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authorVlastimil Babka <vbabka@suse.cz>2022-01-21 22:14:27 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2022-01-22 08:33:37 +0200
commit2dba5eb1c73b6ba2988ced07250edeac0f8cbf5a (patch)
tree3ac3ce5f69c81d91828954af3819c9139199f5cf /lib/stackdepot.c
parent359745d78351c6f5442435f81549f0207ece28aa (diff)
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=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/ Link: https://lkml.kernel.org/r/20211013073005.11351-1-vbabka@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Dmitry Vyukov <dvyukov@google.com> Reviewed-by: Marco Elver <elver@google.com> # stackdepot Cc: Marco Elver <elver@google.com> Cc: Vijayanand Jitta <vjitta@codeaurora.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <mripard@kernel.org> Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: David Airlie <airlied@linux.ie> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Oliver Glitta <glittao@gmail.com> Cc: Imran Khan <imran.f.khan@oracle.com> From: Colin Ian King <colin.king@canonical.com> 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/20211015104159.11282-1-colin.king@canonical.com Signed-off-by: Colin Ian King <colin.king@canonical.com> Cc: Vlastimil Babka <vbabka@suse.cz> From: Vlastimil Babka <vbabka@suse.cz> 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/6abd9213-19a9-6d58-cedc-2414386d2d81@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reported-by: kernel test robot <oliver.sang@intel.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Stephen Rothwell <sfr@canb.auug.org.au> From: Vlastimil Babka <vbabka@suse.cz> 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/2a692365-cfa1-64f2-34e0-8aa5674dce5e@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Jani Nikula <jani.nikula@intel.com> Cc: Naresh Kamboju <naresh.kamboju@linaro.org> Cc: Marco Elver <elver@google.com> Cc: Vijayanand Jitta <vjitta@codeaurora.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <mripard@kernel.org> Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: David Airlie <airlied@linux.ie> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Oliver Glitta <glittao@gmail.com> Cc: Imran Khan <imran.f.khan@oracle.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> From: Vlastimil Babka <vbabka@suse.cz> 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/45c1b738-1a2f-5b5f-2f6d-86fab206d01c@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Eric Dumazet <edumazet@google.com> Cc: Jiri Slab <jirislaby@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/stackdepot.c')
-rw-r--r--lib/stackdepot.c33
1 files changed, 28 insertions, 5 deletions
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index b437ae79aca1..00ccb106f1a8 100644
--- a/lib/stackdepot.c
+++ b/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_disabled(char *str)
}
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)