Merge branch 'kn/reflog-migration-fix-followup'

Code clean-up.

* kn/reflog-migration-fix-followup:
  reftable: prevent 'update_index' changes after adding records
  refs: use 'uint64_t' for 'ref_update.index'
  refs: mark `ref_transaction_update_reflog()` as static

4 files changed, 33 insertions, 13 deletions

diff --git a/reftable/reftable-error.h b/reftable/reftable-error.h
index f404826562..a7e33d964d 100644
--- a/reftable/reftable-error.h
+++ b/reftable/reftable-error.h
@@ -30,6 +30,7 @@ enum reftable_error {
 
 	/* Misuse of the API:
 	 *  - on writing a record with NULL refname.
+	 *  - on writing a record before setting the writer limits.
 	 *  - on writing a reftable_ref_record outside the table limits
 	 *  - on writing a ref or log record before the stack's
 	 * next_update_inde*x
diff --git a/reftable/reftable-writer.h b/reftable/reftable-writer.h
index bfef3b1721..1befe3b07c 100644
--- a/reftable/reftable-writer.h
+++ b/reftable/reftable-writer.h
@@ -124,17 +124,21 @@ int reftable_writer_new(struct reftable_writer **out,
 			int (*flush_func)(void *),
 			void *writer_arg, const struct reftable_write_options *opts);
 
-/* Set the range of update indices for the records we will add. When writing a
-   table into a stack, the min should be at least
-   reftable_stack_next_update_index(), or REFTABLE_API_ERROR is returned.
-
-   For transactional updates to a stack, typically min==max, and the
-   update_index can be obtained by inspeciting the stack. When converting an
-   existing ref database into a single reftable, this would be a range of
-   update-index timestamps.
+/*
+ * Set the range of update indices for the records we will add. When writing a
+ * table into a stack, the min should be at least
+ * reftable_stack_next_update_index(), or REFTABLE_API_ERROR is returned.
+ *
+ * For transactional updates to a stack, typically min==max, and the
+ * update_index can be obtained by inspeciting the stack. When converting an
+ * existing ref database into a single reftable, this would be a range of
+ * update-index timestamps.
+ *
+ * The function should be called before adding any records to the writer. If not
+ * it will fail with REFTABLE_API_ERROR.
  */
-void reftable_writer_set_limits(struct reftable_writer *w, uint64_t min,
-				uint64_t max);
+int reftable_writer_set_limits(struct reftable_writer *w, uint64_t min,
+			       uint64_t max);
 
 /*
   Add a reftable_ref_record. The record should have names that come after
diff --git a/reftable/stack.c b/reftable/stack.c
index f7c1845e15..6c4e8be19b 100644
--- a/reftable/stack.c
+++ b/reftable/stack.c
@@ -1058,8 +1058,10 @@ static int stack_write_compact(struct reftable_stack *st,
 
 	for (size_t i = first; i <= last; i++)
 		st->stats.bytes += st->readers[i]->size;
-	reftable_writer_set_limits(wr, st->readers[first]->min_update_index,
-				   st->readers[last]->max_update_index);
+	err = reftable_writer_set_limits(wr, st->readers[first]->min_update_index,
+					 st->readers[last]->max_update_index);
+	if (err < 0)
+		goto done;
 
 	err = reftable_merged_table_new(&mt, st->readers + first, subtabs_len,
 					st->opts.hash_id);
diff --git a/reftable/writer.c b/reftable/writer.c
index 91d6629486..f3ab1035d6 100644
--- a/reftable/writer.c
+++ b/reftable/writer.c
@@ -179,11 +179,24 @@ int reftable_writer_new(struct reftable_writer **out,
 	return 0;
 }
 
-void reftable_writer_set_limits(struct reftable_writer *w, uint64_t min,
+int reftable_writer_set_limits(struct reftable_writer *w, uint64_t min,
 				uint64_t max)
 {
+	/*
+	  * Set the min/max update index limits for the reftable writer.
+	  * This must be called before adding any records, since:
+	  * - The 'next' field gets set after writing the first block.
+	  * - The 'last_key' field updates with each new record (but resets
+	  *   after sections).
+	  * Returns REFTABLE_API_ERROR if called after writing has begun.
+	 */
+	if (w->next || w->last_key.len)
+		return REFTABLE_API_ERROR;
+
 	w->min_update_index = min;
 	w->max_update_index = max;
+
+	return 0;
 }
 
 static void writer_release(struct reftable_writer *w)