From patchwork Thu Aug 1 09:13:20 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Zhihao Cheng X-Patchwork-Id: 1140361 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=lists.infradead.org (client-ip=2607:7c80:54:e::133; helo=bombadil.infradead.org; envelope-from=linux-mtd-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="WeMiwA3c"; dkim-atps=neutral Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 45zl2n1SRcz9sBF for ; Thu, 1 Aug 2019 19:13:37 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References: Message-ID:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=SQbieHwR7QkhHgMLM7tGxW386GiWYUSgcsXmmvbiuqo=; b=WeMiwA3cC9+pl5 F9/b7vRZUF9TfjkkC4C9BhZ65w6FENgQERiV+r0poC+gk/p/Rp4PXvOA/1LlpjCxqBhoR611f0VDm tLwyH9BTJnbW+LexiWdFv3ntzs0ZDXoQdRtfIRLBgcjLvHgVPEALEfQXascNZMJBq2Qd+QY1BJFNJ tF91JhCQ3UhmXELBNfEYWgbSjzOnVPBLpAiFmegoWMdN/pR/jt8GMM2y2i8U5wtOr4X7VoFMnmWKV +sC8FVl2M6xagWKSvJKE8SckuLPAzjKZ/aQmfzMPxSWp8reY53cXz97ZinRYQ2atRVlWn9ClE418W pSQK270PXlnbkKpDa5JA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1ht79R-000387-OO; Thu, 01 Aug 2019 09:13:33 +0000 Received: from szxga03-in.huawei.com ([45.249.212.189] helo=huawei.com) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1ht79O-00037A-NO for linux-mtd@lists.infradead.org; Thu, 01 Aug 2019 09:13:32 +0000 Received: from dggemi401-hub.china.huawei.com (unknown [172.30.72.54]) by Forcepoint Email with ESMTP id 906E81AEC0426B887148; Thu, 1 Aug 2019 17:13:27 +0800 (CST) Received: from DGGEMI423-HUB.china.huawei.com (10.1.199.152) by dggemi401-hub.china.huawei.com (10.3.17.134) with Microsoft SMTP Server (TLS) id 14.3.439.0; Thu, 1 Aug 2019 17:13:27 +0800 Received: from DGGEMI524-MBX.china.huawei.com ([169.254.7.227]) by dggemi423-hub.china.huawei.com ([10.1.199.152]) with mapi id 14.03.0439.000; Thu, 1 Aug 2019 17:13:20 +0800 From: chengzhihao To: "richard@nod.at" , "zhangyi (F)" Subject: =?gb2312?b?tPC4tDogW1BBVENIIFJGQ10gdWJpOiB1Ymlfd2xfZ2V0X3BlYjog?= =?gb2312?b?UmVwbGFjZSBhIGxpbWl0ZWQgbnVtYmVyIG9mIGF0dGVtcHRzIHdp?= =?gb2312?b?dGggcG9sbGluZyB3aGlsZSBnZXR0aW5nIFBFQg==?= Thread-Topic: [PATCH RFC] ubi: ubi_wl_get_peb: Replace a limited number of attempts with polling while getting PEB Thread-Index: AQHVSEkuRooM7Daz00mNhjuG43MDw6bmAggA Date: Thu, 1 Aug 2019 09:13:20 +0000 Message-ID: <0B80F9D4116B2F4484E7279D5A66984F7A8A13@dggemi524-mbx.china.huawei.com> References: <1564651065-4585-1-git-send-email-chengzhihao1@huawei.com> In-Reply-To: <1564651065-4585-1-git-send-email-chengzhihao1@huawei.com> Accept-Language: en-US Content-Language: zh-CN X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.177.224.82] MIME-Version: 1.0 X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190801_021330_937031_6F67AE0F X-CRM114-Status: GOOD ( 16.78 ) X-Spam-Score: -2.3 (--) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (-2.3 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [45.249.212.189 listed in list.dnswl.org] -0.0 SPF_HELO_PASS SPF: HELO matches SPF record -0.0 SPF_PASS SPF: sender matches SPF record X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "linux-mtd@lists.infradead.org" , "linux-kernel@vger.kernel.org" Sender: "linux-mtd" Errors-To: linux-mtd-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org I don't quite understand why a limited number of attempts have been made to get a free PEB in ubi_wl_get_peb (in fastmap-wl.c). I proposed this PATCH with reference to the implementation of ubi_wl_get_peb (in wl.c). As far as I know, getting PEB by polling probably won't fall into soft-lockup. ubi_update_fastmap may add new tasks (including erase task or wl taskk, wl tasks generally do not generate additional free PEBs) to ubi->works, and produce_free_peb will eventually complete all tasks in ubi->works or obtain an free PEB that can be filled into pool. -----邮件原件----- 发件人: chengzhihao 发送时间: 2019年8月1日 17:18 收件人: richard@nod.at; zhangyi (F) 抄送: linux-mtd@lists.infradead.org; linux-kernel@vger.kernel.org; chengzhihao 主题: [PATCH RFC] ubi: ubi_wl_get_peb: Replace a limited number of attempts with polling while getting PEB Running pressure test io_paral (A pressure ubi test in mtd-utils) on an UBI device with fewer PEBs (fastmap enabled) may cause ENOSPC errors and make UBI device read-only, but there are still free PEBs on the UBI device. This problem can be easily reproduced by performing the following steps on a 2-core machine: $ modprobe nandsim first_id_byte=0x20 second_id_byte=0x33 parts=80 $ modprobe ubi mtd="0,0" fm_autoconvert $ ./io_paral /dev/ubi0 We may see the following verbose: (output) [io_paral] update_volume():105: function write() failed with error 30 (Read-only file system) [io_paral] update_volume():108: failed to write 380 bytes at offset 95920 of volume 2 [io_paral] update_volume():109: update: 97088 bytes [io_paral] write_thread():227: function pwrite() failed with error 28 (No space left on device) [io_paral] write_thread():229: cannot write 15872 bytes to offs 31744, wrote -1 (dmesg) ubi0 error: ubi_wl_get_peb [ubi]: Unable to get a free PEB from user WL pool ubi0 warning: ubi_eba_write_leb [ubi]: switch to read-only mode ubi0 error: ubi_io_write [ubi]: read-only mode CPU: 0 PID: 2027 Comm: io_paral Not tainted 5.3.0-rc2-00001-g5986cd0 #9 ubi0 warning: try_write_vid_and_data [ubi]: failed to write VID header to LEB 2:5, PEB 18 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0 -0-ga698c8995f-prebuilt.qemu.org 04/01/2014 Call Trace: dump_stack+0x85/0xba ubi_eba_write_leb+0xa1e/0xa40 [ubi] vol_cdev_write+0x307/0x520 [ubi] ubi0 error: vol_cdev_write [ubi]: cannot accept more 380 bytes of data, error -30 vfs_write+0xfa/0x280 ksys_pwrite64+0xc5/0xe0 __x64_sys_pwrite64+0x22/0x30 do_syscall_64+0xbf/0x440 In function ubi_wl_get_peb, the operation of filling the pool (ubi_update_fastmap) with free PEBs and fetching a free PEB from the pool is not atomic. After thread A filling the pool with free PEB, free PEB may be taken away by thread B. When thread A checks the expression again, the condition is still unsatisfactory. At this time, there may still be free PEBs on UBI that can be filled into the pool. So, ubi_wl_get_peb (in fastmap-wil.c) should be implemented to obtain a free PEB by polling method. The polling exit condition is that there is no free PEBs on UBI, no free PEBs in pool, and ubi->works_count is 0. Signed-off-by: Zhihao Cheng --- drivers/mtd/ubi/fastmap-wl.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) } if (pool->used == pool->size) { - spin_unlock(&ubi->wl_lock); - if (retried) { + if (!ubi->free.rb_node && ubi->works_count == 0) { ubi_err(ubi, "Unable to get a free PEB from user WL pool"); + ubi_assert(list_empty(&ubi->works)); + spin_unlock(&ubi->wl_lock); ret = -ENOSPC; goto out; } - retried = 1; + spin_unlock(&ubi->wl_lock); up_read(&ubi->fm_eba_sem); ret = produce_free_peb(ubi); if (ret < 0) { -- 2.7.4 diff --git a/drivers/mtd/ubi/fastmap-wl.c b/drivers/mtd/ubi/fastmap-wl.c index d9e2e3a..c5512cf 100644 --- a/drivers/mtd/ubi/fastmap-wl.c +++ b/drivers/mtd/ubi/fastmap-wl.c @@ -196,7 +196,7 @@ static int produce_free_peb(struct ubi_device *ubi) */ int ubi_wl_get_peb(struct ubi_device *ubi) { - int ret, retried = 0; + int ret; struct ubi_fm_pool *pool = &ubi->fm_pool; struct ubi_fm_pool *wl_pool = &ubi->fm_wl_pool; @@ -220,13 +220,14 @@ int ubi_wl_get_peb(struct ubi_device *ubi)