From 67d7864f839037c5188c2a9e7ec5e7b11a7672a2 Mon Sep 17 00:00:00 2001 From: Zach Koopmans Date: Mon, 19 Aug 2019 14:06:22 -0700 Subject: [PATCH] Document RWF_HIPRI not implemented for preadv2/pwritev2. Document limitation of no reasonable implementation for RWF_HIPRI flag (High Priority Read/Write for block-based file systems). PiperOrigin-RevId: 264237589 --- pkg/abi/linux/file.go | 2 ++ pkg/sentry/syscalls/linux/sys_read.go | 3 ++- pkg/sentry/syscalls/linux/sys_write.go | 3 ++- 3 files changed, 6 insertions(+), 2 deletions(-) diff --git a/pkg/abi/linux/file.go b/pkg/abi/linux/file.go index 615e72646..7d742871a 100644 --- a/pkg/abi/linux/file.go +++ b/pkg/abi/linux/file.go @@ -178,6 +178,8 @@ const ( // Values for preadv2/pwritev2. const ( + // Note: gVisor does not implement the RWF_HIPRI feature, but the flag is + // accepted as a valid flag argument for preadv2/pwritev2. RWF_HIPRI = 0x00000001 RWF_DSYNC = 0x00000002 RWF_SYNC = 0x00000004 diff --git a/pkg/sentry/syscalls/linux/sys_read.go b/pkg/sentry/syscalls/linux/sys_read.go index b2474e60d..3ab54271c 100644 --- a/pkg/sentry/syscalls/linux/sys_read.go +++ b/pkg/sentry/syscalls/linux/sys_read.go @@ -191,7 +191,6 @@ func Preadv(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal } // Preadv2 implements linux syscall preadv2(2). -// TODO(b/120162627): Implement RWF_HIPRI functionality. func Preadv2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) { // While the syscall is // preadv2(int fd, struct iovec* iov, int iov_cnt, off_t offset, int flags) @@ -228,6 +227,8 @@ func Preadv2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca } // Check flags field. + // Note: gVisor does not implement the RWF_HIPRI feature, but the flag is + // accepted as a valid flag argument for preadv2. if flags&^linux.RWF_VALID != 0 { return 0, nil, syserror.EOPNOTSUPP } diff --git a/pkg/sentry/syscalls/linux/sys_write.go b/pkg/sentry/syscalls/linux/sys_write.go index 5278c96a6..27cd2c336 100644 --- a/pkg/sentry/syscalls/linux/sys_write.go +++ b/pkg/sentry/syscalls/linux/sys_write.go @@ -191,7 +191,6 @@ func Pwritev(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca } // Pwritev2 implements linux syscall pwritev2(2). -// TODO(b/120162627): Implement RWF_HIPRI functionality. // TODO(b/120161091): Implement O_SYNC and D_SYNC functionality. func Pwritev2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) { // While the syscall is @@ -227,6 +226,8 @@ func Pwritev2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc return 0, nil, syserror.ESPIPE } + // Note: gVisor does not implement the RWF_HIPRI feature, but the flag is + // accepted as a valid flag argument for pwritev2. if flags&^linux.RWF_VALID != 0 { return uintptr(flags), nil, syserror.EOPNOTSUPP }