diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 13a5f4422c79..7e9480150d61 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -188,6 +188,22 @@ static void ifs_free(struct folio *folio)
 	kfree(ifs);
 }
 
+/*
+ * Calculate how many bytes to truncate based off the number of blocks to
+ * truncate and the end position to start truncating from.
+ */
+static size_t iomap_bytes_to_truncate(loff_t end_pos, unsigned block_bits,
+		unsigned blocks_truncated)
+{
+	unsigned block_size = 1 << block_bits;
+	unsigned block_offset = end_pos & (block_size - 1);
+
+	if (!block_offset)
+		return blocks_truncated << block_bits;
+
+	return ((blocks_truncated - 1) << block_bits) + block_offset;
+}
+
 /*
  * Calculate the range inside the folio that we actually need to read.
  */
@@ -233,7 +249,8 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
 		/* truncate len if we find any trailing uptodate block(s) */
 		while (++i <= last) {
 			if (ifs_block_is_uptodate(ifs, i)) {
-				plen -= (last - i + 1) * block_size;
+				plen -= iomap_bytes_to_truncate(*pos + plen,
+						block_bits, last - i + 1);
 				last = i - 1;
 				break;
 			}
@@ -249,7 +266,8 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
 		unsigned end = offset_in_folio(folio, isize - 1) >> block_bits;
 
 		if (first <= end && last > end)
-			plen -= (last - end) * block_size;
+			plen -= iomap_bytes_to_truncate(*pos + plen, block_bits,
+					last - end);
 	}
 
 	*offp = poff;