ static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file)
 {
 	struct fuse_conn *fc;
 	mutex_lock(&fuse_mutex);
-	fc = file->f_dentry->d_inode->u.generic_ip;
+	fc = file->f_dentry->d_inode->i_private;
 	if (fc)
 		fc = fuse_conn_get(fc);
 	mutex_unlock(&fuse_mutex);
@@ -98,7 +98,7 @@ static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
 		inode->i_op = iop;
 	inode->i_fop = fop;
 	inode->i_nlink = nlink;
-	inode->u.generic_ip = fc;
+	inode->i_private = fc;
 	d_add(dentry, inode);
 	return dentry;
 }
@@ -150,7 +150,7 @@ void fuse_ctl_remove_conn(struct fuse_conn *fc)
 
 	for (i = fc->ctl_ndents - 1; i >= 0; i--) {
 		struct dentry *dentry = fc->ctl_dentry[i];
-		dentry->d_inode->u.generic_ip = NULL;
+		dentry->d_inode->i_private = NULL;
 		d_drop(dentry);
 		dput(dentry);
 	}