Re: [libvirt] [PATCH] util: Fix configure.ac check for DEVLINK_CMD_ESWITCH_GET
On 09/18/2017 01:21 PM, John Ferlan wrote:
Rather than checking for whether the devlink.h on the system has
multiple symbols, let's only check for whether the command we want
is defined.
Turns out the mechanism of providing multiple definitions to check via
AC_CHECK_DECLS in order to determine whether HAVE_DECL_DEVLINK should
be set resulted in a false positive since as long as one of the defs
was true, then the HAVE_DECL_DEVLINK got defined.
This is further complicated by a change between kernel 4.8 and 4.11
where the originally defined name DEVLINK_CMD_ESWITCH_MODE_GET was
changed to DEVLINK_CMD_ESWITCH_GET with the comment/caveat that
the old format is obsolete should never be used. Therefore, even
though some kernels will have a couple of the same symbols that
were added at the same time (DEVLINK_ATTR_ESWITCH_MODE and
DEVLINK_ESWITCH_MODE_SWITCHDEV), they won't have the newer name
and thus cause a build failure.
So even though multiple DEVLINK_CMD_SWITCH* symbols are used to
determine whether the set HAVE_DECL_DEVLINK, this should cover
those kernels before 4.11 with the old definition.
Signed-off-by: John Ferlan <jferlan(a)redhat.com>
---
I'd push this as a build breaker, but I don't want to need to go through
the trouble again if i got this wrong, so hopefully someone who's seeing
this can try out the patch... It's also present on a couple of the CI
infrastructure environments (f23, centos-7):
https://ci.centos.org/view/libvirt/job/libvirt-master-build/
configure.ac | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
UGH! While not a total SNAK, I realized sometime early this morning
(who knows why) - this won't work because it has the same problem as the
current code, but with far less AC_CHECK_DECLS options.
I think though what could be done is add:
# ifndef DEVLINK_CMD_ESWITCH_GET
# define DEVLINK_CMD_ESWITCH_GET DEVLINK_CMD_ESWITCH_MODE_GET
# endif
to src/util/virnetdev.c after it includes <linux/devlink.h>
for some reason I have a recollection we've done something like that
before for a similar issue. In the end what the kernel does in 4.11 by
adding a #define DEVLINK_CMD_ESWITCH_MODE_GET DEVLINK_CMD_ESWITCH_GET is
the opposite mechanism.
If that doesn't work, then I think just go with DEVLINK_CMD_ESWITCH_GET
in the AC_CHECK_DECLS below and let someone else figure out how to make
it work right!
John
diff --git a/configure.ac b/configure.ac
index c9509c7f9..73ae7fdd5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -630,12 +630,16 @@ fi
dnl
dnl check for kernel headers required by devlink
dnl
+dnl kernel 4.8 introduced DEVLINK_CMD_ESWITCH_MODE_GET, but that was
+dnl later changed in kernel 4.11 to be just DEVLINK_CMD_ESWITCH_GET, so
+dnl for "completeness" let's allow HAVE_DECL_DEVLINK to be define if
+dnl either is defined.
if test "$with_linux" = "yes"; then
AC_CHECK_HEADERS([linux/devlink.h])
- AC_CHECK_DECLS([DEVLINK_GENL_VERSION, DEVLINK_GENL_NAME, DEVLINK_ATTR_MAX,
DEVLINK_CMD_ESWITCH_GET, DEVLINK_ATTR_BUS_NAME, DEVLINK_ATTR_DEV_NAME,
DEVLINK_ATTR_ESWITCH_MODE, DEVLINK_ESWITCH_MODE_SWITCHDEV],
+ AC_CHECK_DECLS([DEVLINK_CMD_ESWITCH_GET, DEVLINK_CMD_ESWITCH_MODE_GET],
[AC_DEFINE([HAVE_DECL_DEVLINK],
[1],
- [whether devlink declarations are available])],
+ [whether devlink CMD_ESWITCH_GET is available])],
[],
[[#include <linux/devlink.h>]])
fi