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Re: [Qemu-devel] [PATCH 2/2] qga: set file descriptors in qmp_guest_file
From: |
Michael Roth |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] qga: set file descriptors in qmp_guest_file_open non-blocking on Win32 |
Date: |
Mon, 12 Oct 2015 12:38:12 -0500 |
User-agent: |
alot/0.3.6 |
Quoting Denis V. Lunev (2015-10-07 05:59:34)
> From: Olga Krishtal <address@hidden>
>
> Set fd non-blocking to avoid common use cases (like reading from a
> named pipe) from hanging the agent. This was missed in the original
> code.
>
> Restore compatibility with Posix implementation.
>
> The patch adds Win32 specific implementation of qemu_set_nonblock.
>
> On Windows OS there is a separate API for changing flags of file, pipes
> and sockets. Portable way to change file descriptor flags requires
> to detect file descriptor type and proper actions depending of that
> type. The patch adds wrapper qemu_set_fd_nonblocking into Windows specific
> code to handle this stuff properly.
>
> The only problem is that qemu_set_nonblock is void but this should not
> be a big deal.
>
> Signed-off-by: Olga Krishtal <address@hidden>
> Signed-off-by: Denis V. Lunev <address@hidden>
> Reviewed-by: Yuri Pudgorodskiy <address@hidden>
> CC: Michael Roth <address@hidden>
> CC: Stefan Weil <address@hidden>
> ---
> qga/commands-win32.c | 6 ++++++
> util/oslib-win32.c | 52
> +++++++++++++++++++++++++++++++++++++++++++++++-----
> 2 files changed, 53 insertions(+), 5 deletions(-)
>
> diff --git a/qga/commands-win32.c b/qga/commands-win32.c
> index 3374678..3274417 100644
> --- a/qga/commands-win32.c
> +++ b/qga/commands-win32.c
> @@ -34,6 +34,7 @@
> #include "qapi/qmp/qerror.h"
> #include "qemu/queue.h"
> #include "qemu/host-utils.h"
> +#include "qemu/sockets.h"
>
> #ifndef SHTDN_REASON_FLAG_PLANNED
> #define SHTDN_REASON_FLAG_PLANNED 0x80000000
> @@ -158,6 +159,11 @@ int64_t qmp_guest_file_open(const char *path, bool
> has_mode,
> return -1;
> }
>
> + /* set fd non-blocking to avoid common use cases (like reading from a
> + * named pipe) from hanging the agent
> + */
> + qemu_set_nonblock(fileno(fh));
> +
> fd = guest_file_handle_add(fh, errp);
> if (fd < 0) {
> CloseHandle(&fh);
> diff --git a/util/oslib-win32.c b/util/oslib-win32.c
> index 08f5a9c..f19aed5 100644
> --- a/util/oslib-win32.c
> +++ b/util/oslib-win32.c
> @@ -121,17 +121,59 @@ struct tm *localtime_r(const time_t *timep, struct tm
> *result)
> }
> #endif /* CONFIG_LOCALTIME_R */
>
> -void qemu_set_block(int fd)
> +static void qemu_set_fd_nonblocking(int fd, bool nonblocking)
> {
> - unsigned long opt = 0;
> - WSAEventSelect(fd, NULL, 0);
> + HANDLE handle;
> + DWORD file_type, pipe_state;
> +
> + handle = (HANDLE)_get_osfhandle(fd);
> + if (handle == INVALID_HANDLE_VALUE) {
> + return;
> + }
> +
> + file_type = GetFileType(handle);
> + if (file_type != FILE_TYPE_PIPE) {
> + return;
> + }
> +
> + /* If file_type == FILE_TYPE_PIPE, according to msdn
> + * the specified file is socket or named pipe */
> + if (GetNamedPipeHandleState(handle, &pipe_state, NULL,
> + NULL, NULL, NULL, 0)) {
> + /* The fd is named pipe fd */
> + if (!nonblocking == !(pipe_state & PIPE_NOWAIT)) {
> + /* In this case we do not need perform any operation, because
> + * nonblocking = true and PIPE_NOWAIT is already set or
> + * nonblocking = false and PIPE_NOWAIT is not set */
> + return;
> + }
> +
> + if (nonblocking) {
> + pipe_state |= PIPE_NOWAIT;
> + } else {
> + pipe_state &= ~PIPE_NOWAIT;
> + }
> +
> + SetNamedPipeHandleState(handle, &pipe_state, NULL, NULL);
> + return;
> + }
> +
> + /* The fd is socket fd */
> + unsigned long opt = (unsigned long)nonblocking;
> + if (!nonblocking) {
> + WSAEventSelect(fd, NULL, 0);
> + }
> ioctlsocket(fd, FIONBIO, &opt);
> }
>
> +void qemu_set_block(int fd)
> +{
> + qemu_set_fd_nonblocking(fd, false);
> +}
> +
> void qemu_set_nonblock(int fd)
> {
> - unsigned long opt = 1;
> - ioctlsocket(fd, FIONBIO, &opt);
> + qemu_set_fd_nonblocking(fd, true);
> qemu_fd_register(fd);
This still potentially calls qemu_fd_register() on a non-socket FD as
noted in prior review. I think the fix is trivial, but if you can
change and re-test that would be ideal.
Since guest-file* already supports reading/writing to w32 pipes I can
pick this up during soft-freeze if it comes to that.
Since we're still taking the approach of generalizing
qemu_set_nonblock() for win32 I'd really prefer to get Stefan's
Ack/Reviewed-by before applying.
> }
>
> --
> 2.1.4
>