[Libguestfs] [PATCH] Fix broken qemu <= 0.10 which randomly adds a CD-ROM device to the appliance

[Richard W.M. Jones]

qemu <= 0.10 randomly adds a CD-ROM device to the appliance because of
this bit of code:

http://git.savannah.gnu.org/cgit/qemu.git/tree/vl.c?h=stable-0.10#n5495

Thankfully this code has been removed from upstream qemu.

Anyway I'm not quite sure why we never saw this before - it seems like
this code didn't exist in the versions of qemu that were in Fedora, or
somehow this code only runs some of the time.  But anyway, this breaks
the tests in Fedora 11 and RHEL 5.3 right now.

The attached code attempts to work around this stupidity by adding
checks in list_devices and list_partitions to see if the device is
openable, and ignoring any which aren't.  These fake, empty CD drives
fail this extra check with error "No medium found", so they get
ignored.

[I'm still running all the tests with this patch, so not quite sure if
it's correct.]

Rich.

-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into Xen guests.
http://et.redhat.com/~rjones/virt-p2v
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>From 6bb26f2d253b77570c2b9291021db4364597b6df Mon Sep 17 00:00:00 2001
From: Richard Jones <rjones at centos5x32.home.annexia.org>
Date: Wed, 29 Jul 2009 15:02:16 +0100
Subject: [PATCH] Don't show empty CD devices (RHBZ#514505).

---
 daemon/devsparts.c |   27 +++++++++++++++++++++++++++
 1 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/daemon/devsparts.c b/daemon/devsparts.c
index 32d2fa8..a198ccd 100644
--- a/daemon/devsparts.c
+++ b/daemon/devsparts.c
@@ -37,6 +37,7 @@ do_list_devices (void)
   DIR *dir;
   struct dirent *d;
   char buf[256];
+  int fd;
 
   dir = opendir ("/sys/block");
   if (!dir) {
@@ -49,6 +50,18 @@ do_list_devices (void)
 	strncmp (d->d_name, "hd", 2) == 0 ||
 	strncmp (d->d_name, "vd", 2) == 0) {
       snprintf (buf, sizeof buf, "/dev/%s", d->d_name);
+
+      /* RHBZ#514505: Some versions of qemu <= 0.10 device to add a
+       * CD-ROM device even though we didn't request it.  Try to
+       * detect this by seeing if the device contains media.
+       */
+      fd = open (buf, O_RDONLY);
+      if (fd == -1) {
+	perror (buf);
+	continue;
+      }
+      close (fd);
+
       if (add_string (&r, &size, &alloc, buf) == -1) {
 	closedir (dir);
 	return NULL;
@@ -79,6 +92,7 @@ do_list_partitions (void)
   DIR *dir, *dir2;
   struct dirent *d;
   char buf[256], devname[256];
+  int fd;
 
   dir = opendir ("/sys/block");
   if (!dir) {
@@ -90,6 +104,19 @@ do_list_partitions (void)
     if (strncmp (d->d_name, "sd", 2) == 0 ||
 	strncmp (d->d_name, "hd", 2) == 0 ||
 	strncmp (d->d_name, "vd", 2) == 0) {
+      snprintf (buf, sizeof buf, "/dev/%s", d->d_name);
+
+      /* RHBZ#514505: Some versions of qemu <= 0.10 device to add a
+       * CD-ROM device even though we didn't request it.  Try to
+       * detect this by seeing if the device contains media.
+       */
+      fd = open (buf, O_RDONLY);
+      if (fd == -1) {
+	perror (buf);
+	continue;
+      }
+      close (fd);
+
       strncpy (devname, d->d_name, sizeof devname);
       devname[sizeof devname - 1] = '\0';
 
-- 
1.5.5.6