diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c
new file mode 100644
index 3ae2848..3e70792
*** a/src/backend/storage/buffer/buf_init.c
--- b/src/backend/storage/buffer/buf_init.c
*************** InitBufferPool(void)
*** 95,106 ****
  			BufferDesc *buf = GetBufferDescriptor(i);
  
  			CLEAR_BUFFERTAG(buf->tag);
- 			buf->flags = 0;
- 			buf->usage_count = 0;
- 			buf->refcount = 0;
- 			buf->wait_backend_pid = 0;
  
! 			SpinLockInit(&buf->buf_hdr_lock);
  
  			buf->buf_id = i;
  
--- 95,103 ----
  			BufferDesc *buf = GetBufferDescriptor(i);
  
  			CLEAR_BUFFERTAG(buf->tag);
  
! 			pg_atomic_init_u32(&buf->state, 0);
! 			buf->wait_backend_pid = 0;
  
  			buf->buf_id = i;
  
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
new file mode 100644
index 63188a3..2ebd4a9
*** a/src/backend/storage/buffer/bufmgr.c
--- b/src/backend/storage/buffer/bufmgr.c
***************
*** 51,57 ****
  #include "utils/resowner_private.h"
  #include "utils/timestamp.h"
  
- 
  /* Note: these two macros only work on shared buffers, not local ones! */
  #define BufHdrGetBlock(bufHdr)	((Block) (BufferBlocks + ((Size) (bufHdr)->buf_id) * BLCKSZ))
  #define BufferGetLSN(bufHdr)	(PageGetLSN(BufHdrGetBlock(bufHdr)))
--- 51,56 ----
*************** static BufferDesc *PinCountWaitBuf = NUL
*** 126,132 ****
   * entry using ReservePrivateRefCountEntry() and then later, if necessary,
   * fill it with NewPrivateRefCountEntry(). That split lets us avoid doing
   * memory allocations in NewPrivateRefCountEntry() which can be important
!  * because in some scenarios it's called with a spinlock held...
   */
  static struct PrivateRefCountEntry PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES];
  static HTAB *PrivateRefCountHash = NULL;
--- 125,131 ----
   * entry using ReservePrivateRefCountEntry() and then later, if necessary,
   * fill it with NewPrivateRefCountEntry(). That split lets us avoid doing
   * memory allocations in NewPrivateRefCountEntry() which can be important
!  * because in some scenarios it's called with a header lock held...
   */
  static struct PrivateRefCountEntry PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES];
  static HTAB *PrivateRefCountHash = NULL;
*************** ReadBuffer_common(SMgrRelation smgr, cha
*** 774,782 ****
  		 */
  		if (isLocalBuf)
  		{
! 			/* Only need to adjust flags */
! 			Assert(bufHdr->flags & BM_VALID);
! 			bufHdr->flags &= ~BM_VALID;
  		}
  		else
  		{
--- 773,780 ----
  		 */
  		if (isLocalBuf)
  		{
! 			Assert(pg_atomic_read_u32(&bufHdr->state) & BM_VALID);
! 			pg_atomic_fetch_and_u32(&bufHdr->state, ~BM_VALID);
  		}
  		else
  		{
*************** ReadBuffer_common(SMgrRelation smgr, cha
*** 788,795 ****
  			do
  			{
  				LockBufHdr(bufHdr);
! 				Assert(bufHdr->flags & BM_VALID);
! 				bufHdr->flags &= ~BM_VALID;
  				UnlockBufHdr(bufHdr);
  			} while (!StartBufferIO(bufHdr, true));
  		}
--- 786,793 ----
  			do
  			{
  				LockBufHdr(bufHdr);
! 				Assert(pg_atomic_read_u32(&bufHdr->state) & BM_VALID);
! 				pg_atomic_fetch_and_u32(&bufHdr->state, ~BM_VALID);
  				UnlockBufHdr(bufHdr);
  			} while (!StartBufferIO(bufHdr, true));
  		}
*************** ReadBuffer_common(SMgrRelation smgr, cha
*** 807,813 ****
  	 * it's not been recycled) but come right back here to try smgrextend
  	 * again.
  	 */
! 	Assert(!(bufHdr->flags & BM_VALID));		/* spinlock not needed */
  
  	bufBlock = isLocalBuf ? LocalBufHdrGetBlock(bufHdr) : BufHdrGetBlock(bufHdr);
  
--- 805,811 ----
  	 * it's not been recycled) but come right back here to try smgrextend
  	 * again.
  	 */
! 	Assert(!(pg_atomic_read_u32(&bufHdr->state) & BM_VALID)); /* header lock not needed */
  
  	bufBlock = isLocalBuf ? LocalBufHdrGetBlock(bufHdr) : BufHdrGetBlock(bufHdr);
  
*************** ReadBuffer_common(SMgrRelation smgr, cha
*** 885,891 ****
  	if (isLocalBuf)
  	{
  		/* Only need to adjust flags */
! 		bufHdr->flags |= BM_VALID;
  	}
  	else
  	{
--- 883,889 ----
  	if (isLocalBuf)
  	{
  		/* Only need to adjust flags */
! 		pg_atomic_fetch_or_u32(&bufHdr->state, BM_VALID);
  	}
  	else
  	{
*************** BufferAlloc(SMgrRelation smgr, char relp
*** 939,945 ****
  	BufferTag	oldTag;			/* previous identity of selected buffer */
  	uint32		oldHash;		/* hash value for oldTag */
  	LWLock	   *oldPartitionLock;		/* buffer partition lock for it */
! 	BufFlags	oldFlags;
  	int			buf_id;
  	BufferDesc *buf;
  	bool		valid;
--- 937,943 ----
  	BufferTag	oldTag;			/* previous identity of selected buffer */
  	uint32		oldHash;		/* hash value for oldTag */
  	LWLock	   *oldPartitionLock;		/* buffer partition lock for it */
! 	uint32		oldFlags;
  	int			buf_id;
  	BufferDesc *buf;
  	bool		valid;
*************** BufferAlloc(SMgrRelation smgr, char relp
*** 1001,1024 ****
  	/* Loop here in case we have to try another victim buffer */
  	for (;;)
  	{
  		/*
! 		 * Ensure, while the spinlock's not yet held, that there's a free
  		 * refcount entry.
  		 */
  		ReservePrivateRefCountEntry();
  
  		/*
  		 * Select a victim buffer.  The buffer is returned with its header
! 		 * spinlock still held!
  		 */
! 		buf = StrategyGetBuffer(strategy);
  
! 		Assert(buf->refcount == 0);
  
! 		/* Must copy buffer flags while we still hold the spinlock */
! 		oldFlags = buf->flags;
  
! 		/* Pin the buffer and then release the buffer spinlock */
  		PinBuffer_Locked(buf);
  
  		/*
--- 999,1024 ----
  	/* Loop here in case we have to try another victim buffer */
  	for (;;)
  	{
+ 		uint32	state;
+ 
  		/*
! 		 * Ensure, while the header lock isn't yet held, that there's a free
  		 * refcount entry.
  		 */
  		ReservePrivateRefCountEntry();
  
  		/*
  		 * Select a victim buffer.  The buffer is returned with its header
! 		 * lock still held!
  		 */
! 		buf = StrategyGetBuffer(strategy, &state);
  
! 		Assert(BUF_STATE_GET_REFCOUNT(state) == 0);
  
! 		/* Must copy buffer flags while we still hold the header lock */
! 		oldFlags = state & BUF_FLAG_MASK;
  
! 		/* Pin the buffer and then release the buffer header lock */
  		PinBuffer_Locked(buf);
  
  		/*
*************** BufferAlloc(SMgrRelation smgr, char relp
*** 1202,1208 ****
  		/*
  		 * Need to lock the buffer header too in order to change its tag.
  		 */
! 		LockBufHdr(buf);
  
  		/*
  		 * Somebody could have pinned or re-dirtied the buffer while we were
--- 1202,1208 ----
  		/*
  		 * Need to lock the buffer header too in order to change its tag.
  		 */
! 		state = LockBufHdr(buf);
  
  		/*
  		 * Somebody could have pinned or re-dirtied the buffer while we were
*************** BufferAlloc(SMgrRelation smgr, char relp
*** 1210,1217 ****
  		 * recycle this buffer; we must undo everything we've done and start
  		 * over with a new victim buffer.
  		 */
! 		oldFlags = buf->flags;
! 		if (buf->refcount == 1 && !(oldFlags & BM_DIRTY))
  			break;
  
  		UnlockBufHdr(buf);
--- 1210,1217 ----
  		 * recycle this buffer; we must undo everything we've done and start
  		 * over with a new victim buffer.
  		 */
! 		oldFlags = state & BUF_FLAG_MASK;
! 		if (BUF_STATE_GET_REFCOUNT(state) == 1 && !(oldFlags & BM_DIRTY))
  			break;
  
  		UnlockBufHdr(buf);
*************** BufferAlloc(SMgrRelation smgr, char relp
*** 1232,1243 ****
  	 * 1 so that the buffer can survive one clock-sweep pass.)
  	 */
  	buf->tag = newTag;
! 	buf->flags &= ~(BM_VALID | BM_DIRTY | BM_JUST_DIRTIED | BM_CHECKPOINT_NEEDED | BM_IO_ERROR | BM_PERMANENT);
  	if (relpersistence == RELPERSISTENCE_PERMANENT)
! 		buf->flags |= BM_TAG_VALID | BM_PERMANENT;
  	else
! 		buf->flags |= BM_TAG_VALID;
! 	buf->usage_count = 1;
  
  	UnlockBufHdr(buf);
  
--- 1232,1250 ----
  	 * 1 so that the buffer can survive one clock-sweep pass.)
  	 */
  	buf->tag = newTag;
! 	pg_atomic_fetch_and_u32(&buf->state,
! 							~(BM_VALID | BM_DIRTY | BM_JUST_DIRTIED |
! 							  BM_CHECKPOINT_NEEDED | BM_IO_ERROR |
! 							  BM_PERMANENT |
! 							  BUF_USAGECOUNT_MASK));
  	if (relpersistence == RELPERSISTENCE_PERMANENT)
! 		pg_atomic_fetch_or_u32(&buf->state,
! 							   BM_TAG_VALID | BM_PERMANENT |
! 							   BUF_USAGECOUNT_ONE);
  	else
! 		pg_atomic_fetch_or_u32(&buf->state,
! 							   BM_TAG_VALID |
! 							   BUF_USAGECOUNT_ONE);
  
  	UnlockBufHdr(buf);
  
*************** BufferAlloc(SMgrRelation smgr, char relp
*** 1267,1273 ****
   * InvalidateBuffer -- mark a shared buffer invalid and return it to the
   * freelist.
   *
!  * The buffer header spinlock must be held at entry.  We drop it before
   * returning.  (This is sane because the caller must have locked the
   * buffer in order to be sure it should be dropped.)
   *
--- 1274,1280 ----
   * InvalidateBuffer -- mark a shared buffer invalid and return it to the
   * freelist.
   *
!  * The buffer header lock must be held at entry.  We drop it before
   * returning.  (This is sane because the caller must have locked the
   * buffer in order to be sure it should be dropped.)
   *
*************** InvalidateBuffer(BufferDesc *buf)
*** 1286,1294 ****
  	BufferTag	oldTag;
  	uint32		oldHash;		/* hash value for oldTag */
  	LWLock	   *oldPartitionLock;		/* buffer partition lock for it */
! 	BufFlags	oldFlags;
  
! 	/* Save the original buffer tag before dropping the spinlock */
  	oldTag = buf->tag;
  
  	UnlockBufHdr(buf);
--- 1293,1302 ----
  	BufferTag	oldTag;
  	uint32		oldHash;		/* hash value for oldTag */
  	LWLock	   *oldPartitionLock;		/* buffer partition lock for it */
! 	uint32		oldFlags;
! 	uint32		state;
  
! 	/* Save the original buffer tag before dropping the header lock */
  	oldTag = buf->tag;
  
  	UnlockBufHdr(buf);
*************** retry:
*** 1310,1316 ****
  	LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
  
  	/* Re-lock the buffer header */
! 	LockBufHdr(buf);
  
  	/* If it's changed while we were waiting for lock, do nothing */
  	if (!BUFFERTAGS_EQUAL(buf->tag, oldTag))
--- 1318,1324 ----
  	LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
  
  	/* Re-lock the buffer header */
! 	state = LockBufHdr(buf);
  
  	/* If it's changed while we were waiting for lock, do nothing */
  	if (!BUFFERTAGS_EQUAL(buf->tag, oldTag))
*************** retry:
*** 1329,1335 ****
  	 * yet done StartBufferIO, WaitIO will fall through and we'll effectively
  	 * be busy-looping here.)
  	 */
! 	if (buf->refcount != 0)
  	{
  		UnlockBufHdr(buf);
  		LWLockRelease(oldPartitionLock);
--- 1337,1343 ----
  	 * yet done StartBufferIO, WaitIO will fall through and we'll effectively
  	 * be busy-looping here.)
  	 */
! 	if (BUF_STATE_GET_REFCOUNT(state) != 0)
  	{
  		UnlockBufHdr(buf);
  		LWLockRelease(oldPartitionLock);
*************** retry:
*** 1344,1353 ****
  	 * Clear out the buffer's tag and flags.  We must do this to ensure that
  	 * linear scans of the buffer array don't think the buffer is valid.
  	 */
! 	oldFlags = buf->flags;
  	CLEAR_BUFFERTAG(buf->tag);
! 	buf->flags = 0;
! 	buf->usage_count = 0;
  
  	UnlockBufHdr(buf);
  
--- 1352,1360 ----
  	 * Clear out the buffer's tag and flags.  We must do this to ensure that
  	 * linear scans of the buffer array don't think the buffer is valid.
  	 */
! 	oldFlags = state & BUF_FLAG_MASK;
  	CLEAR_BUFFERTAG(buf->tag);
! 	pg_atomic_fetch_and_u32(&buf->state, BM_LOCKED | ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK));
  
  	UnlockBufHdr(buf);
  
*************** void
*** 1381,1386 ****
--- 1388,1394 ----
  MarkBufferDirty(Buffer buffer)
  {
  	BufferDesc *bufHdr;
+ 	uint32		state;
  
  	if (!BufferIsValid(buffer))
  		elog(ERROR, "bad buffer ID: %d", buffer);
*************** MarkBufferDirty(Buffer buffer)
*** 1397,1410 ****
  	/* unfortunately we can't check if the lock is held exclusively */
  	Assert(LWLockHeldByMe(bufHdr->content_lock));
  
! 	LockBufHdr(bufHdr);
  
! 	Assert(bufHdr->refcount > 0);
  
  	/*
  	 * If the buffer was not dirty already, do vacuum accounting.
  	 */
! 	if (!(bufHdr->flags & BM_DIRTY))
  	{
  		VacuumPageDirty++;
  		pgBufferUsage.shared_blks_dirtied++;
--- 1405,1418 ----
  	/* unfortunately we can't check if the lock is held exclusively */
  	Assert(LWLockHeldByMe(bufHdr->content_lock));
  
! 	state = LockBufHdr(bufHdr);
  
! 	Assert(BUF_STATE_GET_REFCOUNT(state) > 0);
  
  	/*
  	 * If the buffer was not dirty already, do vacuum accounting.
  	 */
! 	if (!(state & BM_DIRTY))
  	{
  		VacuumPageDirty++;
  		pgBufferUsage.shared_blks_dirtied++;
*************** MarkBufferDirty(Buffer buffer)
*** 1412,1418 ****
  			VacuumCostBalance += VacuumCostPageDirty;
  	}
  
! 	bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
  
  	UnlockBufHdr(bufHdr);
  }
--- 1420,1426 ----
  			VacuumCostBalance += VacuumCostPageDirty;
  	}
  
! 	pg_atomic_fetch_or_u32(&bufHdr->state, BM_DIRTY | BM_JUST_DIRTIED);
  
  	UnlockBufHdr(bufHdr);
  }
*************** ReleaseAndReadBuffer(Buffer buffer,
*** 1454,1460 ****
  		else
  		{
  			bufHdr = GetBufferDescriptor(buffer - 1);
! 			/* we have pin, so it's ok to examine tag without spinlock */
  			if (bufHdr->tag.blockNum == blockNum &&
  				RelFileNodeEquals(bufHdr->tag.rnode, relation->rd_node) &&
  				bufHdr->tag.forkNum == forkNum)
--- 1462,1468 ----
  		else
  		{
  			bufHdr = GetBufferDescriptor(buffer - 1);
! 			/* we have pin, so it's ok to examine tag without header lock */
  			if (bufHdr->tag.blockNum == blockNum &&
  				RelFileNodeEquals(bufHdr->tag.rnode, relation->rd_node) &&
  				bufHdr->tag.forkNum == forkNum)
*************** ReleaseAndReadBuffer(Buffer buffer,
*** 1482,1488 ****
   * Note that ResourceOwnerEnlargeBuffers must have been done already.
   *
   * Returns TRUE if buffer is BM_VALID, else FALSE.  This provision allows
!  * some callers to avoid an extra spinlock cycle.
   */
  static bool
  PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
--- 1490,1496 ----
   * Note that ResourceOwnerEnlargeBuffers must have been done already.
   *
   * Returns TRUE if buffer is BM_VALID, else FALSE.  This provision allows
!  * some callers to avoid an extra header lock cycle.
   */
  static bool
  PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
*************** PinBuffer(BufferDesc *buf, BufferAccessS
*** 1495,1517 ****
  
  	if (ref == NULL)
  	{
  		ReservePrivateRefCountEntry();
  		ref = NewPrivateRefCountEntry(b);
  
! 		LockBufHdr(buf);
! 		buf->refcount++;
! 		if (strategy == NULL)
! 		{
! 			if (buf->usage_count < BM_MAX_USAGE_COUNT)
! 				buf->usage_count++;
! 		}
! 		else
  		{
! 			if (buf->usage_count == 0)
! 				buf->usage_count = 1;
  		}
! 		result = (buf->flags & BM_VALID) != 0;
! 		UnlockBufHdr(buf);
  	}
  	else
  	{
--- 1503,1542 ----
  
  	if (ref == NULL)
  	{
+ 		uint32 state;
+ 		uint32 oldstate;
+ 
  		ReservePrivateRefCountEntry();
  		ref = NewPrivateRefCountEntry(b);
  
! 
! 		state = pg_atomic_read_u32(&buf->state);
! 		oldstate = state;
! 
! 		while (true)
  		{
! 			/* spin-wait till lock is free */
! 			while (state & BM_LOCKED)
! 			{
! 				pg_spin_delay();
! 				state = pg_atomic_read_u32(&buf->state);
! 				oldstate = state;
! 			}
! 
! 			/* increase refcount */
! 			state += BUF_REFCOUNT_ONE;
! 
! 			/* increase usagecount unless already max */
! 			if (BUF_STATE_GET_USAGECOUNT(state) != BM_MAX_USAGE_COUNT)
! 				state += BUF_USAGECOUNT_ONE;
! 
! 			if (pg_atomic_compare_exchange_u32(&buf->state, &oldstate, state))
! 				break;
! 
! 			/* get ready for next loop, oldstate has been updated by cas */
! 			state = oldstate;
  		}
! 		result = (state & BM_VALID) != 0;
  	}
  	else
  	{
*************** PinBuffer(BufferDesc *buf, BufferAccessS
*** 1527,1535 ****
  
  /*
   * PinBuffer_Locked -- as above, but caller already locked the buffer header.
!  * The spinlock is released before return.
   *
!  * As this function is called with the spinlock held, the caller has to
   * previously call ReservePrivateRefCountEntry().
   *
   * Currently, no callers of this function want to modify the buffer's
--- 1552,1560 ----
  
  /*
   * PinBuffer_Locked -- as above, but caller already locked the buffer header.
!  * The header lock is released before return.
   *
!  * As this function is called with the header lock held, the caller has to
   * previously call ReservePrivateRefCountEntry().
   *
   * Currently, no callers of this function want to modify the buffer's
*************** PinBuffer(BufferDesc *buf, BufferAccessS
*** 1540,1546 ****
   * Also all callers only ever use this function when it's known that the
   * buffer can't have a preexisting pin by this backend. That allows us to skip
   * searching the private refcount array & hash, which is a boon, because the
!  * spinlock is still held.
   *
   * Note: use of this routine is frequently mandatory, not just an optimization
   * to save a spin lock/unlock cycle, because we need to pin a buffer before
--- 1565,1571 ----
   * Also all callers only ever use this function when it's known that the
   * buffer can't have a preexisting pin by this backend. That allows us to skip
   * searching the private refcount array & hash, which is a boon, because the
!  * header lock is still held.
   *
   * Note: use of this routine is frequently mandatory, not just an optimization
   * to save a spin lock/unlock cycle, because we need to pin a buffer before
*************** PinBuffer_Locked(BufferDesc *buf)
*** 1554,1564 ****
  
  	/*
  	 * As explained, We don't expect any preexisting pins. That allows us to
! 	 * manipulate the PrivateRefCount after releasing the spinlock
  	 */
  	Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
  
! 	buf->refcount++;
  	UnlockBufHdr(buf);
  
  	b = BufferDescriptorGetBuffer(buf);
--- 1579,1589 ----
  
  	/*
  	 * As explained, We don't expect any preexisting pins. That allows us to
! 	 * manipulate the PrivateRefCount after releasing the header lock
  	 */
  	Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
  
! 	pg_atomic_fetch_add_u32(&buf->state, 1);
  	UnlockBufHdr(buf);
  
  	b = BufferDescriptorGetBuffer(buf);
*************** UnpinBuffer(BufferDesc *buf, bool fixOwn
*** 1594,1623 ****
  	ref->refcount--;
  	if (ref->refcount == 0)
  	{
  		/* I'd better not still hold any locks on the buffer */
  		Assert(!LWLockHeldByMe(buf->content_lock));
  		Assert(!LWLockHeldByMe(buf->io_in_progress_lock));
  
! 		LockBufHdr(buf);
! 
! 		/* Decrement the shared reference count */
! 		Assert(buf->refcount > 0);
! 		buf->refcount--;
  
  		/* Support LockBufferForCleanup() */
! 		if ((buf->flags & BM_PIN_COUNT_WAITER) &&
! 			buf->refcount == 1)
  		{
! 			/* we just released the last pin other than the waiter's */
! 			int			wait_backend_pid = buf->wait_backend_pid;
  
! 			buf->flags &= ~BM_PIN_COUNT_WAITER;
! 			UnlockBufHdr(buf);
! 			ProcSendSignal(wait_backend_pid);
! 		}
! 		else
! 			UnlockBufHdr(buf);
  
  		ForgetPrivateRefCountEntry(ref);
  	}
  }
--- 1619,1658 ----
  	ref->refcount--;
  	if (ref->refcount == 0)
  	{
+ 		uint32 state;
+ 
  		/* I'd better not still hold any locks on the buffer */
  		Assert(!LWLockHeldByMe(buf->content_lock));
  		Assert(!LWLockHeldByMe(buf->io_in_progress_lock));
  
! 		/*
! 		 * Decrement the shared reference count.
! 		 *
! 		 * Arguably it'd be more robust if we checked for BM_LOCKED here, but
! 		 * currently all manipulation of ->state for shared buffers is through
! 		 * atomics.
! 		 */
! 		state = pg_atomic_fetch_sub_u32(&buf->state, BUF_REFCOUNT_ONE);
! 		Assert(BUF_STATE_GET_REFCOUNT(state) > 0);
  
  		/* Support LockBufferForCleanup() */
! 		if (state & BM_PIN_COUNT_WAITER)
  		{
! 			state = LockBufHdr(buf);
  
! 			if (state & BM_PIN_COUNT_WAITER && BUF_STATE_GET_REFCOUNT(state) == 1)
! 			{
! 				/* we just released the last pin other than the waiter's */
! 				int			wait_backend_pid = buf->wait_backend_pid;
  
+ 				pg_atomic_fetch_and_u32(&buf->state,
+ 										~BM_PIN_COUNT_WAITER);
+ 				UnlockBufHdr(buf);
+ 				ProcSendSignal(wait_backend_pid);
+ 			}
+ 			else
+ 				UnlockBufHdr(buf);
+ 		}
  		ForgetPrivateRefCountEntry(ref);
  	}
  }
*************** UnpinBuffer(BufferDesc *buf, bool fixOwn
*** 1635,1640 ****
--- 1670,1676 ----
  static void
  BufferSync(int flags)
  {
+ 	uint32		state;
  	int			buf_id;
  	int			num_to_scan;
  	int			num_to_write;
*************** BufferSync(int flags)
*** 1675,1688 ****
  		BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
  
  		/*
! 		 * Header spinlock is enough to examine BM_DIRTY, see comment in
  		 * SyncOneBuffer.
  		 */
! 		LockBufHdr(bufHdr);
  
! 		if ((bufHdr->flags & mask) == mask)
  		{
! 			bufHdr->flags |= BM_CHECKPOINT_NEEDED;
  			num_to_write++;
  		}
  
--- 1711,1725 ----
  		BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
  
  		/*
! 		 * Header lock is enough to examine BM_DIRTY, see comment in
  		 * SyncOneBuffer.
  		 */
! 		state = LockBufHdr(bufHdr);
  
! 		if ((state & mask) == mask)
  		{
! 			pg_atomic_fetch_or_u32(&bufHdr->state,
! 								   BM_CHECKPOINT_NEEDED);
  			num_to_write++;
  		}
  
*************** BufferSync(int flags)
*** 1721,1727 ****
  		 * write the buffer though we didn't need to.  It doesn't seem worth
  		 * guarding against this, though.
  		 */
! 		if (bufHdr->flags & BM_CHECKPOINT_NEEDED)
  		{
  			if (SyncOneBuffer(buf_id, false) & BUF_WRITTEN)
  			{
--- 1758,1764 ----
  		 * write the buffer though we didn't need to.  It doesn't seem worth
  		 * guarding against this, though.
  		 */
! 		if (pg_atomic_read_u32(&bufHdr->state) & BM_CHECKPOINT_NEEDED)
  		{
  			if (SyncOneBuffer(buf_id, false) & BUF_WRITTEN)
  			{
*************** SyncOneBuffer(int buf_id, bool skip_rece
*** 2081,2086 ****
--- 2118,2124 ----
  {
  	BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
  	int			result = 0;
+ 	uint32		state;
  
  	ReservePrivateRefCountEntry();
  
*************** SyncOneBuffer(int buf_id, bool skip_rece
*** 2093,2102 ****
  	 * don't worry because our checkpoint.redo points before log record for
  	 * upcoming changes and so we are not required to write such dirty buffer.
  	 */
! 	LockBufHdr(bufHdr);
  
! 	if (bufHdr->refcount == 0 && bufHdr->usage_count == 0)
  		result |= BUF_REUSABLE;
  	else if (skip_recently_used)
  	{
  		/* Caller told us not to write recently-used buffers */
--- 2131,2143 ----
  	 * don't worry because our checkpoint.redo points before log record for
  	 * upcoming changes and so we are not required to write such dirty buffer.
  	 */
! 	state = LockBufHdr(bufHdr);
  
! 	if (BUF_STATE_GET_REFCOUNT(state) == 0 &&
! 		BUF_STATE_GET_USAGECOUNT(state) == 0)
! 	{
  		result |= BUF_REUSABLE;
+ 	}
  	else if (skip_recently_used)
  	{
  		/* Caller told us not to write recently-used buffers */
*************** SyncOneBuffer(int buf_id, bool skip_rece
*** 2104,2110 ****
  		return result;
  	}
  
! 	if (!(bufHdr->flags & BM_VALID) || !(bufHdr->flags & BM_DIRTY))
  	{
  		/* It's clean, so nothing to do */
  		UnlockBufHdr(bufHdr);
--- 2145,2151 ----
  		return result;
  	}
  
! 	if (!(state & BM_VALID) || !(state & BM_DIRTY))
  	{
  		/* It's clean, so nothing to do */
  		UnlockBufHdr(bufHdr);
*************** PrintBufferLeakWarning(Buffer buffer)
*** 2256,2261 ****
--- 2297,2303 ----
  	int32		loccount;
  	char	   *path;
  	BackendId	backend;
+ 	uint32		state;
  
  	Assert(BufferIsValid(buffer));
  	if (BufferIsLocal(buffer))
*************** PrintBufferLeakWarning(Buffer buffer)
*** 2273,2284 ****
  
  	/* theoretically we should lock the bufhdr here */
  	path = relpathbackend(buf->tag.rnode, backend, buf->tag.forkNum);
  	elog(WARNING,
  		 "buffer refcount leak: [%03d] "
  		 "(rel=%s, blockNum=%u, flags=0x%x, refcount=%u %d)",
  		 buffer, path,
! 		 buf->tag.blockNum, buf->flags,
! 		 buf->refcount, loccount);
  	pfree(path);
  }
  
--- 2315,2327 ----
  
  	/* theoretically we should lock the bufhdr here */
  	path = relpathbackend(buf->tag.rnode, backend, buf->tag.forkNum);
+ 	state = pg_atomic_read_u32(&buf->state);
  	elog(WARNING,
  		 "buffer refcount leak: [%03d] "
  		 "(rel=%s, blockNum=%u, flags=0x%x, refcount=%u %d)",
  		 buffer, path,
! 		 buf->tag.blockNum, state & BUF_FLAG_MASK,
! 		 BUF_STATE_GET_REFCOUNT(state), loccount);
  	pfree(path);
  }
  
*************** BufferGetBlockNumber(Buffer buffer)
*** 2333,2339 ****
  	else
  		bufHdr = GetBufferDescriptor(buffer - 1);
  
! 	/* pinned, so OK to read tag without spinlock */
  	return bufHdr->tag.blockNum;
  }
  
--- 2376,2382 ----
  	else
  		bufHdr = GetBufferDescriptor(buffer - 1);
  
! 	/* pinned, so OK to read tag without lock */
  	return bufHdr->tag.blockNum;
  }
  
*************** BufferGetTag(Buffer buffer, RelFileNode 
*** 2356,2362 ****
  	else
  		bufHdr = GetBufferDescriptor(buffer - 1);
  
! 	/* pinned, so OK to read tag without spinlock */
  	*rnode = bufHdr->tag.rnode;
  	*forknum = bufHdr->tag.forkNum;
  	*blknum = bufHdr->tag.blockNum;
--- 2399,2405 ----
  	else
  		bufHdr = GetBufferDescriptor(buffer - 1);
  
! 	/* pinned, so OK to read tag without lock */
  	*rnode = bufHdr->tag.rnode;
  	*forknum = bufHdr->tag.forkNum;
  	*blknum = bufHdr->tag.blockNum;
*************** FlushBuffer(BufferDesc *buf, SMgrRelatio
*** 2424,2430 ****
  	recptr = BufferGetLSN(buf);
  
  	/* To check if block content changes while flushing. - vadim 01/17/97 */
! 	buf->flags &= ~BM_JUST_DIRTIED;
  	UnlockBufHdr(buf);
  
  	/*
--- 2467,2473 ----
  	recptr = BufferGetLSN(buf);
  
  	/* To check if block content changes while flushing. - vadim 01/17/97 */
! 	pg_atomic_fetch_and_u32(&buf->state, ~BM_JUST_DIRTIED);
  	UnlockBufHdr(buf);
  
  	/*
*************** FlushBuffer(BufferDesc *buf, SMgrRelatio
*** 2444,2450 ****
  	 * disastrous system-wide consequences.  To make sure that can't happen,
  	 * skip the flush if the buffer isn't permanent.
  	 */
! 	if (buf->flags & BM_PERMANENT)
  		XLogFlush(recptr);
  
  	/*
--- 2487,2493 ----
  	 * disastrous system-wide consequences.  To make sure that can't happen,
  	 * skip the flush if the buffer isn't permanent.
  	 */
! 	if (pg_atomic_read_u32(&buf->state) & BM_PERMANENT)
  		XLogFlush(recptr);
  
  	/*
*************** BufferIsPermanent(Buffer buffer)
*** 2532,2544 ****
  
  	/*
  	 * BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
! 	 * need not bother with the buffer header spinlock.  Even if someone else
  	 * changes the buffer header flags while we're doing this, we assume that
  	 * changing an aligned 2-byte BufFlags value is atomic, so we'll read the
  	 * old value or the new value, but not random garbage.
  	 */
  	bufHdr = GetBufferDescriptor(buffer - 1);
! 	return (bufHdr->flags & BM_PERMANENT) != 0;
  }
  
  /*
--- 2575,2587 ----
  
  	/*
  	 * BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
! 	 * need not bother with the buffer header lock.  Even if someone else
  	 * changes the buffer header flags while we're doing this, we assume that
  	 * changing an aligned 2-byte BufFlags value is atomic, so we'll read the
  	 * old value or the new value, but not random garbage.
  	 */
  	bufHdr = GetBufferDescriptor(buffer - 1);
! 	return (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT) != 0;
  }
  
  /*
*************** DropRelFileNodeBuffers(RelFileNodeBacken
*** 2638,2644 ****
  		if (RelFileNodeEquals(bufHdr->tag.rnode, rnode.node) &&
  			bufHdr->tag.forkNum == forkNum &&
  			bufHdr->tag.blockNum >= firstDelBlock)
! 			InvalidateBuffer(bufHdr);	/* releases spinlock */
  		else
  			UnlockBufHdr(bufHdr);
  	}
--- 2681,2687 ----
  		if (RelFileNodeEquals(bufHdr->tag.rnode, rnode.node) &&
  			bufHdr->tag.forkNum == forkNum &&
  			bufHdr->tag.blockNum >= firstDelBlock)
! 			InvalidateBuffer(bufHdr);	/* releases lock */
  		else
  			UnlockBufHdr(bufHdr);
  	}
*************** DropRelFileNodesAllBuffers(RelFileNodeBa
*** 2736,2742 ****
  
  		LockBufHdr(bufHdr);
  		if (RelFileNodeEquals(bufHdr->tag.rnode, (*rnode)))
! 			InvalidateBuffer(bufHdr);	/* releases spinlock */
  		else
  			UnlockBufHdr(bufHdr);
  	}
--- 2779,2785 ----
  
  		LockBufHdr(bufHdr);
  		if (RelFileNodeEquals(bufHdr->tag.rnode, (*rnode)))
! 			InvalidateBuffer(bufHdr);	/* releases lock */
  		else
  			UnlockBufHdr(bufHdr);
  	}
*************** DropDatabaseBuffers(Oid dbid)
*** 2778,2784 ****
  
  		LockBufHdr(bufHdr);
  		if (bufHdr->tag.rnode.dbNode == dbid)
! 			InvalidateBuffer(bufHdr);	/* releases spinlock */
  		else
  			UnlockBufHdr(bufHdr);
  	}
--- 2821,2827 ----
  
  		LockBufHdr(bufHdr);
  		if (bufHdr->tag.rnode.dbNode == dbid)
! 			InvalidateBuffer(bufHdr);	/* releases lock */
  		else
  			UnlockBufHdr(bufHdr);
  	}
*************** FlushRelationBuffers(Relation rel)
*** 2874,2880 ****
  		{
  			bufHdr = GetLocalBufferDescriptor(i);
  			if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node) &&
! 				(bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_DIRTY))
  			{
  				ErrorContextCallback errcallback;
  				Page		localpage;
--- 2917,2924 ----
  		{
  			bufHdr = GetLocalBufferDescriptor(i);
  			if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node) &&
! 				(pg_atomic_read_u32(&bufHdr->state) & (BM_VALID | BM_DIRTY))
! 				== (BM_VALID | BM_DIRTY))
  			{
  				ErrorContextCallback errcallback;
  				Page		localpage;
*************** FlushRelationBuffers(Relation rel)
*** 2895,2901 ****
  						  localpage,
  						  false);
  
! 				bufHdr->flags &= ~(BM_DIRTY | BM_JUST_DIRTIED);
  
  				/* Pop the error context stack */
  				error_context_stack = errcallback.previous;
--- 2939,2945 ----
  						  localpage,
  						  false);
  
! 				pg_atomic_fetch_and_u32(&bufHdr->state, ~(BM_DIRTY | BM_JUST_DIRTIED));
  
  				/* Pop the error context stack */
  				error_context_stack = errcallback.previous;
*************** FlushRelationBuffers(Relation rel)
*** 2923,2929 ****
  
  		LockBufHdr(bufHdr);
  		if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node) &&
! 			(bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_DIRTY))
  		{
  			PinBuffer_Locked(bufHdr);
  			LWLockAcquire(bufHdr->content_lock, LW_SHARED);
--- 2967,2974 ----
  
  		LockBufHdr(bufHdr);
  		if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node) &&
! 			(pg_atomic_read_u32(&bufHdr->state) & (BM_VALID | BM_DIRTY))
! 			== (BM_VALID | BM_DIRTY))
  		{
  			PinBuffer_Locked(bufHdr);
  			LWLockAcquire(bufHdr->content_lock, LW_SHARED);
*************** FlushDatabaseBuffers(Oid dbid)
*** 2975,2981 ****
  
  		LockBufHdr(bufHdr);
  		if (bufHdr->tag.rnode.dbNode == dbid &&
! 			(bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_DIRTY))
  		{
  			PinBuffer_Locked(bufHdr);
  			LWLockAcquire(bufHdr->content_lock, LW_SHARED);
--- 3020,3027 ----
  
  		LockBufHdr(bufHdr);
  		if (bufHdr->tag.rnode.dbNode == dbid &&
! 			(pg_atomic_read_u32(&bufHdr->state) & (BM_VALID | BM_DIRTY))
! 			== (BM_VALID | BM_DIRTY))
  		{
  			PinBuffer_Locked(bufHdr);
  			LWLockAcquire(bufHdr->content_lock, LW_SHARED);
*************** MarkBufferDirtyHint(Buffer buffer, bool 
*** 3086,3104 ****
  	 * This routine might get called many times on the same page, if we are
  	 * making the first scan after commit of an xact that added/deleted many
  	 * tuples. So, be as quick as we can if the buffer is already dirty.  We
! 	 * do this by not acquiring spinlock if it looks like the status bits are
  	 * already set.  Since we make this test unlocked, there's a chance we
  	 * might fail to notice that the flags have just been cleared, and failed
  	 * to reset them, due to memory-ordering issues.  But since this function
  	 * is only intended to be used in cases where failing to write out the
  	 * data would be harmless anyway, it doesn't really matter.
  	 */
! 	if ((bufHdr->flags & (BM_DIRTY | BM_JUST_DIRTIED)) !=
  		(BM_DIRTY | BM_JUST_DIRTIED))
  	{
  		XLogRecPtr	lsn = InvalidXLogRecPtr;
  		bool		dirtied = false;
  		bool		delayChkpt = false;
  
  		/*
  		 * If we need to protect hint bit updates from torn writes, WAL-log a
--- 3132,3151 ----
  	 * This routine might get called many times on the same page, if we are
  	 * making the first scan after commit of an xact that added/deleted many
  	 * tuples. So, be as quick as we can if the buffer is already dirty.  We
! 	 * do this by not acquiring header lock if it looks like the status bits are
  	 * already set.  Since we make this test unlocked, there's a chance we
  	 * might fail to notice that the flags have just been cleared, and failed
  	 * to reset them, due to memory-ordering issues.  But since this function
  	 * is only intended to be used in cases where failing to write out the
  	 * data would be harmless anyway, it doesn't really matter.
  	 */
! 	if ((pg_atomic_read_u32(&bufHdr->state) & (BM_DIRTY | BM_JUST_DIRTIED)) !=
  		(BM_DIRTY | BM_JUST_DIRTIED))
  	{
  		XLogRecPtr	lsn = InvalidXLogRecPtr;
  		bool		dirtied = false;
  		bool		delayChkpt = false;
+ 		uint32		state;
  
  		/*
  		 * If we need to protect hint bit updates from torn writes, WAL-log a
*************** MarkBufferDirtyHint(Buffer buffer, bool 
*** 3109,3115 ****
  		 * We don't check full_page_writes here because that logic is included
  		 * when we call XLogInsert() since the value changes dynamically.
  		 */
! 		if (XLogHintBitIsNeeded() && (bufHdr->flags & BM_PERMANENT))
  		{
  			/*
  			 * If we're in recovery we cannot dirty a page because of a hint.
--- 3156,3162 ----
  		 * We don't check full_page_writes here because that logic is included
  		 * when we call XLogInsert() since the value changes dynamically.
  		 */
! 		if (XLogHintBitIsNeeded() && (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT))
  		{
  			/*
  			 * If we're in recovery we cannot dirty a page because of a hint.
*************** MarkBufferDirtyHint(Buffer buffer, bool 
*** 3149,3156 ****
  		}
  
  		LockBufHdr(bufHdr);
! 		Assert(bufHdr->refcount > 0);
! 		if (!(bufHdr->flags & BM_DIRTY))
  		{
  			dirtied = true;		/* Means "will be dirtied by this action" */
  
--- 3196,3207 ----
  		}
  
  		LockBufHdr(bufHdr);
! 
! 		state = pg_atomic_read_u32(&bufHdr->state);
! 
! 		Assert(BUF_STATE_GET_REFCOUNT(state) > 0);
! 
! 		if (!(state & BM_DIRTY))
  		{
  			dirtied = true;		/* Means "will be dirtied by this action" */
  
*************** MarkBufferDirtyHint(Buffer buffer, bool 
*** 3170,3176 ****
  			if (!XLogRecPtrIsInvalid(lsn))
  				PageSetLSN(page, lsn);
  		}
! 		bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
  		UnlockBufHdr(bufHdr);
  
  		if (delayChkpt)
--- 3221,3229 ----
  			if (!XLogRecPtrIsInvalid(lsn))
  				PageSetLSN(page, lsn);
  		}
! 
! 		pg_atomic_fetch_or_u32(&bufHdr->state, BM_DIRTY | BM_JUST_DIRTIED);
! 
  		UnlockBufHdr(bufHdr);
  
  		if (delayChkpt)
*************** UnlockBuffers(void)
*** 3208,3216 ****
  		 * Don't complain if flag bit not set; it could have been reset but we
  		 * got a cancel/die interrupt before getting the signal.
  		 */
! 		if ((buf->flags & BM_PIN_COUNT_WAITER) != 0 &&
  			buf->wait_backend_pid == MyProcPid)
! 			buf->flags &= ~BM_PIN_COUNT_WAITER;
  
  		UnlockBufHdr(buf);
  
--- 3261,3269 ----
  		 * Don't complain if flag bit not set; it could have been reset but we
  		 * got a cancel/die interrupt before getting the signal.
  		 */
! 		if ((pg_atomic_read_u32(&buf->state) & BM_PIN_COUNT_WAITER) != 0 &&
  			buf->wait_backend_pid == MyProcPid)
! 			pg_atomic_fetch_and_u32(&buf->state, ~BM_PIN_COUNT_WAITER);
  
  		UnlockBufHdr(buf);
  
*************** LockBufferForCleanup(Buffer buffer)
*** 3304,3328 ****
  
  	for (;;)
  	{
  		/* Try to acquire lock */
  		LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
! 		LockBufHdr(bufHdr);
! 		Assert(bufHdr->refcount > 0);
! 		if (bufHdr->refcount == 1)
  		{
  			/* Successfully acquired exclusive lock with pincount 1 */
  			UnlockBufHdr(bufHdr);
  			return;
  		}
  		/* Failed, so mark myself as waiting for pincount 1 */
! 		if (bufHdr->flags & BM_PIN_COUNT_WAITER)
  		{
  			UnlockBufHdr(bufHdr);
  			LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
  			elog(ERROR, "multiple backends attempting to wait for pincount 1");
  		}
  		bufHdr->wait_backend_pid = MyProcPid;
! 		bufHdr->flags |= BM_PIN_COUNT_WAITER;
  		PinCountWaitBuf = bufHdr;
  		UnlockBufHdr(bufHdr);
  		LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
--- 3357,3384 ----
  
  	for (;;)
  	{
+ 		int		state;
+ 
  		/* Try to acquire lock */
  		LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
! 		state = LockBufHdr(bufHdr);
! 
! 		Assert(BUF_STATE_GET_REFCOUNT(state) > 0);
! 		if (BUF_STATE_GET_REFCOUNT(state) == 1)
  		{
  			/* Successfully acquired exclusive lock with pincount 1 */
  			UnlockBufHdr(bufHdr);
  			return;
  		}
  		/* Failed, so mark myself as waiting for pincount 1 */
! 		if (state & BM_PIN_COUNT_WAITER)
  		{
  			UnlockBufHdr(bufHdr);
  			LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
  			elog(ERROR, "multiple backends attempting to wait for pincount 1");
  		}
  		bufHdr->wait_backend_pid = MyProcPid;
! 		pg_atomic_fetch_or_u32(&bufHdr->state, BM_PIN_COUNT_WAITER);
  		PinCountWaitBuf = bufHdr;
  		UnlockBufHdr(bufHdr);
  		LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
*************** LockBufferForCleanup(Buffer buffer)
*** 3349,3357 ****
  		 * better be safe.
  		 */
  		LockBufHdr(bufHdr);
! 		if ((bufHdr->flags & BM_PIN_COUNT_WAITER) != 0 &&
  			bufHdr->wait_backend_pid == MyProcPid)
! 			bufHdr->flags &= ~BM_PIN_COUNT_WAITER;
  		UnlockBufHdr(bufHdr);
  
  		PinCountWaitBuf = NULL;
--- 3405,3413 ----
  		 * better be safe.
  		 */
  		LockBufHdr(bufHdr);
! 		if ((pg_atomic_read_u32(&bufHdr->state) & BM_PIN_COUNT_WAITER) != 0 &&
  			bufHdr->wait_backend_pid == MyProcPid)
! 			pg_atomic_fetch_and_u32(&bufHdr->state, ~BM_PIN_COUNT_WAITER);
  		UnlockBufHdr(bufHdr);
  
  		PinCountWaitBuf = NULL;
*************** bool
*** 3393,3414 ****
  ConditionalLockBufferForCleanup(Buffer buffer)
  {
  	BufferDesc *bufHdr;
  
  	Assert(BufferIsValid(buffer));
  
  	if (BufferIsLocal(buffer))
  	{
  		/* There should be exactly one pin */
! 		Assert(LocalRefCount[-buffer - 1] > 0);
! 		if (LocalRefCount[-buffer - 1] != 1)
  			return false;
  		/* Nobody else to wait for */
  		return true;
  	}
  
  	/* There should be exactly one local pin */
! 	Assert(GetPrivateRefCount(buffer) > 0);
! 	if (GetPrivateRefCount(buffer) != 1)
  		return false;
  
  	/* Try to acquire lock */
--- 3449,3474 ----
  ConditionalLockBufferForCleanup(Buffer buffer)
  {
  	BufferDesc *bufHdr;
+ 	uint32		state,
+ 				refcount;
  
  	Assert(BufferIsValid(buffer));
  
  	if (BufferIsLocal(buffer))
  	{
+ 		refcount = LocalRefCount[-buffer - 1];
  		/* There should be exactly one pin */
! 		Assert(refcount > 0);
! 		if (refcount != 1)
  			return false;
  		/* Nobody else to wait for */
  		return true;
  	}
  
  	/* There should be exactly one local pin */
! 	refcount = GetPrivateRefCount(buffer);
! 	Assert(refcount);
! 	if (refcount != 1)
  		return false;
  
  	/* Try to acquire lock */
*************** ConditionalLockBufferForCleanup(Buffer b
*** 3416,3424 ****
  		return false;
  
  	bufHdr = GetBufferDescriptor(buffer - 1);
! 	LockBufHdr(bufHdr);
! 	Assert(bufHdr->refcount > 0);
! 	if (bufHdr->refcount == 1)
  	{
  		/* Successfully acquired exclusive lock with pincount 1 */
  		UnlockBufHdr(bufHdr);
--- 3476,3486 ----
  		return false;
  
  	bufHdr = GetBufferDescriptor(buffer - 1);
! 	state = LockBufHdr(bufHdr);
! 	refcount = BUF_STATE_GET_REFCOUNT(state);
! 
! 	Assert(refcount > 0);
! 	if (refcount == 1)
  	{
  		/* Successfully acquired exclusive lock with pincount 1 */
  		UnlockBufHdr(bufHdr);
*************** WaitIO(BufferDesc *buf)
*** 3456,3472 ****
  	 */
  	for (;;)
  	{
! 		BufFlags	sv_flags;
  
  		/*
! 		 * It may not be necessary to acquire the spinlock to check the flag
  		 * here, but since this test is essential for correctness, we'd better
  		 * play it safe.
  		 */
! 		LockBufHdr(buf);
! 		sv_flags = buf->flags;
  		UnlockBufHdr(buf);
! 		if (!(sv_flags & BM_IO_IN_PROGRESS))
  			break;
  		LWLockAcquire(buf->io_in_progress_lock, LW_SHARED);
  		LWLockRelease(buf->io_in_progress_lock);
--- 3518,3534 ----
  	 */
  	for (;;)
  	{
! 		uint32		state;
  
  		/*
! 		 * It may not be necessary to acquire the header lock to check the flag
  		 * here, but since this test is essential for correctness, we'd better
  		 * play it safe.
  		 */
! 		state = LockBufHdr(buf);
  		UnlockBufHdr(buf);
! 
! 		if (!(state & BM_IO_IN_PROGRESS))
  			break;
  		LWLockAcquire(buf->io_in_progress_lock, LW_SHARED);
  		LWLockRelease(buf->io_in_progress_lock);
*************** WaitIO(BufferDesc *buf)
*** 3494,3499 ****
--- 3556,3563 ----
  static bool
  StartBufferIO(BufferDesc *buf, bool forInput)
  {
+ 	uint32		state;
+ 
  	Assert(!InProgressBuf);
  
  	for (;;)
*************** StartBufferIO(BufferDesc *buf, bool forI
*** 3504,3512 ****
  		 */
  		LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
  
! 		LockBufHdr(buf);
  
! 		if (!(buf->flags & BM_IO_IN_PROGRESS))
  			break;
  
  		/*
--- 3568,3576 ----
  		 */
  		LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
  
! 		state = LockBufHdr(buf);
  
! 		if (!(state & BM_IO_IN_PROGRESS))
  			break;
  
  		/*
*************** StartBufferIO(BufferDesc *buf, bool forI
*** 3522,3528 ****
  
  	/* Once we get here, there is definitely no I/O active on this buffer */
  
! 	if (forInput ? (buf->flags & BM_VALID) : !(buf->flags & BM_DIRTY))
  	{
  		/* someone else already did the I/O */
  		UnlockBufHdr(buf);
--- 3586,3592 ----
  
  	/* Once we get here, there is definitely no I/O active on this buffer */
  
! 	if (forInput ? (state & BM_VALID) : !(state & BM_DIRTY))
  	{
  		/* someone else already did the I/O */
  		UnlockBufHdr(buf);
*************** StartBufferIO(BufferDesc *buf, bool forI
*** 3530,3536 ****
  		return false;
  	}
  
! 	buf->flags |= BM_IO_IN_PROGRESS;
  
  	UnlockBufHdr(buf);
  
--- 3594,3600 ----
  		return false;
  	}
  
! 	pg_atomic_fetch_or_u32(&buf->state, BM_IO_IN_PROGRESS);
  
  	UnlockBufHdr(buf);
  
*************** StartBufferIO(BufferDesc *buf, bool forI
*** 3560,3574 ****
  static void
  TerminateBufferIO(BufferDesc *buf, bool clear_dirty, int set_flag_bits)
  {
  	Assert(buf == InProgressBuf);
  
! 	LockBufHdr(buf);
  
! 	Assert(buf->flags & BM_IO_IN_PROGRESS);
! 	buf->flags &= ~(BM_IO_IN_PROGRESS | BM_IO_ERROR);
! 	if (clear_dirty && !(buf->flags & BM_JUST_DIRTIED))
! 		buf->flags &= ~(BM_DIRTY | BM_CHECKPOINT_NEEDED);
! 	buf->flags |= set_flag_bits;
  
  	UnlockBufHdr(buf);
  
--- 3624,3642 ----
  static void
  TerminateBufferIO(BufferDesc *buf, bool clear_dirty, int set_flag_bits)
  {
+ 	uint32		state;
+ 
  	Assert(buf == InProgressBuf);
  
! 	state = LockBufHdr(buf);
  
! 	Assert(state & BM_IO_IN_PROGRESS);
! 
! 	pg_atomic_fetch_and_u32(&buf->state, ~(BM_IO_IN_PROGRESS | BM_IO_ERROR));
! 	if (clear_dirty && !(pg_atomic_read_u32(&buf->state) & BM_JUST_DIRTIED))
! 		pg_atomic_fetch_and_u32(&buf->state, ~(BM_DIRTY | BM_CHECKPOINT_NEEDED));
! 
! 	pg_atomic_fetch_or_u32(&buf->state, set_flag_bits);
  
  	UnlockBufHdr(buf);
  
*************** AbortBufferIO(void)
*** 3593,3598 ****
--- 3661,3667 ----
  
  	if (buf)
  	{
+ 		uint32	state;
  		/*
  		 * Since LWLockReleaseAll has already been called, we're not holding
  		 * the buffer's io_in_progress_lock. We have to re-acquire it so that
*************** AbortBufferIO(void)
*** 3601,3626 ****
  		 */
  		LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
  
! 		LockBufHdr(buf);
! 		Assert(buf->flags & BM_IO_IN_PROGRESS);
  		if (IsForInput)
  		{
! 			Assert(!(buf->flags & BM_DIRTY));
  			/* We'd better not think buffer is valid yet */
! 			Assert(!(buf->flags & BM_VALID));
  			UnlockBufHdr(buf);
  		}
  		else
  		{
! 			BufFlags	sv_flags;
! 
! 			sv_flags = buf->flags;
! 			Assert(sv_flags & BM_DIRTY);
  			UnlockBufHdr(buf);
  			/* Issue notice if this is not the first failure... */
! 			if (sv_flags & BM_IO_ERROR)
  			{
! 				/* Buffer is pinned, so we can read tag without spinlock */
  				char	   *path;
  
  				path = relpathperm(buf->tag.rnode, buf->tag.forkNum);
--- 3670,3693 ----
  		 */
  		LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
  
! 		state = LockBufHdr(buf);
! 		Assert(state & BM_IO_IN_PROGRESS);
  		if (IsForInput)
  		{
! 			Assert(!(state & BM_DIRTY));
! 
  			/* We'd better not think buffer is valid yet */
! 			Assert(!(state & BM_VALID));
  			UnlockBufHdr(buf);
  		}
  		else
  		{
! 			Assert(state & BM_DIRTY);
  			UnlockBufHdr(buf);
  			/* Issue notice if this is not the first failure... */
! 			if (state & BM_IO_ERROR)
  			{
! 				/* Buffer is pinned, so we can read tag without header lock */
  				char	   *path;
  
  				path = relpathperm(buf->tag.rnode, buf->tag.forkNum);
*************** shared_buffer_write_error_callback(void 
*** 3644,3650 ****
  {
  	BufferDesc *bufHdr = (BufferDesc *) arg;
  
! 	/* Buffer is pinned, so we can read the tag without locking the spinlock */
  	if (bufHdr != NULL)
  	{
  		char	   *path = relpathperm(bufHdr->tag.rnode, bufHdr->tag.forkNum);
--- 3711,3717 ----
  {
  	BufferDesc *bufHdr = (BufferDesc *) arg;
  
! 	/* Buffer is pinned, so we can read the tag without locking the header */
  	if (bufHdr != NULL)
  	{
  		char	   *path = relpathperm(bufHdr->tag.rnode, bufHdr->tag.forkNum);
*************** rnode_comparator(const void *p1, const v
*** 3700,3702 ****
--- 3767,3800 ----
  	else
  		return 0;
  }
+ 
+ uint32
+ LockBufHdr(volatile BufferDesc *desc)
+ {
+ 	uint32 state = pg_atomic_read_u32(&desc->state);
+ 
+ 	for (;;)
+ 	{
+ 		/* wait till lock is free */
+ 		while (state & BM_LOCKED)
+ 		{
+ 			pg_spin_delay();
+ 			state = pg_atomic_read_u32(&desc->state);
+ 
+ 			/* Add exponential backoff? Should seldomly be contended tho. */
+ 		}
+ 
+ 		/* and try to get lock */
+ 		if (pg_atomic_compare_exchange_u32(&desc->state, &state, state | BM_LOCKED))
+ 			break;
+ 	}
+ 	return state | BM_LOCKED;
+ }
+ 
+ void
+ UnlockBufHdr(volatile BufferDesc *desc)
+ {
+ 	Assert(pg_atomic_read_u32(&desc->state) & BM_LOCKED);
+ 
+ 	pg_atomic_sub_fetch_u32(&desc->state, BM_LOCKED);
+ }
diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
new file mode 100644
index 0234572..8b64855
*** a/src/backend/storage/buffer/freelist.c
--- b/src/backend/storage/buffer/freelist.c
*************** typedef struct BufferAccessStrategyData
*** 98,104 ****
  
  
  /* Prototypes for internal functions */
! static BufferDesc *GetBufferFromRing(BufferAccessStrategy strategy);
  static void AddBufferToRing(BufferAccessStrategy strategy,
  				BufferDesc *buf);
  
--- 98,105 ----
  
  
  /* Prototypes for internal functions */
! static BufferDesc *GetBufferFromRing(BufferAccessStrategy strategy,
! 											  uint32 *lockstate);
  static void AddBufferToRing(BufferAccessStrategy strategy,
  				BufferDesc *buf);
  
*************** ClockSweepTick(void)
*** 180,186 ****
   *	return the buffer with the buffer header spinlock still held.
   */
  BufferDesc *
! StrategyGetBuffer(BufferAccessStrategy strategy)
  {
  	BufferDesc *buf;
  	int			bgwprocno;
--- 181,187 ----
   *	return the buffer with the buffer header spinlock still held.
   */
  BufferDesc *
! StrategyGetBuffer(BufferAccessStrategy strategy, uint32 *lockstate)
  {
  	BufferDesc *buf;
  	int			bgwprocno;
*************** StrategyGetBuffer(BufferAccessStrategy s
*** 192,198 ****
  	 */
  	if (strategy != NULL)
  	{
! 		buf = GetBufferFromRing(strategy);
  		if (buf != NULL)
  			return buf;
  	}
--- 193,199 ----
  	 */
  	if (strategy != NULL)
  	{
! 		buf = GetBufferFromRing(strategy, lockstate);
  		if (buf != NULL)
  			return buf;
  	}
*************** StrategyGetBuffer(BufferAccessStrategy s
*** 250,255 ****
--- 251,258 ----
  	{
  		while (true)
  		{
+ 			uint32	state;
+ 
  			/* Acquire the spinlock to remove element from the freelist */
  			SpinLockAcquire(&StrategyControl->buffer_strategy_lock);
  
*************** StrategyGetBuffer(BufferAccessStrategy s
*** 279,289 ****
  			 * it before we got to it.  It's probably impossible altogether as
  			 * of 8.3, but we'd better check anyway.)
  			 */
! 			LockBufHdr(buf);
! 			if (buf->refcount == 0 && buf->usage_count == 0)
  			{
  				if (strategy != NULL)
  					AddBufferToRing(strategy, buf);
  				return buf;
  			}
  			UnlockBufHdr(buf);
--- 282,294 ----
  			 * it before we got to it.  It's probably impossible altogether as
  			 * of 8.3, but we'd better check anyway.)
  			 */
! 			state = LockBufHdr(buf);
! 			if (BUF_STATE_GET_REFCOUNT(state) == 0
! 				&& BUF_STATE_GET_USAGECOUNT(state) == 0)
  			{
  				if (strategy != NULL)
  					AddBufferToRing(strategy, buf);
+ 				*lockstate = state;
  				return buf;
  			}
  			UnlockBufHdr(buf);
*************** StrategyGetBuffer(BufferAccessStrategy s
*** 295,300 ****
--- 300,306 ----
  	trycounter = NBuffers;
  	for (;;)
  	{
+ 		uint32	state;
  
  		buf = GetBufferDescriptor(ClockSweepTick());
  
*************** StrategyGetBuffer(BufferAccessStrategy s
*** 302,313 ****
  		 * If the buffer is pinned or has a nonzero usage_count, we cannot use
  		 * it; decrement the usage_count (unless pinned) and keep scanning.
  		 */
! 		LockBufHdr(buf);
! 		if (buf->refcount == 0)
  		{
! 			if (buf->usage_count > 0)
  			{
! 				buf->usage_count--;
  				trycounter = NBuffers;
  			}
  			else
--- 308,321 ----
  		 * If the buffer is pinned or has a nonzero usage_count, we cannot use
  		 * it; decrement the usage_count (unless pinned) and keep scanning.
  		 */
! 		state = LockBufHdr(buf);
! 
! 		if (BUF_STATE_GET_REFCOUNT(state) == 0)
  		{
! 			if (BUF_STATE_GET_USAGECOUNT(state) != 0)
  			{
! 				pg_atomic_fetch_sub_u32(&buf->state, BUF_USAGECOUNT_ONE);
! 
  				trycounter = NBuffers;
  			}
  			else
*************** StrategyGetBuffer(BufferAccessStrategy s
*** 315,320 ****
--- 323,329 ----
  				/* Found a usable buffer */
  				if (strategy != NULL)
  					AddBufferToRing(strategy, buf);
+ 				*lockstate = state;
  				return buf;
  			}
  		}
*************** FreeAccessStrategy(BufferAccessStrategy 
*** 585,594 ****
   * The bufhdr spin lock is held on the returned buffer.
   */
  static BufferDesc *
! GetBufferFromRing(BufferAccessStrategy strategy)
  {
  	BufferDesc *buf;
  	Buffer		bufnum;
  
  	/* Advance to next ring slot */
  	if (++strategy->current >= strategy->ring_size)
--- 594,604 ----
   * The bufhdr spin lock is held on the returned buffer.
   */
  static BufferDesc *
! GetBufferFromRing(BufferAccessStrategy strategy, uint32 *lockstate)
  {
  	BufferDesc *buf;
  	Buffer		bufnum;
+ 	uint32		state;
  
  	/* Advance to next ring slot */
  	if (++strategy->current >= strategy->ring_size)
*************** GetBufferFromRing(BufferAccessStrategy s
*** 616,625 ****
  	 * shouldn't re-use it.
  	 */
  	buf = GetBufferDescriptor(bufnum - 1);
! 	LockBufHdr(buf);
! 	if (buf->refcount == 0 && buf->usage_count <= 1)
  	{
  		strategy->current_was_in_ring = true;
  		return buf;
  	}
  	UnlockBufHdr(buf);
--- 626,637 ----
  	 * shouldn't re-use it.
  	 */
  	buf = GetBufferDescriptor(bufnum - 1);
! 	state = LockBufHdr(buf);
! 	if (BUF_STATE_GET_REFCOUNT(state) == 0
! 		&& BUF_STATE_GET_USAGECOUNT(state) <= 1)
  	{
  		strategy->current_was_in_ring = true;
+ 		*lockstate = state;
  		return buf;
  	}
  	UnlockBufHdr(buf);
diff --git a/src/backend/storage/buffer/localbuf.c b/src/backend/storage/buffer/localbuf.c
new file mode 100644
index 3144afe..c62a6f2
*** a/src/backend/storage/buffer/localbuf.c
--- b/src/backend/storage/buffer/localbuf.c
*************** LocalBufferAlloc(SMgrRelation smgr, Fork
*** 108,113 ****
--- 108,114 ----
  	int			b;
  	int			trycounter;
  	bool		found;
+ 	uint32		state;
  
  	INIT_BUFFERTAG(newTag, smgr->smgr_rnode.node, forkNum, blockNum);
  
*************** LocalBufferAlloc(SMgrRelation smgr, Fork
*** 128,143 ****
  		fprintf(stderr, "LB ALLOC (%u,%d,%d) %d\n",
  				smgr->smgr_rnode.node.relNode, forkNum, blockNum, -b - 1);
  #endif
  		/* this part is equivalent to PinBuffer for a shared buffer */
  		if (LocalRefCount[b] == 0)
  		{
! 			if (bufHdr->usage_count < BM_MAX_USAGE_COUNT)
! 				bufHdr->usage_count++;
  		}
  		LocalRefCount[b]++;
  		ResourceOwnerRememberBuffer(CurrentResourceOwner,
  									BufferDescriptorGetBuffer(bufHdr));
! 		if (bufHdr->flags & BM_VALID)
  			*foundPtr = TRUE;
  		else
  		{
--- 129,149 ----
  		fprintf(stderr, "LB ALLOC (%u,%d,%d) %d\n",
  				smgr->smgr_rnode.node.relNode, forkNum, blockNum, -b - 1);
  #endif
+ 		state = pg_atomic_read_u32(&bufHdr->state);
+ 
  		/* this part is equivalent to PinBuffer for a shared buffer */
  		if (LocalRefCount[b] == 0)
  		{
! 			if (BUF_STATE_GET_USAGECOUNT(state) < BM_MAX_USAGE_COUNT)
! 			{
! 				state += BUF_USAGECOUNT_ONE;
! 				pg_atomic_write_u32(&bufHdr->state, state);
! 			}
  		}
  		LocalRefCount[b]++;
  		ResourceOwnerRememberBuffer(CurrentResourceOwner,
  									BufferDescriptorGetBuffer(bufHdr));
! 		if (state & BM_VALID)
  			*foundPtr = TRUE;
  		else
  		{
*************** LocalBufferAlloc(SMgrRelation smgr, Fork
*** 169,177 ****
  
  		if (LocalRefCount[b] == 0)
  		{
! 			if (bufHdr->usage_count > 0)
  			{
! 				bufHdr->usage_count--;
  				trycounter = NLocBuffer;
  			}
  			else
--- 175,186 ----
  
  		if (LocalRefCount[b] == 0)
  		{
! 			state = pg_atomic_read_u32(&bufHdr->state);
! 
! 			if (BUF_STATE_GET_USAGECOUNT(state) > 0)
  			{
! 				state -= BUF_USAGECOUNT_ONE;
! 				pg_atomic_write_u32(&bufHdr->state, state);
  				trycounter = NLocBuffer;
  			}
  			else
*************** LocalBufferAlloc(SMgrRelation smgr, Fork
*** 193,199 ****
  	 * this buffer is not referenced but it might still be dirty. if that's
  	 * the case, write it out before reusing it!
  	 */
! 	if (bufHdr->flags & BM_DIRTY)
  	{
  		SMgrRelation oreln;
  		Page		localpage = (char *) LocalBufHdrGetBlock(bufHdr);
--- 202,208 ----
  	 * this buffer is not referenced but it might still be dirty. if that's
  	 * the case, write it out before reusing it!
  	 */
! 	if (state & BM_DIRTY)
  	{
  		SMgrRelation oreln;
  		Page		localpage = (char *) LocalBufHdrGetBlock(bufHdr);
*************** LocalBufferAlloc(SMgrRelation smgr, Fork
*** 211,217 ****
  				  false);
  
  		/* Mark not-dirty now in case we error out below */
! 		bufHdr->flags &= ~BM_DIRTY;
  
  		pgBufferUsage.local_blks_written++;
  	}
--- 220,227 ----
  				  false);
  
  		/* Mark not-dirty now in case we error out below */
! 		state &= ~BM_DIRTY;
! 		pg_atomic_write_u32(&bufHdr->state, state);
  
  		pgBufferUsage.local_blks_written++;
  	}
*************** LocalBufferAlloc(SMgrRelation smgr, Fork
*** 228,234 ****
  	/*
  	 * Update the hash table: remove old entry, if any, and make new one.
  	 */
! 	if (bufHdr->flags & BM_TAG_VALID)
  	{
  		hresult = (LocalBufferLookupEnt *)
  			hash_search(LocalBufHash, (void *) &bufHdr->tag,
--- 238,244 ----
  	/*
  	 * Update the hash table: remove old entry, if any, and make new one.
  	 */
! 	if (state & BM_TAG_VALID)
  	{
  		hresult = (LocalBufferLookupEnt *)
  			hash_search(LocalBufHash, (void *) &bufHdr->tag,
*************** LocalBufferAlloc(SMgrRelation smgr, Fork
*** 237,243 ****
  			elog(ERROR, "local buffer hash table corrupted");
  		/* mark buffer invalid just in case hash insert fails */
  		CLEAR_BUFFERTAG(bufHdr->tag);
! 		bufHdr->flags &= ~(BM_VALID | BM_TAG_VALID);
  	}
  
  	hresult = (LocalBufferLookupEnt *)
--- 247,254 ----
  			elog(ERROR, "local buffer hash table corrupted");
  		/* mark buffer invalid just in case hash insert fails */
  		CLEAR_BUFFERTAG(bufHdr->tag);
! 		state &= ~(BM_VALID | BM_TAG_VALID);
! 		pg_atomic_write_u32(&bufHdr->state, state);
  	}
  
  	hresult = (LocalBufferLookupEnt *)
*************** LocalBufferAlloc(SMgrRelation smgr, Fork
*** 250,258 ****
  	 * it's all ours now.
  	 */
  	bufHdr->tag = newTag;
! 	bufHdr->flags &= ~(BM_VALID | BM_DIRTY | BM_JUST_DIRTIED | BM_IO_ERROR);
! 	bufHdr->flags |= BM_TAG_VALID;
! 	bufHdr->usage_count = 1;
  
  	*foundPtr = FALSE;
  	return bufHdr;
--- 261,271 ----
  	 * it's all ours now.
  	 */
  	bufHdr->tag = newTag;
! 	state &= ~(BM_VALID | BM_DIRTY | BM_JUST_DIRTIED | BM_IO_ERROR);
! 	state |= BM_TAG_VALID;
! 	state &= ~BUF_USAGECOUNT_MASK;
! 	state += BUF_USAGECOUNT_ONE;
! 	pg_atomic_write_u32(&bufHdr->state, state);
  
  	*foundPtr = FALSE;
  	return bufHdr;
*************** MarkLocalBufferDirty(Buffer buffer)
*** 267,272 ****
--- 280,286 ----
  {
  	int			bufid;
  	BufferDesc *bufHdr;
+ 	uint32		state;
  
  	Assert(BufferIsLocal(buffer));
  
*************** MarkLocalBufferDirty(Buffer buffer)
*** 280,289 ****
  
  	bufHdr = GetLocalBufferDescriptor(bufid);
  
! 	if (!(bufHdr->flags & BM_DIRTY))
! 		pgBufferUsage.local_blks_dirtied++;
  
! 	bufHdr->flags |= BM_DIRTY;
  }
  
  /*
--- 294,303 ----
  
  	bufHdr = GetLocalBufferDescriptor(bufid);
  
! 	state = pg_atomic_fetch_or_u32(&bufHdr->state, BM_DIRTY);
  
! 	if (!(state & BM_DIRTY))
! 		pgBufferUsage.local_blks_dirtied++;
  }
  
  /*
*************** DropRelFileNodeLocalBuffers(RelFileNode 
*** 307,314 ****
  	{
  		BufferDesc *bufHdr = GetLocalBufferDescriptor(i);
  		LocalBufferLookupEnt *hresult;
  
! 		if ((bufHdr->flags & BM_TAG_VALID) &&
  			RelFileNodeEquals(bufHdr->tag.rnode, rnode) &&
  			bufHdr->tag.forkNum == forkNum &&
  			bufHdr->tag.blockNum >= firstDelBlock)
--- 321,331 ----
  	{
  		BufferDesc *bufHdr = GetLocalBufferDescriptor(i);
  		LocalBufferLookupEnt *hresult;
+ 		uint32		state;
  
! 		state = pg_atomic_read_u32(&bufHdr->state);
! 
! 		if ((state & BM_TAG_VALID) &&
  			RelFileNodeEquals(bufHdr->tag.rnode, rnode) &&
  			bufHdr->tag.forkNum == forkNum &&
  			bufHdr->tag.blockNum >= firstDelBlock)
*************** DropRelFileNodeLocalBuffers(RelFileNode 
*** 327,334 ****
  				elog(ERROR, "local buffer hash table corrupted");
  			/* Mark buffer invalid */
  			CLEAR_BUFFERTAG(bufHdr->tag);
! 			bufHdr->flags = 0;
! 			bufHdr->usage_count = 0;
  		}
  	}
  }
--- 344,352 ----
  				elog(ERROR, "local buffer hash table corrupted");
  			/* Mark buffer invalid */
  			CLEAR_BUFFERTAG(bufHdr->tag);
! 			state &= ~BUF_FLAG_MASK;
! 			state &= ~BUF_USAGECOUNT_MASK;
! 			pg_atomic_write_u32(&bufHdr->state, state);
  		}
  	}
  }
*************** DropRelFileNodeAllLocalBuffers(RelFileNo
*** 349,356 ****
  	{
  		BufferDesc *bufHdr = GetLocalBufferDescriptor(i);
  		LocalBufferLookupEnt *hresult;
  
! 		if ((bufHdr->flags & BM_TAG_VALID) &&
  			RelFileNodeEquals(bufHdr->tag.rnode, rnode))
  		{
  			if (LocalRefCount[i] != 0)
--- 367,377 ----
  	{
  		BufferDesc *bufHdr = GetLocalBufferDescriptor(i);
  		LocalBufferLookupEnt *hresult;
+ 		uint32		state;
  
! 		state = pg_atomic_read_u32(&bufHdr->state);
! 
! 		if ((state & BM_TAG_VALID) &&
  			RelFileNodeEquals(bufHdr->tag.rnode, rnode))
  		{
  			if (LocalRefCount[i] != 0)
*************** DropRelFileNodeAllLocalBuffers(RelFileNo
*** 367,374 ****
  				elog(ERROR, "local buffer hash table corrupted");
  			/* Mark buffer invalid */
  			CLEAR_BUFFERTAG(bufHdr->tag);
! 			bufHdr->flags = 0;
! 			bufHdr->usage_count = 0;
  		}
  	}
  }
--- 388,396 ----
  				elog(ERROR, "local buffer hash table corrupted");
  			/* Mark buffer invalid */
  			CLEAR_BUFFERTAG(bufHdr->tag);
! 			state &= ~BUF_FLAG_MASK;
! 			state &= ~BUF_USAGECOUNT_MASK;
! 			pg_atomic_write_u32(&bufHdr->state, state);
  		}
  	}
  }
diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h
new file mode 100644
index 19247c4..3d3e0d5
*** a/src/include/storage/buf_internals.h
--- b/src/include/storage/buf_internals.h
***************
*** 20,48 ****
  #include "storage/lwlock.h"
  #include "storage/shmem.h"
  #include "storage/smgr.h"
  #include "storage/spin.h"
  #include "utils/relcache.h"
  
  
  /*
   * Flags for buffer descriptors
   *
   * Note: TAG_VALID essentially means that there is a buffer hashtable
   * entry associated with the buffer's tag.
   */
! #define BM_DIRTY				(1 << 0)		/* data needs writing */
! #define BM_VALID				(1 << 1)		/* data is valid */
! #define BM_TAG_VALID			(1 << 2)		/* tag is assigned */
! #define BM_IO_IN_PROGRESS		(1 << 3)		/* read or write in progress */
! #define BM_IO_ERROR				(1 << 4)		/* previous I/O failed */
! #define BM_JUST_DIRTIED			(1 << 5)		/* dirtied since write started */
! #define BM_PIN_COUNT_WAITER		(1 << 6)		/* have waiter for sole pin */
! #define BM_CHECKPOINT_NEEDED	(1 << 7)		/* must write for checkpoint */
! #define BM_PERMANENT			(1 << 8)		/* permanent relation (not
  												 * unlogged) */
- 
- typedef bits16 BufFlags;
- 
  /*
   * The maximum allowed value of usage_count represents a tradeoff between
   * accuracy and speed of the clock-sweep buffer management algorithm.  A
--- 20,62 ----
  #include "storage/lwlock.h"
  #include "storage/shmem.h"
  #include "storage/smgr.h"
+ #include "port/atomics.h"
  #include "storage/spin.h"
  #include "utils/relcache.h"
  
  
  /*
+  * State is:
+  * 10 bit flags
+  * 4 bit usage count
+  * 18 bit refcount
+  */
+ #define BUF_REFCOUNT_ONE 1
+ #define BUF_REFCOUNT_MASK ((1U << 18) - 1)
+ #define BUF_STATE_GET_REFCOUNT(state) ((state) & BUF_REFCOUNT_MASK)
+ #define BUF_USAGECOUNT_MASK 0x003C0000U
+ #define BUF_USAGECOUNT_ONE (1U << 18)
+ #define BUF_USAGECOUNT_SHIFT 18
+ #define BUF_STATE_GET_USAGECOUNT(state) (((state) & BUF_USAGECOUNT_MASK) >> BUF_USAGECOUNT_SHIFT)
+ #define BUF_FLAG_MASK 0xFFC00000U
+ 
+ /*
   * Flags for buffer descriptors
   *
   * Note: TAG_VALID essentially means that there is a buffer hashtable
   * entry associated with the buffer's tag.
   */
! #define BM_LOCKED				(1U << 22)		/* buffer header is locked */
! #define BM_DIRTY				(1U << 23)		/* data needs writing */
! #define BM_VALID				(1U << 24)		/* data is valid */
! #define BM_TAG_VALID			(1U << 25)		/* tag is assigned */
! #define BM_IO_IN_PROGRESS		(1U << 26)		/* read or write in progress */
! #define BM_IO_ERROR				(1U << 27)		/* previous I/O failed */
! #define BM_JUST_DIRTIED			(1U << 28)		/* dirtied since write started */
! #define BM_PIN_COUNT_WAITER		(1U << 29)		/* have waiter for sole pin */
! #define BM_CHECKPOINT_NEEDED	(1U << 30)		/* must write for checkpoint */
! #define BM_PERMANENT			(1U << 31)		/* permanent relation (not
  												 * unlogged) */
  /*
   * The maximum allowed value of usage_count represents a tradeoff between
   * accuracy and speed of the clock-sweep buffer management algorithm.  A
*************** typedef struct buftag
*** 137,148 ****
  typedef struct BufferDesc
  {
  	BufferTag	tag;			/* ID of page contained in buffer */
- 	BufFlags	flags;			/* see bit definitions above */
- 	uint16		usage_count;	/* usage counter for clock sweep code */
- 	unsigned	refcount;		/* # of backends holding pins on buffer */
- 	int			wait_backend_pid;		/* backend PID of pin-count waiter */
  
! 	slock_t		buf_hdr_lock;	/* protects the above fields */
  
  	int			buf_id;			/* buffer's index number (from 0) */
  	int			freeNext;		/* link in freelist chain */
--- 151,161 ----
  typedef struct BufferDesc
  {
  	BufferTag	tag;			/* ID of page contained in buffer */
  
! 	/* state of the tag, containing flags, refcount and usagecount */
! 	pg_atomic_uint32 state;
! 
! 	int			wait_backend_pid;		/* backend PID of pin-count waiter */
  
  	int			buf_id;			/* buffer's index number (from 0) */
  	int			freeNext;		/* link in freelist chain */
*************** typedef union BufferDescPadded
*** 192,202 ****
  #define FREENEXT_NOT_IN_LIST	(-2)
  
  /*
!  * Macros for acquiring/releasing a shared buffer header's spinlock.
!  * Do not apply these to local buffers!
   */
! #define LockBufHdr(bufHdr)		SpinLockAcquire(&(bufHdr)->buf_hdr_lock)
! #define UnlockBufHdr(bufHdr)	SpinLockRelease(&(bufHdr)->buf_hdr_lock)
  
  
  /* in buf_init.c */
--- 205,215 ----
  #define FREENEXT_NOT_IN_LIST	(-2)
  
  /*
!  * Functions for acquiring/releasing a shared buffer header's spinlock.  Do
!  * not apply these to local buffers! FIXUP!
   */
! extern uint32 LockBufHdr(volatile BufferDesc *desc);
! extern void UnlockBufHdr(volatile BufferDesc *desc);
  
  
  /* in buf_init.c */
*************** extern BufferDesc *LocalBufferDescriptor
*** 211,217 ****
   */
  
  /* freelist.c */
! extern BufferDesc *StrategyGetBuffer(BufferAccessStrategy strategy);
  extern void StrategyFreeBuffer(BufferDesc *buf);
  extern bool StrategyRejectBuffer(BufferAccessStrategy strategy,
  					 BufferDesc *buf);
--- 224,231 ----
   */
  
  /* freelist.c */
! extern BufferDesc *StrategyGetBuffer(BufferAccessStrategy strategy,
! 											  uint32 *state);
  extern void StrategyFreeBuffer(BufferDesc *buf);
  extern bool StrategyRejectBuffer(BufferAccessStrategy strategy,
  					 BufferDesc *buf);