[Qemu-devel] [PATCH 3/3] qga: set file descriptor in qmp_guest_file_open non-blocking on Win32

["Denis V. Lunev" <den@openvz.org>]

From: Olga Krishtal <okrishtal@parallels.com>

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.

The patch introduces analog of qemu_set_non/block for HANDLES.
The usage of handles in qemu_set_non/block is impossible, because for
win32 there is a difference between file discriptors and file handles,
and all file ops are made via Win32 api.

Signed-off-by: Olga Krishtal <okrishtal@parallels.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Michael Roth <mdroth@linux.vnet.ibm.com>
CC: Stefan Weil <sw@weilnetz.de>
---
 include/qemu/sockets.h |  2 ++
 qga/commands-win32.c   |  6 ++++++
 util/oslib-win32.c     | 41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/include/qemu/sockets.h b/include/qemu/sockets.h
index 5a183c5..e2323f4 100644
--- a/include/qemu/sockets.h
+++ b/include/qemu/sockets.h
@@ -39,6 +39,8 @@ int socket_set_cork(int fd, int v);
 int socket_set_nodelay(int fd);
 void qemu_set_block(int fd);
 void qemu_set_nonblock(int fd);
+void qemu_set_nonblock_by_handle(int64_t fh);
+void qemu_set_block_by_handle(int64_t fh);
 int socket_set_fast_reuse(int fd);
 int send_all(int fd, const void *buf, int len1);
 int recv_all(int fd, void *buf, int len1, bool single_read);
diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index 97f19d5..f959d75 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_by_handle((int64_t)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 09f9e98..4a9fd8e 100644
--- a/util/oslib-win32.c
+++ b/util/oslib-win32.c
@@ -121,6 +121,37 @@ struct tm *localtime_r(const time_t *timep, struct tm *result)
 }
 #endif /* CONFIG_LOCALTIME_R */
 
+static void qemu_set_handle_nonblocking(int64_t fh, bool nonblocking)
+{
+    DWORD file_type, pipe_state;
+    HANDLE handle = (HANDLE)fh;
+    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)) {
+        return;
+    }
+    /* 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);
+}
+
 void qemu_set_block(int fd)
 {
     unsigned long opt = 0;
@@ -135,6 +166,16 @@ void qemu_set_nonblock(int fd)
     qemu_fd_register(fd);
 }
 
+void qemu_set_block_by_handle(int64_t fh)
+{
+    qemu_set_handle_nonblocking(fh, false);
+}
+
+void qemu_set_nonblock_by_handle(int64_t fh)
+{
+    qemu_set_handle_nonblocking(fh, true);
+}
+
 int socket_set_fast_reuse(int fd)
 {
     /* Enabling the reuse of an endpoint that was used by a socket still in
-- 
2.1.4