Acquire right to set hint bits in the remaining places

Use BufferPrepareToSetHintBits() in the remaining places that modify buffers
without an exclusive lock. The remaining places are indexes with support for
kill_prior_tuples and the freespace code.

After this we do not need to copy buffers to write them out anymore. That
change is done separately however.

Author:
Reviewed-by:
Discussion: https://postgr.es/m/
Backpatch:

Author: anarazel

src/backend/access/gist/gistget.c

@@ -63,11 +63,7 @@ gistkillitems(IndexScanDesc scan)
 	 * safe.
 	 */
 	if (BufferGetLSNAtomic(buffer) != so->curPageLSN)
-	{
-		UnlockReleaseBuffer(buffer);
-		so->numKilled = 0;		/* reset counter */
-		return;
-	}
+		goto unlock;
 
 	Assert(GistPageIsLeaf(page));
 
@@ -77,6 +73,12 @@ gistkillitems(IndexScanDesc scan)
 	 */
 	for (i = 0; i < so->numKilled; i++)
 	{
+		if (!killedsomething)
+		{
+			if (!BufferPrepareToSetHintBits(buffer))
+				goto unlock;
+		}
+
 		offnum = so->killedItems[i];
 		iid = PageGetItemId(page, offnum);
 		ItemIdMarkDead(iid);
@@ -86,9 +88,10 @@ gistkillitems(IndexScanDesc scan)
 	if (killedsomething)
 	{
 		GistMarkPageHasGarbage(page);
-		MarkBufferDirtyHint(buffer, true);
+		BufferFinishSetHintBits(buffer, true, true);
 	}
 
+unlock:
 	UnlockReleaseBuffer(buffer);
 
 	/*

src/backend/access/hash/hashutil.c

@@ -593,6 +593,9 @@ _hash_kill_items(IndexScanDesc scan)
 
 			if (ItemPointerEquals(&ituple->t_tid, &currItem->heapTid))
 			{
+				if (!BufferPrepareToSetHintBits(so->currPos.buf))
+					goto unlock_page;
+
 				/* found the item */
 				ItemIdMarkDead(iid);
 				killedsomething = true;
@@ -610,9 +613,10 @@ _hash_kill_items(IndexScanDesc scan)
 	if (killedsomething)
 	{
 		opaque->hasho_flag |= LH_PAGE_HAS_DEAD_TUPLES;
-		MarkBufferDirtyHint(buf, true);
+		BufferFinishSetHintBits(so->currPos.buf, true, true);
 	}
 
+unlock_page:
 	if (so->hashso_bucket_buf == so->currPos.buf ||
 		havePin)
 		LockBuffer(so->currPos.buf, BUFFER_LOCK_UNLOCK);

src/backend/access/nbtree/nbtinsert.c

@@ -679,20 +679,29 @@ _bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
 				{
 					/*
 					 * The conflicting tuple (or all HOT chains pointed to by
-					 * all posting list TIDs) is dead to everyone, so mark the
-					 * index entry killed.
+					 * all posting list TIDs) is dead to everyone, so try to
+					 * mark the index entry killed. It's ok if we're not
+					 * allowed to, this isn't required for correctness.
 					 */
-					ItemIdMarkDead(curitemid);
-					opaque->btpo_flags |= BTP_HAS_GARBAGE;
+					Buffer		buf;
 
-					/*
-					 * Mark buffer with a dirty hint, since state is not
-					 * crucial. Be sure to mark the proper buffer dirty.
-					 */
+					/* Be sure to operate on the proper buffer */
 					if (nbuf != InvalidBuffer)
-						MarkBufferDirtyHint(nbuf, true);
+						buf = nbuf;
 					else
-						MarkBufferDirtyHint(insertstate->buf, true);
+						buf = insertstate->buf;
+
+					if (BufferPrepareToSetHintBits(buf))
+					{
+						ItemIdMarkDead(curitemid);
+						opaque->btpo_flags |= BTP_HAS_GARBAGE;
+
+						/*
+						 * Mark buffer with a dirty hint, since state is not
+						 * crucial.
+						 */
+						BufferFinishSetHintBits(buf, true, true);
+					}
 				}
 
 				/*

src/backend/access/nbtree/nbtutils.c

@@ -2492,6 +2492,10 @@ _bt_killitems(IndexScanDesc scan)
 			 */
 			if (killtuple && !ItemIdIsDead(iid))
 			{
+				/* if we're not able to set hint bits, there's no point continuing */
+				if (!killedsomething && !BufferPrepareToSetHintBits(so->currPos.buf))
+					goto unlock_page;
+
 				/* found the item/all posting list items */
 				ItemIdMarkDead(iid);
 				killedsomething = true;
@@ -2511,9 +2515,10 @@ _bt_killitems(IndexScanDesc scan)
 	if (killedsomething)
 	{
 		opaque->btpo_flags |= BTP_HAS_GARBAGE;
-		MarkBufferDirtyHint(so->currPos.buf, true);
+		BufferFinishSetHintBits(so->currPos.buf, true, true);
 	}
 
+unlock_page:
 	_bt_unlockbuf(scan->indexRelation, so->currPos.buf);
 }
 

src/backend/storage/freespace/freespace.c

@@ -904,12 +904,18 @@ fsm_vacuum_page(Relation rel, FSMAddress addr,
 	max_avail = fsm_get_max_avail(page);
 
 	/*
-	 * Reset the next slot pointer. This encourages the use of low-numbered
-	 * pages, increasing the chances that a later vacuum can truncate the
-	 * relation.  We don't bother with a lock here, nor with marking the page
-	 * dirty if it wasn't already, since this is just a hint.
+	 * Try to reset the next slot pointer. This encourages the use of
+	 * low-numbered pages, increasing the chances that a later vacuum can
+	 * truncate the relation.  We don't bother with a lock here, nor with
+	 * marking the page dirty if it wasn't already, since this is just a hint.
+	 *
+	 * FIXME: Should probably use BufferSetHintBits16()
 	 */
-	((FSMPage) PageGetContents(page))->fp_next_slot = 0;
+	if (BufferPrepareToSetHintBits(buf))
+	{
+		((FSMPage) PageGetContents(page))->fp_next_slot = 0;
+		BufferFinishSetHintBits(buf, false, false);
+	}
 
 	ReleaseBuffer(buf);
 

src/backend/storage/freespace/fsmpage.c

@@ -300,7 +300,13 @@ fsm_search_avail(Buffer buf, uint8 minvalue, bool advancenext,
 	 *
 	 * Wrap-around is handled at the beginning of this function.
 	 */
-	fsmpage->fp_next_slot = slot + (advancenext ? 1 : 0);
+	if (exclusive_lock_held || BufferPrepareToSetHintBits(buf))
+	{
+		fsmpage->fp_next_slot = slot + (advancenext ? 1 : 0);
+
+		if (!exclusive_lock_held)
+			BufferFinishSetHintBits(buf, false, true);
+	}
 
 	return slot;
 }