.

wcfs/wcfs.go

@@ -307,9 +307,13 @@ type BigFile struct {
 	// XXX do we need to keep it here explicitly?
 	zconn	*zodb.Connection
 
-	// ZBigFile top-level object. Kept always activated (XXX clarify)
+	// ZBigFile top-level object. Kept activated during lifetime of current transaction.
 	zbf	*ZBigFile
 
+	// zbf.Size(). It is constant during liftime of a transaction
+	// (we do only read-only txn) XXX -> organization overview.
+	zbfSize int64
+
 	// TODO
 	// lastChange	zodb.Tid // last change to whole bigfile as of .zconn.At view
 }
@@ -417,6 +421,12 @@ func (bfroot *BigFileRoot) Mkdir(name string, mode uint32, fctx *fuse.Context) (
 		}
 	}()
 
+	zbfSize, err := zbf.Size(ctx)
+	if err != nil {
+		log.Errorf("/bigfile: mkdir %q: %s", name, err)
+		return nil, fuse.EIO
+	}
+
 	// relock bfroot and either mkdir or EEXIST if the directory was maybe
 	// simultanously created while we were not holding bfroot.mu
 	bfroot.mu.Lock()
@@ -439,6 +449,7 @@ func (bfroot *BigFileRoot) Mkdir(name string, mode uint32, fctx *fuse.Context) (
 		txnCtx:  txnCtx,
 		zconn:   zconn,
 		zbf:     zbf,
+		zbfSize: zbfSize,
 	}
 
 	bfdata := &BigFileData{
@@ -470,26 +481,15 @@ func (bfdata *BigFileData) GetAttr(out *fuse.Attr, _ nodefs.File, fctx *fuse.Con
 	// XXX locking
 
 	bf := bfdata.bigfile
-	zbf := bfdata.bigfile.zbf
-
-	// XXX better ctx = transaction.PutIntoContext(ctx, txn)
-	ctx, cancel := xcontext.Merge(asctx(fctx), bf.txnCtx)
-	defer cancel()
-
-	size, err := zbf.Size(ctx)
-	if err != nil {
-		log.Errorf("%s", err)	// XXX errctx
-		return fuse.EIO		// XXX extract EFBIG when it is the cause?
-	}
 
 	out.Mode = fuse.S_IFREG | 0444
-	out.Size = uint64(size)
+	out.Size = uint64(bf.zbfSize)
 	// .Blocks
 	// .Blksize
 
 	// FIXME lastChange should cover all bigfile data, not only ZBigFile itself
 	//mtime := &bfdata.lastChange.Time().Time
-	lastChange := bfdata.bigfile.zbf.PSerial()
+	lastChange := bf.zbf.PSerial()
 
 	mtime := lastChange.Time().Time
 	out.SetTimes(/*atime=*/nil, /*mtime=*/&mtime, /*ctime=*/&mtime)
@@ -505,17 +505,26 @@ func (bfdata *BigFileData) Read(_ nodefs.File, dest []byte, off int64, fctx *fus
 	bf := bfdata.bigfile
 	zbf := bf.zbf
 
-	// XXX better ctx = transaction.PutIntoContext(ctx, txn)
-	ctx, cancel := xcontext.Merge(asctx(fctx), bf.txnCtx)
-	defer cancel()
+	// cap read request to file size
+	end := off + int64(len(dest))		// XXX overflow?
+	if end > bf.zbfSize {
+		end = bf.zbfSize
+	}
+	if end <= off {
+		// XXX off >= size -> EINVAL? (but when size=0 kernel issues e.g. [0 +4K) read)
+		return fuse.ReadResultData(nil), fuse.OK
+	}
 
 	// widen read request to be aligned with blksize granularity
 	// (we can load only whole ZBlk* blocks)
-	end := off + int64(len(dest))		// XXX overflow?
 	aoff := off - (off % zbf.blksize)
 	aend := end + (zbf.blksize - (end % zbf.blksize))
 	dest = make([]byte, aend - aoff) // ~> [off:aend] in file
 
+	// XXX better ctx = transaction.PutIntoContext(ctx, txn)
+	ctx, cancel := xcontext.Merge(asctx(fctx), bf.txnCtx)
+	defer cancel()
+
 	// read/load all block(s) in parallel
 	wg, ctx := errgroup.WithContext(ctx)
 	for blkoff := aoff; blkoff < aend; blkoff += zbf.blksize {