daemon: Move lvmetad to early in the appliance boot process.

When the daemon starts up it creates a fresh (empty) LVM configuration
and starts up lvmetad (which depends on the LVM configuration).

However this appears to cause problems: Some types of PV seem to
require lvmetad and don't work without it
(https://bugzilla.redhat.com/show_bug.cgi?id=1581810).  If we don't
start lvmetad earlier, the device nodes are not created.

Therefore move the whole initialization step into appliance/init.

Two further changes had to be made:

Now we are using lvmetad all the time, using vgchange is incorrect.
With lvmetad activated early we must use ‘pvscan --cache --activate ay’
to scan all disks for PVs and activate any VGs on them (although the
documentation is complex, confusing and contradictory so I'm not
completely sure about this).

The ‘lvm_system_dir’ local variable in ‘daemon/lvm-filter.c’
previously contained the path of the directory above $LVM_SYSTEM_DIR
(eg. $LVM_SYSTEM_DIR = "/etc/lvm", lvm_system_dir = "/etc").  As this
was highly confusing, I have changed it so the local variable and the
environment variable have identical contents.  This involved removing
the ‘lvm/’ component from a couple of paths since it is now included
in the local variable.

(cherry picked from commit dd162d2cd5)

appliance/init

@@ -133,9 +133,17 @@ fi
 # Scan for MDs but don't run arrays unless all expected drives are present
 mdadm -As --auto=yes --no-degraded
 
+# Set up a clean LVM environment.
+# Empty LVM configuration file means "all defaults".
+mkdir -p /tmp/lvm
+touch /tmp/lvm/lvm.conf
+LVM_SYSTEM_DIR=/tmp/lvm
+export LVM_SYSTEM_DIR
+lvmetad
+
 # Scan for LVM.
 modprobe dm_mod ||:
-lvm vgchange -aay --sysinit
+lvm pvscan --cache --activate ay
 
 # Scan for MDs and run all found arrays even they are in degraded state
 mdadm -As --auto=yes --run
@@ -149,6 +157,7 @@ if test "$guestfs_verbose" = 1 && test "$guestfs_boot_analysis" != 1; then
     ls -lR /dev
     cat /proc/mounts
     cat /proc/mdstat
+    lvm config
     lvm pvs
     lvm vgs
     lvm lvs

daemon/daemon.h

@@ -249,10 +249,6 @@ extern char *get_blkid_tag (const char *device, const char *tag);
 /* lvm.c */
 extern int lv_canonical (const char *device, char **ret);
 
-/* lvm-filter.c */
-extern void clean_lvm_config (void);
-extern void start_lvmetad (void);
-
 /* zero.c */
 extern void wipe_device_before_mkfs (const char *device);
 

daemon/guestfsd.c

@@ -233,14 +233,6 @@ main (int argc, char *argv[])
   _umask (0);
 #endif
 
-  /* Make a private copy of /etc/lvm so we can change the config (see
-   * daemon/lvm-filter.c).
-   */
-  if (!test_mode) {
-    clean_lvm_config ();
-    start_lvmetad ();
-  }
-
   /* Connect to virtio-serial channel. */
   if (!channel)
     channel = VIRTIO_SERIAL_CHANNEL;

daemon/lvm-filter.c

@@ -36,71 +36,36 @@
 #include "daemon.h"
 #include "actions.h"
 
-/* This runs during daemon start up and creates a fresh LVM
- * configuration which we can modify as we desire.  LVM allows
- * configuration to be completely empty (meaning "all defaults").
- *
- * The final directory layout is:
- *
- *   /tmp/lvmXXXXXX                 (lvm_system_dir set to this)
- *   /tmp/lvmXXXXXX/lvm             ($LVM_SYSTEM_DIR set to this)
- *   /tmp/lvmXXXXXX/lvm/lvm.conf    (configuration file - initially empty)
- */
-static char lvm_system_dir[] = "/tmp/lvmXXXXXX";
-
-static void rm_lvm_system_dir (void);
 static void debug_lvm_config (void);
 
-void
-clean_lvm_config (void)
+/* Read LVM_SYSTEM_DIR environment variable, or set it to a default
+ * value if the environment variable is not set.
+ */
+static char *lvm_system_dir;
+static void get_lvm_system_dir (void) __attribute__((constructor));
+static void free_lvm_system_dir (void) __attribute__((destructor));
+
+static void
+get_lvm_system_dir (void)
 {
-  char env[64], conf[64];
-  FILE *fp;
+  const char *p;
 
-  if (mkdtemp (lvm_system_dir) == NULL)
-    error (EXIT_FAILURE, errno, "mkdtemp: %s", lvm_system_dir);
-
-  snprintf (env, sizeof env, "%s/lvm", lvm_system_dir);
-  mkdir (env, 0755);
-  snprintf (conf, sizeof conf, "%s/lvm/lvm.conf", lvm_system_dir);
-  fp = fopen (conf, "w");
-  if (fp == NULL) {
-    perror ("clean_lvm_config: cannot create empty lvm.conf");
-    exit (EXIT_FAILURE);
+  p = getenv ("LVM_SYSTEM_DIR");
+  if (p) {
+    lvm_system_dir = strdup (p);
+    if (lvm_system_dir == NULL) abort ();
   }
-  fclose (fp);
-
-  /* Set environment variable so we use the clean configuration. */
-  setenv ("LVM_SYSTEM_DIR", env, 1);
-
-  /* Set a handler to remove the temporary directory at exit. */
-  atexit (rm_lvm_system_dir);
-
-  debug_lvm_config ();
-}
-
-/* Try to run lvmetad, without failing if it couldn't. */
-void
-start_lvmetad (void)
-{
-  int r;
-
-  if (verbose)
-    printf ("%s\n", "lvmetad");
-  r = system ("lvmetad");
-  if (r == -1)
-    perror ("system/lvmetad");
-  else if (!WIFEXITED (r) || WEXITSTATUS (r) != 0)
-    fprintf (stderr, "warning: lvmetad command failed\n");
+  if (!lvm_system_dir) {
+    lvm_system_dir = strdup ("/etc/lvm");
+    if (lvm_system_dir == NULL) abort ();
+  }
+  fprintf (stderr, "lvm_system_dir = %s\n", lvm_system_dir);
 }
 
 static void
-rm_lvm_system_dir (void)
+free_lvm_system_dir (void)
 {
-  char cmd[64];
-
-  snprintf (cmd, sizeof cmd, "rm -rf %s", lvm_system_dir);
-  ignore_value (system (cmd));
+  free (lvm_system_dir);
 }
 
 /* Rewrite the 'filter = [ ... ]' line in lvm.conf. */
@@ -112,7 +77,7 @@ set_filter (char *const *filters)
   FILE *fp;
   size_t i, j;
 
-  if (asprintf (&conf, "%s/lvm/lvm.conf", lvm_system_dir) == -1) {
+  if (asprintf (&conf, "%s/lvm.conf", lvm_system_dir) == -1) {
     reply_with_perror ("asprintf");
     return -1;
   }
@@ -177,7 +142,7 @@ static int
 rescan (void)
 {
   char lvm_cache[64];
-  snprintf (lvm_cache, sizeof lvm_cache, "%s/lvm/cache/.cache", lvm_system_dir);
+  snprintf (lvm_cache, sizeof lvm_cache, "%s/cache/.cache", lvm_system_dir);
 
   unlink (lvm_cache);