Merge branch 'akpm' (patches from Andrew)

Merge even more updates from Andrew Morton:

 - a few leftovers

 - fault-injector rework

 - add a module loader test driver

* emailed patches from Andrew Morton <[email protected]>:
  kmod: throttle kmod thread limit
  kmod: add test driver to stress test the module loader
  MAINTAINERS: give kmod some maintainer love
  xtensa: use generic fb.h
  fault-inject: add /proc/<pid>/fail-nth
  fault-inject: simplify access check for fail-nth
  fault-inject: make fail-nth read/write interface symmetric
  fault-inject: parse as natural 1-based value for fail-nth write interface
  fault-inject: automatically detect the number base for fail-nth write interface
  kernel/watchdog.c: use better pr_fmt prefix
  MAINTAINERS: move the befs tree to kernel.org
  lib/atomic64_test.c: add a test that atomic64_inc_not_zero() returns an int
  mm: fix overflow check in expand_upwards()

Documentation/fault-injection/fault-injection.txt

@@ -136,12 +136,13 @@ use the boot option:
 
 o proc entries
 
-- /proc/self/task/<current-tid>/fail-nth:
+- /proc/<pid>/fail-nth:
+- /proc/self/task/<tid>/fail-nth:
 
-	Write to this file of integer N makes N-th call in the current task fail
-	(N is 0-based). Read from this file returns a single char 'Y' or 'N'
-	that says if the fault setup with a previous write to this file was
-	injected or not, and disables the fault if it wasn't yet injected.
+	Write to this file of integer N makes N-th call in the task fail.
+	Read from this file returns a integer value. A value of '0' indicates
+	that the fault setup with a previous write to this file was injected.
+	A positive integer N indicates that the fault wasn't yet injected.
 	Note that this file enables all types of faults (slab, futex, etc).
 	This setting takes precedence over all other generic debugfs settings
 	like probability, interval, times, etc. But per-capability settings
@@ -320,26 +321,26 @@ int main()
 	system("echo N > /sys/kernel/debug/failslab/ignore-gfp-wait");
 	sprintf(buf, "/proc/self/task/%ld/fail-nth", syscall(SYS_gettid));
 	fail_nth = open(buf, O_RDWR);
-	for (i = 0;; i++) {
+	for (i = 1;; i++) {
 		sprintf(buf, "%d", i);
 		write(fail_nth, buf, strlen(buf));
 		res = socketpair(AF_LOCAL, SOCK_STREAM, 0, fds);
 		err = errno;
-		read(fail_nth, buf, 1);
+		pread(fail_nth, buf, sizeof(buf), 0);
 		if (res == 0) {
 			close(fds[0]);
 			close(fds[1]);
 		}
-		printf("%d-th fault %c: res=%d/%d\n", i, buf[0], res, err);
-		if (buf[0] != 'Y')
+		printf("%d-th fault %c: res=%d/%d\n", i, atoi(buf) ? 'N' : 'Y',
+			res, err);
+		if (atoi(buf))
 			break;
 	}
 	return 0;
 }
 
 An example output:
 
-0-th fault Y: res=-1/23
 1-th fault Y: res=-1/23
 2-th fault Y: res=-1/23
 3-th fault Y: res=-1/12

MAINTAINERS

@@ -2516,10 +2516,10 @@ S:	Supported
 F:	drivers/media/platform/sti/delta
 
 BEFS FILE SYSTEM
-M:	Luis de Bethencourt <luisbg@osg.samsung.com>
+M:	Luis de Bethencourt <luisbg@kernel.org>
 M:	Salah Triki <[email protected]>
 S:	Maintained
-T:	git git://github.com/luisbg/linux-befs.git
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/luisbg/linux-befs.git
 F:	Documentation/filesystems/befs.txt
 F:	fs/befs/
 
@@ -7554,6 +7554,15 @@ F:	include/linux/kmemleak.h
 F:	mm/kmemleak.c
 F:	mm/kmemleak-test.c
 
+KMOD MODULE USERMODE HELPER
+M:	"Luis R. Rodriguez" <[email protected]>
+L:	[email protected]
+S:	Maintained
+F:	kernel/kmod.c
+F:	include/linux/kmod.h
+F:	lib/test_kmod.c
+F:	tools/testing/selftests/kmod/
+
 KPROBES
 M:	Ananth N Mavinakayanahalli <[email protected]>
 M:	Anil S Keshavamurthy <[email protected]>

arch/xtensa/include/asm/Kbuild

@@ -5,6 +5,7 @@ generic-y += dma-contiguous.h
 generic-y += emergency-restart.h
 generic-y += exec.h
 generic-y += extable.h
+generic-y += fb.h
 generic-y += hardirq.h
 generic-y += irq_regs.h
 generic-y += irq_work.h

fs/proc/base.c

@@ -1360,42 +1360,38 @@ static ssize_t proc_fail_nth_write(struct file *file, const char __user *buf,
 				   size_t count, loff_t *ppos)
 {
 	struct task_struct *task;
-	int err, n;
+	int err;
+	unsigned int n;
+
+	err = kstrtouint_from_user(buf, count, 0, &n);
+	if (err)
+		return err;
 
 	task = get_proc_task(file_inode(file));
 	if (!task)
 		return -ESRCH;
+	WRITE_ONCE(task->fail_nth, n);
 	put_task_struct(task);
-	if (task != current)
-		return -EPERM;
-	err = kstrtoint_from_user(buf, count, 10, &n);
-	if (err)
-		return err;
-	if (n < 0 || n == INT_MAX)
-		return -EINVAL;
-	current->fail_nth = n + 1;
+
 	return count;
 }
 
 static ssize_t proc_fail_nth_read(struct file *file, char __user *buf,
 				  size_t count, loff_t *ppos)
 {
 	struct task_struct *task;
-	int err;
+	char numbuf[PROC_NUMBUF];
+	ssize_t len;
 
 	task = get_proc_task(file_inode(file));
 	if (!task)
 		return -ESRCH;
+	len = snprintf(numbuf, sizeof(numbuf), "%u\n",
+			READ_ONCE(task->fail_nth));
+	len = simple_read_from_buffer(buf, count, ppos, numbuf, len);
 	put_task_struct(task);
-	if (task != current)
-		return -EPERM;
-	if (count < 1)
-		return -EINVAL;
-	err = put_user((char)(current->fail_nth ? 'N' : 'Y'), buf);
-	if (err)
-		return err;
-	current->fail_nth = 0;
-	return 1;
+
+	return len;
 }
 
 static const struct file_operations proc_fail_nth_operations = {
@@ -2966,6 +2962,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 #endif
 #ifdef CONFIG_FAULT_INJECTION
 	REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
+	REG("fail-nth", 0644, proc_fail_nth_operations),
 #endif
 #ifdef CONFIG_ELF_CORE
 	REG("coredump_filter", S_IRUGO|S_IWUSR, proc_coredump_filter_operations),
@@ -3358,11 +3355,7 @@ static const struct pid_entry tid_base_stuff[] = {
 #endif
 #ifdef CONFIG_FAULT_INJECTION
 	REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
-	/*
-	 * Operations on the file check that the task is current,
-	 * so we create it with 0666 to support testing under unprivileged user.
-	 */
-	REG("fail-nth", 0666, proc_fail_nth_operations),
+	REG("fail-nth", 0644, proc_fail_nth_operations),
 #endif
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 	ONE("io",	S_IRUSR, proc_tid_io_accounting),

include/linux/sched.h

@@ -974,7 +974,7 @@ struct task_struct {
 
 #ifdef CONFIG_FAULT_INJECTION
 	int				make_it_fail;
-	int fail_nth;
+	unsigned int			fail_nth;
 #endif
 	/*
 	 * When (nr_dirtied >= nr_dirtied_pause), it's time to call

kernel/kmod.c

@@ -68,6 +68,7 @@ static DECLARE_RWSEM(umhelper_sem);
  */
 #define MAX_KMOD_CONCURRENT 50
 static atomic_t kmod_concurrent_max = ATOMIC_INIT(MAX_KMOD_CONCURRENT);
+static DECLARE_WAIT_QUEUE_HEAD(kmod_wq);
 
 /*
 	modprobe_path is set via /proc/sys.
@@ -140,7 +141,6 @@ int __request_module(bool wait, const char *fmt, ...)
 	va_list args;
 	char module_name[MODULE_NAME_LEN];
 	int ret;
-	static int kmod_loop_msg;
 
 	/*
 	 * We don't allow synchronous module loading from async.  Module
@@ -164,21 +164,19 @@ int __request_module(bool wait, const char *fmt, ...)
 		return ret;
 
 	if (atomic_dec_if_positive(&kmod_concurrent_max) < 0) {
-		/* We may be blaming an innocent here, but unlikely */
-		if (kmod_loop_msg < 5) {
-			printk(KERN_ERR
-			       "request_module: runaway loop modprobe %s\n",
-			       module_name);
-			kmod_loop_msg++;
-		}
-		return -ENOMEM;
+		pr_warn_ratelimited("request_module: kmod_concurrent_max (%u) close to 0 (max_modprobes: %u), for module %s, throttling...",
+				    atomic_read(&kmod_concurrent_max),
+				    MAX_KMOD_CONCURRENT, module_name);
+		wait_event_interruptible(kmod_wq,
+					 atomic_dec_if_positive(&kmod_concurrent_max) >= 0);
 	}
 
 	trace_module_request(module_name, wait, _RET_IP_);
 
 	ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
 
 	atomic_inc(&kmod_concurrent_max);
+	wake_up(&kmod_wq);
 
 	return ret;
 }

kernel/watchdog.c

@@ -9,7 +9,7 @@
  * to those contributors as well.
  */
 
-#define pr_fmt(fmt) "NMI watchdog: " fmt
+#define pr_fmt(fmt) "watchdog: " fmt
 
 #include <linux/mm.h>
 #include <linux/cpu.h>

lib/Kconfig.debug

@@ -1847,6 +1847,33 @@ config BUG_ON_DATA_CORRUPTION
 
 	  If unsure, say N.
 
+config TEST_KMOD
+	tristate "kmod stress tester"
+	default n
+	depends on m
+	depends on BLOCK && (64BIT || LBDAF)	  # for XFS, BTRFS
+	depends on NETDEVICES && NET_CORE && INET # for TUN
+	select TEST_LKM
+	select XFS_FS
+	select TUN
+	select BTRFS_FS
+	help
+	  Test the kernel's module loading mechanism: kmod. kmod implements
+	  support to load modules using the Linux kernel's usermode helper.
+	  This test provides a series of tests against kmod.
+
+	  Although technically you can either build test_kmod as a module or
+	  into the kernel we disallow building it into the kernel since
+	  it stress tests request_module() and this will very likely cause
+	  some issues by taking over precious threads available from other
+	  module load requests, ultimately this could be fatal.
+
+	  To run tests run:
+
+	  tools/testing/selftests/kmod/kmod.sh --help
+
+	  If unsure, say N.
+
 source "samples/Kconfig"
 
 source "lib/Kconfig.kgdb"

lib/Makefile

@@ -61,6 +61,7 @@ obj-$(CONFIG_TEST_PRINTF) += test_printf.o
 obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
 obj-$(CONFIG_TEST_UUID) += test_uuid.o
 obj-$(CONFIG_TEST_PARMAN) += test_parman.o
+obj-$(CONFIG_TEST_KMOD) += test_kmod.o
 
 ifeq ($(CONFIG_DEBUG_KOBJECT),y)
 CFLAGS_kobject.o += -DDEBUG

lib/atomic64_test.c

@@ -153,8 +153,10 @@ static __init void test_atomic64(void)
 	long long v0 = 0xaaa31337c001d00dLL;
 	long long v1 = 0xdeadbeefdeafcafeLL;
 	long long v2 = 0xfaceabadf00df001LL;
+	long long v3 = 0x8000000000000000LL;
 	long long onestwos = 0x1111111122222222LL;
 	long long one = 1LL;
+	int r_int;
 
 	atomic64_t v = ATOMIC64_INIT(v0);
 	long long r = v0;
@@ -240,6 +242,11 @@ static __init void test_atomic64(void)
 	BUG_ON(!atomic64_inc_not_zero(&v));
 	r += one;
 	BUG_ON(v.counter != r);
+
+	/* Confirm the return value fits in an int, even if the value doesn't */
+	INIT(v3);
+	r_int = atomic64_inc_not_zero(&v);
+	BUG_ON(!r_int);
 }
 
 static __init int test_atomics_init(void)

lib/fault-inject.c

@@ -107,9 +107,12 @@ static inline bool fail_stacktrace(struct fault_attr *attr)
 
 bool should_fail(struct fault_attr *attr, ssize_t size)
 {
-	if (in_task() && current->fail_nth) {
-		if (--current->fail_nth == 0)
+	if (in_task()) {
+		unsigned int fail_nth = READ_ONCE(current->fail_nth);
+
+		if (fail_nth && !WRITE_ONCE(current->fail_nth, fail_nth - 1))
 			goto fail;
+
 		return false;
 	}