Perform KABI checks in parallel

Reduce the time required for ./configure to perform the needed
KABI checks by allowing kbuild to compile multiple test cases in
parallel.  This was accomplished by splitting each test's source
code from the logic handling whether that code could be compiled
or not.

By introducing this split it's possible to minimize the number of
times kbuild needs to be invoked.  As importantly, it means all of
the tests can be built in parallel.  This does require a little extra
care since we expect some tests to fail, so the --keep-going (-k)
option must be provided otherwise some tests may not get compiled.
Furthermore, since a failure during the kbuild modpost phase will
result in an early exit; the final linking phase is limited to tests
which passed the initial compilation and produced an object file.

Once everything has been built the configure script proceeds as
previously.  The only significant difference is that it now merely
needs to test for the existence of a .ko file to determine the
result of a given test.  This vastly speeds up the entire process.

New test cases should use ZFS_LINUX_TEST_SRC to declare their test
source code and ZFS_LINUX_TEST_RESULT to check the result.  All of
the existing kernel-*.m4 files have been updated accordingly, see
config/kernel-current-time.m4 for a basic example.  The legacy
ZFS_LINUX_TRY_COMPILE macro has been kept to handle special cases
but it's use is not encouraged.

                  master (secs)   patched (secs)
                  -------------   ----------------
autogen.sh        61              68
configure         137             24  (~17% of current run time)
make -j $(nproc)  44              44
make rpms         287             150

Reviewed-by: Tony Hutter <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #8547 
Closes #9132
Closes #9341 

1 files changed, 32 insertions, 16 deletions

diff --git a/config/kernel-userns-capabilities.m4 b/config/kernel-userns-capabilities.m4
index fa3381978..5dcbc03d3 100644
--- a/config/kernel-userns-capabilities.m4
+++ b/config/kernel-userns-capabilities.m4
@@ -2,16 +2,19 @@ dnl #
 dnl # 2.6.38 API change
 dnl # ns_capable() was introduced
 dnl #
-AC_DEFUN([ZFS_AC_KERNEL_NS_CAPABLE], [
-	AC_MSG_CHECKING([whether ns_capable exists])
-	ZFS_LINUX_TRY_COMPILE([
+AC_DEFUN([ZFS_AC_KERNEL_SRC_NS_CAPABLE], [
+	ZFS_LINUX_TEST_SRC([ns_capable], [
 		#include <linux/capability.h>
 	],[
 		ns_capable((struct user_namespace *)NULL, CAP_SYS_ADMIN);
-	],[
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_NS_CAPABLE], [
+	AC_MSG_CHECKING([whether ns_capable exists])
+	ZFS_LINUX_TEST_RESULT([ns_capable], [
 		AC_MSG_RESULT(yes)
-		AC_DEFINE(HAVE_NS_CAPABLE, 1,
-		    [ns_capable exists])
+		AC_DEFINE(HAVE_NS_CAPABLE, 1, [ns_capable exists])
 	],[
 		AC_MSG_RESULT(no)
 	])
@@ -23,17 +26,20 @@ dnl # struct user_namespace was added to struct cred_t as
 dnl # cred->user_ns member
 dnl # Note that current_user_ns() was added in 2.6.28.
 dnl #
-AC_DEFUN([ZFS_AC_KERNEL_CRED_USER_NS], [
-	AC_MSG_CHECKING([whether cred_t->user_ns exists])
-	ZFS_LINUX_TRY_COMPILE([
+AC_DEFUN([ZFS_AC_KERNEL_SRC_CRED_USER_NS], [
+	ZFS_LINUX_TEST_SRC([cred_user_ns], [
 		#include <linux/cred.h>
 	],[
 		struct cred cr;
 		cr.user_ns = (struct user_namespace *)NULL;
-	],[
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_CRED_USER_NS], [
+	AC_MSG_CHECKING([whether cred_t->user_ns exists])
+	ZFS_LINUX_TEST_RESULT([cred_user_ns], [
 		AC_MSG_RESULT(yes)
-		AC_DEFINE(HAVE_CRED_USER_NS, 1,
-		    [cred_t->user_ns exists])
+		AC_DEFINE(HAVE_CRED_USER_NS, 1, [cred_t->user_ns exists])
 	],[
 		AC_MSG_RESULT(no)
 	])
@@ -44,14 +50,18 @@ dnl # 3.4 API change
 dnl # kuid_has_mapping() and kgid_has_mapping() were added to distinguish
 dnl # between internal kernel uids/gids and user namespace uids/gids.
 dnl #
-AC_DEFUN([ZFS_AC_KERNEL_KUID_HAS_MAPPING], [
-	AC_MSG_CHECKING([whether kuid_has_mapping/kgid_has_mapping exist])
-	ZFS_LINUX_TRY_COMPILE([
+AC_DEFUN([ZFS_AC_KERNEL_SRC_KUID_HAS_MAPPING], [
+	ZFS_LINUX_TEST_SRC([kuid_has_mapping], [
 		#include <linux/uidgid.h>
 	],[
 		kuid_has_mapping((struct user_namespace *)NULL, KUIDT_INIT(0));
 		kgid_has_mapping((struct user_namespace *)NULL, KGIDT_INIT(0));
-	],[
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_KUID_HAS_MAPPING], [
+	AC_MSG_CHECKING([whether kuid_has_mapping/kgid_has_mapping exist])
+	ZFS_LINUX_TEST_RESULT([kuid_has_mapping], [
 		AC_MSG_RESULT(yes)
 		AC_DEFINE(HAVE_KUID_HAS_MAPPING, 1,
 		    [kuid_has_mapping/kgid_has_mapping exist])
@@ -60,6 +70,12 @@ AC_DEFUN([ZFS_AC_KERNEL_KUID_HAS_MAPPING], [
 	])
 ])
 
+AC_DEFUN([ZFS_AC_KERNEL_SRC_USERNS_CAPABILITIES], [
+	ZFS_AC_KERNEL_SRC_NS_CAPABLE
+	ZFS_AC_KERNEL_SRC_CRED_USER_NS
+	ZFS_AC_KERNEL_SRC_KUID_HAS_MAPPING
+])
+
 AC_DEFUN([ZFS_AC_KERNEL_USERNS_CAPABILITIES], [
 	ZFS_AC_KERNEL_NS_CAPABLE
 	ZFS_AC_KERNEL_CRED_USER_NS