[SERVER] Add timer task for saving cache maps

Cache maps will now be saved periodically, but only if either they have
a "dirty" bit set, which happens if any bits in the map get cleared
again (due to corruption), or if new data has been replicated from an
uplink server. This either means at least one byte received and 5
minutes have passed, or at least 500MB have been downloaded. The timer
currently runs every 20 seconds.

1 files changed, 3 insertions, 73 deletions

diff --git a/src/server/uplink.c b/src/server/uplink.c
index 97cb2a9..e5ab9c0 100644
--- a/src/server/uplink.c
+++ b/src/server/uplink.c
@@ -57,7 +57,6 @@ static bool uplink_sendKeepalive(dnbd3_uplink_t *uplink);
 static void uplink_addCrc32(dnbd3_uplink_t *uplink);
 static bool uplink_sendReplicationRequest(dnbd3_uplink_t *uplink);
 static bool uplink_reopenCacheFd(dnbd3_uplink_t *uplink, const bool force);
-static bool uplink_saveCacheMap(dnbd3_uplink_t *uplink);
 static bool uplink_connectionShouldShutdown(dnbd3_uplink_t *uplink);
 static void uplink_connectionFailed(dnbd3_uplink_t *uplink, bool findNew);
 
@@ -103,6 +102,7 @@ bool uplink_init(dnbd3_image_t *image, int sock, dnbd3_host_t *host, int version
 	mutex_init( &uplink->sendMutex, LOCK_UPLINK_SEND );
 	uplink->image = image;
 	uplink->bytesReceived = 0;
+	uplink->bytesReceivedLastSave = 0;
 	uplink->idleTime = 0;
 	uplink->queueLen = 0;
 	uplink->cacheFd = -1;
@@ -445,7 +445,6 @@ static void* uplink_mainloop(void *data)
 	int altCheckInterval = SERVER_RTT_INTERVAL_INIT;
 	int rttTestResult;
 	uint32_t discoverFailCount = 0;
-	uint32_t unsavedSeconds = 0;
 	ticks nextAltCheck, lastKeepalive;
 	char buffer[200];
 	memset( events, 0, sizeof(events) );
@@ -561,12 +560,6 @@ static void* uplink_mainloop(void *data)
 		if ( timepassed >= SERVER_UPLINK_KEEPALIVE_INTERVAL ) {
 			lastKeepalive = now;
 			uplink->idleTime += timepassed;
-			unsavedSeconds += timepassed;
-			if ( unsavedSeconds > 240 || ( unsavedSeconds > 60 && uplink->idleTime >= 20 && uplink->idleTime <= 70 ) ) {
-				// fsync/save every 4 minutes, or every 60 seconds if uplink is idle
-				unsavedSeconds = 0;
-				uplink_saveCacheMap( uplink );
-			}
 			// Keep-alive
 			if ( uplink->current.fd != -1 && uplink->replicationHandle == REP_NONE ) {
 				// Send keep-alive if nothing is happening, and try to trigger background rep.
@@ -639,9 +632,9 @@ static void* uplink_mainloop(void *data)
 		}
 #endif
 	}
-	cleanup: ;
-	uplink_saveCacheMap( uplink );
+cleanup: ;
 	dnbd3_image_t *image = uplink->image;
+	image->mapDirty = true; // Force writeout of cache map
 	mutex_lock( &image->lock );
 	bool exp = false;
 	if ( atomic_compare_exchange_strong( &uplink->shutdown, &exp, true ) ) {
@@ -1135,69 +1128,6 @@ static bool uplink_reopenCacheFd(dnbd3_uplink_t *uplink, const bool force)
 	return uplink->cacheFd != -1;
 }
 
-/**
- * Saves the cache map of the given image.
- * Return true on success.
- * Locks on: imageListLock, image.lock
- */
-static bool uplink_saveCacheMap(dnbd3_uplink_t *uplink)
-{
-	dnbd3_image_t *image = uplink->image;
-	assert( image != NULL );
-
-	if ( uplink->cacheFd != -1 ) {
-		if ( fsync( uplink->cacheFd ) == -1 ) {
-			// A failing fsync means we have no guarantee that any data
-			// since the last fsync (or open if none) has been saved. Apart
-			// from keeping the cache map from the last successful fsync
-			// around and restoring it there isn't much we can do to recover
-			// a consistent state. Bail out.
-			logadd( LOG_ERROR, "fsync() on image file %s failed with errno %d", image->path, errno );
-			logadd( LOG_ERROR, "Bailing out immediately" );
-			exit( 1 );
-		}
-	}
-
-	dnbd3_cache_map_t *cache = ref_get_cachemap( image );
-	if ( cache == NULL )
-		return true;
-	logadd( LOG_DEBUG2, "Saving cache map of %s:%d", image->name, (int)image->rid );
-	const size_t size = IMGSIZE_TO_MAPBYTES(image->virtualFilesize);
-	assert( image->path != NULL );
-	char mapfile[strlen( image->path ) + 4 + 1];
-	strcpy( mapfile, image->path );
-	strcat( mapfile, ".map" );
-
-	int fd = open( mapfile, O_WRONLY | O_CREAT, 0644 );
-	if ( fd == -1 ) {
-		const int err = errno;
-		ref_put( &cache->reference );
-		logadd( LOG_WARNING, "Could not open file to write cache map to disk (errno=%d) file %s", err, mapfile );
-		return false;
-	}
-
-	size_t done = 0;
-	while ( done < size ) {
-		const ssize_t ret = write( fd, cache->map + done, size - done );
-		if ( ret == -1 ) {
-			if ( errno == EINTR ) continue;
-			logadd( LOG_WARNING, "Could not write cache map (errno=%d) file %s", errno, mapfile );
-			break;
-		}
-		if ( ret <= 0 ) {
-			logadd( LOG_WARNING, "Unexpected return value %d for write() to %s", (int)ret, mapfile );
-			break;
-		}
-		done += (size_t)ret;
-	}
-	ref_put( &cache->reference );
-	if ( fsync( fd ) == -1 ) {
-		logadd( LOG_WARNING, "fsync() on image map %s failed with errno %d", mapfile, errno );
-	}
-	close( fd );
-	return true;
-}
-
 static bool uplink_connectionShouldShutdown(dnbd3_uplink_t *uplink)
 {
 	return ( uplink->idleTime > SERVER_UPLINK_IDLE_TIMEOUT