diff --git a/btrfs-sb-mod.c b/btrfs-sb-mod.c
index 16a26f772494..932c2a0432ef 100644
--- a/btrfs-sb-mod.c
+++ b/btrfs-sb-mod.c
@@ -37,7 +37,8 @@ static int check_csum_superblock(void *sb)
 	u32 crc = ~(u32)0;
 
 	crc = btrfs_csum_data((char *)sb + BTRFS_CSUM_SIZE,
-				crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
+				(u8 *)&crc,
+				BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
 	btrfs_csum_final(crc, result);
 
 	return !memcmp(sb, &result, csum_size);
@@ -50,10 +51,12 @@ static void update_block_csum(void *block, int is_sb)
 	u32 crc = ~(u32)0;
 
 	if (is_sb) {
-		crc = btrfs_csum_data((char *)block + BTRFS_CSUM_SIZE, crc,
+		crc = btrfs_csum_data((char *)block + BTRFS_CSUM_SIZE,
+				      (u8 *)&crc,
 				BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
 	} else {
-		crc = btrfs_csum_data((char *)block + BTRFS_CSUM_SIZE, crc,
+		crc = btrfs_csum_data((char *)block + BTRFS_CSUM_SIZE,
+				      (u8 *)&crc,
 				BLOCKSIZE - BTRFS_CSUM_SIZE);
 	}
 	btrfs_csum_final(crc, result);
diff --git a/check/main.c b/check/main.c
index 2e16b4e6f05b..0f02c85368ec 100644
--- a/check/main.c
+++ b/check/main.c
@@ -5660,7 +5660,7 @@ static int check_extent_csums(struct btrfs_root *root, u64 bytenr,
 				tmp = offset + data_checked;
 
 				csum = btrfs_csum_data((char *)data + tmp,
-						csum, fs_info->sectorsize);
+						(u8 *)&csum, fs_info->sectorsize);
 				btrfs_csum_final(csum, (u8 *)&csum);
 
 				csum_offset = leaf_offset +
diff --git a/cmds/inspect-dump-super.c b/cmds/inspect-dump-super.c
index 65fb3506eac6..96ad3deca3d8 100644
--- a/cmds/inspect-dump-super.c
+++ b/cmds/inspect-dump-super.c
@@ -41,7 +41,8 @@ static int check_csum_sblock(void *sb, int csum_size)
 	u32 crc = ~(u32)0;
 
 	crc = btrfs_csum_data((char *)sb + BTRFS_CSUM_SIZE,
-				crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
+				(u8 *)&crc,
+				BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
 	btrfs_csum_final(crc, result);
 
 	return !memcmp(sb, &result, csum_size);
diff --git a/cmds/rescue-chunk-recover.c b/cmds/rescue-chunk-recover.c
index c2a26ad040ee..37c024ed8965 100644
--- a/cmds/rescue-chunk-recover.c
+++ b/cmds/rescue-chunk-recover.c
@@ -1902,7 +1902,7 @@ static int check_one_csum(int fd, u64 start, u32 len, u32 tree_csum)
 		goto out;
 	}
 	ret = 0;
-	csum_result = btrfs_csum_data(data, csum_result, len);
+	csum_result = btrfs_csum_data(data, (u8 *)&csum_result, len);
 	btrfs_csum_final(csum_result, (u8 *)&csum_result);
 	if (csum_result != tree_csum)
 		ret = 1;
diff --git a/convert/common.c b/convert/common.c
index f8bbb23cba89..ab8e6b9f4749 100644
--- a/convert/common.c
+++ b/convert/common.c
@@ -65,7 +65,8 @@ static inline int write_temp_super(int fd, struct btrfs_super_block *sb,
        u32 crc = ~(u32)0;
        int ret;
 
-       crc = btrfs_csum_data((char *)sb + BTRFS_CSUM_SIZE, crc,
+       crc = btrfs_csum_data((char *)sb + BTRFS_CSUM_SIZE,
+			     (u8 *)&crc,
                              BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
        btrfs_csum_final(crc, &sb->csum[0]);
        ret = pwrite(fd, sb, BTRFS_SUPER_INFO_SIZE, sb_bytenr);
diff --git a/disk-io.c b/disk-io.c
index a4995a628210..a0c37c569d58 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -138,9 +138,9 @@ static void print_tree_block_error(struct btrfs_fs_info *fs_info,
 	}
 }
 
-u32 btrfs_csum_data(char *data, u32 seed, size_t len)
+u32 btrfs_csum_data(char *data, u8 *seed, size_t len)
 {
-	return crc32c(seed, data, len);
+	return crc32c(*(u32*)seed, data, len);
 }
 
 void btrfs_csum_final(u32 crc, u8 *result)
@@ -156,7 +156,7 @@ static int __csum_tree_block_size(struct extent_buffer *buf, u16 csum_size,
 	u32 crc = ~(u32)0;
 
 	len = buf->len - BTRFS_CSUM_SIZE;
-	crc = btrfs_csum_data(buf->data + BTRFS_CSUM_SIZE, crc, len);
+	crc = btrfs_csum_data(buf->data + BTRFS_CSUM_SIZE, (u8 *)&crc, len);
 	btrfs_csum_final(crc, result);
 
 	if (verify) {
@@ -1376,7 +1376,7 @@ int btrfs_check_super(struct btrfs_super_block *sb, unsigned sbflags)
 	csum_size = btrfs_csum_sizes[csum_type];
 
 	crc = ~(u32)0;
-	crc = btrfs_csum_data((char *)sb + BTRFS_CSUM_SIZE, crc,
+	crc = btrfs_csum_data((char *)sb + BTRFS_CSUM_SIZE, (u8 *)&crc,
 			      BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
 	btrfs_csum_final(crc, result);
 
@@ -1631,7 +1631,7 @@ static int write_dev_supers(struct btrfs_fs_info *fs_info,
 	if (fs_info->super_bytenr != BTRFS_SUPER_INFO_OFFSET) {
 		btrfs_set_super_bytenr(sb, fs_info->super_bytenr);
 		crc = ~(u32)0;
-		crc = btrfs_csum_data((char *)sb + BTRFS_CSUM_SIZE, crc,
+		crc = btrfs_csum_data((char *)sb + BTRFS_CSUM_SIZE, (u8 *)&crc,
 				      BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
 		btrfs_csum_final(crc, &sb->csum[0]);
 
@@ -1667,7 +1667,7 @@ static int write_dev_supers(struct btrfs_fs_info *fs_info,
 		btrfs_set_super_bytenr(sb, bytenr);
 
 		crc = ~(u32)0;
-		crc = btrfs_csum_data((char *)sb + BTRFS_CSUM_SIZE, crc,
+		crc = btrfs_csum_data((char *)sb + BTRFS_CSUM_SIZE, (u8 *)&crc,
 				      BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
 		btrfs_csum_final(crc, &sb->csum[0]);
 
diff --git a/disk-io.h b/disk-io.h
index 394997ad72cb..92c87f28f8b2 100644
--- a/disk-io.h
+++ b/disk-io.h
@@ -186,7 +186,7 @@ int btrfs_free_fs_root(struct btrfs_root *root);
 void btrfs_mark_buffer_dirty(struct extent_buffer *buf);
 int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid);
 int btrfs_set_buffer_uptodate(struct extent_buffer *buf);
-u32 btrfs_csum_data(char *data, u32 seed, size_t len);
+u32 btrfs_csum_data(char *data, u8 *seed, size_t len);
 void btrfs_csum_final(u32 crc, u8 *result);
 
 int btrfs_open_device(struct btrfs_device *dev);
diff --git a/file-item.c b/file-item.c
index 3bf48c68913d..5f6548e9a74f 100644
--- a/file-item.c
+++ b/file-item.c
@@ -312,7 +312,7 @@ csum:
 	item = (struct btrfs_csum_item *)((unsigned char *)item +
 					  csum_offset * csum_size);
 found:
-	csum_result = btrfs_csum_data(data, csum_result, len);
+	csum_result = btrfs_csum_data(data, (u8 *)&csum_result, len);
 	btrfs_csum_final(csum_result, (u8 *)&csum_result);
 	if (csum_result == 0) {
 		printk("csum result is 0 for block %llu\n",
