xfs: factor out log write ordering from xlog_cil_push_work()

So we can use it for start record ordering as well as commit record
ordering in future.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/xfs/xfs_log_cil.c

@@ -656,9 +656,54 @@ xlog_cil_set_ctx_write_state(
 
 
 /*
- * Write out the commit record of a checkpoint transaction associated with the
- * given ticket to close off a running log write. Return the lsn of the commit
- * record.
+ * Ensure that the order of log writes follows checkpoint sequence order. This
+ * relies on the context LSN being zero until the log write has guaranteed the
+ * LSN that the log write will start at via xlog_state_get_iclog_space().
+ */
+static int
+xlog_cil_order_write(
+	struct xfs_cil		*cil,
+	xfs_csn_t		sequence)
+{
+	struct xfs_cil_ctx	*ctx;
+
+restart:
+	spin_lock(&cil->xc_push_lock);
+	list_for_each_entry(ctx, &cil->xc_committing, committing) {
+		/*
+		 * Avoid getting stuck in this loop because we were woken by the
+		 * shutdown, but then went back to sleep once already in the
+		 * shutdown state.
+		 */
+		if (xlog_is_shutdown(cil->xc_log)) {
+			spin_unlock(&cil->xc_push_lock);
+			return -EIO;
+		}
+
+		/*
+		 * Higher sequences will wait for this one so skip them.
+		 * Don't wait for our own sequence, either.
+		 */
+		if (ctx->sequence >= sequence)
+			continue;
+		if (!ctx->commit_lsn) {
+			/*
+			 * It is still being pushed! Wait for the push to
+			 * complete, then start again from the beginning.
+			 */
+			xlog_wait(&cil->xc_commit_wait, &cil->xc_push_lock);
+			goto restart;
+		}
+	}
+	spin_unlock(&cil->xc_push_lock);
+	return 0;
+}
+
+/*
+ * Write out the commit record of a checkpoint transaction to close off a
+ * running log write. These commit records are strictly ordered in ascending CIL
+ * sequence order so that log recovery will always replay the checkpoints in the
+ * correct order.
  */
 static int
 xlog_cil_write_commit_record(
@@ -904,39 +949,9 @@ xlog_cil_push_work(
 	if (error)
 		goto out_abort_free_ticket;
 
-	/*
-	 * now that we've written the checkpoint into the log, strictly
-	 * order the commit records so replay will get them in the right order.
-	 */
-restart:
-	spin_lock(&cil->xc_push_lock);
-	list_for_each_entry(new_ctx, &cil->xc_committing, committing) {
-		/*
-		 * Avoid getting stuck in this loop because we were woken by the
-		 * shutdown, but then went back to sleep once already in the
-		 * shutdown state.
-		 */
-		if (xlog_is_shutdown(log)) {
-			spin_unlock(&cil->xc_push_lock);
+	error = xlog_cil_order_write(ctx->cil, ctx->sequence);
+	if (error)
 		goto out_abort_free_ticket;
-		}
-
-		/*
-		 * Higher sequences will wait for this one so skip them.
-		 * Don't wait for our own sequence, either.
-		 */
-		if (new_ctx->sequence >= ctx->sequence)
-			continue;
-		if (!new_ctx->commit_lsn) {
-			/*
-			 * It is still being pushed! Wait for the push to
-			 * complete, then start again from the beginning.
-			 */
-			xlog_wait(&cil->xc_commit_wait, &cil->xc_push_lock);
-			goto restart;
-		}
-	}
-	spin_unlock(&cil->xc_push_lock);
 
 	error = xlog_cil_write_commit_record(ctx, &commit_iclog);
 	if (error)