[v3,09/13] btrfs: Simplify btrfs_check_super_csum() and get rid of size assumptions

Commit Message

Johannes Thumshirn May 22, 2019, 8:19 a.m. UTC

Now that we have already checked for a valid checksum type before calling
btrfs_check_super_csum(), it can be simplified even further.

While at it get rid of the implicit size assumption of the resulting
checksum as well.

This is a preparation for changing all checksum functionality to use the
crypto layer later.

Signed-off-by: Johannes Thumshirn <[e-mail]>
Reviewed-by: Nikolay Borisov <[e-mail]>

---
Changes to v1:
- Check for disk_sb->csum instead of raw buffer (Nikolay)
---
 fs/btrfs/disk-io.c | 45 ++++++++++++++++++---------------------------
 1 file changed, 18 insertions(+), 27 deletions(-)

Patch

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index f541d3c15d99..b1c30a5cef9d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -375,30 +375,20 @@  static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
 {
 	struct btrfs_super_block *disk_sb =
 		(struct btrfs_super_block *)raw_disk_sb;
-	u16 csum_type = btrfs_super_csum_type(disk_sb);
-
-	if (!btrfs_supported_super_csum(csum_type)) {
-		btrfs_err(fs_info, "unsupported checksum algorithm %u",
-			  csum_type);
-		return 1;
-	}
-
-	if (csum_type == BTRFS_CSUM_TYPE_CRC32) {
-		u32 crc = ~(u32)0;
-		char result[sizeof(crc)];
+	u32 crc = ~(u32)0;
+	char result[BTRFS_CSUM_SIZE];
 
-		/*
-		 * The super_block structure does not span the whole
-		 * BTRFS_SUPER_INFO_SIZE range, we expect that the unused space
-		 * is filled with zeros and is included in the checksum.
-		 */
-		crc = btrfs_csum_data(raw_disk_sb + BTRFS_CSUM_SIZE,
-				crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
-		btrfs_csum_final(crc, result);
+	/*
+	 * The super_block structure does not span the whole
+	 * BTRFS_SUPER_INFO_SIZE range, we expect that the unused space
+	 * is filled with zeros and is included in the checksum.
+	 */
+	crc = btrfs_csum_data(raw_disk_sb + BTRFS_CSUM_SIZE,
+			      crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
+	btrfs_csum_final(crc, result);
 
-		if (memcmp(raw_disk_sb, result, sizeof(result)))
-			return 1;
-	}
+	if (memcmp(disk_sb->csum, result, btrfs_super_csum_size(disk_sb)))
+		return 1;
 
 	return 0;
 }
@@ -2586,7 +2576,7 @@  static int btrfs_validate_write_super(struct btrfs_fs_info *fs_info,
 	ret = validate_super(fs_info, sb, -1);
 	if (ret < 0)
 		goto out;
-	if (!btrfs_supported_super_csum(sb)) {
+	if (!btrfs_supported_super_csum(btrfs_super_csum_type(sb))) {
 		ret = -EUCLEAN;
 		btrfs_err(fs_info, "invalid csum type, has %u want %u",
 			  btrfs_super_csum_type(sb), BTRFS_CSUM_TYPE_CRC32);
@@ -2616,6 +2606,7 @@  int open_ctree(struct super_block *sb,
 	u32 stripesize;
 	u64 generation;
 	u64 features;
+	u16 csum_type;
 	struct btrfs_key location;
 	struct buffer_head *bh;
 	struct btrfs_super_block *disk_super;
@@ -2821,11 +2812,11 @@  int open_ctree(struct super_block *sb,
 		goto fail_alloc;
 	}
 
-	if (!btrfs_supported_super_csum((struct btrfs_super_block *)
-					bh->b_data)) {
+	csum_type = btrfs_super_csum_type((struct btrfs_super_block *)
+					  bh->b_data);
+	if (!btrfs_supported_super_csum(csum_type)) {
 		btrfs_err(fs_info, "unsupported checksum algorithm: %d",
-			  btrfs_super_csum_type((struct btrfs_super_block *)
-						bh->b_data));
+			  csum_type);
 		err = -EINVAL;
 		brelse(bh);
 		goto fail_alloc;