[55/69] lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()

Commit Message

Andrew Morton Jan. 22, 2022, 6:14 a.m. UTC

From: Vlastimil Babka <[e-mail]>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()

Currently, enabling CONFIG_STACKDEPOT means its stack_table will be
allocated from memblock, even if stack depot ends up not actually used. 
The default size of stack_table is 4MB on 32-bit, 8MB on 64-bit.

This is fine for use-cases such as KASAN which is also a config option and
has overhead on its own.  But it's an issue for functionality that has to
be actually enabled on boot (page_owner) or depends on hardware (GPU
drivers) and thus the memory might be wasted.  This was raised as an issue
[1] when attempting to add stackdepot support for SLUB's debug object
tracking functionality.  It's common to build kernels with
CONFIG_SLUB_DEBUG and enable slub_debug on boot only when needed, or
create only specific kmem caches with debugging for testing purposes.

It would thus be more efficient if stackdepot's table was allocated only
when actually going to be used.  This patch thus makes the allocation (and
whole stack_depot_init() call) optional:

- Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current
  well-defined point of allocation as part of mem_init(). Make CONFIG_KASAN
  select this flag.
- Other users have to call stack_depot_init() as part of their own init when
  it's determined that stack depot will actually be used. This may depend on
  both config and runtime conditions. Convert current users which are
  page_owner and several in the DRM subsystem. Same will be done for SLUB
  later.
- Because the init might now be called after the boot-time memblock allocation
  has given all memory to the buddy allocator, change stack_depot_init() to
  allocate stack_table with kvmalloc() when memblock is no longer available.
  Also handle allocation failure by disabling stackdepot (could have
  theoretically happened even with memblock allocation previously), and don't
  unnecessarily align the memblock allocation to its own size anymore.

[1] https://lore.kernel.org/all/CAMuHMdW=[e-mail]/

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Vlastimil Babka <[e-mail]>
Acked-by: Dmitry Vyukov <[e-mail]>
Reviewed-by: Marco Elver <[e-mail]> # stackdepot
Cc: Marco Elver <[e-mail]>
Cc: Vijayanand Jitta <[e-mail]>
Cc: Maarten Lankhorst <[e-mail]>
Cc: Maxime Ripard <[e-mail]>
Cc: Thomas Zimmermann <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Andrey Ryabinin <[e-mail]>
Cc: Alexander Potapenko <[e-mail]>
Cc: Andrey Konovalov <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Cc: Oliver Glitta <[e-mail]>
Cc: Imran Khan <[e-mail]>
From: Colin Ian King <[e-mail]>
Subject: lib/stackdepot: fix spelling mistake and grammar in pr_err message

There is a spelling mistake of the work allocation so fix this and
re-phrase the message to make it easier to read.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Colin Ian King <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
From: Vlastimil Babka <[e-mail]>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup

On FLATMEM, we call page_ext_init_flatmem_late() just before
kmem_cache_init() which means stack_depot_init() (called by page owner
init) will not recognize properly it should use kvmalloc() and not
memblock_alloc().  memblock_alloc() will also not issue a warning and
return a block memory that can be invalid and cause kernel page fault when
saving stacks, as reported by the kernel test robot [1].

Fix this by moving page_ext_init_flatmem_late() below kmem_cache_init() so
that slab_is_available() is true during stack_depot_init().  SPARSEMEM
doesn't have this issue, as it doesn't do page_ext_init_flatmem_late(),
but a different page_ext_init() even later in the boot process.

Thanks to Mike Rapoport for pointing out the FLATMEM init ordering issue.

While at it, also actually resolve a checkpatch warning in stack_depot_init()
from DRM CI, which was supposed to be in the original patch already.

[1] https://lore.kernel.org/all/20211014085450.GC18719@xsang-OptiPlex-9020/

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Vlastimil Babka <[e-mail]>
Reported-by: kernel test robot <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Stephen Rothwell <[e-mail]>
From: Vlastimil Babka <[e-mail]>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup3

Due to cd06ab2fd48f ("drm/locking: add backtrace for locking contended
locks without backoff") landing recently to -next adding a new stack depot
user in drivers/gpu/drm/drm_modeset_lock.c we need to add an appropriate
call to stack_depot_init() there as well.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Vlastimil Babka <[e-mail]>
Cc: Jani Nikula <[e-mail]>
Cc: Naresh Kamboju <[e-mail]>
Cc: Marco Elver <[e-mail]>
Cc: Vijayanand Jitta <[e-mail]>
Cc: Maarten Lankhorst <[e-mail]>
Cc: Maxime Ripard <[e-mail]>
Cc: Thomas Zimmermann <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Andrey Ryabinin <[e-mail]>
Cc: Alexander Potapenko <[e-mail]>
Cc: Andrey Konovalov <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Cc: Oliver Glitta <[e-mail]>
Cc: Imran Khan <[e-mail]>
Cc: Stephen Rothwell <[e-mail]>
From: Vlastimil Babka <[e-mail]>
Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup4

Due to 4e66934eaadc ("lib: add reference counting tracking
infrastructure") landing recently to net-next adding a new stack depot
user in lib/ref_tracker.c we need to add an appropriate call to
stack_depot_init() there as well.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Vlastimil Babka <[e-mail]>
Reviewed-by: Eric Dumazet <[e-mail]>
Cc: Jiri Slab <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 drivers/gpu/drm/drm_dp_mst_topology.c   |    1 
 drivers/gpu/drm/drm_mm.c                |    4 ++
 drivers/gpu/drm/drm_modeset_lock.c      |    9 ++++++
 drivers/gpu/drm/i915/intel_runtime_pm.c |    3 ++
 include/linux/ref_tracker.h             |    2 +
 include/linux/stackdepot.h              |   25 ++++++++++------
 init/main.c                             |    9 ++++--
 lib/Kconfig                             |    4 ++
 lib/Kconfig.kasan                       |    2 -
 lib/stackdepot.c                        |   33 ++++++++++++++++++----
 mm/page_owner.c                         |    2 +
 11 files changed, 76 insertions(+), 18 deletions(-)

Patch

--- a/drivers/gpu/drm/drm_dp_mst_topology.c~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc
+++ a/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -5511,6 +5511,7 @@  int drm_dp_mst_topology_mgr_init(struct
 	mutex_init(&mgr->probe_lock);
 #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
 	mutex_init(&mgr->topology_ref_history_lock);
+	stack_depot_init();
 #endif
 	INIT_LIST_HEAD(&mgr->tx_msg_downq);
 	INIT_LIST_HEAD(&mgr->destroy_port_list);
--- a/drivers/gpu/drm/drm_mm.c~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc
+++ a/drivers/gpu/drm/drm_mm.c
@@ -980,6 +980,10 @@  void drm_mm_init(struct drm_mm *mm, u64
 	add_hole(&mm->head_node);
 
 	mm->scan_active = 0;
+
+#ifdef CONFIG_DRM_DEBUG_MM
+	stack_depot_init();
+#endif
 }
 EXPORT_SYMBOL(drm_mm_init);
 
--- a/drivers/gpu/drm/drm_modeset_lock.c~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc
+++ a/drivers/gpu/drm/drm_modeset_lock.c
@@ -107,6 +107,11 @@  static void __drm_stack_depot_print(depo
 
 	kfree(buf);
 }
+
+static void __drm_stack_depot_init(void)
+{
+	stack_depot_init();
+}
 #else /* CONFIG_DRM_DEBUG_MODESET_LOCK */
 static depot_stack_handle_t __drm_stack_depot_save(void)
 {
@@ -115,6 +120,9 @@  static depot_stack_handle_t __drm_stack_
 static void __drm_stack_depot_print(depot_stack_handle_t stack_depot)
 {
 }
+static void __drm_stack_depot_init(void)
+{
+}
 #endif /* CONFIG_DRM_DEBUG_MODESET_LOCK */
 
 /**
@@ -359,6 +367,7 @@  void drm_modeset_lock_init(struct drm_mo
 {
 	ww_mutex_init(&lock->mutex, &crtc_ww_class);
 	INIT_LIST_HEAD(&lock->head);
+	__drm_stack_depot_init();
 }
 EXPORT_SYMBOL(drm_modeset_lock_init);
 
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc
+++ a/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -68,6 +68,9 @@  static noinline depot_stack_handle_t __s
 static void init_intel_runtime_pm_wakeref(struct intel_runtime_pm *rpm)
 {
 	spin_lock_init(&rpm->debug.lock);
+
+	if (rpm->available)
+		stack_depot_init();
 }
 
 static noinline depot_stack_handle_t
--- a/include/linux/ref_tracker.h~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc
+++ a/include/linux/ref_tracker.h
@@ -4,6 +4,7 @@ 
 #include <linux/refcount.h>
 #include <linux/types.h>
 #include <linux/spinlock.h>
+#include <linux/stackdepot.h>
 
 struct ref_tracker;
 
@@ -26,6 +27,7 @@  static inline void ref_tracker_dir_init(
 	spin_lock_init(&dir->lock);
 	dir->quarantine_avail = quarantine_count;
 	refcount_set(&dir->untracked, 1);
+	stack_depot_init();
 }
 
 void ref_tracker_dir_exit(struct ref_tracker_dir *dir);
--- a/include/linux/stackdepot.h~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc
+++ a/include/linux/stackdepot.h
@@ -19,6 +19,22 @@  depot_stack_handle_t __stack_depot_save(
 					unsigned int nr_entries,
 					gfp_t gfp_flags, bool can_alloc);
 
+/*
+ * Every user of stack depot has to call this during its own init when it's
+ * decided that it will be calling stack_depot_save() later.
+ *
+ * The alternative is to select STACKDEPOT_ALWAYS_INIT to have stack depot
+ * enabled as part of mm_init(), for subsystems where it's known at compile time
+ * that stack depot will be used.
+ */
+int stack_depot_init(void);
+
+#ifdef CONFIG_STACKDEPOT_ALWAYS_INIT
+static inline int stack_depot_early_init(void)	{ return stack_depot_init(); }
+#else
+static inline int stack_depot_early_init(void)	{ return 0; }
+#endif
+
 depot_stack_handle_t stack_depot_save(unsigned long *entries,
 				      unsigned int nr_entries, gfp_t gfp_flags);
 
@@ -30,13 +46,4 @@  int stack_depot_snprint(depot_stack_hand
 
 void stack_depot_print(depot_stack_handle_t stack);
 
-#ifdef CONFIG_STACKDEPOT
-int stack_depot_init(void);
-#else
-static inline int stack_depot_init(void)
-{
-	return 0;
-}
-#endif	/* CONFIG_STACKDEPOT */
-
 #endif
--- a/init/main.c~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc
+++ a/init/main.c
@@ -834,12 +834,15 @@  static void __init mm_init(void)
 	init_mem_debugging_and_hardening();
 	kfence_alloc_pool();
 	report_meminit();
-	stack_depot_init();
+	stack_depot_early_init();
 	mem_init();
 	mem_init_print_info();
-	/* page_owner must be initialized after buddy is ready */
-	page_ext_init_flatmem_late();
 	kmem_cache_init();
+	/*
+	 * page_owner must be initialized after buddy is ready, and also after
+	 * slab is ready so that stack_depot_init() works properly
+	 */
+	page_ext_init_flatmem_late();
 	kmemleak_init();
 	pgtable_init();
 	debug_objects_mem_init();
--- a/lib/Kconfig~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc
+++ a/lib/Kconfig
@@ -673,6 +673,10 @@  config STACKDEPOT
 	bool
 	select STACKTRACE
 
+config STACKDEPOT_ALWAYS_INIT
+	bool
+	select STACKDEPOT
+
 config STACK_HASH_ORDER
 	int "stack depot hash size (12 => 4KB, 20 => 1024KB)"
 	range 12 20
--- a/lib/Kconfig.kasan~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc
+++ a/lib/Kconfig.kasan
@@ -38,7 +38,7 @@  menuconfig KASAN
 		    CC_HAS_WORKING_NOSANITIZE_ADDRESS) || \
 		   HAVE_ARCH_KASAN_HW_TAGS
 	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
-	select STACKDEPOT
+	select STACKDEPOT_ALWAYS_INIT
 	help
 	  Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
 	  designed to find out-of-bounds accesses and use-after-free bugs.
--- a/lib/stackdepot.c~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc
+++ a/lib/stackdepot.c
@@ -23,6 +23,7 @@ 
 #include <linux/jhash.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
+#include <linux/mutex.h>
 #include <linux/percpu.h>
 #include <linux/printk.h>
 #include <linux/slab.h>
@@ -161,18 +162,40 @@  static int __init is_stack_depot_disable
 }
 early_param("stack_depot_disable", is_stack_depot_disabled);
 
-int __init stack_depot_init(void)
+/*
+ * __ref because of memblock_alloc(), which will not be actually called after
+ * the __init code is gone, because at that point slab_is_available() is true
+ */
+__ref int stack_depot_init(void)
 {
-	if (!stack_depot_disable) {
+	static DEFINE_MUTEX(stack_depot_init_mutex);
+
+	mutex_lock(&stack_depot_init_mutex);
+	if (!stack_depot_disable && !stack_table) {
 		size_t size = (STACK_HASH_SIZE * sizeof(struct stack_record *));
 		int i;
 
-		stack_table = memblock_alloc(size, size);
-		for (i = 0; i < STACK_HASH_SIZE;  i++)
-			stack_table[i] = NULL;
+		if (slab_is_available()) {
+			pr_info("Stack Depot allocating hash table with kvmalloc\n");
+			stack_table = kvmalloc(size, GFP_KERNEL);
+		} else {
+			pr_info("Stack Depot allocating hash table with memblock_alloc\n");
+			stack_table = memblock_alloc(size, SMP_CACHE_BYTES);
+		}
+		if (stack_table) {
+			for (i = 0; i < STACK_HASH_SIZE;  i++)
+				stack_table[i] = NULL;
+		} else {
+			pr_err("Stack Depot hash table allocation failed, disabling\n");
+			stack_depot_disable = true;
+			mutex_unlock(&stack_depot_init_mutex);
+			return -ENOMEM;
+		}
 	}
+	mutex_unlock(&stack_depot_init_mutex);
 	return 0;
 }
+EXPORT_SYMBOL_GPL(stack_depot_init);
 
 /* Calculate hash for a stack */
 static inline u32 hash_stack(unsigned long *entries, unsigned int size)
--- a/mm/page_owner.c~lib-stackdepot-allow-optional-init-and-stack_table-allocation-by-kvmalloc
+++ a/mm/page_owner.c
@@ -80,6 +80,8 @@  static __init void init_page_owner(void)
 	if (!page_owner_enabled)
 		return;
 
+	stack_depot_init();
+
 	register_dummy_stack();
 	register_failure_stack();
 	register_early_stack();