Function writePhysicalBlock

fdbserver/VersionedBTree.actor.cpp:2684–2721

	// Write one block of a page of a physical page in the page file.  Futures returned must be allowed to complete.
	ACTOR static UNCANCELLABLE Future<Void> writePhysicalBlock(DWALPager* self,
	                                                           Reference<ArenaPage> page,
	                                                           int blockNum,
	                                                           int blockSize,
	                                                           PhysicalPageID pageID,
	                                                           PagerEventReasons reason,
	                                                           unsigned int level,
	                                                           bool header) {

		state PriorityMultiLock::Lock lock = wait(self->ioLock.lock(header ? ioMaxPriority : ioMinPriority));
		++g_redwoodMetrics.metric.pagerDiskWrite;
		g_redwoodMetrics.level(level).metrics.events.addEventReason(PagerEvents::PageWrite, reason);
		if (self->memoryOnly) {
			return Void();
		}

		// If a truncation up to include pageID has not yet been completed
		if (pageID >= self->filePageCount) {
			// And no extension pending will include pageID
			if (pageID >= self->filePageCountPending) {
				// Update extension to a new one that waits on the old one and extends further
				self->fileExtension = extendToCover(self, pageID, self->fileExtension);
			}

			// Wait for extension that covers pageID to complete;
			wait(self->fileExtension);
		}

		// Note:  Not using forwardError here so a write error won't be discovered until commit time.
		debug_printf("DWALPager(%s) op=writeBlock %s\n", self->filename.c_str(), toString(pageID).c_str());
		wait(self->pageFile->write(page->rawData() + (blockNum * blockSize), blockSize, (int64_t)pageID * blockSize));

		// This next line could crash on shutdown because this actor can't be cancelled so self could be destroyed after
		// write, so enable this line with caution when debugging.
		// debug_printf("DWALPager(%s) op=writeBlockDone %s\n", self->filename.c_str(), toString(pageID).c_str());

		return Void();
	}

	ACTOR static Future<Void> extendToCover(DWALPager* self, uint64_t pageID, Future<Void> previousExtension) {
		// Calculate new page count, round up to nearest multiple of growth size > pageID