[FUSE] In panic mode, use a pending range for alt check

If we lost connection and then go check all known alt
servers, see if we have some pending request queued and
if so, use its offset and length for the alt server probe.
This ensures that the server being tested is able to
satisfy at least the next request we'll send.

1 files changed, 43 insertions, 5 deletions

diff --git a/src/fuse/connection.c b/src/fuse/connection.c
index f29b439..8f28c09 100644
--- a/src/fuse/connection.c
+++ b/src/fuse/connection.c
@@ -13,6 +13,7 @@
 #include <unistd.h>
 #include <errno.h>
 #include <time.h>
+#include <inttypes.h>
 
 /* Constants */
 static const size_t SHORTBUF = 100;
@@ -547,6 +548,22 @@ static void probeAltServers()
 	bool doSwitch;
 	const bool panic = connection.sockFd == -1;
 
+	uint64_t testOffset = 0;
+	uint32_t testLength = RTT_BLOCK_SIZE;
+	dnbd3_async_t *request = NULL;
+	if ( panic ) {
+		pthread_spin_lock( &requests.lock );
+		if ( requests.head != NULL ) {
+			request = requests.head;
+			testOffset = requests.head->offset;
+			testLength = requests.head->length;
+		}
+		pthread_spin_unlock( &requests.lock );
+		if ( testOffset != 0 ) {
+			logadd( LOG_DEBUG1, "Panic with pending %" PRIu64 ":%" PRIu32, testOffset, testLength );
+		}
+	}
+
 	for ( int altIndex = 0; altIndex < (panic ? MAX_ALTS : MAX_ALTS_ACTIVE); ++altIndex ) {
 		alt_server_t * const srv = &altservers[altIndex];
 		if ( srv->host.type == 0 )
@@ -586,16 +603,37 @@ static void probeAltServers()
 			srv->consecutiveFails += 10;
 			goto fail;
 		}
-		if ( !dnbd3_get_block( sock, 0, RTT_BLOCK_SIZE, 0, 0 ) ) {
+		if ( !dnbd3_get_block( sock, testOffset, testLength, 0, 0 ) ) {
 			logadd( LOG_DEBUG1, "-> block request fail" );
 			goto fail;
 		}
-		int a = 111, b = 111;
-		if ( !(a = dnbd3_get_reply( sock, &reply )) || reply.size != RTT_BLOCK_SIZE
-				|| !(b = throwDataAway( sock, RTT_BLOCK_SIZE )) ) {
-			logadd( LOG_DEBUG1, "<- block payload fail %d %d %d", a, (int)reply.size, b );
+		int a = 111;
+		if ( !(a = dnbd3_get_reply( sock, &reply )) || reply.size != testLength ) {
+			logadd( LOG_DEBUG1, "<- get block reply fail %d %d", a, (int)reply.size );
 			goto fail;
 		}
+		if ( request != NULL && removeRequest( request ) != NULL ) {
+			// Request successfully removed from queue
+			const ssize_t ret = sock_recv( sock, request->buffer, request->length );
+			if ( ret != (ssize_t)request->length ) {
+				logadd( LOG_DEBUG1, "[RTT] receiving payload for a block reply failed" );
+				// Failure, add to queue again
+				connection_read( request );
+				goto fail;
+			}
+			// Success, wake up caller
+			logadd( LOG_DEBUG1, "[RTT] Successful direct probe" );
+			request->success = true;
+			request->finished = true;
+			signal_call( request->signal );
+		} else {
+			// Wasn't a request that's in our request queue
+			if ( !throwDataAway( sock, testLength ) ) {
+				logadd( LOG_DEBUG1, "<- get block reply payload fail" );
+				goto fail;
+			}
+		}
+
 		// Yay, success
 		// Panic mode? Just switch to server
 		if ( panic ) {