ext4: Simplify the usage of clear_opt() and set_opt() macros

Change clear_opt() and set_opt() to take a superblock pointer instead
of a pointer to EXT4_SB(sb)->s_mount_opt.  This makes it easier for us
to support a second mount option field.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -917,8 +917,10 @@ struct ext4_inode_info {
 #define EXT4_MOUNT_DISCARD		0x40000000 /* Issue DISCARD requests */
 #define EXT4_MOUNT_INIT_INODE_TABLE	0x80000000 /* Initialize uninitialized itables */
 
-#define clear_opt(o, opt)		o &= ~EXT4_MOUNT_##opt
-#define set_opt(o, opt)			o |= EXT4_MOUNT_##opt
+#define clear_opt(sb, opt)		EXT4_SB(sb)->s_mount_opt &= \
+						~EXT4_MOUNT_##opt
+#define set_opt(sb, opt)		EXT4_SB(sb)->s_mount_opt |= \
+						EXT4_MOUNT_##opt
 #define test_opt(sb, opt)		(EXT4_SB(sb)->s_mount_opt & \
 					 EXT4_MOUNT_##opt)
 

fs/ext4/mballoc.c

@@ -2617,7 +2617,7 @@ static inline int ext4_issue_discard(struct super_block *sb,
 	ret = sb_issue_discard(sb, discard_block, count, GFP_NOFS, 0);
 	if (ret == -EOPNOTSUPP) {
 		ext4_warning(sb, "discard not supported, disabling");
-		clear_opt(EXT4_SB(sb)->s_mount_opt, DISCARD);
+		clear_opt(sb, DISCARD);
 	}
 	return ret;
 }