Re: [Qemu-devel] [PATCH 01/10] util, qga: drop guest_file_toggle_flags

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting Denis V. Lunev (2015-07-07 03:19:07)
> On 30/06/15 13:25, Denis V. Lunev wrote:
> > From: Olga Krishtal <okrishtal@virtuozzo.com>
> >
> > guest_file_toggle_flags is a copy from semi-portable qemu_set_nonblock.
> > The latter is not working properly for Windows due to reduced Windows
> > Posix implementation.
> >
> > 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 problem.
> >
> > Signed-off-by: Olga Krishtal <okrishtal@virtuozzo.com>
> > Signed-off-by: Denis V. Lunev <den@openvz.org>
> > CC: Eric Blake <eblake@redhat.com>
> > CC: Michael Roth <mdroth@linux.vnet.ibm.com>
> Michael, Eric,
> 
> can you please consider merging of this patch. This is a
> semi-independent cleanup which has sense on its own.

I think this is more a "feature" in the sense that it's adding
support for pipes to qemu_set_nonblock(). Since the
guest-open-pipe* stuff is likely the first user of the feature
it should probably wait on those.

> 
> Den
> 
> 
> > ---
> >   qga/commands-posix.c | 27 ++-------------------------
> >   util/oslib-win32.c   | 52 +++++++++++++++++++++++++++++++++++++++++++++++-----
> >   2 files changed, 49 insertions(+), 30 deletions(-)
> >
> > diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> > index befd00b..40dbe25 100644
> > --- a/qga/commands-posix.c
> > +++ b/qga/commands-posix.c
> > @@ -28,6 +28,7 @@
> >   #include "qapi/qmp/qerror.h"
> >   #include "qemu/queue.h"
> >   #include "qemu/host-utils.h"
> > +#include "qemu/sockets.h"
> >   
> >   #ifndef CONFIG_HAS_ENVIRON
> >   #ifdef __APPLE__
> > @@ -376,27 +377,6 @@ safe_open_or_create(const char *path, const char *mode, Error **errp)
> >       return NULL;
> >   }
> >   
> > -static int guest_file_toggle_flags(int fd, int flags, bool set, Error **err)
> > -{
> > -    int ret, old_flags;
> > -
> > -    old_flags = fcntl(fd, F_GETFL);
> > -    if (old_flags == -1) {
> > -        error_setg_errno(err, errno, QERR_QGA_COMMAND_FAILED,
> > -                         "failed to fetch filehandle flags");
> > -        return -1;
> > -    }
> > -
> > -    ret = fcntl(fd, F_SETFL, set ? (old_flags | flags) : (old_flags & ~flags));
> > -    if (ret == -1) {
> > -        error_setg_errno(err, errno, QERR_QGA_COMMAND_FAILED,
> > -                         "failed to set filehandle flags");
> > -        return -1;
> > -    }
> > -
> > -    return ret;
> > -}
> > -
> >   int64_t qmp_guest_file_open(const char *path, bool has_mode, const char *mode,
> >                               Error **errp)
> >   {
> > @@ -417,10 +397,7 @@ int64_t qmp_guest_file_open(const char *path, bool has_mode, const char *mode,
> >       /* set fd non-blocking to avoid common use cases (like reading from a
> >        * named pipe) from hanging the agent
> >        */
> > -    if (guest_file_toggle_flags(fileno(fh), O_NONBLOCK, true, errp) < 0) {
> > -        fclose(fh);
> > -        return -1;
> > -    }
> > +    qemu_set_nonblock(fileno(fh));
> >   
> >       handle = guest_file_handle_add(fh, errp);
> >       if (handle < 0) {
> > diff --git a/util/oslib-win32.c b/util/oslib-win32.c
> > index 730a670..1a6ae72 100644
> > --- a/util/oslib-win32.c
> > +++ b/util/oslib-win32.c
> > @@ -119,17 +119,59 @@ struct tm *localtime_r(const time_t *timep, struct tm *result)
> >       return p;
> >   }
> >   
> > -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);
> >   }
> >   
>