[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>

7 files changed, 12 insertions, 12 deletions

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 218621b9958e..32e03000420c 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -555,7 +555,7 @@ static int usbdev_open(struct inode *inode, struct file *file)
         if (imajor(inode) == USB_DEVICE_MAJOR)
                 dev = usbdev_lookup_minor(iminor(inode));
         if (!dev)
-                dev = inode->u.generic_ip;
+                dev = inode->i_private;
         if (!dev) {
                 kfree(ps);
                 goto out;
diff --git a/drivers/usb/core/inode.c b/drivers/usb/core/inode.c
index 3182c2224ba2..482f253085e5 100644
--- a/drivers/usb/core/inode.c
+++ b/drivers/usb/core/inode.c
@@ -402,8 +402,8 @@ static loff_t default_file_lseek (struct file *file, loff_t offset, int orig)
 
 static int default_open (struct inode *inode, struct file *file)
 {
-        if (inode->u.generic_ip)
-                file->private_data = inode->u.generic_ip;
+        if (inode->i_private)
+                file->private_data = inode->i_private;
 
         return 0;
 }
@@ -509,7 +509,7 @@ static struct dentry *fs_create_file (const char *name, mode_t mode,
         } else {
                 if (dentry->d_inode) {
                         if (data)
-                                dentry->d_inode->u.generic_ip = data;
+                                dentry->d_inode->i_private = data;
                         if (fops)
                                 dentry->d_inode->i_fop = fops;
                         dentry->d_inode->i_uid = uid;
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;
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;
diff --git a/drivers/usb/mon/mon_stat.c b/drivers/usb/mon/mon_stat.c
index 1fe01d994a79..86ad2b381c4b 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 f961a770cee2..2fd39b4fa166 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");