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launch: For /dev/null drives, create a temporary disk.

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This is a workaround for a bug with virtio-scsi in qemu 1.2:
https://bugzilla.redhat.com/show_bug.cgi?id=847549
This commit is contained in:
Richard W.M. Jones
2012-08-15 15:44:18 +01:00
parent 7f9f281865
commit 5abd7bfc4c
1 changed files with 52 additions and 18 deletions
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70
src/launch.c
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@@ -131,6 +131,56 @@ add_drive (guestfs_h *g, const char *path,
(*drv)->use_cache_none = use_cache_none;
}
/* Traditionally you have been able to use /dev/null as a filename, as
* many times as you like. Ancient KVM (RHEL 5) cannot handle adding
* /dev/null readonly. qemu 1.2 + virtio-scsi segfaults when you use
* any zero-sized file including /dev/null. Therefore, we replace
* /dev/null with a non-zero sized temporary file. This shouldn't
* make any difference since users are not supposed to try and access
* a null drive.
*/
static int
add_null_drive (guestfs_h *g, int readonly, const char *format,
const char *iface, const char *name)
{
char *tmpfile = NULL;
int fd = -1;
if (format && STRNEQ (format, "raw")) {
error (g, _("for device '/dev/null', format must be 'raw'"));
return -1;
}
if (guestfs___lazy_make_tmpdir (g) == -1)
return -1;
tmpfile = safe_asprintf (g, "%s/devnull%d", g->tmpdir, ++g->unique);
fd = open (tmpfile, O_WRONLY|O_CREAT|O_NOCTTY|O_CLOEXEC, 0600);
if (fd == -1) {
perrorf (g, "open: %s", tmpfile);
goto err;
}
if (ftruncate (fd, 4096) == -1) {
perrorf (g, "truncate: %s", tmpfile);
goto err;
}
if (close (fd) == -1) {
perrorf (g, "close: %s", tmpfile);
goto err;
}
add_drive (g, tmpfile, readonly, format, iface, name, 0);
free (tmpfile);
return 0;
err:
free (tmpfile);
if (fd >= 0)
close (fd);
return -1;
}
int
guestfs__add_drive_opts (guestfs_h *g, const char *filename,
const struct guestfs_add_drive_opts_argv *optargs)
@@ -140,7 +190,6 @@ guestfs__add_drive_opts (guestfs_h *g, const char *filename,
const char *iface;
const char *name;
int use_cache_none;
int is_null;
if (strchr (filename, ':') != NULL) {
error (g, _("filename cannot contain ':' (colon) character. "
@@ -168,23 +217,8 @@ guestfs__add_drive_opts (guestfs_h *g, const char *filename,
return -1;
}
/* Traditionally you have been able to use /dev/null as a filename,
* as many times as you like. Treat this as a special case, because
* old versions of qemu have some problems.
*/
is_null = STREQ (filename, "/dev/null");
if (is_null) {
if (format && STRNEQ (format, "raw")) {
error (g, _("for device '/dev/null', format must be 'raw'"));
goto err_out;
}
/* Ancient KVM (RHEL 5) cannot handle the case where we try to add
* a snapshot on top of /dev/null. Modern qemu can handle it OK,
* but the device size is still 0, so it shouldn't matter whether
* or not this is readonly.
*/
readonly = 0;
}
if (STREQ (filename, "/dev/null"))
return add_null_drive (g, readonly, format, iface, name);
/* For writable files, see if we can use cache=none. This also
* checks for the existence of the file. For readonly we have