Reimplement -serialize_reads flag using new SyncRead mount flag

Let the kernel do the work for us.

See https://github.com/hanwen/go-fuse/commit/15a8bb029a4e1a51e10043c370970596b1fbb737
for more info.

1 files changed, 8 insertions, 1 deletions

diff --git a/mount.go b/mount.go
index 44d5878..60ff1ba 100644
--- a/mount.go
+++ b/mount.go
@@ -273,7 +273,6 @@ func initFuseFrontend(args *argContainer) (rootNode fs.InodeEmbedder, wipeKeys f
 		LongNames:          args.longnames,
 		ConfigCustom:       args._configCustom,
 		NoPrealloc:         args.noprealloc,
-		SerializeReads:     args.serialize_reads,
 		ForceDecode:        args.forcedecode,
 		ForceOwner:         args._forceOwner,
 		Exclude:            args.exclude,
@@ -377,6 +376,14 @@ func initGoFuse(rootNode fs.InodeEmbedder, args *argContainer) *fuse.Server {
 		MaxWrite: fuse.MAX_KERNEL_WRITE,
 		Options:  []string{fmt.Sprintf("max_read=%d", fuse.MAX_KERNEL_WRITE)},
 		Debug:    args.fusedebug,
+		// The kernel usually submits multiple read requests in parallel,
+		// which means we serve them in any order. Out-of-order reads are
+		// expensive on some backing network filesystems
+		// ( https://github.com/rfjakob/gocryptfs/issues/92 ).
+		//
+		// Setting SyncRead disables FUSE_CAP_ASYNC_READ. This makes the kernel
+		// do everything in-order without parallelism.
+		SyncRead: args.serialize_reads,
 	}
 
 	mOpts := &fuseOpts.MountOptions