vfs: reorganize 'struct inode' layout a bit

This tries to make the 'struct inode' accesses denser in the data cache
by moving a commonly accessed field (i_security) closer to other fields
that are accessed often.

It also makes 'i_state' just an 'unsigned int' rather than 'unsigned
long', since we only use a few bits of that field, and moves it next to
the existing 'i_flags' so that we potentially get better structure
layout (although depending on config options, i_flags may already have
packed in the same word as i_lock, so this improves packing only for the
case of spinlock debugging)

Out 'struct inode' is still way too big, and we should probably move
some other fields around too (the acl fields in particular) for better
data cache access density. Other fields (like the inode hash) are
likely to be entirely irrelevant under most loads.

Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/fs.h

···
 
 	spinlock_t		i_lock;	/* i_blocks, i_bytes, maybe i_size */
 	unsigned int		i_flags;
+	unsigned int		i_state;
+#ifdef CONFIG_SECURITY
+	void			*i_security;
+#endif
 	struct mutex		i_mutex;
 
-	unsigned long		i_state;
+
 	unsigned long		dirtied_when;	/* jiffies of first dirtying */
 
 	struct hlist_node	i_hash;
···
 	atomic_t		i_readcount; /* struct files open RO */
 #endif
 	atomic_t		i_writecount;
-#ifdef CONFIG_SECURITY
-	void			*i_security;
-#endif
 #ifdef CONFIG_FS_POSIX_ACL
 	struct posix_acl	*i_acl;
 	struct posix_acl	*i_default_acl;