From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68B46C33CAF for ; Tue, 21 Jan 2020 05:19:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 253B322314 for ; Tue, 21 Jan 2020 05:19:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 253B322314 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AB1C46B0003; Tue, 21 Jan 2020 00:19:22 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A63BC6B0005; Tue, 21 Jan 2020 00:19:22 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 953E86B0006; Tue, 21 Jan 2020 00:19:22 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0071.hostedemail.com [216.40.44.71]) by kanga.kvack.org (Postfix) with ESMTP id 7CF946B0003 for ; Tue, 21 Jan 2020 00:19:22 -0500 (EST) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 34C76180AD806 for ; Tue, 21 Jan 2020 05:19:22 +0000 (UTC) X-FDA: 76400488164.25.tail35_8be520afb6f06 X-HE-Tag: tail35_8be520afb6f06 X-Filterd-Recvd-Size: 6454 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf03.hostedemail.com (Postfix) with ESMTP for ; Tue, 21 Jan 2020 05:19:21 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5143F31B; Mon, 20 Jan 2020 21:19:20 -0800 (PST) Received: from [10.162.16.78] (p8cg001049571a15.blr.arm.com [10.162.16.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E03213F52E; Mon, 20 Jan 2020 21:19:18 -0800 (PST) Subject: Re: [Patch v2 1/4] mm: enable dump several reasons for __dump_page() To: Wei Yang Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, rientjes@google.com References: <20200120030415.15925-1-richardw.yang@linux.intel.com> <20200120030415.15925-2-richardw.yang@linux.intel.com> <8426f31b-606e-deca-acbe-dd59b193e113@arm.com> <20200120085530.GB18028@richard> From: Anshuman Khandual Message-ID: <1c2e1cd6-5b65-79d7-f332-b866d5446c71@arm.com> Date: Tue, 21 Jan 2020 10:50:41 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200120085530.GB18028@richard> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 01/20/2020 02:25 PM, Wei Yang wrote: > On Mon, Jan 20, 2020 at 11:42:30AM +0530, Anshuman Khandual wrote: >> >> >> On 01/20/2020 08:34 AM, Wei Yang wrote: >>> This is a preparation to dump all reasons during check page. >> >> This really makes sense rather then just picking the reason from >> the last "if" statement. >> >>> >>> Signed-off-by: Wei Yang >>> --- >>> include/linux/mmdebug.h | 2 +- >>> mm/debug.c | 11 ++++++----- >>> mm/page_alloc.c | 2 +- >>> 3 files changed, 8 insertions(+), 7 deletions(-) >>> >>> diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h >>> index 2ad72d2c8cc5..f0a612db8bae 100644 >>> --- a/include/linux/mmdebug.h >>> +++ b/include/linux/mmdebug.h >>> @@ -10,7 +10,7 @@ struct vm_area_struct; >>> struct mm_struct; >>> >>> extern void dump_page(struct page *page, const char *reason); >>> -extern void __dump_page(struct page *page, const char *reason); >>> +extern void __dump_page(struct page *page, int num, const char **reason); >>> void dump_vma(const struct vm_area_struct *vma); >>> void dump_mm(const struct mm_struct *mm); >>> >>> diff --git a/mm/debug.c b/mm/debug.c >>> index 0461df1207cb..a8ac6f951f9f 100644 >>> --- a/mm/debug.c >>> +++ b/mm/debug.c >>> @@ -42,11 +42,11 @@ const struct trace_print_flags vmaflag_names[] = { >>> {0, NULL} >>> }; >>> >>> -void __dump_page(struct page *page, const char *reason) >>> +void __dump_page(struct page *page, int num, const char **reason) >>> { >>> struct address_space *mapping; >>> bool page_poisoned = PagePoisoned(page); >>> - int mapcount; >>> + int mapcount, i; >>> >>> /* >>> * If struct page is poisoned don't access Page*() functions as that >>> @@ -97,8 +97,9 @@ void __dump_page(struct page *page, const char *reason) >>> sizeof(unsigned long), page, >>> sizeof(struct page), false); >>> >>> - if (reason) >>> - pr_warn("page dumped because: %s\n", reason); >>> + pr_warn("page dumped because:\n"); >>> + for (i = 0; i < num; i++) >>> + pr_warn("\t%s\n", reason[i]); >> >> We should have a NR_BAD_PAGE_REASONS or something to cap this iteration >> and also check reason[i] for non-NULL before trying to print the array. >> There might be call sites like the following which will be problematic >> otherwise. >> >> split_huge_page_to_list() -> dump_page(head, NULL) >> > > You are right, I missed this case. > >>> >>> #ifdef CONFIG_MEMCG >>> if (!page_poisoned && page->mem_cgroup) >> >> While here, will it be better to move the above debug print block after >> mem_cgroup block instead ? >> > > Not sure, let's see whether others have some idea. > >>> @@ -108,7 +109,7 @@ void __dump_page(struct page *page, const char *reason) >>> >>> void dump_page(struct page *page, const char *reason) >>> { >>> - __dump_page(page, reason); >>> + __dump_page(page, 1, &reason); >>> dump_page_owner(page); >>> } >>> EXPORT_SYMBOL(dump_page); >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index d047bf7d8fd4..0cf6218aaba7 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -638,7 +638,7 @@ static void bad_page(struct page *page, const char *reason, >>> >>> pr_alert("BUG: Bad page state in process %s pfn:%05lx\n", >>> current->comm, page_to_pfn(page)); >>> - __dump_page(page, reason); >>> + __dump_page(page, 1, &reason); >>> bad_flags &= page->flags; >>> if (bad_flags) >>> pr_alert("bad because of flags: %#lx(%pGp)\n", >>> >> >> Do we still need to have bad_flags ? After consolidating all reasons making >> a page bad should not we just print page->flags unconditionally each time and >> let the user decipher it instead. __dump_page() will print page->flags for >> each case (atleast after the new patch from Vlastimil). AFAICS, the only >> place currently consuming bad_flags is bad_page() which seems redundant after >> first calling __dump_page(). > > Hmm... I don't catch this. The work in __dump_page() seems a little different > from this one. Not sure we could remove it. Lets look at 'bad_flags' as it exists today without this series. It gets evaluated in free_pages_check_bad() and check_new_page_bad() before being passed into bad_page(). All other call sites for bad_page() just pass 0 for 'bad_flags'. Now in bad_page(), we have __dump_page(page, reason); bad_flags &= page->flags; if (bad_flags) pr_alert("bad because of flags: %#lx(%pGp)\n", bad_flags, &bad_flags); Here, bad_flags &= page->flags will always be positive when 'reason' is either "PAGE_FLAGS_CHECK_AT_FREE flag(s) set" or "PAGE_FLAGS_CHECK_AT_PREP flag set" The point here is we dont need to print bad_flags here as __dump_page() already prints page->flags universally along with the "bad_reason" after the following change. [1] https://patchwork.kernel.org/patch/11332035/