On Thu, 3 Mar 2022 at 20:19, Vlastimil Babka <vbabka@xxxxxxx> wrote: > > Here's an updated version based on feedback so I don't re-send everything > so soon after v2. Also in git: > https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=slub-stackdepot-v3r0 > There are only trivial adaptations in patch 3/6 to the stack depot init > changes otherwise. > Thanks, Vlastimil > > ----8<---- > From 230ebae0f83540574d167f9ba1f71d3f602ca410 Mon Sep 17 00:00:00 2001 > From: Vlastimil Babka <vbabka@xxxxxxx> > Date: Wed, 2 Mar 2022 12:02:22 +0100 > Subject: [PATCH v3 1/6] lib/stackdepot: allow requesting early initialization > dynamically > > In a later patch we want to add stackdepot support for object owner > tracking in slub caches, which is enabled by slub_debug boot parameter. > This creates a bootstrap problem as some caches are created early in > boot when slab_is_available() is false and thus stack_depot_init() > tries to use memblock. But, as reported by Hyeonggon Yoo [1] we are > already beyond memblock_free_all(). Ideally memblock allocation should > fail, yet it succeeds, but later the system crashes, which is a > separately handled issue. > > To resolve this boostrap issue in a robust way, this patch adds another > way to request stack_depot_early_init(), which happens at a well-defined > point of time. In addition to build-time CONFIG_STACKDEPOT_ALWAYS_INIT, > code that's e.g. processing boot parameters (which happens early enough) > can call a new function stack_depot_want_early_init(), which sets a flag > that stack_depot_early_init() will check. > > In this patch we also convert page_owner to this approach. While it > doesn't have the bootstrap issue as slub, it's also a functionality > enabled by a boot param and can thus request stack_depot_early_init() > with memblock allocation instead of later initialization with > kvmalloc(). > > As suggested by Mike, make stack_depot_early_init() only attempt > memblock allocation and stack_depot_init() only attempt kvmalloc(). > Also change the latter to kvcalloc(). In both cases we can lose the > explicit array zeroing, which the allocations do already. > > As suggested by Marco, provide empty implementations of the init > functions for !CONFIG_STACKDEPOT builds to simplify the callers. > > [1] https://lore.kernel.org/all/YhnUcqyeMgCrWZbd@xxxxxxxxxxxxxxxxxxx-northeast-1.compute.internal/ > > Reported-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> > Suggested-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> > Suggested-by: Marco Elver <elver@xxxxxxxxxx> > Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> Looks good, thanks! Reviewed-by: Marco Elver <elver@xxxxxxxxxx> > --- > include/linux/stackdepot.h | 26 ++++++++++++--- > lib/stackdepot.c | 67 +++++++++++++++++++++++++------------- > mm/page_owner.c | 9 +++-- > 3 files changed, 73 insertions(+), 29 deletions(-) > > diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h > index 17f992fe6355..bc2797955de9 100644 > --- a/include/linux/stackdepot.h > +++ b/include/linux/stackdepot.h > @@ -20,18 +20,36 @@ depot_stack_handle_t __stack_depot_save(unsigned long *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. > + * Every user of stack depot has to call stack_depot_init() during its own init > + * when it's decided that it will be calling stack_depot_save() later. This is > + * recommended for e.g. modules initialized later in the boot process, when > + * slab_is_available() is true. > * > * 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. > + * > + * Another alternative is to call stack_depot_want_early_init(), when the > + * decision to use stack depot is taken e.g. when evaluating kernel boot > + * parameters, which precedes the enablement point in mm_init(). > + * > + * stack_depot_init() and stack_depot_want_early_init() can be called regardless > + * of CONFIG_STACKDEPOT and are no-op when disabled. The actual save/fetch/print > + * functions should only be called from code that makes sure CONFIG_STACKDEPOT > + * is enabled. > */ > +#ifdef CONFIG_STACKDEPOT > int stack_depot_init(void); > > -#ifdef CONFIG_STACKDEPOT_ALWAYS_INIT > -static inline int stack_depot_early_init(void) { return stack_depot_init(); } > +void __init stack_depot_want_early_init(void); > + > +/* This is supposed to be called only from mm_init() */ > +int __init stack_depot_early_init(void); > #else > +static inline int stack_depot_init(void) { return 0; } > + > +static inline void stack_depot_want_early_init(void) { } > + > static inline int stack_depot_early_init(void) { return 0; } > #endif > > diff --git a/lib/stackdepot.c b/lib/stackdepot.c > index bf5ba9af0500..0a5916f1e7a3 100644 > --- a/lib/stackdepot.c > +++ b/lib/stackdepot.c > @@ -66,6 +66,9 @@ struct stack_record { > unsigned long entries[]; /* Variable-sized array of entries. */ > }; > > +static bool __stack_depot_want_early_init __initdata = IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT); > +static bool __stack_depot_early_init_passed __initdata; > + > static void *stack_slabs[STACK_ALLOC_MAX_SLABS]; > > static int depot_index; > @@ -162,38 +165,58 @@ static int __init is_stack_depot_disabled(char *str) > } > early_param("stack_depot_disable", is_stack_depot_disabled); > > -/* > - * __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) > +void __init stack_depot_want_early_init(void) > +{ > + /* Too late to request early init now */ > + WARN_ON(__stack_depot_early_init_passed); > + > + __stack_depot_want_early_init = true; > +} > + > +int __init stack_depot_early_init(void) > +{ > + size_t size; > + int i; > + > + /* This is supposed to be called only once, from mm_init() */ > + if (WARN_ON(__stack_depot_early_init_passed)) > + return 0; > + > + __stack_depot_early_init_passed = true; > + > + if (!__stack_depot_want_early_init || stack_depot_disable) > + return 0; > + > + pr_info("Stack Depot early init allocating hash table with memblock_alloc\n"); > + size = (STACK_HASH_SIZE * sizeof(struct stack_record *)); > + stack_table = memblock_alloc(size, SMP_CACHE_BYTES); > + > + if (!stack_table) { > + pr_err("Stack Depot hash table allocation failed, disabling\n"); > + stack_depot_disable = true; > + return -ENOMEM; > + } > + > + return 0; > +} > + > +int stack_depot_init(void) > { > static DEFINE_MUTEX(stack_depot_init_mutex); > + int ret = 0; > > mutex_lock(&stack_depot_init_mutex); > if (!stack_depot_disable && !stack_table) { > - size_t size = (STACK_HASH_SIZE * sizeof(struct stack_record *)); > - int i; > - > - 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_info("Stack Depot allocating hash table with kvcalloc\n"); > + stack_table = kvcalloc(STACK_HASH_SIZE, sizeof(struct stack_record *), GFP_KERNEL); > + if (!stack_table) { > pr_err("Stack Depot hash table allocation failed, disabling\n"); > stack_depot_disable = true; > - mutex_unlock(&stack_depot_init_mutex); > - return -ENOMEM; > + ret = -ENOMEM; > } > } > mutex_unlock(&stack_depot_init_mutex); > - return 0; > + return ret; > } > EXPORT_SYMBOL_GPL(stack_depot_init); > > diff --git a/mm/page_owner.c b/mm/page_owner.c > index 99e360df9465..4313f8212a83 100644 > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -42,7 +42,12 @@ static void init_early_allocated_pages(void); > > static int __init early_page_owner_param(char *buf) > { > - return kstrtobool(buf, &page_owner_enabled); > + int ret = kstrtobool(buf, &page_owner_enabled); > + > + if (page_owner_enabled) > + stack_depot_want_early_init(); > + > + return ret; > } > early_param("page_owner", early_page_owner_param); > > @@ -80,8 +85,6 @@ static __init void init_page_owner(void) > if (!page_owner_enabled) > return; > > - stack_depot_init(); > - > register_dummy_stack(); > register_failure_stack(); > register_early_stack(); > -- > 2.35.1 > >
