[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, 5 insertions, 5 deletions

diff --git a/drivers/oprofile/oprofilefs.c b/drivers/oprofile/oprofilefs.c
index 71c2da277d6..deb37354785 100644
--- a/drivers/oprofile/oprofilefs.c
+++ b/drivers/oprofile/oprofilefs.c
@@ -110,8 +110,8 @@ static ssize_t ulong_write_file(struct file * file, char const __user * buf, siz
 
 static int default_open(struct inode * inode, struct file * filp)
 {
-        if (inode->u.generic_ip)
-                filp->private_data = inode->u.generic_ip;
+        if (inode->i_private)
+                filp->private_data = inode->i_private;
         return 0;
 }
 
@@ -158,7 +158,7 @@ int oprofilefs_create_ulong(struct super_block * sb, struct dentry * root,
         if (!d)
                 return -EFAULT;
 
-        d->d_inode->u.generic_ip = val;
+        d->d_inode->i_private = val;
         return 0;
 }
 
@@ -171,7 +171,7 @@ int oprofilefs_create_ro_ulong(struct super_block * sb, struct dentry * root,
         if (!d)
                 return -EFAULT;
 
-        d->d_inode->u.generic_ip = val;
+        d->d_inode->i_private = val;
         return 0;
 }
 
@@ -197,7 +197,7 @@ int oprofilefs_create_ro_atomic(struct super_block * sb, struct dentry * root,
         if (!d)
                 return -EFAULT;
 
-        d->d_inode->u.generic_ip = val;
+        d->d_inode->i_private = val;
         return 0;
 }