[PATCH v4 1/4] kmemleak: free internal objects only if there're no leaks to be reported

[PATCH v4 1/4] kmemleak: free internal objects only if there're no leaks to be reported

[Li Zefan]

Currently if you stop kmemleak thread before disabling kmemleak,
kmemleak objects will be freed and so you won't be able to check
previously reported leaks.

With this patch, kmemleak objects won't be freed if there're leaks
that can be reported.

v2: s/kmemleak_as_leaks/kmemleak_found_leaks

Acked-by: Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>
Signed-off-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
---
 mm/kmemleak.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 31f01c5..474379e 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -218,7 +218,8 @@ static int kmemleak_stack_scan = 1;
 static DEFINE_MUTEX(scan_mutex);
 /* setting kmemleak=on, will set this var, skipping the disable */
 static int kmemleak_skip_disable;
-
+/* If there are leaks that can be reported */
+static bool kmemleak_found_leaks;
 
 /*
  * Early object allocation/freeing logging. Kmemleak is initialized after the
@@ -1382,9 +1383,12 @@ static void kmemleak_scan(void)
 	}
 	rcu_read_unlock();
 
-	if (new_leaks)
+	if (new_leaks) {
+		kmemleak_found_leaks = true;
+
 		pr_info("%d new suspected memory leaks (see "
 			"/sys/kernel/debug/kmemleak)\n", new_leaks);
+	}
 
 }
 
@@ -1592,6 +1596,8 @@ static void kmemleak_clear(void)
 		spin_unlock_irqrestore(&object->lock, flags);
 	}
 	rcu_read_unlock();
+
+	kmemleak_found_leaks = false;
 }
 
 /*
@@ -1685,12 +1691,11 @@ static const struct file_operations kmemleak_fops = {
 static void kmemleak_do_cleanup(struct work_struct *work)
 {
 	struct kmemleak_object *object;
-	bool cleanup = scan_thread == NULL;
 
 	mutex_lock(&scan_mutex);
 	stop_scan_thread();
 
-	if (cleanup) {
+	if (!kmemleak_found_leaks) {
 		rcu_read_lock();
 		list_for_each_entry_rcu(object, &object_list, object_list)
 			delete_object_full(object->pointer);
-- 
1.8.0.2

[PATCH v4 2/4] kmemleak: allow freeing internal objects after kmemleak was disabled

[Li Zefan]

Currently if kmemleak is disabled, the kmemleak objects can never be
freed, no matter if it's disabled by a user or due to fatal errors.

Those objects can be a big waste of memory.

  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME
1200264 1197433  99%    0.30K  46164       26    369312K kmemleak_object

With this patch, after kmemleak was disabled you can reclaim memory with:

	# echo clear > /sys/kernel/debug/kmemleak

Also inform users about this with a printk.

v4: rephrase the printk string.

v3: Catalin wasn't suggesting to use "off" handler, but he wants to be
    able to read memory leaks even when kmemleak is explicitly disabled.

v2: use "off" handler instead of "clear" handler to do this, suggested
    by Catalin.

Acked-by: Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>
Signed-off-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
---
 Documentation/kmemleak.txt | 15 ++++++++++++++-
 mm/kmemleak.c              | 46 ++++++++++++++++++++++++++++++++--------------
 2 files changed, 46 insertions(+), 15 deletions(-)

diff --git a/Documentation/kmemleak.txt b/Documentation/kmemleak.txt
index 6dc8013..a7563ec 100644
--- a/Documentation/kmemleak.txt
+++ b/Documentation/kmemleak.txt
@@ -51,7 +51,8 @@ Memory scanning parameters can be modified at run-time by writing to the
 		  (default 600, 0 to stop the automatic scanning)
   scan		- trigger a memory scan
   clear		- clear list of current memory leak suspects, done by
-		  marking all current reported unreferenced objects grey
+		  marking all current reported unreferenced objects grey,
+		  or free all kmemleak objects if kmemleak has been disabled.
   dump=<addr>	- dump information about the object found at <addr>
 
 Kmemleak can also be disabled at boot-time by passing "kmemleak=off" on
@@ -118,6 +119,18 @@ Then as usual to get your report with:
 
   # cat /sys/kernel/debug/kmemleak
 
+Freeing kmemleak internal objects
+---------------------------------
+
+To allow access to previosuly found memory leaks after kmemleak has been
+disabled by the user or due to an fatal error, internal kmemleak objects
+won't be freed when kmemleak is disabled, and those objects may occupy
+a large part of physical memory.
+
+In this situation, you may reclaim memory with:
+
+  # echo clear > /sys/kernel/debug/kmemleak
+
 Kmemleak API
 ------------
 
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 474379e..06cd220 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1600,6 +1600,8 @@ static void kmemleak_clear(void)
 	kmemleak_found_leaks = false;
 }
 
+static void __kmemleak_do_cleanup(void);
+
 /*
  * File write operation to configure kmemleak at run-time. The following
  * commands can be written to the /sys/kernel/debug/kmemleak file:
@@ -1612,7 +1614,8 @@ static void kmemleak_clear(void)
  *		  disable it)
  *   scan	- trigger a memory scan
  *   clear	- mark all current reported unreferenced kmemleak objects as
- *		  grey to ignore printing them
+ *		  grey to ignore printing them, or free all kmemleak objects
+ *		  if kmemleak has been disabled.
  *   dump=...	- dump information about the object found at the given address
  */
 static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
@@ -1622,9 +1625,6 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
 	int buf_size;
 	int ret;
 
-	if (!atomic_read(&kmemleak_enabled))
-		return -EBUSY;
-
 	buf_size = min(size, (sizeof(buf) - 1));
 	if (strncpy_from_user(buf, user_buf, buf_size) < 0)
 		return -EFAULT;
@@ -1634,6 +1634,19 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
 	if (ret < 0)
 		return ret;
 
+	if (strncmp(buf, "clear", 5) == 0) {
+		if (atomic_read(&kmemleak_enabled))
+			kmemleak_clear();
+		else
+			__kmemleak_do_cleanup();
+		goto out;
+	}
+
+	if (!atomic_read(&kmemleak_enabled)) {
+		ret = -EBUSY;
+		goto out;
+	}
+
 	if (strncmp(buf, "off", 3) == 0)
 		kmemleak_disable();
 	else if (strncmp(buf, "stack=on", 8) == 0)
@@ -1657,8 +1670,6 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
 		}
 	} else if (strncmp(buf, "scan", 4) == 0)
 		kmemleak_scan();
-	else if (strncmp(buf, "clear", 5) == 0)
-		kmemleak_clear();
 	else if (strncmp(buf, "dump=", 5) == 0)
 		ret = dump_str_object_info(buf + 5);
 	else
@@ -1683,6 +1694,16 @@ static const struct file_operations kmemleak_fops = {
 	.release	= kmemleak_release,
 };
 
+static void __kmemleak_do_cleanup(void)
+{
+	struct kmemleak_object *object;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(object, &object_list, object_list)
+		delete_object_full(object->pointer);
+	rcu_read_unlock();
+}
+
 /*
  * Stop the memory scanning thread and free the kmemleak internal objects if
  * no previous scan thread (otherwise, kmemleak may still have some useful
@@ -1690,17 +1711,14 @@ static const struct file_operations kmemleak_fops = {
  */
 static void kmemleak_do_cleanup(struct work_struct *work)
 {
-	struct kmemleak_object *object;
-
 	mutex_lock(&scan_mutex);
 	stop_scan_thread();
 
-	if (!kmemleak_found_leaks) {
-		rcu_read_lock();
-		list_for_each_entry_rcu(object, &object_list, object_list)
-			delete_object_full(object->pointer);
-		rcu_read_unlock();
-	}
+	if (!kmemleak_found_leaks)
+		__kmemleak_do_cleanup();
+	else
+		pr_info("Kmemleak disabled without freeing internal data. "
+			"Reclaim the memory with \"echo clear > /sys/kernel/debug/kmemleak\"\n");
 	mutex_unlock(&scan_mutex);
 }
 
-- 
1.8.0.2

[PATCH v4 3/4] kmemleak: remove redundant code

[Li Zefan]

- remove kmemleak_padding().
- remove kmemleak_release().

Acked-by: Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>
Signed-off-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
---
 include/linux/kmemleak.h | 2 --
 mm/kmemleak.c            | 7 +------
 2 files changed, 1 insertion(+), 8 deletions(-)

diff --git a/include/linux/kmemleak.h b/include/linux/kmemleak.h
index 2a5e554..5bb4246 100644
--- a/include/linux/kmemleak.h
+++ b/include/linux/kmemleak.h
@@ -30,8 +30,6 @@ extern void kmemleak_alloc_percpu(const void __percpu *ptr, size_t size) __ref;
 extern void kmemleak_free(const void *ptr) __ref;
 extern void kmemleak_free_part(const void *ptr, size_t size) __ref;
 extern void kmemleak_free_percpu(const void __percpu *ptr) __ref;
-extern void kmemleak_padding(const void *ptr, unsigned long offset,
-			     size_t size) __ref;
 extern void kmemleak_not_leak(const void *ptr) __ref;
 extern void kmemleak_ignore(const void *ptr) __ref;
 extern void kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp) __ref;
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 06cd220..6f90d00 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1549,11 +1549,6 @@ static int kmemleak_open(struct inode *inode, struct file *file)
 	return seq_open(file, &kmemleak_seq_ops);
 }
 
-static int kmemleak_release(struct inode *inode, struct file *file)
-{
-	return seq_release(inode, file);
-}
-
 static int dump_str_object_info(const char *str)
 {
 	unsigned long flags;
@@ -1691,7 +1686,7 @@ static const struct file_operations kmemleak_fops = {
 	.read		= seq_read,
 	.write		= kmemleak_write,
 	.llseek		= seq_lseek,
-	.release	= kmemleak_release,
+	.release	= seq_release,
 };
 
 static void __kmemleak_do_cleanup(void)
-- 
1.8.0.2

[PATCH v4 4/4] kmemleak: change some global variables to int

[Li Zefan]

They don't have to be atomic_t, because they are simple boolean
toggles.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Li Zefan <lizefan@huawei.com>
---
 mm/kmemleak.c | 80 +++++++++++++++++++++++++++++------------------------------
 1 file changed, 40 insertions(+), 40 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 6f90d00..91d67ea 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -192,15 +192,15 @@ static struct kmem_cache *object_cache;
 static struct kmem_cache *scan_area_cache;
 
 /* set if tracing memory operations is enabled */
-static atomic_t kmemleak_enabled = ATOMIC_INIT(0);
+static int kmemleak_enabled;
 /* set in the late_initcall if there were no errors */
-static atomic_t kmemleak_initialized = ATOMIC_INIT(0);
+static int kmemleak_initialized;
 /* enables or disables early logging of the memory operations */
-static atomic_t kmemleak_early_log = ATOMIC_INIT(1);
+static int kmemleak_early_log = 1;
 /* set if a kmemleak warning was issued */
-static atomic_t kmemleak_warning = ATOMIC_INIT(0);
+static int kmemleak_warning;
 /* set if a fatal kmemleak error has occurred */
-static atomic_t kmemleak_error = ATOMIC_INIT(0);
+static int kmemleak_error;
 
 /* minimum and maximum address that may be valid pointers */
 static unsigned long min_addr = ULONG_MAX;
@@ -268,7 +268,7 @@ static void kmemleak_disable(void);
 #define kmemleak_warn(x...)	do {		\
 	pr_warning(x);				\
 	dump_stack();				\
-	atomic_set(&kmemleak_warning, 1);	\
+	kmemleak_warning = 1;			\
 } while (0)
 
 /*
@@ -806,7 +806,7 @@ static void __init log_early(int op_type, const void *ptr, size_t size,
 	unsigned long flags;
 	struct early_log *log;
 
-	if (atomic_read(&kmemleak_error)) {
+	if (kmemleak_error) {
 		/* kmemleak stopped recording, just count the requests */
 		crt_early_log++;
 		return;
@@ -841,7 +841,7 @@ static void early_alloc(struct early_log *log)
 	unsigned long flags;
 	int i;
 
-	if (!atomic_read(&kmemleak_enabled) || !log->ptr || IS_ERR(log->ptr))
+	if (!kmemleak_enabled || !log->ptr || IS_ERR(log->ptr))
 		return;
 
 	/*
@@ -894,9 +894,9 @@ void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
 {
 	pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);
 
-	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
+	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
 		create_object((unsigned long)ptr, size, min_count, gfp);
-	else if (atomic_read(&kmemleak_early_log))
+	else if (kmemleak_early_log)
 		log_early(KMEMLEAK_ALLOC, ptr, size, min_count);
 }
 EXPORT_SYMBOL_GPL(kmemleak_alloc);
@@ -920,11 +920,11 @@ void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size)
 	 * Percpu allocations are only scanned and not reported as leaks
 	 * (min_count is set to 0).
 	 */
-	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
+	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
 		for_each_possible_cpu(cpu)
 			create_object((unsigned long)per_cpu_ptr(ptr, cpu),
 				      size, 0, GFP_KERNEL);
-	else if (atomic_read(&kmemleak_early_log))
+	else if (kmemleak_early_log)
 		log_early(KMEMLEAK_ALLOC_PERCPU, ptr, size, 0);
 }
 EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu);
@@ -940,9 +940,9 @@ void __ref kmemleak_free(const void *ptr)
 {
 	pr_debug("%s(0x%p)\n", __func__, ptr);
 
-	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
+	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
 		delete_object_full((unsigned long)ptr);
-	else if (atomic_read(&kmemleak_early_log))
+	else if (kmemleak_early_log)
 		log_early(KMEMLEAK_FREE, ptr, 0, 0);
 }
 EXPORT_SYMBOL_GPL(kmemleak_free);
@@ -960,9 +960,9 @@ void __ref kmemleak_free_part(const void *ptr, size_t size)
 {
 	pr_debug("%s(0x%p)\n", __func__, ptr);
 
-	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
+	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
 		delete_object_part((unsigned long)ptr, size);
-	else if (atomic_read(&kmemleak_early_log))
+	else if (kmemleak_early_log)
 		log_early(KMEMLEAK_FREE_PART, ptr, size, 0);
 }
 EXPORT_SYMBOL_GPL(kmemleak_free_part);
@@ -980,11 +980,11 @@ void __ref kmemleak_free_percpu(const void __percpu *ptr)
 
 	pr_debug("%s(0x%p)\n", __func__, ptr);
 
-	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
+	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
 		for_each_possible_cpu(cpu)
 			delete_object_full((unsigned long)per_cpu_ptr(ptr,
 								      cpu));
-	else if (atomic_read(&kmemleak_early_log))
+	else if (kmemleak_early_log)
 		log_early(KMEMLEAK_FREE_PERCPU, ptr, 0, 0);
 }
 EXPORT_SYMBOL_GPL(kmemleak_free_percpu);
@@ -1000,9 +1000,9 @@ void __ref kmemleak_not_leak(const void *ptr)
 {
 	pr_debug("%s(0x%p)\n", __func__, ptr);
 
-	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
+	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
 		make_gray_object((unsigned long)ptr);
-	else if (atomic_read(&kmemleak_early_log))
+	else if (kmemleak_early_log)
 		log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0);
 }
 EXPORT_SYMBOL(kmemleak_not_leak);
@@ -1020,9 +1020,9 @@ void __ref kmemleak_ignore(const void *ptr)
 {
 	pr_debug("%s(0x%p)\n", __func__, ptr);
 
-	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
+	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
 		make_black_object((unsigned long)ptr);
-	else if (atomic_read(&kmemleak_early_log))
+	else if (kmemleak_early_log)
 		log_early(KMEMLEAK_IGNORE, ptr, 0, 0);
 }
 EXPORT_SYMBOL(kmemleak_ignore);
@@ -1042,9 +1042,9 @@ void __ref kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp)
 {
 	pr_debug("%s(0x%p)\n", __func__, ptr);
 
-	if (atomic_read(&kmemleak_enabled) && ptr && size && !IS_ERR(ptr))
+	if (kmemleak_enabled && ptr && size && !IS_ERR(ptr))
 		add_scan_area((unsigned long)ptr, size, gfp);
-	else if (atomic_read(&kmemleak_early_log))
+	else if (kmemleak_early_log)
 		log_early(KMEMLEAK_SCAN_AREA, ptr, size, 0);
 }
 EXPORT_SYMBOL(kmemleak_scan_area);
@@ -1062,9 +1062,9 @@ void __ref kmemleak_no_scan(const void *ptr)
 {
 	pr_debug("%s(0x%p)\n", __func__, ptr);
 
-	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
+	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
 		object_no_scan((unsigned long)ptr);
-	else if (atomic_read(&kmemleak_early_log))
+	else if (kmemleak_early_log)
 		log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0);
 }
 EXPORT_SYMBOL(kmemleak_no_scan);
@@ -1089,7 +1089,7 @@ static bool update_checksum(struct kmemleak_object *object)
  */
 static int scan_should_stop(void)
 {
-	if (!atomic_read(&kmemleak_enabled))
+	if (!kmemleak_enabled)
 		return 1;
 
 	/*
@@ -1630,14 +1630,14 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
 		return ret;
 
 	if (strncmp(buf, "clear", 5) == 0) {
-		if (atomic_read(&kmemleak_enabled))
+		if (kmemleak_enabled)
 			kmemleak_clear();
 		else
 			__kmemleak_do_cleanup();
 		goto out;
 	}
 
-	if (!atomic_read(&kmemleak_enabled)) {
+	if (!kmemleak_enabled) {
 		ret = -EBUSY;
 		goto out;
 	}
@@ -1726,14 +1726,14 @@ static DECLARE_WORK(cleanup_work, kmemleak_do_cleanup);
 static void kmemleak_disable(void)
 {
 	/* atomically check whether it was already invoked */
-	if (atomic_cmpxchg(&kmemleak_error, 0, 1))
+	if (cmpxchg(&kmemleak_error, 0, 1))
 		return;
 
 	/* stop any memory operation tracing */
-	atomic_set(&kmemleak_enabled, 0);
+	kmemleak_enabled = 0;
 
 	/* check whether it is too early for a kernel thread */
-	if (atomic_read(&kmemleak_initialized))
+	if (kmemleak_initialized)
 		schedule_work(&cleanup_work);
 
 	pr_info("Kernel memory leak detector disabled\n");
@@ -1775,9 +1775,10 @@ void __init kmemleak_init(void)
 	int i;
 	unsigned long flags;
 
+	kmemleak_early_log = 0;
+
 #ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
 	if (!kmemleak_skip_disable) {
-		atomic_set(&kmemleak_early_log, 0);
 		kmemleak_disable();
 		return;
 	}
@@ -1795,12 +1796,11 @@ void __init kmemleak_init(void)
 
 	/* the kernel is still in UP mode, so disabling the IRQs is enough */
 	local_irq_save(flags);
-	atomic_set(&kmemleak_early_log, 0);
-	if (atomic_read(&kmemleak_error)) {
+	if (kmemleak_error) {
 		local_irq_restore(flags);
 		return;
 	} else
-		atomic_set(&kmemleak_enabled, 1);
+		kmemleak_enabled = 1;
 	local_irq_restore(flags);
 
 	/*
@@ -1844,9 +1844,9 @@ void __init kmemleak_init(void)
 				      log->op_type);
 		}
 
-		if (atomic_read(&kmemleak_warning)) {
+		if (kmemleak_warning) {
 			print_log_trace(log);
-			atomic_set(&kmemleak_warning, 0);
+			kmemleak_warning = 0;
 		}
 	}
 }
@@ -1858,9 +1858,9 @@ static int __init kmemleak_late_init(void)
 {
 	struct dentry *dentry;
 
-	atomic_set(&kmemleak_initialized, 1);
+	kmemleak_initialized = 1;
 
-	if (atomic_read(&kmemleak_error)) {
+	if (kmemleak_error) {
 		/*
 		 * Some error occurred and kmemleak was disabled. There is a
 		 * small chance that kmemleak_disable() was called immediately
-- 
1.8.0.2