[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, 2 insertions, 2 deletions

diff --git a/fs/autofs/inode.c b/fs/autofs/inode.c
index c81d6b8c2828..d39d2acd9b38 100644
--- a/fs/autofs/inode.c
+++ b/fs/autofs/inode.c
@@ -241,7 +241,7 @@ static void autofs_read_inode(struct inode *inode)
                 
                 inode->i_op = &autofs_symlink_inode_operations;
                 sl = &sbi->symlink[n];
-                inode->u.generic_ip = sl;
+                inode->i_private = sl;
                 inode->i_mode = S_IFLNK | S_IRWXUGO;
                 inode->i_mtime.tv_sec = inode->i_ctime.tv_sec = sl->mtime;
                 inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 0;
diff --git a/fs/autofs/symlink.c b/fs/autofs/symlink.c
index 52e8772b066e..c74f2eb65775 100644
--- a/fs/autofs/symlink.c
+++ b/fs/autofs/symlink.c
@@ -15,7 +15,7 @@
 /* Nothing to release.. */
 static void *autofs_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
-        char *s=((struct autofs_symlink *)dentry->d_inode->u.generic_ip)->data;
+        char *s=((struct autofs_symlink *)dentry->d_inode->i_private)->data;
         nd_set_link(nd, s);
         return NULL;
 }