[PATCH] reduce sizeof(struct file)

Now that RCU applied on 'struct file' seems stable, we can place f_rcuhead
in a memory location that is not anymore used at call_rcu(&f->f_rcuhead,
file_free_rcu) time, to reduce the size of this critical kernel object.

The trick I used is to move f_rcuhead and f_list in an union called f_u

The callers are changed so that f_rcuhead becomes f_u.fu_rcuhead and f_list
becomes f_u.f_list

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/super.c b/fs/super.c
index 6e57ee252e14..f60155ec7780 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -513,7 +513,7 @@ static void mark_files_ro(struct super_block *sb)
         struct file *f;
 
         file_list_lock();
-        list_for_each_entry(f, &sb->s_files, f_list) {
+        list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
                 if (S_ISREG(f->f_dentry->d_inode->i_mode) && file_count(f))
                         f->f_mode &= ~FMODE_WRITE;
         }