From patchwork Tue Mar 19 08:38:42 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 10859107 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 230F217E9 for ; Tue, 19 Mar 2019 08:38:57 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F26FB295B3 for ; Tue, 19 Mar 2019 08:38:56 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E6A06295D3; Tue, 19 Mar 2019 08:38:56 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D0394295B3 for ; Tue, 19 Mar 2019 08:38:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726452AbfCSIiz (ORCPT ); Tue, 19 Mar 2019 04:38:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49008 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725978AbfCSIiz (ORCPT ); Tue, 19 Mar 2019 04:38:55 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9C44F3082B69; Tue, 19 Mar 2019 08:38:54 +0000 (UTC) Received: from localhost (ovpn-8-29.pek2.redhat.com [10.72.8.29]) by smtp.corp.redhat.com (Postfix) with ESMTP id E514E5C545; Tue, 19 Mar 2019 08:38:48 +0000 (UTC) From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Ming Lei , Omar Sandoval , Yi Zhang , "jianchao.wang" Subject: [PATCH V2] sbitmap: order READ/WRITE freed instance and setting clear bit Date: Tue, 19 Mar 2019 16:38:42 +0800 Message-Id: <20190319083842.30059-1-ming.lei@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Tue, 19 Mar 2019 08:38:54 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Inside sbitmap_queue_clear(), once the clear bit is set, it will be visiable to allocation path immediately. Meantime READ/WRITE on old associated instance(such as request in case of blk-mq) may be out-of-order with the setting clear bit, so race with re-allocation may be triggered. Adds one memory barrier for ordering READ/WRITE of the freed associated instance with setting clear bit for avoiding race with re-allocation. The following kernel oops triggerd by block/006 on aarch64 may be fixed: [ 142.330954] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000330 [ 142.338794] Mem abort info: [ 142.341554] ESR = 0x96000005 [ 142.344632] Exception class = DABT (current EL), IL = 32 bits [ 142.350500] SET = 0, FnV = 0 [ 142.353544] EA = 0, S1PTW = 0 [ 142.356678] Data abort info: [ 142.359528] ISV = 0, ISS = 0x00000005 [ 142.363343] CM = 0, WnR = 0 [ 142.366305] user pgtable: 64k pages, 48-bit VAs, pgdp = 000000002a3c51c0 [ 142.372983] [0000000000000330] pgd=0000000000000000, pud=0000000000000000 [ 142.379777] Internal error: Oops: 96000005 [#1] SMP [ 142.384613] Modules linked in: null_blk ib_isert iscsi_target_mod ib_srpt target_core_mod ib_srp scsi_transport_srp vfat fat rpcrdma sunrpc rdma_ucm ib_iser rdma_cm iw_cm libiscsi ib_umad scsi_transport_iscsi ib_ipoib ib_cm mlx5_ib ib_uverbs ib_core sbsa_gwdt crct10dif_ce ghash_ce ipmi_ssif sha2_ce ipmi_devintf sha256_arm64 sg sha1_ce ipmi_msghandler ip_tables xfs libcrc32c mlx5_core sdhci_acpi mlxfw ahci_platform at803x sdhci libahci_platform qcom_emac mmc_core hdma hdma_mgmt i2c_dev [last unloaded: null_blk] [ 142.429753] CPU: 7 PID: 1983 Comm: fio Not tainted 5.0.0.cki #2 [ 142.449458] pstate: 00400005 (nzcv daif +PAN -UAO) [ 142.454239] pc : __blk_mq_free_request+0x4c/0xa8 [ 142.458830] lr : blk_mq_free_request+0xec/0x118 [ 142.463344] sp : ffff00003360f6a0 [ 142.466646] x29: ffff00003360f6a0 x28: ffff000010e70000 [ 142.471941] x27: ffff801729a50048 x26: 0000000000010000 [ 142.477232] x25: ffff00003360f954 x24: ffff7bdfff021440 [ 142.482529] x23: 0000000000000000 x22: 00000000ffffffff [ 142.487830] x21: ffff801729810000 x20: 0000000000000000 [ 142.493123] x19: ffff801729a50000 x18: 0000000000000000 [ 142.498413] x17: 0000000000000000 x16: 0000000000000001 [ 142.503709] x15: 00000000000000ff x14: ffff7fe000000000 [ 142.509003] x13: ffff8017dcde09a0 x12: 0000000000000000 [ 142.514308] x11: 0000000000000001 x10: 0000000000000008 [ 142.519597] x9 : ffff8017dcde09a0 x8 : 0000000000002000 [ 142.524889] x7 : ffff8017dcde0a00 x6 : 000000015388f9be [ 142.530187] x5 : 0000000000000001 x4 : 0000000000000000 [ 142.535478] x3 : 0000000000000000 x2 : 0000000000000000 [ 142.540777] x1 : 0000000000000001 x0 : ffff00001041b194 [ 142.546071] Process fio (pid: 1983, stack limit = 0x000000006460a0ea) [ 142.552500] Call trace: [ 142.554926] __blk_mq_free_request+0x4c/0xa8 [ 142.559181] blk_mq_free_request+0xec/0x118 [ 142.563352] blk_mq_end_request+0xfc/0x120 [ 142.567444] end_cmd+0x3c/0xa8 [null_blk] [ 142.571434] null_complete_rq+0x20/0x30 [null_blk] [ 142.576194] blk_mq_complete_request+0x108/0x148 [ 142.580797] null_handle_cmd+0x1d4/0x718 [null_blk] [ 142.585662] null_queue_rq+0x60/0xa8 [null_blk] [ 142.590171] blk_mq_try_issue_directly+0x148/0x280 [ 142.594949] blk_mq_try_issue_list_directly+0x9c/0x108 [ 142.600064] blk_mq_sched_insert_requests+0xb0/0xd0 [ 142.604926] blk_mq_flush_plug_list+0x16c/0x2a0 [ 142.609441] blk_flush_plug_list+0xec/0x118 [ 142.613608] blk_finish_plug+0x3c/0x4c [ 142.617348] blkdev_direct_IO+0x3b4/0x428 [ 142.621336] generic_file_read_iter+0x84/0x180 [ 142.625761] blkdev_read_iter+0x50/0x78 [ 142.629579] aio_read.isra.6+0xf8/0x190 [ 142.633409] __io_submit_one.isra.8+0x148/0x738 [ 142.637912] io_submit_one.isra.9+0x88/0xb8 [ 142.642078] __arm64_sys_io_submit+0xe0/0x238 [ 142.646428] el0_svc_handler+0xa0/0x128 [ 142.650238] el0_svc+0x8/0xc [ 142.653104] Code: b9402a63 f9000a7f 3100047f 540000a0 (f9419a81) [ 142.659202] ---[ end trace 467586bc175eb09d ]--- Fixes: ea86ea2cdced20057da ("sbitmap: ammortize cost of clearing bits") Reported-and-bisected-by: Yi Zhang Cc: Omar Sandoval Cc: Yi Zhang Cc: "jianchao.wang" Signed-off-by: Ming Lei Tested-by: Yi Zhang --- V2: - use smp_mb__before_atomic() as suggested by jianchao Zhang Yi, could you re-test V2? lib/sbitmap.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 5b382c1244ed..941a46495e12 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -591,6 +591,17 @@ EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up); void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, unsigned int cpu) { + /* + * Once the clear bit is set, the bit may be allocated out. + * + * Orders READ/WRITE on the asssociated instance(such as request + * of blk_mq) by this bit for avoiding race with re-allocation, + * and its pair is the memory barrier implied in __sbitmap_get_word. + * + * One invarient is that the clear bit has to be zero when the bit + * is in use. + */ + smp_mb__before_atomic(); sbitmap_deferred_clear_bit(&sbq->sb, nr); /*