[PATCH] Change libguestfs to use virtio block devices
by Richard W.M. Jones
The following set of patches changes libguestfs to use virtio block
devices by default.
Device names change from /dev/sd* to /dev/vd*, but device name
translation should hide this change in most cases:
http://libguestfs.org/guestfs.3.html#block_device_naming
The change isn't totally straightforward. The CHS for virtio disks is
different from the CHS for IDE disks (even where the disks have
identical size). These caused sfdisk with explicit cylinder numbers
to fail, so I had to change all these. This is the reasoning behind
patch 2 and most of patch 3.
Patch 1: Just changes the way some messages are displayed from the
test suite.
Patch 2: Changes the statvfs test so it doesn't get affected by the
CHS change.
Patch 3: (a) We change the list-devices and list-partitions functions
so that they see and return /dev/vd* devices. (b) The udev fix
previously posted to this list. (c) Change the partition sizes
because of the CHS change - see above. (d) Add ,if=virtio to -drive
parameters so that block devices are exported as virtio disks.
Patch 4: The generated code, just shown for completeness.
The tests all pass except one. A single test fails because pvremove
from the previous test causes sfdisk to fail (apparently the previous
pvremove is still happening, so sfdisk refuses to partition the device
because it is in use). I believe this is an underlying failure
revealed by this change to virtio, not caused by the change itself.
There doesn't appear to be any noticable increase in speed when
running the tests, but I didn't measure anything. The main reason to
use virtio is that it's inherently simpler than emulating IDE or SCSI
devices.
Rich.
--
Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones
libguestfs lets you edit virtual machines. Supports shell scripting,
bindings from many languages. http://et.redhat.com/~rjones/libguestfs/
See what it can do: http://et.redhat.com/~rjones/libguestfs/recipes.html
14 years, 9 months
[PATCH] add comments suggesting memory-handling improvements
by Jim Meyering
Hi Rich,
Looking at the sole remaining uses of asprintf, I noticed these
and some realloc/strdup results that needed to be checked.
Re asprintf, note that one must always check it for failure,
and when it fails, you cannot use the (undefined) pointer result.
Obviously this patch is just for reference, i.e, not to apply.
>From 7b7df29516dad78a3c815ea1ef301da89d4b5323 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyering(a)redhat.com>
Date: Wed, 1 Jul 2009 16:09:33 +0200
Subject: [PATCH] add comments suggesting memory-handling improvements
* fish/destpaths.c: Don't deref NULL or undef on failed heap alloc.
---
fish/destpaths.c | 13 ++++++++++---
1 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/fish/destpaths.c b/fish/destpaths.c
index 6cddafa..a5ece2a 100644
--- a/fish/destpaths.c
+++ b/fish/destpaths.c
@@ -55,7 +55,7 @@ complete_dest_paths_generator (const char *text, int state)
static int len, index;
static char **words = NULL;
- static int nr_words = 0;
+ static int nr_words = 0; // nr_words should be size_t
char *word;
guestfs_error_handler_cb old_error_cb;
void *old_error_cb_data;
@@ -75,6 +75,7 @@ complete_dest_paths_generator (const char *text, int state)
char **strs;
int i, n;
+ // len should be of type size_t; index and "i", too
len = strlen (text);
index = 0;
@@ -92,8 +93,11 @@ complete_dest_paths_generator (const char *text, int state)
#define APPEND_STRS_AND_FREE \
if (strs) { \
+ // n should be unsigned, like size_t
n = count_strings (strs); \
+ // handle the case in which sizeof (char *) * (nr_words + n)) overflows
words = realloc (words, sizeof (char *) * (nr_words + n)); \
+ // handle failed realloc
for (i = 0; i < n; ++i) \
words[nr_words++] = strs[i]; \
free (strs); \
@@ -120,17 +124,20 @@ complete_dest_paths_generator (const char *text, int state)
p = strrchr (text, '/');
dir = p && p > text ? strndup (text, p - text) : strdup ("/");
+ // handle failed strdup
strs = guestfs_ls (g, dir);
/* Prepend directory to names. */
if (strs) {
for (i = 0; strs[i]; ++i) {
+ int err;
p = NULL;
if (strcmp (dir, "/") == 0)
- asprintf (&p, "/%s", strs[i]);
+ err = asprintf (&p, "/%s", strs[i]);
else
- asprintf (&p, "%s/%s", dir, strs[i]);
+ err = asprintf (&p, "%s/%s", dir, strs[i]);
+ // handle failed asprintf, i.e., err < 0
free (strs[i]);
strs[i] = p;
}
--
1.6.3.3.483.g4f5e
14 years, 9 months
libguestfs and yum
by David Huff
Anyone see any issues with libguestfs and yum working weirdly??
If I mount an disk image with guestfish and try to install new packages
with yum, it gives rpmdb errors. However if I "launch" the disk images
as a guest in a fill virt container like qemu, there are no rpmdb error
and I can install new packages with yum....
Also, if I remove the rpmdb and rebuild via guestfish, then yum seems to
be working fine....
command "rm -f /var/lib/rpm/__db.004"
command "rpm --rebuilddb"
Then yum seems to work:
command "yum install vim-enhanced"
It looks like yum is still using something outside of guestfish, anyone
have any comments/ideas on this??
Thanks,
David
14 years, 9 months
best Fedora virtualization
by Rich Mahn
I am planning on running several virtual machines on a single host. I
will have two or three Linux baeed virtual machines and one or two
Windoze. I plan on using a F11 host system.
I need most of these to run automatically on boot-up of the host
system. It would be really nice if I could use something like the
Ctl-Alt-FN to be able to access and switch between virtual machines.
This needs to be stable. The machines that these virtual machines are
intended to replace are often running hundreds of days between
reboots.
My gut feel is that the virt-manager suite might be the way to go,
editting the apropriate xml files as required. I also see there
is a qemu launcher and it seems to work okay. I suspect there are
others as well.
What tends to be the consensus here on the various virtual machine
managers? Are there white papers somewhere that could give some
insight?
Thanks
Rich
14 years, 9 months
disk perf again
by Tom Horsley
In my xen virtual machines, I found that switching my disk
image files from file: to tap:aio: made the machines (all
HVMs) run much better with far fewer hangs and glitches.
If I were to try to run with KVM rather than XEN, is there
some equivalent of something like tap:aio that provides
better disk performance, or is the KVM equivalent of file:
the only way to access a disk image in a file?
(I hasten to add I have absolutely no idea what the
heck file: versus tap:aio: means, I just tried it when
I saw it mentioned somewhere and it worked much much
better :-).
14 years, 9 months
[PATCH] don't dereference or free undefined "msg" upon OOM
by Jim Meyering
Hi Rich,
Here's a tiny patch to prevent misbehavior on an OOM failure:
I prefer the decl-after-stmt (c99) syntax, but if you're
not assuming that already, just move the declaration of err "up".
>From bb57a823975019ab1be6f5f88e8276b53e8b4023 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyering(a)redhat.com>
Date: Wed, 1 Jul 2009 15:45:01 +0200
Subject: [PATCH] don't dereference or free undefined "msg" upon OOM
* src/guestfs.c (guestfs_error): Handle failing vasprintf.
---
src/guestfs.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/src/guestfs.c b/src/guestfs.c
index 5743a07..87b0d86 100644
--- a/src/guestfs.c
+++ b/src/guestfs.c
@@ -404,9 +404,11 @@ guestfs_error (guestfs_h *g, const char *fs, ...)
char *msg;
va_start (args, fs);
- vasprintf (&msg, fs, args);
+ int err = vasprintf (&msg, fs, args);
va_end (args);
+ if (err < 0) return;
+
if (g->error_cb) g->error_cb (g, g->error_cb_data, msg);
set_last_error (g, msg);
--
1.6.3.3.483.g4f5e
14 years, 9 months
