xfs: log recovery tracepoints to track current lsn and buffer submission

Log recovery has particular rules around buffer submission along with
tricky corner cases where independent transactions can share an LSN. As
such, it can be difficult to follow when/why buffers are submitted
during recovery.

Add a couple tracepoints to post the current LSN of a record when a new
record is being processed and when a buffer is being skipped due to LSN
ordering. Also, update the recover item class to include the LSN of the
current transaction for the item being processed.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_log_recover.c

@@ -2804,6 +2804,7 @@ xlog_recover_buffer_pass2(
 	 */
 	lsn = xlog_recover_get_buf_lsn(mp, bp);
 	if (lsn && lsn != -1 && XFS_LSN_CMP(lsn, current_lsn) >= 0) {
+		trace_xfs_log_recover_buf_skip(log, buf_f);
 		xlog_recover_validate_buf_type(mp, bp, buf_f, NULLCOMMITLSN);
 		goto out_release;
 	}
@@ -4319,6 +4320,7 @@ xlog_recover_process_data(
 	if (xlog_header_check_recover(log->l_mp, rhead))
 		return -EIO;
 
+	trace_xfs_log_recover_record(log, rhead, pass);
 	while ((dp < end) && num_logops) {
 
 		ohead = (struct xlog_op_header *)dp;

fs/xfs/xfs_trace.h

@@ -1984,6 +1984,29 @@ DEFINE_EVENT(xfs_swap_extent_class, name, \
 DEFINE_SWAPEXT_EVENT(xfs_swap_extent_before);
 DEFINE_SWAPEXT_EVENT(xfs_swap_extent_after);
 
+TRACE_EVENT(xfs_log_recover_record,
+	TP_PROTO(struct xlog *log, struct xlog_rec_header *rhead, int pass),
+	TP_ARGS(log, rhead, pass),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(xfs_lsn_t, lsn)
+		__field(int, len)
+		__field(int, num_logops)
+		__field(int, pass)
+	),
+	TP_fast_assign(
+		__entry->dev = log->l_mp->m_super->s_dev;
+		__entry->lsn = be64_to_cpu(rhead->h_lsn);
+		__entry->len = be32_to_cpu(rhead->h_len);
+		__entry->num_logops = be32_to_cpu(rhead->h_num_logops);
+		__entry->pass = pass;
+	),
+	TP_printk("dev %d:%d lsn 0x%llx len 0x%x num_logops 0x%x pass %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->lsn, __entry->len, __entry->num_logops,
+		   __entry->pass)
+)
+
 DECLARE_EVENT_CLASS(xfs_log_recover_item_class,
 	TP_PROTO(struct xlog *log, struct xlog_recover *trans,
 		struct xlog_recover_item *item, int pass),
@@ -1992,6 +2015,7 @@ DECLARE_EVENT_CLASS(xfs_log_recover_item_class,
 		__field(dev_t, dev)
 		__field(unsigned long, item)
 		__field(xlog_tid_t, tid)
+		__field(xfs_lsn_t, lsn)
 		__field(int, type)
 		__field(int, pass)
 		__field(int, count)
@@ -2001,15 +2025,17 @@ DECLARE_EVENT_CLASS(xfs_log_recover_item_class,
 		__entry->dev = log->l_mp->m_super->s_dev;
 		__entry->item = (unsigned long)item;
 		__entry->tid = trans->r_log_tid;
+		__entry->lsn = trans->r_lsn;
 		__entry->type = ITEM_TYPE(item);
 		__entry->pass = pass;
 		__entry->count = item->ri_cnt;
 		__entry->total = item->ri_total;
 	),
-	TP_printk("dev %d:%d trans 0x%x, pass %d, item 0x%p, item type %s "
-		  "item region count/total %d/%d",
+	TP_printk("dev %d:%d tid 0x%x lsn 0x%llx, pass %d, item 0x%p, "
+		  "item type %s item region count/total %d/%d",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
 		  __entry->tid,
+		  __entry->lsn,
 		  __entry->pass,
 		  (void *)__entry->item,
 		  __print_symbolic(__entry->type, XFS_LI_TYPE_DESC),
@@ -2068,6 +2094,7 @@ DEFINE_LOG_RECOVER_BUF_ITEM(xfs_log_recover_buf_cancel);
 DEFINE_LOG_RECOVER_BUF_ITEM(xfs_log_recover_buf_cancel_add);
 DEFINE_LOG_RECOVER_BUF_ITEM(xfs_log_recover_buf_cancel_ref_inc);
 DEFINE_LOG_RECOVER_BUF_ITEM(xfs_log_recover_buf_recover);
+DEFINE_LOG_RECOVER_BUF_ITEM(xfs_log_recover_buf_skip);
 DEFINE_LOG_RECOVER_BUF_ITEM(xfs_log_recover_buf_inode_buf);
 DEFINE_LOG_RECOVER_BUF_ITEM(xfs_log_recover_buf_reg_buf);
 DEFINE_LOG_RECOVER_BUF_ITEM(xfs_log_recover_buf_dquot_buf);