btrfs: fix unnecessary increment of read error stat on write error

Current btrfs_log_dev_io_error() increases the read error count even if the
erroneous IO is a WRITE request. This is because it forget to use "else
if", and all the error WRITE requests counts as READ error as there is (of
course) no REQ_RAHEAD bit set.

Fixes: c3a62baf ("btrfs: use chained bios when cloning")
CC: stable@vger.kernel.org # 6.1+
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/bio.c

@@ -287,7 +287,7 @@ static void btrfs_log_dev_io_error(struct bio *bio, struct btrfs_device *dev)
 
 	if (btrfs_op(bio) == BTRFS_MAP_WRITE)
 		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
-	if (!(bio->bi_opf & REQ_RAHEAD))
+	else if (!(bio->bi_opf & REQ_RAHEAD))
 		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
 	if (bio->bi_opf & REQ_PREFLUSH)
 		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_FLUSH_ERRS);