reftable: adapt write_object_record() to propagate block_writer_add() errors

Previously, write_object_record() would flush the current block and retry
appending the record whenever block_writer_add() returned any nonzero
error. This forced an assumption that every failure meant the block was
full, even when errors such as memory allocation or I/O failures occurred.

Update the write_object_record() to inspect the error code returned by
block_writer_add() and flush and reinitialize the writer iff the
error is REFTABLE_ENTRY_TOO_BIG_ERROR. For any other error, immediately
propagate it.

If the flush and reinitialization still fail with
REFTABLE_ENTRY_TOO_BIG_ERROR, reset the record's offset length to zero
before a final attempt.

All call sites now handle various error codes returned by
block_writer_add().

Signed-off-by: Meet Soni <[email protected]>
Acked-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: inosmeet

reftable/writer.c

@@ -620,10 +620,22 @@ static void write_object_record(void *void_arg, void *key)
 	if (arg->err < 0)
 		goto done;
 
+	/*
+	 * Try to add the record to the writer. If this succeeds then we're
+	 * done. Otherwise the block writer may have hit the block size limit
+	 * and needs to be flushed.
+	 */
 	arg->err = block_writer_add(arg->w->block_writer, &rec);
 	if (arg->err == 0)
 		goto done;
 
+	if (arg->err != REFTABLE_ENTRY_TOO_BIG_ERROR)
+		goto done;
+
+	/*
+	 * The current block is full, so we need to flush and reinitialize the
+	 * writer to start writing the next block.
+	 */
 	arg->err = writer_flush_block(arg->w);
 	if (arg->err < 0)
 		goto done;
@@ -632,10 +644,17 @@ static void write_object_record(void *void_arg, void *key)
 	if (arg->err < 0)
 		goto done;
 
+	/*
+	 * If this still fails then we may need to reset record's offset
+	 * length to reduce the data size to be written.
+	 */
 	arg->err = block_writer_add(arg->w->block_writer, &rec);
 	if (arg->err == 0)
 		goto done;
 
+	if (arg->err != REFTABLE_ENTRY_TOO_BIG_ERROR)
+		goto done;
+
 	rec.u.obj.offset_len = 0;
 	arg->err = block_writer_add(arg->w->block_writer, &rec);