Adjust vm.max_wired in order to avoid hitting EAGAIN artificially

Set vm.max_wired to INT_MAX in :mlock_err, :mlock_mmap, and :mlock_nested to
avoid hitting EAGAIN artificially on the system when running the tests

Require root privileges in order to set the sysctl

Add allow_sysctl_side_effects to require.config as this test is now adjusting
sysctls that can affect the global system state

Unlike the version submitted by cem in OneFS, this version uses a scratch file
to save/restore the previous value of the sysctl. I _really_, _really_ wish
there were better hooks in atf/kyua for per test suite setup/teardown -- using
a file is kludgy, but it's the best I can do to avoid situations where (for
instance), sysctl(3) may fail and drop a core outside the kyua sandbox.

Based on a patch submitted by cem, but modified to take business logic out of
ATF_TP_ADD_TCS(3).

Differential Revision: https://reviews.freebsd.org/D4779
MFC after: 1 month
Sponsored by: EMC / Isilon Storage Division

contrib/netbsd-tests/lib/libc/sys/t_mlock.c

@@ -47,12 +47,89 @@ __RCSID("$NetBSD: t_mlock.c,v 1.5 2014/02/26 20:49:26 martin Exp $");
 #include <unistd.h>
 
 #ifdef __FreeBSD__
+#include <limits.h>
 #define _KMEMUSER
 #include <machine/vmparam.h>
 #endif
 
 static long page = 0;
 
+#ifdef __FreeBSD__
+#define	VM_MAX_WIRED "vm.max_wired"
+
+static void
+vm_max_wired_sysctl(int *old_value, int *new_value)
+{
+	size_t old_len;
+	size_t new_len = (new_value == NULL ? 0 : sizeof(int));
+
+	if (old_value == NULL)
+		printf("Setting the new value to %d\n", *new_value);
+	else {
+		ATF_REQUIRE_MSG(sysctlbyname(VM_MAX_WIRED, NULL, &old_len,
+		    new_value, new_len) == 0,
+		    "sysctlbyname(%s) failed: %s", VM_MAX_WIRED, strerror(errno));
+	}
+
+	ATF_REQUIRE_MSG(sysctlbyname(VM_MAX_WIRED, old_value, &old_len,
+	    new_value, new_len) == 0,
+	    "sysctlbyname(%s) failed: %s", VM_MAX_WIRED, strerror(errno));
+
+	if (old_value != NULL)
+		printf("Saved the old value (%d)\n", *old_value);
+}
+
+static void
+set_vm_max_wired(int new_value)
+{
+	FILE *fp;
+	int old_value;
+
+	fp = fopen(VM_MAX_WIRED, "w");
+	if (fp == NULL) {
+		atf_tc_skip("could not open %s for writing: %s",
+		    VM_MAX_WIRED, strerror(errno));
+		return;
+	}
+
+	vm_max_wired_sysctl(&old_value, NULL);
+
+	ATF_REQUIRE_MSG(fprintf(fp, "%d", old_value) > 0,
+	    "saving %s failed", VM_MAX_WIRED);
+
+	fclose(fp);
+
+	vm_max_wired_sysctl(NULL, &new_value);
+}
+
+static void
+restore_vm_max_wired(void)
+{
+	FILE *fp;
+	int saved_max_wired;
+
+	fp = fopen(VM_MAX_WIRED, "r");
+	if (fp == NULL) {
+		perror("fopen failed\n");
+		return;
+	}
+
+	if (fscanf(fp, "%d", &saved_max_wired) != 1) {
+		perror("fscanf failed\n");
+		fclose(fp);
+		return;
+	}
+
+	fclose(fp);
+	printf("old value in %s: %d\n", VM_MAX_WIRED, saved_max_wired);
+
+	if (saved_max_wired == 0) /* This will cripple the test host */
+		return;
+
+	vm_max_wired_sysctl(NULL, &saved_max_wired);
+}
+#endif
+
 ATF_TC(mlock_clip);
 ATF_TC_HEAD(mlock_clip, tc)
 {
@@ -78,11 +155,19 @@ ATF_TC_BODY(mlock_clip, tc)
 	free(buf);
 }
 
+#ifdef __FreeBSD__
+ATF_TC_WITH_CLEANUP(mlock_err);
+#else
 ATF_TC(mlock_err);
+#endif
 ATF_TC_HEAD(mlock_err, tc)
 {
 	atf_tc_set_md_var(tc, "descr",
 	    "Test error conditions in mlock(2) and munlock(2)");
+#ifdef __FreeBSD__
+	atf_tc_set_md_var(tc, "require.config", "allow_sysctl_side_effects");
+	atf_tc_set_md_var(tc, "require.user", "root");
+#endif
 }
 
 ATF_TC_BODY(mlock_err, tc)
@@ -99,6 +184,8 @@ ATF_TC_BODY(mlock_err, tc)
 	if ((uintptr_t)VM_MIN_ADDRESS > 0)
 		null_errno = EINVAL;	/* NULL is not inside user VM */
 #endif
+	/* Set max_wired really really high to avoid EAGAIN */
+	set_vm_max_wired(INT_MAX);
 #else
 	if (sysctlbyname("vm.minaddress", &vmin, &len, NULL, 0) != 0)
 		atf_tc_fail("failed to read vm.minaddress");
@@ -139,6 +226,14 @@ ATF_TC_BODY(mlock_err, tc)
 	ATF_REQUIRE_ERRNO(ENOMEM, munlock(invalid_ptr, page) == -1);
 }
 
+#ifdef __FreeBSD__
+ATF_TC_CLEANUP(mlock_err, tc)
+{
+
+	restore_vm_max_wired();
+}
+#endif
+
 ATF_TC(mlock_limits);
 ATF_TC_HEAD(mlock_limits, tc)
 {
@@ -200,10 +295,18 @@ ATF_TC_BODY(mlock_limits, tc)
 	free(buf);
 }
 
+#ifdef __FreeBSD__
+ATF_TC_WITH_CLEANUP(mlock_mmap);
+#else
 ATF_TC(mlock_mmap);
+#endif
 ATF_TC_HEAD(mlock_mmap, tc)
 {
 	atf_tc_set_md_var(tc, "descr", "Test mlock(2)-mmap(2) interaction");
+#ifdef __FreeBSD__
+	atf_tc_set_md_var(tc, "require.config", "allow_sysctl_side_effects");
+	atf_tc_set_md_var(tc, "require.user", "root");
+#endif
 }
 
 ATF_TC_BODY(mlock_mmap, tc)
@@ -215,6 +318,11 @@ ATF_TC_BODY(mlock_mmap, tc)
 #endif
 	void *buf;
 
+#ifdef __FreeBSD__
+	/* Set max_wired really really high to avoid EAGAIN */
+	set_vm_max_wired(INT_MAX);
+#endif
+
 	/*
 	 * Make a wired RW mapping and check that mlock(2)
 	 * does not fail for the (already locked) mapping.
@@ -248,11 +356,27 @@ ATF_TC_BODY(mlock_mmap, tc)
 	ATF_REQUIRE(munmap(buf, page) == 0);
 }
 
+#ifdef __FreeBSD__
+ATF_TC_CLEANUP(mlock_mmap, tc)
+{
+
+	restore_vm_max_wired();
+}
+#endif
+
+#ifdef __FreeBSD__
+ATF_TC_WITH_CLEANUP(mlock_nested);
+#else
 ATF_TC(mlock_nested);
+#endif
 ATF_TC_HEAD(mlock_nested, tc)
 {
 	atf_tc_set_md_var(tc, "descr",
 	    "Test that consecutive mlock(2) calls succeed");
+#ifdef __FreeBSD__
+	atf_tc_set_md_var(tc, "require.config", "allow_sysctl_side_effects");
+	atf_tc_set_md_var(tc, "require.user", "root");
+#endif
 }
 
 ATF_TC_BODY(mlock_nested, tc)
@@ -260,6 +384,11 @@ ATF_TC_BODY(mlock_nested, tc)
 	const size_t maxiter = 100;
 	void *buf;
 
+#ifdef __FreeBSD__
+	/* Set max_wired really really high to avoid EAGAIN */
+	set_vm_max_wired(INT_MAX);
+#endif
+
 	buf = malloc(page);
 	ATF_REQUIRE(buf != NULL);
 
@@ -270,6 +399,14 @@ ATF_TC_BODY(mlock_nested, tc)
 	free(buf);
 }
 
+#ifdef __FreeBSD__
+ATF_TC_CLEANUP(mlock_nested, tc)
+{
+
+	restore_vm_max_wired();
+}
+#endif
+
 ATF_TP_ADD_TCS(tp)
 {