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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id 33si20629460plt.161.2019.04.24.12.18.32 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 24 Apr 2019 12:18:32 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=mrQLtjdF; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=P+OfGyLgTHL2L1RnCJWgVoo8gkrh4zgwRL/+i5lcAZE=; b=mrQLtjdFQvWaJbGQaT55TTvth NOVOud4leyMRqSMYunVTLEw/Td40gtqCM0TCBkuC5uvAOduxbypNOG3qqbfATcl8n+W7IaH7+XtLK +hJ+ZISDncsKBPkEJEDg9XsfxcKM/UXlk3LJ9/KuuDP7RCJrEQPhbmzI7lbkrrX9LaP7T2PPjd8Zz MYmOOsXis2V1APWd8wnaYW6rXwKX4qhEuHWxji2rV3R4ZNir78GSm8YMAMvI/k+n7Wg0A9j5OHQ26 DBgps9O0g04jCIvjxLm6aD4lqh08SDujttlnL9iMztT3xcStfimyJP3KNy5MyH5aC2o/YCxgMicUj IrldlGUNg==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1hJNPa-0003Yt-Qz; Wed, 24 Apr 2019 19:18:30 +0000 Date: Wed, 24 Apr 2019 12:18:30 -0700 From: Matthew Wilcox To: Aaro Koskinen Cc: linux-mips@vger.kernel.org, linux-mm@kvack.org Subject: Re: MIPS/CI20: BUG: Bad page state Message-ID: <20190424191830.GF19031@bombadil.infradead.org> References: <20190424182012.GA21072@darkstar.musicnaut.iki.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190424182012.GA21072@darkstar.musicnaut.iki.fi> User-Agent: Mutt/1.9.2 (2017-12-15) 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 Wed, Apr 24, 2019 at 09:20:12PM +0300, Aaro Koskinen wrote: > [33617.740799] BUG: Bad page state in process cc1plus pfn:3df51 > [33617.746545] page:81023764 count:0 mapcount:-64768 mapping:00000000 index:0x1 > [33617.753577] flags: 0x40000000() > [33617.756716] raw: 40000000 00000100 00000200 00000000 00000001 00000000 ffff02ff 00000000 > [33617.742940] raw: 00000000 > [33617.745548] page dumped because: nonzero mapcount When a page is freed, it's not supposed to be mapped to userspace any more, so mapcount should be 0. In your case, it's either -64768, which is a massive underflow, or it's 0xffff02ff which is a nonsensical combination of flags. Or a user is putting their own information into that field (as, eg, slab does). Or it's become corrupted for some reason unknown to me. > [33617.760052] Call Trace: > [33617.740656] [<80019c7c>] show_stack+0x8c/0x130 > [33617.745092] [<8009cf78>] bad_page+0x138/0x140 > [33617.749437] [<8009d764>] free_pcppages_bulk+0x15c/0x4dc > [33617.754652] [<8009eca8>] free_unref_page_list+0x130/0x168 > [33617.760041] [<800a7b90>] release_pages+0x98/0x404 > [33617.742894] [<800cea78>] tlb_flush_mmu_free+0x54/0x60 > [33617.747934] [<800c5874>] unmap_page_range+0x574/0x864 > [33617.752972] [<800c5cf8>] unmap_vmas+0x70/0x78 > [33617.757319] [<800cc690>] exit_mmap+0x110/0x1b8 Given this stack trace, the page was mapped into userspace, so something's gone terribly wrong. My money is on corruption; I haven't seen anyone report anything like this before.