2 files changed, 50 insertions, 0 deletions
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index df4c9d71094..58b0a975c0f 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -3745,6 +3745,55 @@ ConditionalLockBufferForCleanup(Buffer buffer)
 	return false;
 }
 
+/*
+ * IsBufferCleanupOK - as above, but we already have the lock
+ *
+ * Check whether it's OK to perform cleanup on a buffer we've already
+ * locked.  If we observe that the pin count is 1, our exclusive lock
+ * happens to be a cleanup lock, and we can proceed with anything that
+ * would have been allowable had we sought a cleanup lock originally.
+ */
+bool
+IsBufferCleanupOK(Buffer buffer)
+{
+	BufferDesc *bufHdr;
+	uint32		buf_state;
+
+	Assert(BufferIsValid(buffer));
+
+	if (BufferIsLocal(buffer))
+	{
+		/* There should be exactly one pin */
+		if (LocalRefCount[-buffer - 1] != 1)
+			return false;
+		/* Nobody else to wait for */
+		return true;
+	}
+
+	/* There should be exactly one local pin */
+	if (GetPrivateRefCount(buffer) != 1)
+		return false;
+
+	bufHdr = GetBufferDescriptor(buffer - 1);
+
+	/* caller must hold exclusive lock on buffer */
+	Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
+								LW_EXCLUSIVE));
+
+	buf_state = LockBufHdr(bufHdr);
+
+	Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
+	if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
+	{
+		/* pincount is OK. */
+		UnlockBufHdr(bufHdr, buf_state);
+		return true;
+	}
+
+	UnlockBufHdr(bufHdr, buf_state);
+	return false;
+}
+
 
 /*
  *	Functions for buffer I/O handling
diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h
index 7b6ba960001..821bee5ecea 100644
--- a/src/include/storage/bufmgr.h
+++ b/src/include/storage/bufmgr.h
@@ -227,6 +227,7 @@ extern void LockBuffer(Buffer buffer, int mode);
 extern bool ConditionalLockBuffer(Buffer buffer);
 extern void LockBufferForCleanup(Buffer buffer);
 extern bool ConditionalLockBufferForCleanup(Buffer buffer);
+extern bool IsBufferCleanupOK(Buffer buffer);
 extern bool HoldingBufferPinThatDelaysRecovery(void);
 
 extern void AbortBufferIO(void);