f2fs: Always enable discard for zoned blocks devices

Zone write pointer reset acts as discard for zoned block
devices. So if the zoned block device feature is enabled,
always declare that discard is enabled, even if the device
does not actually support the command.
For the same reason, prevent the use the "nodicard" mount
option.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -1111,13 +1111,6 @@ static inline void clear_ckpt_flags(struct f2fs_sb_info *sbi, unsigned int f)
 	spin_unlock(&sbi->cp_lock);
 }
 
-static inline bool f2fs_discard_en(struct f2fs_sb_info *sbi)
-{
-	struct request_queue *q = bdev_get_queue(sbi->sb->s_bdev);
-
-	return blk_queue_discard(q);
-}
-
 static inline void f2fs_lock_op(struct f2fs_sb_info *sbi)
 {
 	down_read(&sbi->cp_rwsem);
@@ -2423,6 +2416,13 @@ static inline int f2fs_sb_mounted_blkzoned(struct super_block *sb)
 	return F2FS_HAS_FEATURE(sb, F2FS_FEATURE_BLKZONED);
 }
 
+static inline bool f2fs_discard_en(struct f2fs_sb_info *sbi)
+{
+	struct request_queue *q = bdev_get_queue(sbi->sb->s_bdev);
+
+	return blk_queue_discard(q) || f2fs_sb_mounted_blkzoned(sbi->sb);
+}
+
 static inline void set_opt_mode(struct f2fs_sb_info *sbi, unsigned int mt)
 {
 	clear_opt(sbi, ADAPTIVE);

fs/f2fs/super.c

@@ -419,6 +419,11 @@ static int parse_options(struct super_block *sb, char *options)
 			}
 			break;
 		case Opt_nodiscard:
+			if (f2fs_sb_mounted_blkzoned(sb)) {
+				f2fs_msg(sb, KERN_WARNING,
+					"discard is required for zoned block devices");
+				return -EINVAL;
+			}
 			clear_opt(sbi, DISCARD);
 			break;
 		case Opt_noheap: