jbd2: factor out common descriptor block initialization

Descriptor block header is initialized in several places. Factor out the
common code into jbd2_journal_get_descriptor_buffer().
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/jbd2/commit.c

@@ -131,14 +131,12 @@ static int journal_submit_commit_record(journal_t *journal,
 	if (is_journal_aborted(journal))
 		return 0;
 
-	bh = jbd2_journal_get_descriptor_buffer(journal);
+	bh = jbd2_journal_get_descriptor_buffer(commit_transaction,
+						JBD2_COMMIT_BLOCK);
 	if (!bh)
 		return 1;
 
 	tmp = (struct commit_header *)bh->b_data;
-	tmp->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
-	tmp->h_blocktype = cpu_to_be32(JBD2_COMMIT_BLOCK);
-	tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
 	tmp->h_commit_sec = cpu_to_be64(now.tv_sec);
 	tmp->h_commit_nsec = cpu_to_be32(now.tv_nsec);
 
@@ -379,7 +377,6 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 	ktime_t start_time;
 	u64 commit_time;
 	char *tagp = NULL;
-	journal_header_t *header;
 	journal_block_tag_t *tag = NULL;
 	int space_left = 0;
 	int first_tag = 0;
@@ -615,7 +612,9 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 
 			jbd_debug(4, "JBD2: get descriptor\n");
 
-			descriptor = jbd2_journal_get_descriptor_buffer(journal);
+			descriptor = jbd2_journal_get_descriptor_buffer(
+							commit_transaction,
+							JBD2_DESCRIPTOR_BLOCK);
 			if (!descriptor) {
 				jbd2_journal_abort(journal, -EIO);
 				continue;
@@ -624,11 +623,6 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 			jbd_debug(4, "JBD2: got buffer %llu (%p)\n",
 				(unsigned long long)descriptor->b_blocknr,
 				descriptor->b_data);
-			header = (journal_header_t *)descriptor->b_data;
-			header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
-			header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
-			header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
-
 			tagp = &descriptor->b_data[sizeof(journal_header_t)];
 			space_left = descriptor->b_size -
 						sizeof(journal_header_t);

fs/jbd2/journal.c

@@ -805,10 +805,13 @@ int jbd2_journal_bmap(journal_t *journal, unsigned long blocknr,
  * But we don't bother doing that, so there will be coherency problems with
  * mmaps of blockdevs which hold live JBD-controlled filesystems.
  */
-struct buffer_head *jbd2_journal_get_descriptor_buffer(journal_t *journal)
+struct buffer_head *
+jbd2_journal_get_descriptor_buffer(transaction_t *transaction, int type)
 {
+	journal_t *journal = transaction->t_journal;
 	struct buffer_head *bh;
 	unsigned long long blocknr;
+	journal_header_t *header;
 	int err;
 
 	err = jbd2_journal_next_log_block(journal, &blocknr);
@@ -821,6 +824,10 @@ struct buffer_head *jbd2_journal_get_descriptor_buffer(journal_t *journal)
 		return NULL;
 	lock_buffer(bh);
 	memset(bh->b_data, 0, journal->j_blocksize);
+	header = (journal_header_t *)bh->b_data;
+	header->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
+	header->h_blocktype = cpu_to_be32(type);
+	header->h_sequence = cpu_to_be32(transaction->t_tid);
 	set_buffer_uptodate(bh);
 	unlock_buffer(bh);
 	BUFFER_TRACE(bh, "return this buffer");

fs/jbd2/revoke.c

@@ -570,7 +570,6 @@ static void write_one_revoke_record(transaction_t *transaction,
 	int csum_size = 0;
 	struct buffer_head *descriptor;
 	int sz, offset;
-	journal_header_t *header;
 
 	/* If we are already aborting, this all becomes a noop.  We
            still need to go round the loop in
@@ -600,13 +599,10 @@ static void write_one_revoke_record(transaction_t *transaction,
 	}
 
 	if (!descriptor) {
-		descriptor = jbd2_journal_get_descriptor_buffer(journal);
+		descriptor = jbd2_journal_get_descriptor_buffer(transaction,
+							JBD2_REVOKE_BLOCK);
 		if (!descriptor)
 			return;
-		header = (journal_header_t *)descriptor->b_data;
-		header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
-		header->h_blocktype = cpu_to_be32(JBD2_REVOKE_BLOCK);
-		header->h_sequence  = cpu_to_be32(transaction->t_tid);
 
 		/* Record it so that we can wait for IO completion later */
 		BUFFER_TRACE(descriptor, "file in log_bufs");

include/linux/jbd2.h

@@ -1137,7 +1137,7 @@ static inline void jbd2_unfile_log_bh(struct buffer_head *bh)
 }
 
 /* Log buffer allocation */
-struct buffer_head *jbd2_journal_get_descriptor_buffer(journal_t *journal);
+struct buffer_head *jbd2_journal_get_descriptor_buffer(transaction_t *, int);
 int jbd2_journal_next_log_block(journal_t *, unsigned long long *);
 int jbd2_journal_get_log_tail(journal_t *journal, tid_t *tid,
 			      unsigned long *block);