New API: lvm-canonical-lv-name: make LV name canonical.

When logical volume names appear in places like /etc/fstab
files they can have the form "/dev/mapper/foo-bar".  This
function takes such names and makes them canonical.

Note that this operation cannot be performed using the current
API, because 'guestfs_stat' does not work on device names, and
we don't really want to make a 'stat-device' call since that
exposes too much non-useful detail about the appliance.

With this patch you can do this:

><fs> debug ll /dev/mapper
total 8
drwxrwxr-x  2 root root   4096 Oct 25 12:51 .
drwxr-xr-x 16 root root   4096 Oct 25 12:51 ..
crw-------  1 root root 10, 62 Oct 25 12:51 control
lrwxrwxrwx  1 root root      7 Oct 25 12:51 vg_f13x64-lv_root -> ../dm-0
lrwxrwxrwx  1 root root      7 Oct 25 12:51 vg_f13x64-lv_swap -> ../dm-1

><fs> lvm-canonical-lv-name /dev/mapper/vg_f13x64-lv_root
/dev/vg_f13x64/lv_root
><fs> lvm-canonical-lv-name /dev/mapper/vg_f13x64-lv_swap
/dev/vg_f13x64/lv_swap
><fs> lvm-canonical-lv-name /dev/mapper/foo
libguestfs: error: lvm_canonical_lv_name: lvm_canonical_lv_name_stub: /dev/mapper/foo: No such file or directory
><fs> lvm-canonical-lv-name /dev/mapper/control
libguestfs: error: lvm_canonical_lv_name: /dev/mapper/control: not a logical volume
><fs> lvm-canonical-lv-name /dev/vg_f13x64/lv_root
/dev/vg_f13x64/lv_root

daemon/lvm.c

@@ -709,3 +709,45 @@ do_is_lv (const char *device)
   free_strings (lvs);
   return 0;
 }
+
+/* Similar to is_lv above (RHBZ#638899). */
+char *
+do_lvm_canonical_lv_name (const char *device)
+{
+  struct stat stat1, stat2;
+
+  int r = stat (device, &stat1);
+  if (r == -1) {
+    reply_with_perror ("stat: %s", device);
+    return NULL;
+  }
+
+  char **lvs = do_lvs ();
+  if (lvs == NULL)
+    return NULL;
+
+  size_t i;
+  for (i = 0; lvs[i] != NULL; ++i) {
+    r = stat (lvs[i], &stat2);
+    if (r == -1) {
+      reply_with_perror ("stat: %s", lvs[i]);
+      free_strings (lvs);
+      return NULL;
+    }
+    if (stat1.st_rdev == stat2.st_rdev) { /* found it */
+      char *r = strdup (lvs[i]);
+      if (r == NULL) {
+        reply_with_perror ("strdup");
+        free_strings (lvs);
+      }
+      free_strings (lvs);
+      return r;
+    }
+  }
+
+  free_strings (lvs);
+
+  /* not found */
+  reply_with_error ("%s: not a logical volume", device);
+  return NULL;
+}

generator/generator_actions.ml

@@ -5208,6 +5208,22 @@ see the L<pread(2)> system call.
 
 See also C<guestfs_pread>.");
 
+  ("lvm_canonical_lv_name", (RString "lv", [Device "lvname"], []), 277, [],
+   [InitBasicFSonLVM, IfAvailable "lvm2", TestOutput (
+    [["lvm_canonical_lv_name"; "/dev/mapper/VG-LV"]], "/dev/VG/LV");
+    InitBasicFSonLVM, IfAvailable "lvm2", TestOutput (
+    [["lvm_canonical_lv_name"; "/dev/VG/LV"]], "/dev/VG/LV")],
+   "get canonical name of an LV",
+   "\
+This converts alternative naming schemes for LVs that you
+might find to the canonical name.  For example, C</dev/mapper/VG-LV>
+is converted to C</dev/VG/LV>.
+
+This command returns an error if the C<lvname> parameter does
+not refer to a logical volume.
+
+See also C<guestfs_is_lv>.");
+
 ]
 
 let all_functions = non_daemon_functions @ daemon_functions

src/MAX_PROC_NR

@@ -1 +1 @@
-276
+277