diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index d3814789304f..8a54ed862049 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -809,6 +809,8 @@ enables the feature at boot time. By default, it is disabled and the system will work mostly the same as a kernel built without CONFIG_DEBUG_PAGEALLOC. + Note: to get most of debug_pagealloc error reports, it's + useful to also enable the page_owner functionality. on: enable the feature debugpat [X86] Enable PAT debugging diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug index 82b6a20898bd..327b3ebf23bf 100644 --- a/mm/Kconfig.debug +++ b/mm/Kconfig.debug @@ -21,7 +21,9 @@ config DEBUG_PAGEALLOC Also, the state of page tracking structures is checked more often as pages are being allocated and freed, as unexpected state changes often happen for same reasons as memory corruption (e.g. double free, - use-after-free). + use-after-free). The error reports for these checks can be augmented + with stack traces of last allocation and freeing of the page, when + PAGE_OWNER is also selected and enabled on boot. For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC, fill the pages with poison patterns after free_pages() and verify diff --git a/mm/page_owner.c b/mm/page_owner.c index 4a48e018dbdf..dee931184788 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -24,6 +24,9 @@ struct page_owner { short last_migrate_reason; gfp_t gfp_mask; depot_stack_handle_t handle; +#ifdef CONFIG_DEBUG_PAGEALLOC + depot_stack_handle_t free_handle; +#endif }; static bool page_owner_disabled = true; @@ -102,19 +105,6 @@ static inline struct page_owner *get_page_owner(struct page_ext *page_ext) return (void *)page_ext + page_owner_ops.offset; } -void __reset_page_owner(struct page *page, unsigned int order) -{ - int i; - struct page_ext *page_ext; - - for (i = 0; i < (1 << order); i++) { - page_ext = lookup_page_ext(page + i); - if (unlikely(!page_ext)) - continue; - __clear_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags); - } -} - static inline bool check_recursive_alloc(unsigned long *entries, unsigned int nr_entries, unsigned long ip) @@ -154,6 +144,32 @@ static noinline depot_stack_handle_t save_stack(gfp_t flags) return handle; } +void __reset_page_owner(struct page *page, unsigned int order) +{ + int i; + struct page_ext *page_ext; +#ifdef CONFIG_DEBUG_PAGEALLOC + depot_stack_handle_t handle = 0; + struct page_owner *page_owner; + + if (debug_pagealloc_enabled()) + handle = save_stack(GFP_NOWAIT | __GFP_NOWARN); +#endif + + for (i = 0; i < (1 << order); i++) { + page_ext = lookup_page_ext(page + i); + if (unlikely(!page_ext)) + continue; + __clear_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags); +#ifdef CONFIG_DEBUG_PAGEALLOC + if (debug_pagealloc_enabled()) { + page_owner = get_page_owner(page_ext); + page_owner->free_handle = handle; + } +#endif + } +} + static inline void __set_page_owner_handle(struct page *page, struct page_ext *page_ext, depot_stack_handle_t handle, unsigned int order, gfp_t gfp_mask) @@ -435,6 +451,17 @@ void __dump_page_owner(struct page *page) stack_trace_print(entries, nr_entries, 0); } +#ifdef CONFIG_DEBUG_PAGEALLOC + handle = READ_ONCE(page_owner->free_handle); + if (!handle) { + pr_alert("page_owner free stack trace missing\n"); + } else { + nr_entries = stack_depot_fetch(handle, &entries); + pr_alert("page last free stack trace:\n"); + stack_trace_print(entries, nr_entries, 0); + } +#endif + if (page_owner->last_migrate_reason != -1) pr_alert("page has been migrated, last migrate reason: %s\n", migrate_reason_names[page_owner->last_migrate_reason]);