Improve WritebackContextInit() comment and prototype argument names.

Author: Masahiko Sawada
Discussion: CAD21AoBD=Of1OzL90Xx4Q-3j=-2q7=S87cs75HfutE=eCday2w@mail.gmail.com

src/backend/storage/buffer/bufmgr.c

@@ -4160,12 +4160,10 @@ ts_ckpt_progress_comparator(Datum a, Datum b, void *arg)
 /*
  * Initialize a writeback context, discarding potential previous state.
  *
- * *max_coalesce is a pointer to a variable containing the current maximum
- * number of writeback requests that will be coalesced into a bigger one. A
- * value <= 0 means that no writeback control will be performed. max_pending
- * is a pointer instead of an immediate value, so the coalesce limits can
- * easily changed by the GUC mechanism, and so calling code does not have to
- * check the current configuration.
+ * *max_pending is a pointer instead of an immediate value, so the coalesce
+ * limits can easily changed by the GUC mechanism, and so calling code does
+ * not have to check the current configuration. A value is 0 means that no
+ * writeback control will be performed.
  */
 void
 WritebackContextInit(WritebackContext *context, int *max_pending)

src/include/storage/buf_internals.h

@@ -300,7 +300,7 @@ extern CkptSortItem *CkptBufferIds;
  * Internal buffer management routines
  */
 /* bufmgr.c */
-extern void WritebackContextInit(WritebackContext *context, int *max_coalesce);
+extern void WritebackContextInit(WritebackContext *context, int *max_pending);
 extern void IssuePendingWritebacks(WritebackContext *context);
 extern void ScheduleBufferTagForWriteback(WritebackContext *context, BufferTag *tag);