vfs: update ctime when changing the file's permission by setfacl

generic_acl_set didn't update the ctime of the file when its permission was
changed.

Steps to reproduce:
 # touch aaa
 # stat -c %Z aaa
 1275289822
 # setfacl -m  'u::x,g::x,o::x' aaa
 # stat -c %Z aaa
 1275289822                         <- unchanged

But, according to the spec of the ctime, vfs must update it.

Port of ext3 patch by Miao Xie <miaox@cn.fujitsu.com>.

CC: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/generic_acl.c

@@ -94,6 +94,7 @@ generic_acl_set(struct dentry *dentry, const char *name, const void *value,
 			if (error < 0)
 				goto failed;
 			inode->i_mode = mode;
+			inode->i_ctime = CURRENT_TIME;
 			if (error == 0) {
 				posix_acl_release(acl);
 				acl = NULL;