From 8151c7a35d8bd8a12e93538ef7963ea209b6ab41 Mon Sep 17 00:00:00 2001 From: Oscar Salvador Date: Thu, 15 Feb 2024 22:59:02 +0100 Subject: lib/stackdepot: move stack_record struct definition into the header In order to move the heavy lifting into page_owner code, this one needs to have access to the stack_record structure, which right now sits in lib/stackdepot.c. Move it to the stackdepot.h header so page_owner can access stack_record's struct fields. Link: https://lkml.kernel.org/r/20240215215907.20121-3-osalvador@suse.de Signed-off-by: Oscar Salvador Reviewed-by: Marco Elver Reviewed-by: Vlastimil Babka Acked-by: Andrey Konovalov Cc: Alexander Potapenko Cc: Michal Hocko Signed-off-by: Andrew Morton --- include/linux/stackdepot.h | 47 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) (limited to 'include/linux/stackdepot.h') diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index adcbb8f23600..c4b5ad57c066 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -30,6 +30,53 @@ typedef u32 depot_stack_handle_t; */ #define STACK_DEPOT_EXTRA_BITS 5 +#define DEPOT_HANDLE_BITS (sizeof(depot_stack_handle_t) * 8) + +#define DEPOT_POOL_ORDER 2 /* Pool size order, 4 pages */ +#define DEPOT_POOL_SIZE (1LL << (PAGE_SHIFT + DEPOT_POOL_ORDER)) +#define DEPOT_STACK_ALIGN 4 +#define DEPOT_OFFSET_BITS (DEPOT_POOL_ORDER + PAGE_SHIFT - DEPOT_STACK_ALIGN) +#define DEPOT_POOL_INDEX_BITS (DEPOT_HANDLE_BITS - DEPOT_OFFSET_BITS - \ + STACK_DEPOT_EXTRA_BITS) + +#ifdef CONFIG_STACKDEPOT +/* Compact structure that stores a reference to a stack. */ +union handle_parts { + depot_stack_handle_t handle; + struct { + /* pool_index is offset by 1 */ + u32 pool_index : DEPOT_POOL_INDEX_BITS; + u32 offset : DEPOT_OFFSET_BITS; + u32 extra : STACK_DEPOT_EXTRA_BITS; + }; +}; + +struct stack_record { + struct list_head hash_list; /* Links in the hash table */ + u32 hash; /* Hash in hash table */ + u32 size; /* Number of stored frames */ + union handle_parts handle; /* Constant after initialization */ + refcount_t count; + union { + unsigned long entries[CONFIG_STACKDEPOT_MAX_FRAMES]; /* Frames */ + struct { + /* + * An important invariant of the implementation is to + * only place a stack record onto the freelist iff its + * refcount is zero. Because stack records with a zero + * refcount are never considered as valid, it is safe to + * union @entries and freelist management state below. + * Conversely, as soon as an entry is off the freelist + * and its refcount becomes non-zero, the below must not + * be accessed until being placed back on the freelist. + */ + struct list_head free_list; /* Links in the freelist */ + unsigned long rcu_state; /* RCU cookie */ + }; + }; +}; +#endif + typedef u32 depot_flags_t; /* -- cgit v1.2.3 From 4bedfb314bdd85c1662ecc46fa25b33b998f994d Mon Sep 17 00:00:00 2001 From: Oscar Salvador Date: Thu, 15 Feb 2024 22:59:03 +0100 Subject: mm,page_owner: maintain own list of stack_records structs page_owner needs to increment a stack_record refcount when a new allocation occurs, and decrement it on a free operation. In order to do that, we need to have a way to get a stack_record from a handle. Implement __stack_depot_get_stack_record() which just does that, and make it public so page_owner can use it. Also, traversing all stackdepot buckets comes with its own complexity, plus we would have to implement a way to mark only those stack_records that were originated from page_owner, as those are the ones we are interested in. For that reason, page_owner maintains its own list of stack_records, because traversing that list is faster than traversing all buckets while keeping at the same time a low complexity. For now, add to stack_list only the stack_records of dummy_handle and failure_handle, and set their refcount of 1. Further patches will add code to increment or decrement stack_records count on allocation and free operation. Link: https://lkml.kernel.org/r/20240215215907.20121-4-osalvador@suse.de Signed-off-by: Oscar Salvador Reviewed-by: Vlastimil Babka Reviewed-by: Marco Elver Acked-by: Andrey Konovalov Cc: Alexander Potapenko Cc: Michal Hocko Signed-off-by: Andrew Morton --- include/linux/stackdepot.h | 11 +++++++++++ lib/stackdepot.c | 8 ++++++++ mm/page_owner.c | 15 +++++++++++++++ 3 files changed, 34 insertions(+) (limited to 'include/linux/stackdepot.h') diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index c4b5ad57c066..3c6caa5abc7c 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -178,6 +178,17 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries, depot_stack_handle_t stack_depot_save(unsigned long *entries, unsigned int nr_entries, gfp_t gfp_flags); +/** + * __stack_depot_get_stack_record - Get a pointer to a stack_record struct + * + * @handle: Stack depot handle + * + * This function is only for internal purposes. + * + * Return: Returns a pointer to a stack_record struct + */ +struct stack_record *__stack_depot_get_stack_record(depot_stack_handle_t handle); + /** * stack_depot_fetch - Fetch a stack trace from stack depot * diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 514b8d40ff57..8c795bb20afb 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -687,6 +687,14 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries, } EXPORT_SYMBOL_GPL(stack_depot_save); +struct stack_record *__stack_depot_get_stack_record(depot_stack_handle_t handle) +{ + if (!handle) + return NULL; + + return depot_fetch_stack(handle); +} + unsigned int stack_depot_fetch(depot_stack_handle_t handle, unsigned long **entries) { diff --git a/mm/page_owner.c b/mm/page_owner.c index 5634e5d890f8..33e342b15d9b 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -36,6 +36,14 @@ struct page_owner { pid_t free_tgid; }; +struct stack { + struct stack_record *stack_record; + struct stack *next; +}; +static struct stack dummy_stack; +static struct stack failure_stack; +static struct stack *stack_list; + static bool page_owner_enabled __initdata; DEFINE_STATIC_KEY_FALSE(page_owner_inited); @@ -95,6 +103,13 @@ static __init void init_page_owner(void) register_early_stack(); static_branch_enable(&page_owner_inited); init_early_allocated_pages(); + /* Initialize dummy and failure stacks and link them to stack_list */ + dummy_stack.stack_record = __stack_depot_get_stack_record(dummy_handle); + failure_stack.stack_record = __stack_depot_get_stack_record(failure_handle); + refcount_set(&dummy_stack.stack_record->count, 1); + refcount_set(&failure_stack.stack_record->count, 1); + dummy_stack.next = &failure_stack; + stack_list = &dummy_stack; } struct page_ext_operations page_owner_ops = { -- cgit v1.2.3