From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f197.google.com (mail-qt0-f197.google.com [209.85.216.197]) by kanga.kvack.org (Postfix) with ESMTP id 959ED6B0003 for ; Thu, 8 Feb 2018 14:29:45 -0500 (EST) Received: by mail-qt0-f197.google.com with SMTP id t31so4532697qtc.12 for ; Thu, 08 Feb 2018 11:29:45 -0800 (PST) Received: from mx1.redhat.com (mx3-rdu2.redhat.com. [66.187.233.73]) by mx.google.com with ESMTPS id z195si599991qkb.293.2018.02.08.11.29.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 08 Feb 2018 11:29:44 -0800 (PST) Date: Thu, 8 Feb 2018 21:29:39 +0200 From: "Michael S. Tsirkin" Subject: Re: [PATCH v28 3/4] mm/page_poison: add a function to expose page poison val to kernel modules Message-ID: <20180208212514-mutt-send-email-mst@kernel.org> References: <1518083420-11108-1-git-send-email-wei.w.wang@intel.com> <1518083420-11108-4-git-send-email-wei.w.wang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1518083420-11108-4-git-send-email-wei.w.wang@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Wei Wang Cc: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, akpm@linux-foundation.org, pbonzini@redhat.com, liliang.opensource@gmail.com, yang.zhang.wz@gmail.com, quan.xu0@gmail.com, nilal@redhat.com, riel@redhat.com, huangzhichao@huawei.com On Thu, Feb 08, 2018 at 05:50:19PM +0800, Wei Wang wrote: > Move the PAGE_POISON value to page_poison.c and add a function to enable > callers from a kernel module to get the poison value if the page poisoning > feature is in use. This also avoids callers directly checking PAGE_POISON > regardless of whether the feature is enabled. > > Signed-off-by: Wei Wang > Cc: Andrew Morton > Cc: Michal Hocko > Cc: Michael S. Tsirkin > --- > include/linux/mm.h | 2 ++ > include/linux/poison.h | 7 ------- > mm/page_poison.c | 24 ++++++++++++++++++++++++ > 3 files changed, 26 insertions(+), 7 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 1c77d88..d95e5d3 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2469,11 +2469,13 @@ extern int apply_to_page_range(struct mm_struct *mm, unsigned long address, > extern bool page_poisoning_enabled(void); > extern void kernel_poison_pages(struct page *page, int numpages, int enable); > extern bool page_is_poisoned(struct page *page); > +extern bool page_poison_val_get(u8 *val); > #else > static inline bool page_poisoning_enabled(void) { return false; } > static inline void kernel_poison_pages(struct page *page, int numpages, > int enable) { } > static inline bool page_is_poisoned(struct page *page) { return false; } > +static inline bool page_poison_val_get(u8 *val) { return false; }; > #endif > > #ifdef CONFIG_DEBUG_PAGEALLOC Thinking more about it, page_poisoning_enabled already exists. I would just add "u8 page_poison_val_get(void)" and don't add a stub since compiler will drop the call with poisoning off. > diff --git a/include/linux/poison.h b/include/linux/poison.h > index 15927eb..348bf67 100644 > --- a/include/linux/poison.h > +++ b/include/linux/poison.h > @@ -30,13 +30,6 @@ > */ > #define TIMER_ENTRY_STATIC ((void *) 0x300 + POISON_POINTER_DELTA) > > -/********** mm/debug-pagealloc.c **********/ > -#ifdef CONFIG_PAGE_POISONING_ZERO > -#define PAGE_POISON 0x00 > -#else > -#define PAGE_POISON 0xaa > -#endif > - > /********** mm/page_alloc.c ************/ > I'd split this chunk out, this patchset is at v28 as it is. > #define TAIL_MAPPING ((void *) 0x400 + POISON_POINTER_DELTA) > diff --git a/mm/page_poison.c b/mm/page_poison.c > index e83fd44..9a07973 100644 > --- a/mm/page_poison.c > +++ b/mm/page_poison.c > @@ -7,6 +7,13 @@ > #include > #include > > +/********** mm/debug-pagealloc.c **********/ This file no longer exists. > +#ifdef CONFIG_PAGE_POISONING_ZERO > +#define PAGE_POISON 0x00 > +#else > +#define PAGE_POISON 0xaa > +#endif > + > static bool want_page_poisoning __read_mostly; > > static int early_page_poison_param(char *buf) > @@ -30,6 +37,23 @@ bool page_poisoning_enabled(void) > debug_pagealloc_enabled())); > } > > +/** > + * page_poison_val_get - get the page poison value if page poisoning is enabled > + * @val: the caller's memory to get the page poison value > + * > + * Return true with @val stores the poison value if page poisoning is enabled. > + * Otherwise, return false with @val unchanged. > + */ > +bool page_poison_val_get(u8 *val) > +{ > + if (!page_poisoning_enabled()) > + return false; > + > + *val = PAGE_POISON; > + return true; > +} > +EXPORT_SYMBOL_GPL(page_poison_val_get); > + > static void poison_page(struct page *page) > { > void *addr = kmap_atomic(page); > -- > 2.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org