diff --git a/block/bio.c b/block/bio.c
index c822ceb7c4de..906da3581a3e 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -535,6 +535,16 @@ void zero_fill_bio_iter(struct bio *bio, struct bvec_iter start)
 }
 EXPORT_SYMBOL(zero_fill_bio_iter);
 
+/**
+ * bio_truncate - truncate the bio to small size of @new_size
+ * @bio:	the bio to be truncated
+ * @new_size:	new size for truncating the bio
+ *
+ * Description:
+ *   Truncate the bio to new size of @new_size. If bio_op(bio) is
+ *   REQ_OP_READ, zero the truncated part. This function should only
+ *   be used for handling corner cases, such as bio eod.
+ */
 void bio_truncate(struct bio *bio, unsigned new_size)
 {
 	struct bio_vec bv;
@@ -545,7 +555,7 @@ void bio_truncate(struct bio *bio, unsigned new_size)
 	if (new_size >= bio->bi_iter.bi_size)
 		return;
 
-	if (bio_data_dir(bio) != READ)
+	if (bio_op(bio) != REQ_OP_READ)
 		goto exit;
 
 	bio_for_each_segment(bv, bio, iter) {
diff --git a/fs/buffer.c b/fs/buffer.c
index 7744488f7bde..91ceca52d14f 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2991,7 +2991,7 @@ static void end_bio_bh_io_sync(struct bio *bio)
  * errors, this only handles the "we need to be able to
  * do IO at the final sector" case.
  */
-void guard_bio_eod(int op, struct bio *bio)
+void guard_bio_eod(struct bio *bio)
 {
 	sector_t maxsector;
 	struct hd_struct *part;
@@ -3055,15 +3055,15 @@ static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
 	bio->bi_end_io = end_bio_bh_io_sync;
 	bio->bi_private = bh;
 
-	/* Take care of bh's that straddle the end of the device */
-	guard_bio_eod(op, bio);
-
 	if (buffer_meta(bh))
 		op_flags |= REQ_META;
 	if (buffer_prio(bh))
 		op_flags |= REQ_PRIO;
 	bio_set_op_attrs(bio, op, op_flags);
 
+	/* Take care of bh's that straddle the end of the device */
+	guard_bio_eod(bio);
+
 	if (wbc) {
 		wbc_init_bio(wbc, bio);
 		wbc_account_cgroup_owner(wbc, bh->b_page, bh->b_size);
diff --git a/fs/internal.h b/fs/internal.h
index 315fcd8d237c..7651e8b8ef13 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -38,7 +38,7 @@ static inline int __sync_blockdev(struct block_device *bdev, int wait)
 /*
  * buffer.c
  */
-extern void guard_bio_eod(int rw, struct bio *bio);
+extern void guard_bio_eod(struct bio *bio);
 extern int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
 		get_block_t *get_block, struct iomap *iomap);
 
diff --git a/fs/mpage.c b/fs/mpage.c
index a63620cdb73a..ccba3c4c4479 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -62,7 +62,7 @@ static struct bio *mpage_bio_submit(int op, int op_flags, struct bio *bio)
 {
 	bio->bi_end_io = mpage_end_io;
 	bio_set_op_attrs(bio, op, op_flags);
-	guard_bio_eod(op, bio);
+	guard_bio_eod(bio);
 	submit_bio(bio);
 	return NULL;
 }