[PATCH] fs.h: ifdef security fields

[assuming BSD security levels are deleted]
The only user of i_security, f_security, s_security fields is SELinux,
however, quite a few security modules are trying to get into kernel.
So, wrap them under CONFIG_SECURITY. Adding config option for each
security field is likely an overkill.

Following Stephen Smalley's suggestion, i_security initialization is
moved to security_inode_alloc() to not clutter core code with ifdefs
and make alloc_inode() codepath tiny little bit smaller and faster.

The user of (highly greppable) struct fown_struct::security field is
still to be found. I've checked every "fown_struct" and every "f_owner"
occurence. Additionally it's removal doesn't break i386 allmodconfig
build.

struct inode, struct file, struct super_block, struct fown_struct
become smaller.

P.S. Combined with two reiserfs inode shrinking patches sent to
linux-fsdevel, I can finally suck 12 reiserfs inodes into one page.

		/proc/slabinfo

	-ext2_inode_cache	388	10
	+ext2_inode_cache	384	10
	-inode_cache		280	14
	+inode_cache		276	14
	-proc_inode_cache	296	13
	+proc_inode_cache	292	13
	-reiser_inode_cache	336	11
	+reiser_inode_cache	332	12 <=
	-shmem_inode_cache	372	10
	+shmem_inode_cache	368	10
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/inode.c

@@ -133,7 +133,6 @@ static struct inode *alloc_inode(struct super_block *sb)
 		inode->i_bdev = NULL;
 		inode->i_cdev = NULL;
 		inode->i_rdev = 0;
-		inode->i_security = NULL;
 		inode->dirtied_when = 0;
 		if (security_inode_alloc(inode)) {
 			if (inode->i_sb->s_op->destroy_inode)

include/linux/fs.h

@@ -553,7 +553,9 @@ struct inode {
 	unsigned int		i_flags;
 
 	atomic_t		i_writecount;
+#ifdef CONFIG_SECURITY
 	void			*i_security;
+#endif
 	void			*i_private; /* fs or device private pointer */
 #ifdef __NEED_I_SIZE_ORDERED
 	seqcount_t		i_size_seqcount;
@@ -645,7 +647,6 @@ struct fown_struct {
 	rwlock_t lock;          /* protects pid, uid, euid fields */
 	int pid;		/* pid or -pgrp where SIGIO should be sent */
 	uid_t uid, euid;	/* uid/euid of process setting the owner */
-	void *security;
 	int signum;		/* posix.1b rt signal to be delivered on IO */
 };
 
@@ -688,8 +689,9 @@ struct file {
 	struct file_ra_state	f_ra;
 
 	unsigned long		f_version;
+#ifdef CONFIG_SECURITY
 	void			*f_security;
-
+#endif
 	/* needed for tty driver, and maybe others */
 	void			*private_data;
 
@@ -877,7 +879,9 @@ struct super_block {
 	int			s_syncing;
 	int			s_need_sync_fs;
 	atomic_t		s_active;
+#ifdef CONFIG_SECURITY
 	void                    *s_security;
+#endif
 	struct xattr_handler	**s_xattr;
 
 	struct list_head	s_inodes;	/* all inodes */

include/linux/security.h

@@ -1595,6 +1595,7 @@ static inline void security_sb_post_pivotroot (struct nameidata *old_nd,
 
 static inline int security_inode_alloc (struct inode *inode)
 {
+	inode->i_security = NULL;
 	return security_ops->inode_alloc_security (inode);
 }