[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>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f83d997..6d62267 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -574,7 +574,14 @@
#define RA_FLAG_INCACHE 0x02 /* file is already in cache */
struct file {
- struct list_head f_list;
+ /*
+ * fu_list becomes invalid after file_free is called and queued via
+ * fu_rcuhead for RCU freeing
+ */
+ union {
+ struct list_head fu_list;
+ struct rcu_head fu_rcuhead;
+ } f_u;
struct dentry *f_dentry;
struct vfsmount *f_vfsmnt;
struct file_operations *f_op;
@@ -598,7 +605,6 @@
spinlock_t f_ep_lock;
#endif /* #ifdef CONFIG_EPOLL */
struct address_space *f_mapping;
- struct rcu_head f_rcuhead;
};
extern spinlock_t files_lock;
#define file_list_lock() spin_lock(&files_lock);