[Libguestfs] [PATCH RFC] blkid: start using libblkid directly instead

[Wanlong Gao]

Hi Rich:
What do you think about this idea?
although this still has some problems like do 'vfs-type /dev/vda'.
Can you give some comments about this? Is this a bad idea?

Thanks
-Wanlong Gao

-----------------------------------------------------------------------------
Use libblkid directly instead of the binary command in blkid.

Signed-off-by: Wanlong Gao <gaowanlong at cn.fujitsu.com>
---
 appliance/packagelist.in |    1 +
 configure.ac             |   10 ++++++++
 daemon/Makefile.am       |    1 +
 daemon/blkid.c           |   55 ++++++++++++++++++++++-----------------------
 4 files changed, 39 insertions(+), 28 deletions(-)

diff --git a/appliance/packagelist.in b/appliance/packagelist.in
index 2ab6b80..575b8dd 100644
--- a/appliance/packagelist.in
+++ b/appliance/packagelist.in
@@ -45,6 +45,7 @@
   vim-minimal
   xz
   zfs-fuse
+  libblkid
 #endif /* REDHAT */
 
 #ifdef DEBIAN
diff --git a/configure.ac b/configure.ac
index cc11b2f..0beef28 100644
--- a/configure.ac
+++ b/configure.ac
@@ -393,6 +393,16 @@ if test "x$have_libselinux" = "xyes"; then
         AC_DEFINE([HAVE_LIBSELINUX],[1],[Define to 1 if you have libselinux])
 fi
 AC_SUBST([SELINUX_LIB])
+AC_CHECK_HEADERS([blkid/blkid.h])
+AC_CHECK_LIB([blkid],[blkid_new_probe],[
+        have_libblkid="$ac_cv_header_blkid_blkid_h"
+        LIBBLKID="-lblkid"
+        LIBS="$LIBS $LIBBLKID"
+        ],[have_libblkid=no])
+if test "x$have_libblkid" = "xyes"; then
+        AC_DEFINE([HAVE_LIBBLKID],[1],[Define to 1 if you have libblkid])
+fi
+AC_SUBST([LIBBLKID])
 
 dnl Check for systemtap/DTrace userspace probes (optional).
 dnl http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps
diff --git a/daemon/Makefile.am b/daemon/Makefile.am
index 3a698cc..5e4db57 100644
--- a/daemon/Makefile.am
+++ b/daemon/Makefile.am
@@ -167,6 +167,7 @@ guestfsd_LDADD = \
 	liberrnostring.a \
 	libprotocol.a \
 	$(SELINUX_LIB) \
+	$(LIBBLKID) \
 	$(AUGEAS_LIBS) \
 	$(top_builddir)/gnulib/lib/.libs/libgnu.a \
 	$(GETADDRINFO_LIB) \
diff --git a/daemon/blkid.c b/daemon/blkid.c
index 8728c29..0c4ca71 100644
--- a/daemon/blkid.c
+++ b/daemon/blkid.c
@@ -23,6 +23,8 @@
 #include <string.h>
 #include <unistd.h>
 #include <limits.h>
+#include <fcntl.h>
+#include <blkid/blkid.h>
 
 #include "daemon.h"
 #include "actions.h"
@@ -30,40 +32,37 @@
 static char *
 get_blkid_tag (const char *device, const char *tag)
 {
-  char *out, *err;
-  int r;
+  int fd, rc;
+  const char *data = NULL;
+  blkid_probe blkprobe;
 
-  r = commandr (&out, &err,
-                "blkid",
-                /* Adding -c option kills all caching, even on RHEL 5. */
-                "-c", "/dev/null",
-                "-o", "value", "-s", tag, device, NULL);
-  if (r != 0 && r != 2) {
-    if (r >= 0)
-      reply_with_error ("%s: %s (blkid returned %d)", device, err, r);
-    else
-      reply_with_error ("%s: %s", device, err);
-    free (out);
-    free (err);
+  if (!device || !tag)
     return NULL;
-  }
 
-  free (err);
+  fd = open (device, O_RDONLY);
+  if (fd < 0)
+    return NULL;
 
-  if (r == 2) {                 /* means UUID etc not found */
-    free (out);
-    out = strdup ("");
-    if (out == NULL)
-      reply_with_perror ("strdup");
-    return out;
-  }
+  blkprobe = blkid_new_probe ();
+  if (!blkprobe)
+    goto done;
+  if (blkid_probe_set_device (blkprobe, fd, 0, 0))
+    goto done;
+
+  blkid_probe_enable_superblocks(blkprobe, 1);
+
+  blkid_probe_set_superblocks_flags (blkprobe, BLKID_SUBLKS_LABEL |
+                                     BLKID_SUBLKS_UUID | BLKID_SUBLKS_TYPE);
 
-  /* Trim trailing \n if present. */
-  size_t len = strlen (out);
-  if (len > 0 && out[len-1] == '\n')
-    out[len-1] = '\0';
+  rc = blkid_do_safeprobe (blkprobe);
+  if (!rc)
+    blkid_probe_lookup_value (blkprobe, tag, &data, NULL);
 
-  return out;                   /* caller frees */
+done:
+  close (fd);
+  if (blkprobe)
+    blkid_free_probe (blkprobe);
+  return data ? strdup ((char *) data) : NULL;
 }
 
 char *
-- 
1.7.9