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[192.55.52.115]) by mx.google.com with ESMTPS id d11si36949965pga.407.2019.08.06.14.12.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 06 Aug 2019 14:12:19 -0700 (PDT) Received-SPF: pass (google.com: domain of sai.praneeth.prakhya@intel.com designates 192.55.52.115 as permitted sender) client-ip=192.55.52.115; Authentication-Results: mx.google.com; spf=pass (google.com: domain of sai.praneeth.prakhya@intel.com designates 192.55.52.115 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 fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Aug 2019 14:12:18 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,353,1559545200"; d="scan'208";a="349548305" Received: from sai-dev-mach.sc.intel.com ([143.183.140.153]) by orsmga005.jf.intel.com with ESMTP; 06 Aug 2019 14:12:17 -0700 From: Sai Praneeth Prakhya To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: dave.hansen@intel.com, anshuman.khandual@arm.com, vbabka@suse.cz, mhocko@suse.com, Sai Praneeth Prakhya , Ingo Molnar , Peter Zijlstra , Andrew Morton Subject: [PATCH V3] fork: Improve error message for corrupted page tables Date: Tue, 6 Aug 2019 14:09:07 -0700 Message-Id: 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). The loop index in check_mm() is used to index rss_stat[] which represents individual memory type stats. Hence, instead of printing index, print memory type, thereby improving error message. 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 Also, change print function (from printk(KERN_ALERT, ..) to pr_alert()) so that it matches the other print statement. Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Andrew Morton Acked-by: Michal Hocko Acked-by: Vlastimil Babka Acked-by: Dave Hansen Suggested-by: Dave Hansen Reviewed-by: Anshuman Khandual Signed-off-by: Sai Praneeth Prakhya --- Changes from V2 to V3: ---------------------- 1. Add comment that suggests to update resident_page_types[] if there are any changes to exisiting page types in 2. Add a build check to enforce resident_page_types[] is always in sync 3. Use a macro to populate elements of resident_page_types[] Changes from V1 to V2: ---------------------- 1. Move struct definition from header file to fork.c file, so that it won't be included in every compilation unit. As this struct is used *only* in fork.c, include the definition in fork.c itself. 2. Index the struct to match respective macros. 3. Mention about print function change in commit message. include/linux/mm_types_task.h | 4 ++++ kernel/fork.c | 16 ++++++++++++++-- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/include/linux/mm_types_task.h b/include/linux/mm_types_task.h index d7016dcb245e..c1bc6731125c 100644 --- a/include/linux/mm_types_task.h +++ b/include/linux/mm_types_task.h @@ -36,6 +36,10 @@ struct vmacache { struct vm_area_struct *vmas[VMACACHE_SIZE]; }; +/* + * When updating this, please also update struct resident_page_types[] in + * kernel/fork.c + */ enum { MM_FILEPAGES, /* Resident file mapping pages */ MM_ANONPAGES, /* Resident anonymous pages */ diff --git a/kernel/fork.c b/kernel/fork.c index d8ae0f1b4148..7583e0fde0ed 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -125,6 +125,15 @@ int nr_threads; /* The idle threads do not count.. */ static int max_threads; /* tunable limit on nr_threads */ +#define NAMED_ARRAY_INDEX(x) [x] = __stringify(x) + +static const char * const resident_page_types[] = { + NAMED_ARRAY_INDEX(MM_FILEPAGES), + NAMED_ARRAY_INDEX(MM_ANONPAGES), + NAMED_ARRAY_INDEX(MM_SWAPENTS), + NAMED_ARRAY_INDEX(MM_SHMEMPAGES), +}; + DEFINE_PER_CPU(unsigned long, process_counts) = 0; __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ @@ -645,12 +654,15 @@ static void check_mm(struct mm_struct *mm) { int i; + BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS, + "Please make sure 'struct resident_page_types[]' is updated as well"); + for (i = 0; i < NR_MM_COUNTERS; i++) { 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)) -- 2.7.4