syscallcompat: retry ops on EINTR

Retry operations that have been shown to throw EINTR
errors on CIFS.

Todo: Solution for this pain in the back:

	warning: unix.Getdents returned errno 2 in the middle of data
	rm: cannot remove 'linux-3.0.old3/Documentation/ABI/removed': Input/output error

Progress towards fixing https://github.com/rfjakob/gocryptfs/issues/483 .

1 files changed, 48 insertions, 0 deletions

diff --git a/internal/syscallcompat/eintr.go b/internal/syscallcompat/eintr.go
new file mode 100644
index 0000000..122af9b
--- /dev/null
+++ b/internal/syscallcompat/eintr.go
@@ -0,0 +1,48 @@
+package syscallcompat
+
+import (
+	"syscall"
+)
+
+// retryEINTR executes operation `op` and retries if it gets EINTR.
+//
+// Like ignoringEINTR() in the Go stdlib:
+// https://github.com/golang/go/blob/d2a80f3fb5b44450e0b304ac5a718f99c053d82a/src/os/file_posix.go#L243
+//
+// This is needed because CIFS throws lots of EINTR errors:
+// https://github.com/rfjakob/gocryptfs/issues/483
+func retryEINTR(op func() error) error {
+	for {
+		err := op()
+		if err != syscall.EINTR {
+			return err
+		}
+	}
+}
+
+// retryEINTR2 is like retryEINTR but for functions that return an (int, error)
+// pair like syscall.Create().
+func retryEINTR2(op func() (int, error)) (int, error) {
+	for {
+		ret, err := op()
+		if err != syscall.EINTR {
+			return ret, err
+		}
+	}
+}
+
+// Open wraps syscall.Open.
+// Retries on EINTR.
+func Open(path string, mode int, perm uint32) (fd int, err error) {
+	fd, err = retryEINTR2(func() (int, error) {
+		return syscall.Open(path, mode, perm)
+	})
+	return fd, err
+}
+
+// Close wraps syscall.Close.
+// Retries on EINTR.
+func Close(fd int) (err error) {
+	err = retryEINTR(func() error { return syscall.Close(fd) })
+	return err
+}