[PATCH 5/8] xfs: factor out log write ordering from xlog_cil_push_work()

[Dave Chinner <david@fromorbit.com>]

From: Dave Chinner <dchinner@redhat.com>

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>
---
 fs/xfs/xfs_log_cil.c | 89 ++++++++++++++++++++++++++------------------
 1 file changed, 52 insertions(+), 37 deletions(-)

diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index 35fc3e57d870..f993ec69fc97 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -784,9 +784,54 @@ xlog_cil_build_trans_hdr(
 }
 
 /*
- * 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_FORCED_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.
  */
 int
 xlog_cil_write_commit_record(
@@ -816,6 +861,10 @@ xlog_cil_write_commit_record(
 	if (XLOG_FORCED_SHUTDOWN(log))
 		return -EIO;
 
+	error = xlog_cil_order_write(ctx->cil, ctx->sequence);
+	if (error)
+		return error;
+
 	/* account for space used by record data */
 	ctx->ticket->t_curr_res -= reg.i_len;
 	error = xlog_write(log, ctx, &lv_chain, ctx->ticket, iclog, reg.i_len);
@@ -1048,40 +1097,6 @@ 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_FORCED_SHUTDOWN(log)) {
-			spin_unlock(&cil->xc_push_lock);
-			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)
 		goto out_abort_free_ticket;
-- 
2.31.1