jbd2: change disk layout for metadata checksumming

Define flags and allocate space in on-disk journal structures to support
checksumming of journal metadata.
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/jbd2/commit.c

@@ -627,7 +627,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 
 		tag = (journal_block_tag_t *) tagp;
 		write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
-		tag->t_flags = cpu_to_be32(tag_flag);
+		tag->t_flags = cpu_to_be16(tag_flag);
 		tagp += tag_bytes;
 		space_left -= tag_bytes;
 
@@ -651,7 +651,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
                            submitting the IOs.  "tag" still points to
                            the last tag we set up. */
 
-			tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
+			tag->t_flags |= cpu_to_be16(JBD2_FLAG_LAST_TAG);
 
 start_journal_io:
 			for (i = 0; i < bufs; i++) {

fs/jbd2/recovery.c

@@ -193,10 +193,10 @@ static int count_tags(journal_t *journal, struct buffer_head *bh)
 
 		nr++;
 		tagp += tag_bytes;
-		if (!(tag->t_flags & cpu_to_be32(JBD2_FLAG_SAME_UUID)))
+		if (!(tag->t_flags & cpu_to_be16(JBD2_FLAG_SAME_UUID)))
 			tagp += 16;
 
-		if (tag->t_flags & cpu_to_be32(JBD2_FLAG_LAST_TAG))
+		if (tag->t_flags & cpu_to_be16(JBD2_FLAG_LAST_TAG))
 			break;
 	}
 
@@ -485,7 +485,7 @@ static int do_one_pass(journal_t *journal,
 				unsigned long io_block;
 
 				tag = (journal_block_tag_t *) tagp;
-				flags = be32_to_cpu(tag->t_flags);
+				flags = be16_to_cpu(tag->t_flags);
 
 				io_block = next_log_block++;
 				wrap(journal, next_log_block);

include/linux/jbd2.h

@@ -147,12 +147,24 @@ typedef struct journal_header_s
 #define JBD2_CRC32_CHKSUM   1
 #define JBD2_MD5_CHKSUM     2
 #define JBD2_SHA1_CHKSUM    3
+#define JBD2_CRC32C_CHKSUM  4
 
 #define JBD2_CRC32_CHKSUM_SIZE 4
 
 #define JBD2_CHECKSUM_BYTES (32 / sizeof(u32))
 /*
  * Commit block header for storing transactional checksums:
+ *
+ * NOTE: If FEATURE_COMPAT_CHECKSUM (checksum v1) is set, the h_chksum*
+ * fields are used to store a checksum of the descriptor and data blocks.
+ *
+ * If FEATURE_INCOMPAT_CSUM_V2 (checksum v2) is set, then the h_chksum
+ * field is used to store crc32c(uuid+commit_block).  Each journal metadata
+ * block gets its own checksum, and data block checksums are stored in
+ * journal_block_tag (in the descriptor).  The other h_chksum* fields are
+ * not used.
+ *
+ * Checksum v1 and v2 are mutually exclusive features.
  */
 struct commit_header {
 	__be32		h_magic;
@@ -175,13 +187,19 @@ struct commit_header {
 typedef struct journal_block_tag_s
 {
 	__be32		t_blocknr;	/* The on-disk block number */
-	__be32		t_flags;	/* See below */
+	__be16		t_checksum;	/* truncated crc32c(uuid+seq+block) */
+	__be16		t_flags;	/* See below */
 	__be32		t_blocknr_high; /* most-significant high 32bits. */
 } journal_block_tag_t;
 
 #define JBD2_TAG_SIZE32 (offsetof(journal_block_tag_t, t_blocknr_high))
 #define JBD2_TAG_SIZE64 (sizeof(journal_block_tag_t))
 
+/* Tail of descriptor block, for checksumming */
+struct jbd2_journal_block_tail {
+	__be32		t_checksum;	/* crc32c(uuid+descr_block) */
+};
+
 /*
  * The revoke descriptor: used on disk to describe a series of blocks to
  * be revoked from the log
@@ -192,6 +210,10 @@ typedef struct jbd2_journal_revoke_header_s
 	__be32		 r_count;	/* Count of bytes used in the block */
 } jbd2_journal_revoke_header_t;
 
+/* Tail of revoke block, for checksumming */
+struct jbd2_journal_revoke_tail {
+	__be32		r_checksum;	/* crc32c(uuid+revoke_block) */
+};
 
 /* Definitions for the journal tag flags word: */
 #define JBD2_FLAG_ESCAPE		1	/* on-disk block is escaped */
@@ -241,7 +263,10 @@ typedef struct journal_superblock_s
 	__be32	s_max_trans_data;	/* Limit of data blocks per trans. */
 
 /* 0x0050 */
-	__u32	s_padding[44];
+	__u8	s_checksum_type;	/* checksum type */
+	__u8	s_padding2[3];
+	__u32	s_padding[42];
+	__be32	s_checksum;		/* crc32c(superblock) */
 
 /* 0x0100 */
 	__u8	s_users[16*48];		/* ids of all fs'es sharing the log */
@@ -263,6 +288,7 @@ typedef struct journal_superblock_s
 #define JBD2_FEATURE_INCOMPAT_REVOKE		0x00000001
 #define JBD2_FEATURE_INCOMPAT_64BIT		0x00000002
 #define JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT	0x00000004
+#define JBD2_FEATURE_INCOMPAT_CSUM_V2		0x00000008
 
 /* Features known to this kernel version: */
 #define JBD2_KNOWN_COMPAT_FEATURES	JBD2_FEATURE_COMPAT_CHECKSUM