From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id 56E0D6B0005 for ; Wed, 2 May 2018 11:27:36 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id k3so13122655pff.23 for ; Wed, 02 May 2018 08:27:36 -0700 (PDT) Received: from bombadil.infradead.org (bombadil.infradead.org. [2607:7c80:54:e::133]) by mx.google.com with ESMTPS id z6si11710753pfk.194.2018.05.02.08.27.34 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 02 May 2018 08:27:34 -0700 (PDT) Date: Wed, 2 May 2018 08:27:33 -0700 From: Matthew Wilcox Subject: [RFC] Distinguish vmalloc pages Message-ID: <20180502152733.GB2737@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: Igor Stoppa For diagnosing various performance and memory-leak problems, it is helpful to be able to distinguish pages which are in use as VMalloc pages. Unfortunately, we cannot use the page_type field in struct page, as this is in use for mapcount by some drivers which map vmalloced pages to userspace. Use a special page->mapping value to distinguish VMalloc pages from other kinds of pages. Also record a pointer to the vm_struct and the offset within the area in struct page to help reconstruct exactly what this page is being used for. Signed-off-by: Matthew Wilcox --- This patch would be a superset of Igor's patch to add an ->area field to struct page. It's on top of my recent series to rearrange struct page. I think it's a nice demonstration of how you don't have to go hunting around for fields that may or may not be in use; you just add your own little struct to the union, and you're done. As well as being *really* useful for debugging, of course! fs/proc/page.c | 2 ++ include/linux/mm_types.h | 5 +++++ include/linux/page-flags.h | 25 +++++++++++++++++++++++++ include/uapi/linux/kernel-page-flags.h | 1 + mm/vmalloc.c | 5 ++++- tools/vm/page-types.c | 1 + 6 files changed, 38 insertions(+), 1 deletion(-) diff --git a/fs/proc/page.c b/fs/proc/page.c index 792c78a49174..fc83dae1af7b 100644 --- a/fs/proc/page.c +++ b/fs/proc/page.c @@ -156,6 +156,8 @@ u64 stable_page_flags(struct page *page) u |= 1 << KPF_BALLOON; if (PageTable(page)) u |= 1 << KPF_PGTABLE; + if (PageVMalloc(page)) + u |= 1 << KPF_VMALLOC; if (page_is_idle(page)) u |= 1 << KPF_IDLE; diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 42619e16047f..c51ddd27bfb4 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -141,6 +141,11 @@ struct page { spinlock_t ptl; #endif }; + struct { /* VMalloc pages */ + struct vm_struct *vm_area; + unsigned long vm_offset; + unsigned long _vm_id; /* MAPPING_VMalloc */ + }; /** @rcu_head: You can use this to free a page by RCU. */ struct rcu_head rcu_head; diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 901943e4754b..5232433175c1 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -699,6 +699,31 @@ PAGE_TYPE_OPS(Kmemcg, kmemcg) */ PAGE_TYPE_OPS(Table, table) +/* + * vmalloc pages may be mapped to userspace, so we need some other way + * to distinguish them from other kinds of pages. Use page->mapping + * for this purpose. Values below 0x1000 cannot be real pointers. + */ +#define MAPPING_VMalloc (void *)0x440 + +#define PAGE_MAPPING_OPS(name) \ +static __always_inline int Page##name(struct page *page) \ +{ \ + return page->mapping == MAPPING_##name; \ +} \ +static __always_inline void __SetPage##name(struct page *page) \ +{ \ + VM_BUG_ON_PAGE(page->mapping != NULL, page); \ + page->mapping = MAPPING_##name; \ +} \ +static __always_inline void __ClearPage##name(struct page *page) \ +{ \ + VM_BUG_ON_PAGE(page->mapping != MAPPING_##name, page); \ + page->mapping = NULL; \ +} + +PAGE_MAPPING_OPS(VMalloc) + extern bool is_free_buddy_page(struct page *page); __PAGEFLAG(Isolated, isolated, PF_ANY); diff --git a/include/uapi/linux/kernel-page-flags.h b/include/uapi/linux/kernel-page-flags.h index 21b9113c69da..6800968b8f47 100644 --- a/include/uapi/linux/kernel-page-flags.h +++ b/include/uapi/linux/kernel-page-flags.h @@ -36,5 +36,6 @@ #define KPF_ZERO_PAGE 24 #define KPF_IDLE 25 #define KPF_PGTABLE 26 +#define KPF_VMALLOC 27 #endif /* _UAPILINUX_KERNEL_PAGE_FLAGS_H */ diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 5fbf27e7f956..98bc690d472d 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1535,7 +1535,7 @@ static void __vunmap(const void *addr, int deallocate_pages) for (i = 0; i < area->nr_pages; i++) { struct page *page = area->pages[i]; - BUG_ON(!page); + __ClearPageVMalloc(page); __free_pages(page, 0); } @@ -1704,6 +1704,9 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, area->nr_pages = i; goto fail; } + __SetPageVMalloc(page); + page->vm_area = area; + page->vm_offset = i; area->pages[i] = page; if (gfpflags_allow_blocking(gfp_mask)) cond_resched(); diff --git a/tools/vm/page-types.c b/tools/vm/page-types.c index cce853dca691..25cc21855be4 100644 --- a/tools/vm/page-types.c +++ b/tools/vm/page-types.c @@ -132,6 +132,7 @@ static const char * const page_flag_names[] = { [KPF_THP] = "t:thp", [KPF_BALLOON] = "o:balloon", [KPF_PGTABLE] = "g:pgtable", + [KPF_VMALLOC] = "V:vmalloc", [KPF_ZERO_PAGE] = "z:zero_page", [KPF_IDLE] = "i:idle_page", -- 2.17.0