Include RelFileLocator fields individually in BufferTag.

This is preparatory work for a project to increase the number of bits in a RelFileNumber from 32 to 56. Along the way, introduce static inline accessor functions for a couple of BufferTag fields. Dilip Kumar, reviewed by me. The overall patch series has also had review at various times from Andres Freund, Ashutosh Sharma, Hannu Krosing, Vignesh C, Álvaro Herrera, and Tom Lane. Discussion: http://postgr.es/m/CAFiTN-trubju5YbWAq-BSpZ90-Z6xCVBQE8BVqXqANOZAF1Znw@mail.gmail.com
3 years ago · 82ac34db20
parent 396d348b04
commit 82ac34db20
5 changed files with 145 additions and 73 deletions
--- a/contrib/pg_buffercache/pg_buffercache_pages.c
+++ b/contrib/pg_buffercache/pg_buffercache_pages.c
@ -153,10 +153,10 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 			buf_state = LockBufHdr(bufHdr);

 			fctx->record[i].bufferid = BufferDescriptorGetBuffer(bufHdr);
-			fctx->record[i].relfilenumber = bufHdr->tag.rlocator.relNumber;
-			fctx->record[i].reltablespace = bufHdr->tag.rlocator.spcOid;
-			fctx->record[i].reldatabase = bufHdr->tag.rlocator.dbOid;
-			fctx->record[i].forknum = bufHdr->tag.forkNum;
+			fctx->record[i].relfilenumber = BufTagGetRelNumber(&bufHdr->tag);
+			fctx->record[i].reltablespace = bufHdr->tag.spcOid;
+			fctx->record[i].reldatabase = bufHdr->tag.dbOid;
+			fctx->record[i].forknum = BufTagGetForkNum(&bufHdr->tag);
 			fctx->record[i].blocknum = bufHdr->tag.blockNum;
 			fctx->record[i].usagecount = BUF_STATE_GET_USAGECOUNT(buf_state);
 			fctx->record[i].pinning_backends = BUF_STATE_GET_REFCOUNT(buf_state);
--- a/contrib/pg_prewarm/autoprewarm.c
+++ b/contrib/pg_prewarm/autoprewarm.c
@ -630,10 +630,12 @@ apw_dump_now(bool is_bgworker, bool dump_unlogged)
 		if (buf_state & BM_TAG_VALID &&
 			((buf_state & BM_PERMANENT) || dump_unlogged))
 		{
-			block_info_array[num_blocks].database = bufHdr->tag.rlocator.dbOid;
-			block_info_array[num_blocks].tablespace = bufHdr->tag.rlocator.spcOid;
-			block_info_array[num_blocks].filenumber = bufHdr->tag.rlocator.relNumber;
-			block_info_array[num_blocks].forknum = bufHdr->tag.forkNum;
+			block_info_array[num_blocks].database = bufHdr->tag.dbOid;
+			block_info_array[num_blocks].tablespace = bufHdr->tag.spcOid;
+			block_info_array[num_blocks].filenumber =
+				BufTagGetRelNumber(&bufHdr->tag);
+			block_info_array[num_blocks].forknum =
+				BufTagGetForkNum(&bufHdr->tag);
 			block_info_array[num_blocks].blocknum = bufHdr->tag.blockNum;
 			++num_blocks;
 		}
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@ -1657,8 +1657,8 @@ ReleaseAndReadBuffer(Buffer buffer,
 		{
 			bufHdr = GetLocalBufferDescriptor(-buffer - 1);
 			if (bufHdr->tag.blockNum == blockNum &&
-				RelFileLocatorEquals(bufHdr->tag.rlocator, relation->rd_locator) &&
-				bufHdr->tag.forkNum == forkNum)
+				BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
+				BufTagGetForkNum(&bufHdr->tag) == forkNum)
 				return buffer;
 			ResourceOwnerForgetBuffer(CurrentResourceOwner, buffer);
 			LocalRefCount[-buffer - 1]--;
@ -1668,8 +1668,8 @@ ReleaseAndReadBuffer(Buffer buffer,
 			bufHdr = GetBufferDescriptor(buffer - 1);
 			/* we have pin, so it's ok to examine tag without spinlock */
 			if (bufHdr->tag.blockNum == blockNum &&
-				RelFileLocatorEquals(bufHdr->tag.rlocator, relation->rd_locator) &&
-				bufHdr->tag.forkNum == forkNum)
+				BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
+				BufTagGetForkNum(&bufHdr->tag) == forkNum)
 				return buffer;
 			UnpinBuffer(bufHdr, true);
 		}
@ -2010,9 +2010,9 @@ BufferSync(int flags)

 			item = &CkptBufferIds[num_to_scan++];
 			item->buf_id = buf_id;
-			item->tsId = bufHdr->tag.rlocator.spcOid;
-			item->relNumber = bufHdr->tag.rlocator.relNumber;
-			item->forkNum = bufHdr->tag.forkNum;
+			item->tsId = bufHdr->tag.spcOid;
+			item->relNumber = BufTagGetRelNumber(&bufHdr->tag);
+			item->forkNum = BufTagGetForkNum(&bufHdr->tag);
 			item->blockNum = bufHdr->tag.blockNum;
 		}

@ -2718,7 +2718,8 @@ PrintBufferLeakWarning(Buffer buffer)
 	}

 	/* theoretically we should lock the bufhdr here */
-	path = relpathbackend(buf->tag.rlocator, backend, buf->tag.forkNum);
+	path = relpathbackend(BufTagGetRelFileLocator(&buf->tag), backend,
+						  BufTagGetForkNum(&buf->tag));
 	buf_state = pg_atomic_read_u32(&buf->state);
 	elog(WARNING,
 		 "buffer refcount leak: [%03d] "
@ -2797,8 +2798,8 @@ BufferGetTag(Buffer buffer, RelFileLocator *rlocator, ForkNumber *forknum,
 		bufHdr = GetBufferDescriptor(buffer - 1);

 	/* pinned, so OK to read tag without spinlock */
-	*rlocator = bufHdr->tag.rlocator;
-	*forknum = bufHdr->tag.forkNum;
+	*rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
+	*forknum = BufTagGetForkNum(&bufHdr->tag);
 	*blknum = bufHdr->tag.blockNum;
 }

@ -2848,9 +2849,9 @@ FlushBuffer(BufferDesc *buf, SMgrRelation reln)

 	/* Find smgr relation for buffer */
 	if (reln == NULL)
-		reln = smgropen(buf->tag.rlocator, InvalidBackendId);
+		reln = smgropen(BufTagGetRelFileLocator(&buf->tag), InvalidBackendId);

-	TRACE_POSTGRESQL_BUFFER_FLUSH_START(buf->tag.forkNum,
+	TRACE_POSTGRESQL_BUFFER_FLUSH_START(BufTagGetForkNum(&buf->tag),
 										buf->tag.blockNum,
 										reln->smgr_rlocator.locator.spcOid,
 										reln->smgr_rlocator.locator.dbOid,
@ -2909,7 +2910,7 @@ FlushBuffer(BufferDesc *buf, SMgrRelation reln)
 	 * bufToWrite is either the shared buffer or a copy, as appropriate.
 	 */
 	smgrwrite(reln,
-			  buf->tag.forkNum,
+			  BufTagGetForkNum(&buf->tag),
 			  buf->tag.blockNum,
 			  bufToWrite,
 			  false);
@ -2930,7 +2931,7 @@ FlushBuffer(BufferDesc *buf, SMgrRelation reln)
 	 */
 	TerminateBufferIO(buf, true, 0);

-	TRACE_POSTGRESQL_BUFFER_FLUSH_DONE(buf->tag.forkNum,
+	TRACE_POSTGRESQL_BUFFER_FLUSH_DONE(BufTagGetForkNum(&buf->tag),
 									   buf->tag.blockNum,
 									   reln->smgr_rlocator.locator.spcOid,
 									   reln->smgr_rlocator.locator.dbOid,
@ -3151,15 +3152,15 @@ DropRelationBuffers(SMgrRelation smgr_reln, ForkNumber *forkNum,
 		 * We could check forkNum and blockNum as well as the rlocator, but
 		 * the incremental win from doing so seems small.
 		 */
-		if (!RelFileLocatorEquals(bufHdr->tag.rlocator, rlocator.locator))
+		if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator))
 			continue;

 		buf_state = LockBufHdr(bufHdr);

 		for (j = 0; j < nforks; j++)
 		{
-			if (RelFileLocatorEquals(bufHdr->tag.rlocator, rlocator.locator) &&
-				bufHdr->tag.forkNum == forkNum[j] &&
+			if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator) &&
+				BufTagGetForkNum(&bufHdr->tag) == forkNum[j] &&
 				bufHdr->tag.blockNum >= firstDelBlock[j])
 			{
 				InvalidateBuffer(bufHdr);	/* releases spinlock */
@ -3309,7 +3310,7 @@ DropRelationsAllBuffers(SMgrRelation *smgr_reln, int nlocators)

 			for (j = 0; j < n; j++)
 			{
-				if (RelFileLocatorEquals(bufHdr->tag.rlocator, locators[j]))
+				if (BufTagMatchesRelFileLocator(&bufHdr->tag, &locators[j]))
 				{
 					rlocator = &locators[j];
 					break;
@ -3318,7 +3319,10 @@ DropRelationsAllBuffers(SMgrRelation *smgr_reln, int nlocators)
 		}
 		else
 		{
-			rlocator = bsearch((const void *) &(bufHdr->tag.rlocator),
+			RelFileLocator locator;
+
+			locator = BufTagGetRelFileLocator(&bufHdr->tag);
+			rlocator = bsearch((const void *) &(locator),
 							   locators, n, sizeof(RelFileLocator),
 							   rlocator_comparator);
 		}
@ -3328,7 +3332,7 @@ DropRelationsAllBuffers(SMgrRelation *smgr_reln, int nlocators)
 			continue;

 		buf_state = LockBufHdr(bufHdr);
-		if (RelFileLocatorEquals(bufHdr->tag.rlocator, (*rlocator)))
+		if (BufTagMatchesRelFileLocator(&bufHdr->tag, rlocator))
 			InvalidateBuffer(bufHdr);	/* releases spinlock */
 		else
 			UnlockBufHdr(bufHdr, buf_state);
@ -3388,8 +3392,8 @@ FindAndDropRelationBuffers(RelFileLocator rlocator, ForkNumber forkNum,
 		 */
 		buf_state = LockBufHdr(bufHdr);

-		if (RelFileLocatorEquals(bufHdr->tag.rlocator, rlocator) &&
-			bufHdr->tag.forkNum == forkNum &&
+		if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator) &&
+			BufTagGetForkNum(&bufHdr->tag) == forkNum &&
 			bufHdr->tag.blockNum >= firstDelBlock)
 			InvalidateBuffer(bufHdr);	/* releases spinlock */
 		else
@ -3427,11 +3431,11 @@ DropDatabaseBuffers(Oid dbid)
 		 * As in DropRelationBuffers, an unlocked precheck should be
 		 * safe and saves some cycles.
 		 */
-		if (bufHdr->tag.rlocator.dbOid != dbid)
+		if (bufHdr->tag.dbOid != dbid)
 			continue;

 		buf_state = LockBufHdr(bufHdr);
-		if (bufHdr->tag.rlocator.dbOid == dbid)
+		if (bufHdr->tag.dbOid == dbid)
 			InvalidateBuffer(bufHdr);	/* releases spinlock */
 		else
 			UnlockBufHdr(bufHdr, buf_state);
@ -3461,7 +3465,8 @@ PrintBufferDescs(void)
 			 "[%02d] (freeNext=%d, rel=%s, "
 			 "blockNum=%u, flags=0x%x, refcount=%u %d)",
 			 i, buf->freeNext,
-			 relpathbackend(buf->tag.rlocator, InvalidBackendId, buf->tag.forkNum),
+			 relpathbackend(BufTagGetRelFileLocator(&buf->tag),
+							InvalidBackendId, BufTagGetForkNum(&buf->tag)),
 			 buf->tag.blockNum, buf->flags,
 			 buf->refcount, GetPrivateRefCount(b));
 	}
@ -3486,7 +3491,8 @@ PrintPinnedBufs(void)
 				 "[%02d] (freeNext=%d, rel=%s, "
 				 "blockNum=%u, flags=0x%x, refcount=%u %d)",
 				 i, buf->freeNext,
-				 relpathperm(buf->tag.rlocator, buf->tag.forkNum),
+				 relpathperm(BufTagGetRelFileLocator(&buf->tag),
+							 BufTagGetForkNum(&buf->tag)),
 				 buf->tag.blockNum, buf->flags,
 				 buf->refcount, GetPrivateRefCount(b));
 		}
@ -3525,7 +3531,7 @@ FlushRelationBuffers(Relation rel)
 			uint32		buf_state;

 			bufHdr = GetLocalBufferDescriptor(i);
-			if (RelFileLocatorEquals(bufHdr->tag.rlocator, rel->rd_locator) &&
+			if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
 				((buf_state = pg_atomic_read_u32(&bufHdr->state)) &
 				 (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
 			{
@ -3543,7 +3549,7 @@ FlushRelationBuffers(Relation rel)
 				PageSetChecksumInplace(localpage, bufHdr->tag.blockNum);

 				smgrwrite(RelationGetSmgr(rel),
-						  bufHdr->tag.forkNum,
+						  BufTagGetForkNum(&bufHdr->tag),
 						  bufHdr->tag.blockNum,
 						  localpage,
 						  false);
@ -3572,13 +3578,13 @@ FlushRelationBuffers(Relation rel)
 		 * As in DropRelationBuffers, an unlocked precheck should be
 		 * safe and saves some cycles.
 		 */
-		if (!RelFileLocatorEquals(bufHdr->tag.rlocator, rel->rd_locator))
+		if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator))
 			continue;

 		ReservePrivateRefCountEntry();

 		buf_state = LockBufHdr(bufHdr);
-		if (RelFileLocatorEquals(bufHdr->tag.rlocator, rel->rd_locator) &&
+		if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
 			(buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
 		{
 			PinBuffer_Locked(bufHdr);
@ -3652,7 +3658,7 @@ FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)

 			for (j = 0; j < nrels; j++)
 			{
-				if (RelFileLocatorEquals(bufHdr->tag.rlocator, srels[j].rlocator))
+				if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srels[j].rlocator))
 				{
 					srelent = &srels[j];
 					break;
@ -3661,7 +3667,10 @@ FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)
 		}
 		else
 		{
-			srelent = bsearch((const void *) &(bufHdr->tag.rlocator),
+			RelFileLocator rlocator;
+
+			rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
+			srelent = bsearch((const void *) &(rlocator),
 							  srels, nrels, sizeof(SMgrSortArray),
 							  rlocator_comparator);
 		}
@ -3673,7 +3682,7 @@ FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)
 		ReservePrivateRefCountEntry();

 		buf_state = LockBufHdr(bufHdr);
-		if (RelFileLocatorEquals(bufHdr->tag.rlocator, srelent->rlocator) &&
+		if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srelent->rlocator) &&
 			(buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
 		{
 			PinBuffer_Locked(bufHdr);
@ -3877,13 +3886,13 @@ FlushDatabaseBuffers(Oid dbid)
 		 * As in DropRelationBuffers, an unlocked precheck should be
 		 * safe and saves some cycles.
 		 */
-		if (bufHdr->tag.rlocator.dbOid != dbid)
+		if (bufHdr->tag.dbOid != dbid)
 			continue;

 		ReservePrivateRefCountEntry();

 		buf_state = LockBufHdr(bufHdr);
-		if (bufHdr->tag.rlocator.dbOid == dbid &&
+		if (bufHdr->tag.dbOid == dbid &&
 			(buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
 		{
 			PinBuffer_Locked(bufHdr);
@ -4052,7 +4061,7 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
 			 * See src/backend/storage/page/README for longer discussion.
 			 */
 			if (RecoveryInProgress() ||
-				RelFileLocatorSkippingWAL(bufHdr->tag.rlocator))
+				RelFileLocatorSkippingWAL(BufTagGetRelFileLocator(&bufHdr->tag)))
 				return;

 			/*
@ -4661,7 +4670,8 @@ AbortBufferIO(void)
 				/* Buffer is pinned, so we can read tag without spinlock */
 				char	   *path;

-				path = relpathperm(buf->tag.rlocator, buf->tag.forkNum);
+				path = relpathperm(BufTagGetRelFileLocator(&buf->tag),
+								   BufTagGetForkNum(&buf->tag));
 				ereport(WARNING,
 						(errcode(ERRCODE_IO_ERROR),
 						 errmsg("could not write block %u of %s",
@ -4685,7 +4695,8 @@ shared_buffer_write_error_callback(void *arg)
 	/* Buffer is pinned, so we can read the tag without locking the spinlock */
 	if (bufHdr != NULL)
 	{
-		char	   *path = relpathperm(bufHdr->tag.rlocator, bufHdr->tag.forkNum);
+		char	   *path = relpathperm(BufTagGetRelFileLocator(&bufHdr->tag),
+									   BufTagGetForkNum(&bufHdr->tag));

 		errcontext("writing block %u of relation %s",
 				   bufHdr->tag.blockNum, path);
@ -4703,8 +4714,9 @@ local_buffer_write_error_callback(void *arg)

 	if (bufHdr != NULL)
 	{
-		char	   *path = relpathbackend(bufHdr->tag.rlocator, MyBackendId,
-										  bufHdr->tag.forkNum);
+		char	   *path = relpathbackend(BufTagGetRelFileLocator(&bufHdr->tag),
+										  MyBackendId,
+										  BufTagGetForkNum(&bufHdr->tag));

 		errcontext("writing block %u of relation %s",
 				   bufHdr->tag.blockNum, path);
@ -4798,15 +4810,20 @@ static inline int
 buffertag_comparator(const BufferTag *ba, const BufferTag *bb)
 {
 	int			ret;
+	RelFileLocator rlocatora;
+	RelFileLocator rlocatorb;

-	ret = rlocator_comparator(&ba->rlocator, &bb->rlocator);
+	rlocatora = BufTagGetRelFileLocator(ba);
+	rlocatorb = BufTagGetRelFileLocator(bb);
+
+	ret = rlocator_comparator(&rlocatora, &rlocatorb);

 	if (ret != 0)
 		return ret;

-	if (ba->forkNum < bb->forkNum)
+	if (BufTagGetForkNum(ba) < BufTagGetForkNum(bb))
 		return -1;
-	if (ba->forkNum > bb->forkNum)
+	if (BufTagGetForkNum(ba) > BufTagGetForkNum(bb))
 		return 1;

 	if (ba->blockNum < bb->blockNum)
@ -4956,10 +4973,12 @@ IssuePendingWritebacks(WritebackContext *context)
 		SMgrRelation reln;
 		int			ahead;
 		BufferTag	tag;
+		RelFileLocator currlocator;
 		Size		nblocks = 1;

 		cur = &context->pending_writebacks[i];
 		tag = cur->tag;
+		currlocator = BufTagGetRelFileLocator(&tag);

 		/*
 		 * Peek ahead, into following writeback requests, to see if they can
@ -4967,11 +4986,13 @@ IssuePendingWritebacks(WritebackContext *context)
 		 */
 		for (ahead = 0; i + ahead + 1 < context->nr_pending; ahead++)
 		{
+
 			next = &context->pending_writebacks[i + ahead + 1];

 			/* different file, stop */
-			if (!RelFileLocatorEquals(cur->tag.rlocator, next->tag.rlocator) ||
-				cur->tag.forkNum != next->tag.forkNum)
+			if (!RelFileLocatorEquals(currlocator,
+									  BufTagGetRelFileLocator(&next->tag)) ||
+				BufTagGetForkNum(&cur->tag) != BufTagGetForkNum(&next->tag))
 				break;

 			/* ok, block queued twice, skip */
@ -4989,8 +5010,8 @@ IssuePendingWritebacks(WritebackContext *context)
 		i += ahead;

 		/* and finally tell the kernel to write the data to storage */
-		reln = smgropen(tag.rlocator, InvalidBackendId);
-		smgrwriteback(reln, tag.forkNum, tag.blockNum, nblocks);
+		reln = smgropen(currlocator, InvalidBackendId);
+		smgrwriteback(reln, BufTagGetForkNum(&tag), tag.blockNum, nblocks);
 	}

 	context->nr_pending = 0;
--- a/src/backend/storage/buffer/localbuf.c
+++ b/src/backend/storage/buffer/localbuf.c
@ -215,13 +215,13 @@ LocalBufferAlloc(SMgrRelation smgr, ForkNumber forkNum, BlockNumber blockNum,
 		Page		localpage = (char *) LocalBufHdrGetBlock(bufHdr);

 		/* Find smgr relation for buffer */
-		oreln = smgropen(bufHdr->tag.rlocator, MyBackendId);
+		oreln = smgropen(BufTagGetRelFileLocator(&bufHdr->tag), MyBackendId);

 		PageSetChecksumInplace(localpage, bufHdr->tag.blockNum);

 		/* And write... */
 		smgrwrite(oreln,
-				  bufHdr->tag.forkNum,
+				  BufTagGetForkNum(&bufHdr->tag),
 				  bufHdr->tag.blockNum,
 				  localpage,
 				  false);
@ -337,16 +337,18 @@ DropRelationLocalBuffers(RelFileLocator rlocator, ForkNumber forkNum,
 		buf_state = pg_atomic_read_u32(&bufHdr->state);

 		if ((buf_state & BM_TAG_VALID) &&
-			RelFileLocatorEquals(bufHdr->tag.rlocator, rlocator) &&
-			bufHdr->tag.forkNum == forkNum &&
+			BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator) &&
+			BufTagGetForkNum(&bufHdr->tag) == forkNum &&
 			bufHdr->tag.blockNum >= firstDelBlock)
 		{
 			if (LocalRefCount[i] != 0)
 				elog(ERROR, "block %u of %s is still referenced (local %u)",
 					 bufHdr->tag.blockNum,
-					 relpathbackend(bufHdr->tag.rlocator, MyBackendId,
-									bufHdr->tag.forkNum),
+					 relpathbackend(BufTagGetRelFileLocator(&bufHdr->tag),
+									MyBackendId,
+									BufTagGetForkNum(&bufHdr->tag)),
 					 LocalRefCount[i]);
+
 			/* Remove entry from hashtable */
 			hresult = (LocalBufferLookupEnt *)
 				hash_search(LocalBufHash, (void *) &bufHdr->tag,
@ -383,13 +385,14 @@ DropRelationAllLocalBuffers(RelFileLocator rlocator)
 		buf_state = pg_atomic_read_u32(&bufHdr->state);

 		if ((buf_state & BM_TAG_VALID) &&
-			RelFileLocatorEquals(bufHdr->tag.rlocator, rlocator))
+			BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator))
 		{
 			if (LocalRefCount[i] != 0)
 				elog(ERROR, "block %u of %s is still referenced (local %u)",
 					 bufHdr->tag.blockNum,
-					 relpathbackend(bufHdr->tag.rlocator, MyBackendId,
-									bufHdr->tag.forkNum),
+					 relpathbackend(BufTagGetRelFileLocator(&bufHdr->tag),
+									MyBackendId,
+									BufTagGetForkNum(&bufHdr->tag)),
 					 LocalRefCount[i]);
 			/* Remove entry from hashtable */
 			hresult = (LocalBufferLookupEnt *)
--- a/src/include/storage/buf_internals.h
+++ b/src/include/storage/buf_internals.h
@ -90,18 +90,51 @@
 */
 typedef struct buftag
 {
-	RelFileLocator rlocator;	/* physical relation identifier */
-	ForkNumber	forkNum;
+	Oid			spcOid;			/* tablespace oid */
+	Oid			dbOid;			/* database oid */
+	RelFileNumber relNumber;	/* relation file number */
+	ForkNumber	forkNum;		/* fork number */
 	BlockNumber blockNum;		/* blknum relative to begin of reln */
 } BufferTag;

+static inline RelFileNumber
+BufTagGetRelNumber(const BufferTag *tag)
+{
+	return tag->relNumber;
+}
+
+static inline ForkNumber
+BufTagGetForkNum(const BufferTag *tag)
+{
+	return tag->forkNum;
+}
+
+static inline void
+BufTagSetRelForkDetails(BufferTag *tag, RelFileNumber relnumber,
+						ForkNumber forknum)
+{
+	tag->relNumber = relnumber;
+	tag->forkNum = forknum;
+}
+
+static inline RelFileLocator
+BufTagGetRelFileLocator(const BufferTag *tag)
+{
+	RelFileLocator rlocator;
+
+	rlocator.spcOid = tag->spcOid;
+	rlocator.dbOid = tag->dbOid;
+	rlocator.relNumber = BufTagGetRelNumber(tag);
+
+	return rlocator;
+}
+
 static inline void
 ClearBufferTag(BufferTag *tag)
 {
-	tag->rlocator.spcOid = InvalidOid;
-	tag->rlocator.dbOid = InvalidOid;
-	tag->rlocator.relNumber = InvalidRelFileNumber;
-	tag->forkNum = InvalidForkNumber;
+	tag->spcOid = InvalidOid;
+	tag->dbOid = InvalidOid;
+	BufTagSetRelForkDetails(tag, InvalidRelFileNumber, InvalidForkNumber);
 	tag->blockNum = InvalidBlockNumber;
 }

@ -109,19 +142,32 @@ static inline void
 InitBufferTag(BufferTag *tag, const RelFileLocator *rlocator,
 			  ForkNumber forkNum, BlockNumber blockNum)
 {
-	tag->rlocator = *rlocator;
-	tag->forkNum = forkNum;
+	tag->spcOid = rlocator->spcOid;
+	tag->dbOid = rlocator->dbOid;
+	BufTagSetRelForkDetails(tag, rlocator->relNumber, forkNum);
 	tag->blockNum = blockNum;
 }

 static inline bool
 BufferTagsEqual(const BufferTag *tag1, const BufferTag *tag2)
 {
-	return RelFileLocatorEquals(tag1->rlocator, tag2->rlocator) &&
+	return (tag1->spcOid == tag2->spcOid) &&
+		(tag1->dbOid == tag2->dbOid) &&
+		(tag1->relNumber == tag2->relNumber) &&
 		(tag1->blockNum == tag2->blockNum) &&
 		(tag1->forkNum == tag2->forkNum);
 }

+static inline bool
+BufTagMatchesRelFileLocator(const BufferTag *tag,
+							const RelFileLocator *rlocator)
+{
+	return (tag->spcOid == rlocator->spcOid) &&
+		(tag->dbOid == rlocator->dbOid) &&
+		(BufTagGetRelNumber(tag) == rlocator->relNumber);
+}
+
+
 /*
 * The shared buffer mapping table is partitioned to reduce contention.
 * To determine which partition lock a given tag requires, compute the tag's