[Libguestfs] [PATCH v3 1/2] daemon: run 'udevadm settle' with --exit-if-exists option

[Pavel Butsykin]

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 at virtuozzo.com>
---
 daemon/daemon.h   |  2 ++
 daemon/guestfsd.c | 31 ++++++++++++++++++++++++-------
 2 files changed, 26 insertions(+), 7 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..635f5b1d2 100644
--- a/daemon/guestfsd.c
+++ b/daemon/guestfsd.c
@@ -63,6 +63,8 @@
 
 #include "daemon.h"
 
+#define MAX_ARGS 64
+
 GUESTFSD_EXT_CMD(str_udevadm, udevadm);
 GUESTFSD_EXT_CMD(str_uuidgen, uuidgen);
 
@@ -1213,22 +1215,37 @@ random_name (char *template)
  * fussed if it fails.
  */
 void
-udev_settle (void)
+udev_settle_file (const char *file)
 {
-  char cmd[80];
+  const char *argv[MAX_ARGS];
+  CLEANUP_FREE char *err = NULL;
+  size_t i = 0;
   int r;
 
-  snprintf (cmd, sizeof cmd, "%s%s settle",
-            str_udevadm, verbose ? " --debug" : "");
+  ADD_ARG (argv, i, str_udevadm);
   if (verbose)
-    printf ("%s\n", cmd);
-  r = system (cmd);
+    ADD_ARG (argv, i, "--debug");
+
+  ADD_ARG (argv, i, "settle");
+  if (file) {
+    ADD_ARG (argv, i, "-E");
+    ADD_ARG (argv, i, file);
+  }
+  ADD_ARG (argv, i, NULL);
+
+  r = commandrv (NULL, &err, argv);
   if (r == -1)
-    perror ("system");
+    fprintf (stderr, "%s\n", err);
   else if (!WIFEXITED (r) || WEXITSTATUS (r) != 0)
     fprintf (stderr, "warning: udevadm command failed\n");
 }
 
+void
+udev_settle (void)
+{
+  udev_settle_file (NULL);
+}
+
 char *
 get_random_uuid (void)
 {
-- 
2.11.0