Use loop-control to allocate loop device.

This patch changes virFileLoopDeviceOpen() to use the new loop-control
device to allocate a new loop device.  If this behavior is unsupported
we fall back to the previous method of searching /dev for a free device.

With this patch you can start as many image based LXC domains as you
like (well almost).

Fixes bug https://bugzilla.redhat.com/show_bug.cgi?id=995543
This commit is contained in:
Ian Main 2013-09-05 12:04:33 +01:00 committed by Daniel P. Berrange
parent 1583dfda7c
commit 9ba230d4f2
2 changed files with 81 additions and 1 deletions

View File

@ -921,6 +921,18 @@ if test "$with_lxc" = "yes" || test "$with_lxc" = "check"; then
AC_MSG_ERROR([Required kernel features for LXC were not found])
fi
])
AC_LINK_IFELSE([AC_LANG_PROGRAM(
[[
#include <sched.h>
#include <linux/loop.h>
#include <sys/epoll.h>
]], [[
unshare(!(LOOP_CTL_GET_FREE));
]])], [
AC_DEFINE([HAVE_DECL_LOOP_CTL_GET_FREE], [1],
[Define to 1 if you have the declaration of `LOOP_CTL_GET_FREE',
and to 0 if you don't.])
])
fi
if test "$with_lxc" = "yes" ; then
AC_DEFINE_UNQUOTED([WITH_LXC], 1, [whether LXC driver is enabled])

View File

@ -528,7 +528,56 @@ int virFileUpdatePerm(const char *path,
#if defined(__linux__) && HAVE_DECL_LO_FLAGS_AUTOCLEAR
static int virFileLoopDeviceOpen(char **dev_name)
# if HAVE_DECL_LOOP_CTL_GET_FREE
/* virFileLoopDeviceOpenLoopCtl() returns -1 when a real failure has occured
* while in the process of allocating or opening the loop device. On success
* we return 0 and modify the fd to the appropriate file descriptor.
* If /dev/loop-control does not exist, we return 0 and do not set fd. */
static int virFileLoopDeviceOpenLoopCtl(char **dev_name, int *fd)
{
int devnr;
int ctl_fd;
char *looppath = NULL;
VIR_DEBUG("Opening loop-control device");
if ((ctl_fd = open("/dev/loop-control", O_RDWR)) < 0) {
if (errno == ENOENT)
return 0;
virReportSystemError(errno, "%s",
_("Unable to open /dev/loop-control"));
return -1;
}
if ((devnr = ioctl(ctl_fd, LOOP_CTL_GET_FREE)) < 0) {
virReportSystemError(errno, "%s",
_("Unable to get free loop device via ioctl"));
close(ctl_fd);
return -1;
}
close(ctl_fd);
VIR_DEBUG("Found free loop device number %i", devnr);
if (virAsprintf(&looppath, "/dev/loop%i", devnr) < 0)
return -1;
if ((*fd = open(looppath, O_RDWR)) < 0) {
virReportSystemError(errno,
_("Unable to open %s"), looppath);
VIR_FREE(looppath);
return -1;
}
*dev_name = looppath;
return 0;
}
# endif /* HAVE_DECL_LOOP_CTL_GET_FREE */
static int virFileLoopDeviceOpenSearch(char **dev_name)
{
int fd = -1;
DIR *dh = NULL;
@ -601,6 +650,25 @@ cleanup:
return fd;
}
static int virFileLoopDeviceOpen(char **dev_name)
{
int loop_fd = -1;
# if HAVE_DECL_LOOP_CTL_GET_FREE
if (virFileLoopDeviceOpenLoopCtl(dev_name, &loop_fd) < 0)
return -1;
VIR_DEBUG("Return from loop-control got fd %d\n", loop_fd);
if (loop_fd >= 0)
return loop_fd;
# endif /* HAVE_DECL_LOOP_CTL_GET_FREE */
/* Without the loop control device we just use the old technique. */
loop_fd = virFileLoopDeviceOpenSearch(dev_name);
return loop_fd;
}
int virFileLoopDeviceAssociate(const char *file,
char **dev)