From 93664d38d26afb1086fc4a56ef9e6e58dcb1a3ec Mon Sep 17 00:00:00 2001
From: Pavel Butsykin <pbutsykin@virtuozzo.com>
Date: Thu, 13 Apr 2017 19:44:06 +0300
Subject: [PATCH] daemon: run 'udevadm settle' with --exit-if-exists option

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@virtuozzo.com>

RWMJ:
 - Use local variable for MAX_ARGS.
 - Use commandv instead of commandrv, fix checking of return code.
---
 daemon/daemon.h   |  2 ++
 daemon/guestfsd.c | 32 +++++++++++++++++++++++---------
 2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/daemon/daemon.h b/daemon/daemon.h
index abec087cd..332e2966a 100644
--- a/daemon/daemon.h
+++ b/daemon/daemon.h
@@ -142,6 +142,8 @@ 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 a848fe139..1daa46471 100644
--- a/daemon/guestfsd.c
+++ b/daemon/guestfsd.c
@@ -1213,20 +1213,34 @@ random_name (char *template)
  * fussed if it fails.
  */
 void
-udev_settle (void)
+udev_settle_file (const char *file)
 {
-  char cmd[80];
+  const size_t MAX_ARGS = 64;
+  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 = commandv (NULL, &err, argv);
   if (r == -1)
-    perror ("system");
-  else if (!WIFEXITED (r) || WEXITSTATUS (r) != 0)
-    fprintf (stderr, "warning: udevadm command failed\n");
+    fprintf (stderr, "udevadm settle: %s\n", err);
+}
+
+void
+udev_settle (void)
+{
+  udev_settle_file (NULL);
 }
 
 char *