mount,cmount: clip the number of blocks to 2^32-1 on macOS

OSX FUSE only supports 32 bit number of blocks which means that block
counts have been wrapping.  This causes f_bavail to be 0 which in turn
causes problems with programs like borg backup.

Fixes #2356

cmd/cmount/fs.go

@@ -8,11 +8,11 @@ import (
 	"io"
 	"os"
 	"path"
-	"runtime"
 	"sync"
 	"time"
 
 	"github.com/billziss-gh/cgofuse/fuse"
+	"github.com/ncw/rclone/cmd/mountlib"
 	"github.com/ncw/rclone/fs"
 	"github.com/ncw/rclone/fs/log"
 	"github.com/ncw/rclone/vfs"
@@ -263,10 +263,7 @@ func (fsys *FS) Releasedir(path string, fh uint64) (errc int) {
 func (fsys *FS) Statfs(path string, stat *fuse.Statfs_t) (errc int) {
 	defer log.Trace(path, "")("stat=%+v, errc=%d", stat, &errc)
 	const blockSize = 4096
-	fsBlocks := uint64(1 << 50)
+	const fsBlocks = (1 << 50) / blockSize
-	if runtime.GOOS == "windows" {
-		fsBlocks = (1 << 43) - 1
-	}
 	stat.Blocks = fsBlocks  // Total data blocks in file system.
 	stat.Bfree = fsBlocks   // Free blocks in file system.
 	stat.Bavail = fsBlocks  // Free blocks in file system if you're not root.
@@ -285,6 +282,9 @@ func (fsys *FS) Statfs(path string, stat *fuse.Statfs_t) (errc int) {
 	if free >= 0 {
 		stat.Bavail = uint64(free) / blockSize
 	}
+	mountlib.ClipBlocks(&stat.Blocks)
+	mountlib.ClipBlocks(&stat.Bfree)
+	mountlib.ClipBlocks(&stat.Bavail)
 	return 0
 }
 

cmd/mount/fs.go

@@ -9,6 +9,7 @@ import (
 
 	"bazil.org/fuse"
 	fusefs "bazil.org/fuse/fs"
+	"github.com/ncw/rclone/cmd/mountlib"
 	"github.com/ncw/rclone/fs"
 	"github.com/ncw/rclone/fs/log"
 	"github.com/ncw/rclone/vfs"
@@ -72,6 +73,9 @@ func (f *FS) Statfs(ctx context.Context, req *fuse.StatfsRequest, resp *fuse.Sta
 	if free >= 0 {
 		resp.Bavail = uint64(free) / blockSize
 	}
+	mountlib.ClipBlocks(&resp.Blocks)
+	mountlib.ClipBlocks(&resp.Bfree)
+	mountlib.ClipBlocks(&resp.Bavail)
 	return nil
 }
 

cmd/mountlib/mount.go

@@ -293,3 +293,22 @@ be copied to the vfs cache before opening with --vfs-cache-mode full.
 
 	return commandDefintion
 }
+
+// ClipBlocks clips the blocks pointed to to the OS max
+func ClipBlocks(b *uint64) {
+	var max uint64
+	switch runtime.GOOS {
+	case "windows":
+		max = (1 << 43) - 1
+	case "darwin":
+		// OSX FUSE only supports 32 bit number of blocks
+		// https://github.com/osxfuse/osxfuse/issues/396
+		max = (1 << 32) - 1
+	default:
+		// no clipping
+		return
+	}
+	if *b > max {
+		*b = max
+	}
+}