[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, 8 insertions, 8 deletions

diff --git a/drivers/misc/ibmasm/ibmasmfs.c b/drivers/misc/ibmasm/ibmasmfs.c
index 4a35caff5d02..0e909b617226 100644
--- a/drivers/misc/ibmasm/ibmasmfs.c
+++ b/drivers/misc/ibmasm/ibmasmfs.c
@@ -175,7 +175,7 @@ static struct dentry *ibmasmfs_create_file (struct super_block *sb,
         }
 
         inode->i_fop = fops;
-        inode->u.generic_ip = data;
+        inode->i_private = data;
 
         d_add(dentry, inode);
         return dentry;
@@ -244,7 +244,7 @@ static int command_file_open(struct inode *inode, struct file *file)
 {
         struct ibmasmfs_command_data *command_data;
 
-        if (!inode->u.generic_ip)
+        if (!inode->i_private)
                 return -ENODEV;
 
         command_data = kmalloc(sizeof(struct ibmasmfs_command_data), GFP_KERNEL);
@@ -252,7 +252,7 @@ static int command_file_open(struct inode *inode, struct file *file)
                 return -ENOMEM;
 
         command_data->command = NULL;
-        command_data->sp = inode->u.generic_ip;
+        command_data->sp = inode->i_private;
         file->private_data = command_data;
         return 0;
 }
@@ -351,10 +351,10 @@ static int event_file_open(struct inode *inode, struct file *file)
         struct ibmasmfs_event_data *event_data;
         struct service_processor *sp; 
 
-        if (!inode->u.generic_ip)
+        if (!inode->i_private)
                 return -ENODEV;
 
-        sp = inode->u.generic_ip;
+        sp = inode->i_private;
 
         event_data = kmalloc(sizeof(struct ibmasmfs_event_data), GFP_KERNEL);
         if (!event_data)
@@ -439,14 +439,14 @@ static int r_heartbeat_file_open(struct inode *inode, struct file *file)
 {
         struct ibmasmfs_heartbeat_data *rhbeat;
 
-        if (!inode->u.generic_ip)
+        if (!inode->i_private)
                 return -ENODEV;
 
         rhbeat = kmalloc(sizeof(struct ibmasmfs_heartbeat_data), GFP_KERNEL);
         if (!rhbeat)
                 return -ENOMEM;
 
-        rhbeat->sp = (struct service_processor *)inode->u.generic_ip;
+        rhbeat->sp = inode->i_private;
         rhbeat->active = 0;
         ibmasm_init_reverse_heartbeat(rhbeat->sp, &rhbeat->heartbeat);
         file->private_data = rhbeat;
@@ -508,7 +508,7 @@ static ssize_t r_heartbeat_file_write(struct file *file, const char __user *buf,
 
 static int remote_settings_file_open(struct inode *inode, struct file *file)
 {
-        file->private_data = inode->u.generic_ip;
+        file->private_data = inode->i_private;
         return 0;
 }