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[192.55.52.88]) by mx.google.com with ESMTPS id y4si30092103pfq.222.2019.07.30.15.21.50 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 30 Jul 2019 15:21:51 -0700 (PDT) Received-SPF: pass (google.com: domain of sai.praneeth.prakhya@intel.com designates 192.55.52.88 as permitted sender) client-ip=192.55.52.88; Authentication-Results: mx.google.com; spf=pass (google.com: domain of sai.praneeth.prakhya@intel.com designates 192.55.52.88 as permitted sender) smtp.mailfrom=sai.praneeth.prakhya@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Jul 2019 15:21:50 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,327,1559545200"; d="scan'208";a="347277138" Received: from sai-dev-mach.sc.intel.com ([143.183.140.153]) by orsmga005.jf.intel.com with ESMTP; 30 Jul 2019 15:21:49 -0700 From: Sai Praneeth Prakhya To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: dave.hansen@intel.com, Sai Praneeth Prakhya , Ingo Molnar , Peter Zijlstra , Andrew Morton Subject: [PATCH] fork: Improve error message for corrupted page tables Date: Tue, 30 Jul 2019 15:18:20 -0700 Message-Id: <20190730221820.7738-1-sai.praneeth.prakhya@intel.com> X-Mailer: git-send-email 2.19.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: When a user process exits, the kernel cleans up the mm_struct of the user process and during cleanup, check_mm() checks the page tables of the user process for corruption (E.g: unexpected page flags set/cleared). For corrupted page tables, the error message printed by check_mm() isn't very clear as it prints the loop index instead of page table type (E.g: Resident file mapping pages vs Resident shared memory pages). Hence, improve the error message so that it's more informative. Without patch: -------------- [ 204.836425] mm/pgtable-generic.c:29: bad p4d 0000000089eb4e92(800000025f941467) [ 204.836544] BUG: Bad rss-counter state mm:00000000f75895ea idx:0 val:2 [ 204.836615] BUG: Bad rss-counter state mm:00000000f75895ea idx:1 val:5 [ 204.836685] BUG: non-zero pgtables_bytes on freeing mm: 20480 With patch: ----------- [ 69.815453] mm/pgtable-generic.c:29: bad p4d 0000000084653642(800000025ca37467) [ 69.815872] BUG: Bad rss-counter state mm:00000000014a6c03 type:MM_FILEPAGES val:2 [ 69.815962] BUG: Bad rss-counter state mm:00000000014a6c03 type:MM_ANONPAGES val:5 [ 69.816050] BUG: non-zero pgtables_bytes on freeing mm: 20480 Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Andrew Morton Suggested-by/Acked-by: Dave Hansen Signed-off-by: Sai Praneeth Prakhya --- include/linux/mm_types_task.h | 7 +++++++ kernel/fork.c | 4 ++-- 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/include/linux/mm_types_task.h b/include/linux/mm_types_task.h index d7016dcb245e..881f4ea3a1b5 100644 --- a/include/linux/mm_types_task.h +++ b/include/linux/mm_types_task.h @@ -44,6 +44,13 @@ enum { NR_MM_COUNTERS }; +static const char * const resident_page_types[NR_MM_COUNTERS] = { + "MM_FILEPAGES", + "MM_ANONPAGES", + "MM_SWAPENTS", + "MM_SHMEMPAGES", +}; + #if USE_SPLIT_PTE_PTLOCKS && defined(CONFIG_MMU) #define SPLIT_RSS_COUNTING /* per-thread cached information, */ diff --git a/kernel/fork.c b/kernel/fork.c index 2852d0e76ea3..6aef5842d4e0 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -649,8 +649,8 @@ static void check_mm(struct mm_struct *mm) long x = atomic_long_read(&mm->rss_stat.count[i]); if (unlikely(x)) - printk(KERN_ALERT "BUG: Bad rss-counter state " - "mm:%p idx:%d val:%ld\n", mm, i, x); + pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n", + mm, resident_page_types[i], x); } if (mm_pgtables_bytes(mm)) -- 2.19.1