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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 1A9DCC4321D for ; Thu, 16 Aug 2018 01:32:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 26510214F0 for ; Thu, 16 Aug 2018 01:32:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 26510214F0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726336AbeHPE1i (ORCPT ); Thu, 16 Aug 2018 00:27:38 -0400 Received: from mga02.intel.com ([134.134.136.20]:52156 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725925AbeHPE1i (ORCPT ); Thu, 16 Aug 2018 00:27:38 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 15 Aug 2018 18:32:46 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,245,1531810800"; d="scan'208";a="224983576" Received: from jxiao12-mobl.ccr.corp.intel.com (HELO [10.239.200.167]) ([10.239.200.167]) by orsmga004.jf.intel.com with ESMTP; 15 Aug 2018 18:32:44 -0700 Subject: Re: dm-bufio: adjust the reserved buffer for dm-verify-target. To: Mike Snitzer , Mikulas Patocka Cc: agk@redhat.com, dm-devel@redhat.com, linux-kernel@vger.kernel.org, yanmin.zhang@intel.com References: <1533710457-6411-1-git-send-email-jin.xiao@intel.com> <20180814203245.GA15636@redhat.com> From: "Xiao, Jin" Message-ID: <3995084e-4250-9c28-2fa1-b61add5fb2e9@intel.com> Date: Thu, 16 Aug 2018 09:32:43 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <20180814203245.GA15636@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/15/2018 4:32 AM, Mike Snitzer wrote: > On Wed, Aug 08 2018 at 2:40am -0400, > xiao jin wrote: > >> We hit the BUG() report at include/linux/scatterlist.h:144! >> The callback is as bellow: >> => verity_work >> => verity_hash_for_block >> => verity_verify_level >> => verity_hash >> => verity_hash_update >> => sg_init_one >> => sg_set_buf >> >> More debug shows the root cause. When creating dufio client it >> uses the __vmalloc() to allocate the buffer data for the reserved >> dm_buffer. The buffer that allocated by the __vmalloc() is invalid >> according to the __virt_addr_valid(). >> >> Mostly the reserved dm_buffer is not touched. But occasionally >> it might fail to allocate the dm_buffer data when we try to >> allocate in the __alloc_buffer_wait_no_callback(). Then it has >> to take the reserved dm_buffer for usage. Finally it reports the >> BUG() as virt_addr_valid() detects the buffer data address is invalid. >> >> The patch is to adjust the reserved buffer for dm-verity-target. We >> allocated two dm_buffers into the reserved buffers list when creating >> the buffer interface. The first dm_buffer in the reserved buffer list >> is allocated by the __vmalloc(), it's not used after that. The second >> dm_buffer in the reserved buffer list is allocated by the >> __get_free_pages() which can be consumed after that. >> >> Signed-off-by: xiao jin >> --- >> drivers/md/dm-bufio.c | 4 ++-- >> drivers/md/dm-verity-target.c | 2 +- >> 2 files changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c >> index dc385b7..3b7ca5e 100644 >> --- a/drivers/md/dm-bufio.c >> +++ b/drivers/md/dm-bufio.c >> @@ -841,7 +841,7 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client >> tried_noio_alloc = true; >> } >> >> - if (!list_empty(&c->reserved_buffers)) { >> + if (!c->need_reserved_buffers) { >> b = list_entry(c->reserved_buffers.next, >> struct dm_buffer, lru_list); >> list_del(&b->lru_list); >> @@ -1701,7 +1701,7 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign >> goto bad; >> } >> >> - while (c->need_reserved_buffers) { >> + if (list_empty(&c->reserved_buffers)) { >> struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL); >> >> if (!b) { > Point was to allocate N buffers (as accounted in > c->need_reserved_buffers). This change just allocates a single one. > Why? > > Your header isn't clear on this at all. Hi Mike, Currently alloc_buffer() when creating the client will use the __vmalloc() to get the buffer data for c->reserved_buffers. If the c->reserved_buffers is read to use in the failures case of buffer allocation in the __alloc_buffer_wait_no_callback(), and the CONFIG_DEBUG_SG is enabled, we will hit the BUG() report. That's the problem I find in reality. I have some thinking to solve such issue. I think to keep the initial buffer with the data from __vmalloc() in the c->reserved_buffers. But the reserved buffer with the data from __vmalloc() can't be read to use. We can allocate more buffers with the data mode of DATA_MODE_SLAB or DATA_MODE_GET_FREE_PAGES for c->reserved_buffers. Such reserved buffers can be used in the failures case of buffer allocation in the __alloc_buffer_wait_no_callback(). I test the code on my device. I never see the BUG() report again. Feel free to correct me. Thanks. Jin >> diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c >> index 12decdbd7..40c66fc 100644 >> --- a/drivers/md/dm-verity-target.c >> +++ b/drivers/md/dm-verity-target.c >> @@ -1107,7 +1107,7 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv) >> v->hash_blocks = hash_position; >> >> v->bufio = dm_bufio_client_create(v->hash_dev->bdev, >> - 1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux), >> + 1 << v->hash_dev_block_bits, 2, sizeof(struct buffer_aux), >> dm_bufio_alloc_callback, NULL); >> if (IS_ERR(v->bufio)) { >> ti->error = "Cannot initialize dm-bufio"; >> -- >> 2.7.4 >> >> -- >> dm-devel mailing list >> dm-devel@redhat.com >> https://www.redhat.com/mailman/listinfo/dm-devel > It isn't at all clear from my initial review that what you're doing > makes any sense. > > Seems like you're just papering over bufio's use of !__virt_addr_valid() > memory in unintuitive ways. > > Mikulas, can you see a better way forward? > > Mike