From 7e28eda20a24b3475f37627189d984fd33ccefb4 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sat, 17 Jul 2021 13:27:00 -0700 Subject: [PATCH] Revert "mm/slub: use stackdepot to save stack trace in objects" This reverts commit 23cf722e8ecc506b49fe559533811c04ff7c93df. It's not clear why, but it causes unexplained problems in entirely unrelated xfs code. The most likely explanation is some slab corruption, possibly triggered due to CONFIG_SLUB_DEBUG_ON. See [1]. It ends up having a few other problems too, like build errors on arch/arc, and Geert reporting it using much more memory on m68k [3] (it probably does so elsewhere too, but it is probably just more noticeable on m68k). The architecture issues (both build and memory use) are likely just because this change effectively force-enabled STACKDEPOT (along with a very bad default value for the stackdepot hash size). But together with the xfs issue, this all smells like "this commit was not ready" to me. Link: https://lore.kernel.org/linux-xfs/YPE3l82acwgI2OiV@infradead.org/ [1] Link: https://lore.kernel.org/lkml/202107150600.LkGNb4Vb-lkp@intel.com/ [2] Link: https://lore.kernel.org/lkml/CAMuHMdW=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/ [3] Reported-by: Christoph Hellwig Reported-by: kernel test robot Reported-by: Geert Uytterhoeven Cc: Andrew Morton Cc: Vlastimil Babka Cc: Randy Dunlap Signed-off-by: Linus Torvalds --- init/Kconfig | 1 - mm/slub.c | 79 ++++++++++++++++++++-------------------------------- 2 files changed, 30 insertions(+), 50 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index bb0d6e6262b15..55f9f7738ebb4 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1847,7 +1847,6 @@ config SLUB_DEBUG default y bool "Enable SLUB debugging support" if EXPERT depends on SLUB && SYSFS - select STACKDEPOT if STACKTRACE_SUPPORT help SLUB has extensive debug support features. Disabling these can result in significant savings in code size. This also disables diff --git a/mm/slub.c b/mm/slub.c index e1644ac6ee7bf..090fa14628f92 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -26,7 +26,6 @@ #include #include #include -#include #include #include #include @@ -207,8 +206,8 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s) #define TRACK_ADDRS_COUNT 16 struct track { unsigned long addr; /* Called from address */ -#ifdef CONFIG_STACKDEPOT - depot_stack_handle_t handle; +#ifdef CONFIG_STACKTRACE + unsigned long addrs[TRACK_ADDRS_COUNT]; /* Called from address */ #endif int cpu; /* Was running on cpu */ int pid; /* Pid context */ @@ -612,27 +611,22 @@ static struct track *get_track(struct kmem_cache *s, void *object, return kasan_reset_tag(p + alloc); } -#ifdef CONFIG_STACKDEPOT -static depot_stack_handle_t save_stack_depot_trace(gfp_t flags) -{ - unsigned long entries[TRACK_ADDRS_COUNT]; - depot_stack_handle_t handle; - unsigned int nr_entries; - - nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 4); - handle = stack_depot_save(entries, nr_entries, flags); - return handle; -} -#endif - static void set_track(struct kmem_cache *s, void *object, enum track_item alloc, unsigned long addr) { struct track *p = get_track(s, object, alloc); if (addr) { -#ifdef CONFIG_STACKDEPOT - p->handle = save_stack_depot_trace(GFP_NOWAIT); +#ifdef CONFIG_STACKTRACE + unsigned int nr_entries; + + metadata_access_enable(); + nr_entries = stack_trace_save(kasan_reset_tag(p->addrs), + TRACK_ADDRS_COUNT, 3); + metadata_access_disable(); + + if (nr_entries < TRACK_ADDRS_COUNT) + p->addrs[nr_entries] = 0; #endif p->addr = addr; p->cpu = smp_processor_id(); @@ -659,19 +653,14 @@ static void print_track(const char *s, struct track *t, unsigned long pr_time) pr_err("%s in %pS age=%lu cpu=%u pid=%d\n", s, (void *)t->addr, pr_time - t->when, t->cpu, t->pid); -#ifdef CONFIG_STACKDEPOT +#ifdef CONFIG_STACKTRACE { - depot_stack_handle_t handle; - unsigned long *entries; - unsigned int nr_entries; - - handle = READ_ONCE(t->handle); - if (!handle) { - pr_err("object allocation/free stack trace missing\n"); - } else { - nr_entries = stack_depot_fetch(handle, &entries); - stack_trace_print(entries, nr_entries, 0); - } + int i; + for (i = 0; i < TRACK_ADDRS_COUNT; i++) + if (t->addrs[i]) + pr_err("\t%pS\n", (void *)t->addrs[i]); + else + break; } #endif } @@ -4045,26 +4034,18 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page) objp = fixup_red_left(s, objp); trackp = get_track(s, objp, TRACK_ALLOC); kpp->kp_ret = (void *)trackp->addr; -#ifdef CONFIG_STACKDEPOT - { - depot_stack_handle_t handle; - unsigned long *entries; - unsigned int nr_entries; - - handle = READ_ONCE(trackp->handle); - if (handle) { - nr_entries = stack_depot_fetch(handle, &entries); - for (i = 0; i < KS_ADDRS_COUNT && i < nr_entries; i++) - kpp->kp_stack[i] = (void *)entries[i]; - } +#ifdef CONFIG_STACKTRACE + for (i = 0; i < KS_ADDRS_COUNT && i < TRACK_ADDRS_COUNT; i++) { + kpp->kp_stack[i] = (void *)trackp->addrs[i]; + if (!kpp->kp_stack[i]) + break; + } - trackp = get_track(s, objp, TRACK_FREE); - handle = READ_ONCE(trackp->handle); - if (handle) { - nr_entries = stack_depot_fetch(handle, &entries); - for (i = 0; i < KS_ADDRS_COUNT && i < nr_entries; i++) - kpp->kp_free_stack[i] = (void *)entries[i]; - } + trackp = get_track(s, objp, TRACK_FREE); + for (i = 0; i < KS_ADDRS_COUNT && i < TRACK_ADDRS_COUNT; i++) { + kpp->kp_free_stack[i] = (void *)trackp->addrs[i]; + if (!kpp->kp_free_stack[i]) + break; } #endif #endif -- 2.39.5