[#1600] fstree: Handle incomplete writes

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/local_object_storage/blobstor/fstree/fstree_write_linux.go

@@ -69,10 +69,13 @@ func (w *linuxWriter) writeFile(p string, data []byte) error {
 	if err != nil {
 		return err
 	}
+	written := 0
 	tmpPath := "/proc/self/fd/" + strconv.FormatUint(uint64(fd), 10)
 	n, err := unix.Write(fd, data)
-	if err == nil {
-		if n == len(data) {
+	for err == nil {
+		written += n
+
+		if written == len(data) {
 			err = unix.Linkat(unix.AT_FDCWD, tmpPath, unix.AT_FDCWD, p, unix.AT_SYMLINK_FOLLOW)
 			if err == nil {
 				w.fileCounter.Inc(uint64(len(data)))
@@ -80,9 +83,23 @@ func (w *linuxWriter) writeFile(p string, data []byte) error {
 			if errors.Is(err, unix.EEXIST) {
 				err = nil
 			}
-		} else {
-			err = errors.New("incomplete write")
+			break
 		}
+
+		// From man 2 write:
+		// https://www.man7.org/linux/man-pages/man2/write.2.html
+		//
+		// Note that a successful write() may transfer fewer than count
+		// bytes.  Such partial writes can occur for various reasons; for
+		// example, because there was insufficient space on the disk device
+		// to write all of the requested bytes, or because a blocked write()
+		// to a socket, pipe, or similar was interrupted by a signal handler
+		// after it had transferred some, but before it had transferred all
+		// of the requested bytes.  In the event of a partial write, the
+		// caller can make another write() call to transfer the remaining
+		// bytes.  The subsequent call will either transfer further bytes or
+		// may result in an error (e.g., if the disk is now full).
+		n, err = unix.Write(fd, data[written:])
 	}
 	errClose := unix.Close(fd)
 	if err != nil {

pkg/local_object_storage/blobstor/fstree/fstree_write_linux_test.go

@@ -0,0 +1,42 @@
+//go:build linux && integration
+
+package fstree
+
+import (
+	"context"
+	"errors"
+	"os"
+	"testing"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/sys/unix"
+)
+
+func TestENOSPC(t *testing.T) {
+	dir, err := os.MkdirTemp(t.TempDir(), "ramdisk")
+	require.NoError(t, err)
+
+	f, err := os.CreateTemp(t.TempDir(), "ramdisk_*")
+	require.NoError(t, err)
+
+	err = unix.Mount(f.Name(), dir, "tmpfs", 0, "size=1M")
+	if errors.Is(err, unix.EPERM) {
+		t.Skipf("skip size tests: no permission to mount: %v", err)
+		return
+	}
+	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, unix.Unmount(dir, 0))
+	}()
+
+	fst := New(WithPath(dir), WithDepth(1))
+	require.NoError(t, fst.Open(mode.ComponentReadWrite))
+	require.NoError(t, fst.Init())
+
+	_, err = fst.Put(context.Background(), common.PutPrm{
+		RawData: make([]byte, 10<<20),
+	})
+	require.ErrorIs(t, err, common.ErrNoSpace)
+}