Re: [Libguestfs] [PATCH 1/2] daemon: run 'udevadm settle' with --exit-if-exists option

On Wed, Apr 12, 2017 at 05:01:10PM +0300, Pavel Butsykin wrote: > Add udev_settle_file() to run 'udevadm settle' with --exit-if-exists option. It > will slightly reduce the waiting-time for pending events if we need to wait > for events related to a particular device/file. > > Signed-off-by: Pavel Butsykin <pbutsykin(a)virtuozzo.com&gt; > --- > daemon/daemon.h | 2 ++ > daemon/guestfsd.c | 20 ++++++++++++++++---- > 2 files changed, 18 insertions(+), 4 deletions(-) > > diff --git a/daemon/daemon.h b/daemon/daemon.h > index 79a5288f6..90ebaafbe 100644 > --- a/daemon/daemon.h > +++ b/daemon/daemon.h > @@ -141,6 +141,8 @@ extern int parse_btrfsvol (const char *desc, mountable_t *mountable); > > extern int prog_exists (const char *prog); > > +extern void udev_settle_file (const char *file); > + > extern void udev_settle (void); > > extern int random_name (char *template); > diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c > index 85ce5d2ad..dccfa15bc 100644 > --- a/daemon/guestfsd.c > +++ b/daemon/guestfsd.c > @@ -1213,13 +1213,18 @@ random_name (char *template) > * fussed if it fails. > */ > void > -udev_settle (void) > +udev_settle_file (const char *file) > { > - char cmd[80]; > + size_t cmd_size = strlen (str_udevadm) + > + sizeof (" settle") + > + sizeof (" --debug") + > + (file ? sizeof (" --exit-if-exists=") + strlen (file) : 0); > + char *cmd = malloc (cmd_size); > int r; > > - snprintf (cmd, sizeof cmd, "%s%s settle", > - str_udevadm, verbose ? " --debug" : ""); > + snprintf(cmd, cmd_size, "%s%s settle%s%s", > + str_udevadm, verbose ? " --debug" : "", > + file ? " --exit-if-exists=" : "", file ? file : ""); > if (verbose) > printf ("%s\n", cmd); > r = system (cmd); > @@ -1227,6 +1232,13 @@ udev_settle (void) > perror ("system"); > else if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) > fprintf (stderr, "warning: udevadm command failed\n"); > + free (cmd); There are some ugly quoting (and hence, possibly, security) problems with this patch. It's more secure and also much simpler to call ADD_ARG + commandv here. For an example of how to use it, see: https://github.com/libguestfs/libguestfs/blob/master/daemon/mkfs.c#L41-L247

Rich.