[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, 3 insertions, 3 deletions

diff --git a/drivers/usb/mon/mon_stat.c b/drivers/usb/mon/mon_stat.c
index 1fe01d9..86ad2b3 100644
--- a/drivers/usb/mon/mon_stat.c
+++ b/drivers/usb/mon/mon_stat.c
@@ -28,7 +28,7 @@ static int mon_stat_open(struct inode *inode, struct file *file)
 	if ((sp = kmalloc(sizeof(struct snap), GFP_KERNEL)) == NULL)
 		return -ENOMEM;
 
-	mbus = inode->u.generic_ip;
+	mbus = inode->i_private;
 
 	sp->slen = snprintf(sp->str, STAT_BUF_SIZE,
 	    "nreaders %d events %u text_lost %u\n",
diff --git a/drivers/usb/mon/mon_text.c b/drivers/usb/mon/mon_text.c
index f961a77..2fd39b4 100644
--- a/drivers/usb/mon/mon_text.c
+++ b/drivers/usb/mon/mon_text.c
@@ -238,7 +238,7 @@ static int mon_text_open(struct inode *inode, struct file *file)
 	int rc;
 
 	mutex_lock(&mon_lock);
-	mbus = inode->u.generic_ip;
+	mbus = inode->i_private;
 	ubus = mbus->u_bus;
 
 	rp = kzalloc(sizeof(struct mon_reader_text), GFP_KERNEL);
@@ -401,7 +401,7 @@ static int mon_text_release(struct inode *inode, struct file *file)
 	struct mon_event_text *ep;
 
 	mutex_lock(&mon_lock);
-	mbus = inode->u.generic_ip;
+	mbus = inode->i_private;
 
 	if (mbus->nreaders <= 0) {
 		printk(KERN_ERR TAG ": consistency error on close\n");