From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1522230595; cv=none; d=google.com; s=arc-20160816; b=hQ0i9RCk83r96ALbWMXk9jy+z4IcbQaa6n6ky0iqvCjBq1OWdyQCk5axHLHPVexsao 4ZThV/fpuGm8bxMMH0PgpHMzEvnByEJ69Dputu6+oy8oEhfV1HxqKYLsRf1uUUcusnDs xwV0WxTjCCPgLZSChWVkwaXGBde/G+pZNntyhWc+BtQBQMayFuEvJfSaIjpUgd9HaT5i SI2rfK+aqhj0ct3XF70oOHW1ZEImI5dIqAVvDJBYoC7cOeJtf/0jVjnSztEY7ytSdEDy 0TRqkXBpQKfEecNqrTHH0X5LBqhwB0cKJo0hAaqnfpRp3SqM14YdAioKTrB+edl9yCrv flmA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:in-reply-to:mime-version:user-agent:date :message-id:from:references:cc:to:subject:dkim-signature :arc-authentication-results; bh=j7Y3xcQgvmc9G654bkP/H+kwAvFLH4w8H3Lc9BK/PX0=; b=bL2Q8rB+IXzRcaRjp9OZlEL4HuJx/kA2oCZUkm8UEDU3e6m526F09z6WZ9cY7bPoww mTxoENMvOAVE5VEYlBGS+7APrI82M5f1PeawAqTUpjY6WxWCE/iFyapvPAgkH3S+XWvG 7VpqigVD24tiS0CoUhOvQewlvu8bSbLjM5ZOmca8qFRqsoG0ZUGxR5/JMhs2LKazaJkZ Z8jcj9niXwaRPumH7/GG3q+sDQ4uFAYXQFsb+REzOlEpv9i9y5zj0ij6j9X/aC1GTefy 85j4BqBRa28EEc6aRQUPdZidNTiWPzjbHMdwF+iie1VAKMnX3mRb2pnwALklFwhzqcg4 EZ0g== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Y9oKlhAg; spf=pass (google.com: domain of hejianet@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=hejianet@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Y9oKlhAg; spf=pass (google.com: domain of hejianet@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=hejianet@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com X-Google-Smtp-Source: AIpwx48fQS7lGWQZgWXyiydpjuc+LPGxHV5vg5iQGWfLPnmLROmrONyyNztG3XmGLMGSy1oylnNf+A== Subject: Re: [PATCH v3 1/5] mm: page_alloc: remain memblock_next_valid_pfn() when CONFIG_HAVE_ARCH_PFN_VALID is enable To: Wei Yang Cc: Andrew Morton , Michal Hocko , Catalin Marinas , Mel Gorman , Will Deacon , Mark Rutland , Ard Biesheuvel , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Pavel Tatashin , Daniel Jordan , AKASHI Takahiro , Gioh Kim , Steven Sistare , Daniel Vacek , Eugeniu Rosca , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org, James Morse , Steve Capper , x86@kernel.org, Greg Kroah-Hartman , Kate Stewart , Philippe Ombredanne , Johannes Weiner , Kemi Wang , Petr Tesarik , YASUAKI ISHIMATSU , Andrey Ryabinin , Nikolay Borisov , Jia He References: <1522033340-6575-1-git-send-email-hejianet@gmail.com> <1522033340-6575-2-git-send-email-hejianet@gmail.com> <20180328091800.GB97260@WeideMacBook-Pro.local> From: Jia He Message-ID: Date: Wed, 28 Mar 2018 17:49:23 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180328091800.GB97260@WeideMacBook-Pro.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1595967673442117233?= X-GMAIL-MSGID: =?utf-8?q?1596174468531527249?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 3/28/2018 5:18 PM, Wei Yang Wrote: > Oops, I should reply this thread. Forget about the reply on another thread. > > On Sun, Mar 25, 2018 at 08:02:15PM -0700, Jia He wrote: >> Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns >> where possible") optimized the loop in memmap_init_zone(). But it causes >> possible panic bug. So Daniel Vacek reverted it later. >> > Why this has a bug? Do you have some link about it? > > If the audience could know the potential risk, it would be helpful to review > the code and decide whether to take it back. Hi Wei Paul firstly submit a commit b92df1de5 to improve the loop in memmap_init_zone. And Daniel tried to fix a bug_on panic issue on X86 in commit 864b75f9d6b because there is evidence that this bug_on was caused by b92df1de5 [1]. But things didn't get better, 864b75f9d6b caused booting hang issue on arm{64} [2] So maintainer decided to reverted both b92df1de5 and 864b75f9d6b [1] https://patchwork.kernel.org/patch/10251145/ [2] https://lkml.org/lkml/2018/3/14/469 > >> But memblock_next_valid_pfn is valid when CONFIG_HAVE_ARCH_PFN_VALID is >> enable. And as verified by Eugeniu Rosca, arm can benifit from this >> commit. So remain the memblock_next_valid_pfn. >> >> Signed-off-by: Jia He >> --- >> include/linux/memblock.h | 4 ++++ >> mm/memblock.c | 29 +++++++++++++++++++++++++++++ >> mm/page_alloc.c | 11 ++++++++++- >> 3 files changed, 43 insertions(+), 1 deletion(-) >> >> diff --git a/include/linux/memblock.h b/include/linux/memblock.h >> index 0257aee..efbbe4b 100644 >> --- a/include/linux/memblock.h >> +++ b/include/linux/memblock.h >> @@ -203,6 +203,10 @@ void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn, >> i >= 0; __next_mem_pfn_range(&i, nid, p_start, p_end, p_nid)) >> #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */ >> >> +#ifdef CONFIG_HAVE_ARCH_PFN_VALID >> +unsigned long memblock_next_valid_pfn(unsigned long pfn); >> +#endif >> + >> /** >> * for_each_free_mem_range - iterate through free memblock areas >> * @i: u64 used as loop variable >> diff --git a/mm/memblock.c b/mm/memblock.c >> index ba7c878..bea5a9c 100644 >> --- a/mm/memblock.c >> +++ b/mm/memblock.c >> @@ -1102,6 +1102,35 @@ void __init_memblock __next_mem_pfn_range(int *idx, int nid, >> *out_nid = r->nid; >> } >> >> +#ifdef CONFIG_HAVE_ARCH_PFN_VALID >> +unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn) >> +{ >> + struct memblock_type *type = &memblock.memory; >> + unsigned int right = type->cnt; >> + unsigned int mid, left = 0; >> + phys_addr_t addr = PFN_PHYS(++pfn); >> + >> + do { >> + mid = (right + left) / 2; >> + >> + if (addr < type->regions[mid].base) >> + right = mid; >> + else if (addr >= (type->regions[mid].base + >> + type->regions[mid].size)) >> + left = mid + 1; >> + else { >> + /* addr is within the region, so pfn is valid */ >> + return pfn; >> + } >> + } while (left < right); >> + >> + if (right == type->cnt) >> + return -1UL; >> + else >> + return PHYS_PFN(type->regions[right].base); >> +} >> +#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/ >> + >> /** >> * memblock_set_node - set node ID on memblock regions >> * @base: base of area to set node ID for >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index c19f5ac..2a967f7 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -5483,8 +5483,17 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, >> if (context != MEMMAP_EARLY) >> goto not_early; >> >> - if (!early_pfn_valid(pfn)) >> + if (!early_pfn_valid(pfn)) { >> +#if (defined CONFIG_HAVE_MEMBLOCK) && (defined CONFIG_HAVE_ARCH_PFN_VALID) > In commit b92df1de5d28, it use CONFIG_HAVE_MEMBLOCK_NODE_MAP. > > Not get the point of your change. Please get more information about the reason why using CONFIG_HAVE_MEMBLOCK in d49d47e mm: page_alloc: skip over regions of invalid pfns on UMA And this commit is dependent on b92df1de, so it is also reverted. Cheers, Jia > >> + /* >> + * Skip to the pfn preceding the next valid one (or >> + * end_pfn), such that we hit a valid pfn (or end_pfn) >> + * on our next iteration of the loop. >> + */ >> + pfn = memblock_next_valid_pfn(pfn) - 1; >> +#endif >> continue; >> + } >> if (!early_pfn_in_nid(pfn, nid)) >> continue; >> if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised)) >> -- >> 2.7.4 -- Cheers, Jia