xfs: cleanup xlog_get_iclog_buffer_size

We don't really need all the messy branches in the function, as it
really does three things, out of which 2 are common for all branches:

 1) set up mount point log buffer size and count values if not already
    done from mount options
 2) calculate the number of log headers
 3) set up all the values in struct xlog based on the above
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_log.c

@@ -1301,56 +1301,26 @@ xlog_iodone(xfs_buf_t *bp)
  * If the filesystem blocksize is too large, we may need to choose a
  * larger size since the directory code currently logs entire blocks.
  */
-
 STATIC void
 xlog_get_iclog_buffer_size(
 	struct xfs_mount	*mp,
 	struct xlog		*log)
 {
-	int xhdrs;
-
 	if (mp->m_logbufs <= 0)
-		log->l_iclog_bufs = XLOG_MAX_ICLOGS;
-	else
-		log->l_iclog_bufs = mp->m_logbufs;
+		mp->m_logbufs = XLOG_MAX_ICLOGS;
+	if (mp->m_logbsize <= 0)
+		mp->m_logbsize = XLOG_BIG_RECORD_BSIZE;
+
+	log->l_iclog_bufs = mp->m_logbufs;
+	log->l_iclog_size = mp->m_logbsize;
 
 	/*
-	 * Buffer size passed in from mount system call.
+	 * # headers = size / 32k - one header holds cycles from 32k of data.
 	 */
-	if (mp->m_logbsize > 0) {
-		if (xfs_sb_version_haslogv2(&mp->m_sb)) {
-			/* # headers = size / 32k
-			 * one header holds cycles from 32k of data
-			 */
-
-			xhdrs = mp->m_logbsize / XLOG_HEADER_CYCLE_SIZE;
-			if (mp->m_logbsize % XLOG_HEADER_CYCLE_SIZE)
-				xhdrs++;
-			log->l_iclog_hsize = xhdrs << BBSHIFT;
-			log->l_iclog_heads = xhdrs;
-		} else {
-			ASSERT(mp->m_logbsize <= XLOG_BIG_RECORD_BSIZE);
-			log->l_iclog_hsize = BBSIZE;
-			log->l_iclog_heads = 1;
-		}
-		goto done;
-	}
-
-	/* All machines use 32kB buffers by default. */
-	log->l_iclog_size = XLOG_BIG_RECORD_BSIZE;
-
-	/* the default log size is 16k or 32k which is one header sector */
-	log->l_iclog_hsize = BBSIZE;
-	log->l_iclog_heads = 1;
-
-done:
-	/* are we being asked to make the sizes selected above visible? */
-	if (mp->m_logbufs == 0)
-		mp->m_logbufs = log->l_iclog_bufs;
-	if (mp->m_logbsize == 0)
-		mp->m_logbsize = log->l_iclog_size;
-}	/* xlog_get_iclog_buffer_size */
-
+	log->l_iclog_heads =
+		DIV_ROUND_UP(mp->m_logbsize, XLOG_HEADER_CYCLE_SIZE);
+	log->l_iclog_hsize = log->l_iclog_heads << BBSHIFT;
+}
 
 void
 xfs_log_work_queue(