New APIs: lvm-set-filter and lvm-clear-filter.

These APIs allow you to change the device filter, the list of
block devices that LVM "sees".  Either you can set it to a fixed
list of devices / partitions, or you can clear it so that LVM sees
everything.

1 files changed, 244 insertions, 0 deletions

diff --git a/daemon/lvm-filter.c b/daemon/lvm-filter.c
new file mode 100644
index 00000000..e487c6be
--- /dev/null
+++ b/daemon/lvm-filter.c
@@ -0,0 +1,244 @@
+/* libguestfs - the guestfsd daemon
+ * Copyright (C) 2010 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <inttypes.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "daemon.h"
+#include "c-ctype.h"
+#include "actions.h"
+
+/* Does the current line match the regexp /^\s*filter\s*=/ */
+static int
+is_filter_line (const char *line)
+{
+  while (*line && c_isspace (*line))
+    line++;
+  if (!*line)
+    return 0;
+
+  if (! STRPREFIX (line, "filter"))
+    return 0;
+  line += 6;
+
+  while (*line && c_isspace (*line))
+    line++;
+  if (!*line)
+    return 0;
+
+  if (*line != '=')
+    return 0;
+
+  return 1;
+}
+
+/* Rewrite the 'filter = [ ... ]' line in /etc/lvm/lvm.conf. */
+static int
+set_filter (const char *filter)
+{
+  if (verbose)
+    fprintf (stderr, "LVM: setting device filter to %s\n", filter);
+
+  FILE *ifp = fopen ("/etc/lvm/lvm.conf", "r");
+  if (ifp == NULL) {
+    reply_with_perror ("open: /etc/lvm/lvm.conf");
+    return -1;
+  }
+  FILE *ofp = fopen ("/etc/lvm/lvm.conf.new", "w");
+  if (ofp == NULL) {
+    reply_with_perror ("open: /etc/lvm/lvm.conf.new");
+    fclose (ifp);
+    return -1;
+  }
+
+  char *line = NULL;
+  size_t len = 0;
+  while (getline (&line, &len, ifp) != -1) {
+    int r;
+    if (is_filter_line (line)) {
+      if (verbose)
+        fprintf (stderr, "LVM: replacing config line:\n%s", line);
+      r = fprintf (ofp, "    filter = [ %s ]\n", filter);
+    } else {
+      r = fprintf (ofp, "%s", line);
+    }
+    if (r < 0) {
+      /* NB. fprintf doesn't set errno on error. */
+      reply_with_error ("/etc/lvm/lvm.conf.new: write failed");
+      fclose (ifp);
+      fclose (ofp);
+      free (line);
+      unlink ("/etc/lvm/lvm.conf.new");
+      return -1;
+    }
+  }
+
+  free (line);
+
+  if (fclose (ifp) == EOF) {
+    reply_with_perror ("/etc/lvm/lvm.conf.new");
+    unlink ("/etc/lvm/lvm.conf.new");
+    fclose (ofp);
+    return -1;
+  }
+  if (fclose (ofp) == EOF) {
+    reply_with_perror ("/etc/lvm/lvm.conf.new");
+    unlink ("/etc/lvm/lvm.conf.new");
+    return -1;
+  }
+
+  if (rename ("/etc/lvm/lvm.conf.new", "/etc/lvm/lvm.conf") == -1) {
+    reply_with_perror ("rename: /etc/lvm/lvm.conf");
+    unlink ("/etc/lvm/lvm.conf.new");
+    return -1;
+  }
+
+  return 0;
+}
+
+static int
+vgchange (const char *vgchange_flag)
+{
+  char *err;
+  int r = command (NULL, &err, "lvm", "vgchange", vgchange_flag, NULL);
+  if (r == -1) {
+    reply_with_error ("vgscan: %s", err);
+    free (err);
+    return -1;
+  }
+
+  free (err);
+  return 0;
+}
+
+/* Deactivate all VGs. */
+static int
+deactivate (void)
+{
+  return vgchange ("-an");
+}
+
+/* Reactivate all VGs. */
+static int
+reactivate (void)
+{
+  return vgchange ("-ay");
+}
+
+/* Clear the cache and rescan. */
+static int
+rescan (void)
+{
+  unlink ("/etc/lvm/cache/.cache");
+
+  char *err;
+  int r = command (NULL, &err, "lvm", "vgscan", NULL);
+  if (r == -1) {
+    reply_with_error ("vgscan: %s", err);
+    free (err);
+    return -1;
+  }
+
+  free (err);
+  return 0;
+}
+
+/* Construct the new, specific filter string.  We can assume that
+ * the 'devices' array does not contain any regexp metachars,
+ * because it's already been checked by the stub code.
+ */
+static char *
+make_filter_string (char *const *devices)
+{
+  size_t i;
+  size_t len = 64;
+  for (i = 0; devices[i] != NULL; ++i)
+    len += strlen (devices[i]) + 16;
+
+  char *filter = malloc (len);
+  if (filter == NULL) {
+    reply_with_perror ("malloc");
+    return NULL;
+  }
+
+  char *p = filter;
+  for (i = 0; devices[i] != NULL; ++i) {
+    /* Because of the way matching works in LVM, each match clause
+     * should be either:
+     *   "a|^/dev/sda|",      for whole block devices, or
+     *   "a|^/dev/sda1$|",    for single partitions
+     * (the assumption being we have <= 26 block devices XXX).
+     */
+    size_t slen = strlen (devices[i]);
+    char str[slen+16];
+
+    if (c_isdigit (devices[i][slen-1]))
+      snprintf (str, slen+16, "\"a|^%s$|\", ", devices[i]);
+    else
+      snprintf (str, slen+16, "\"a|^%s|\", ", devices[i]);
+
+    strcpy (p, str);
+    p += strlen (str);
+  }
+  strcpy (p, "\"r|.*|\"");
+
+  return filter;                /* Caller must free. */
+}
+
+int
+do_lvm_set_filter (char *const *devices)
+{
+  char *filter = make_filter_string (devices);
+  if (filter == NULL)
+    return -1;
+
+  if (deactivate () == -1) {
+    free (filter);
+    return -1;
+  }
+
+  int r = set_filter (filter);
+  free (filter);
+  if (r == -1)
+    return -1;
+
+  if (rescan () == -1)
+    return -1;
+
+  return reactivate ();
+}
+
+int
+do_lvm_clear_filter (void)
+{
+  if (deactivate () == -1)
+    return -1;
+
+  if (set_filter ("\"a/.*/\"") == -1)
+    return -1;
+
+  if (rescan () == -1)
+    return -1;
+
+  return reactivate ();
+}