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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9B37CC433F5 for ; Tue, 11 Jan 2022 07:27:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235279AbiAKH1u convert rfc822-to-8bit (ORCPT ); Tue, 11 Jan 2022 02:27:50 -0500 Received: from lithops.sigma-star.at ([195.201.40.130]:43618 "EHLO lithops.sigma-star.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234583AbiAKH1t (ORCPT ); Tue, 11 Jan 2022 02:27:49 -0500 Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id 59D8E614E2C4; Tue, 11 Jan 2022 08:27:47 +0100 (CET) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id uuSnmgFaZ1C8; Tue, 11 Jan 2022 08:27:46 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id 46CB0614E2CB; Tue, 11 Jan 2022 08:27:46 +0100 (CET) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id YYWVwdluUz5c; Tue, 11 Jan 2022 08:27:46 +0100 (CET) Received: from lithops.sigma-star.at (lithops.sigma-star.at [195.201.40.130]) by lithops.sigma-star.at (Postfix) with ESMTP id 201D2614E2C4; Tue, 11 Jan 2022 08:27:46 +0100 (CET) Date: Tue, 11 Jan 2022 08:27:46 +0100 (CET) From: Richard Weinberger To: chengzhihao1 Cc: Miquel Raynal , Vignesh Raghavendra , mcoquelin stm32 , kirill shutemov , Sascha Hauer , linux-mtd , linux-kernel Message-ID: <244238061.248369.1641886066066.JavaMail.zimbra@nod.at> In-Reply-To: <6f7df7ba-9557-58a3-7978-e5d14a72f234@huawei.com> References: <20211227032246.2886878-1-chengzhihao1@huawei.com> <20211227032246.2886878-13-chengzhihao1@huawei.com> <361758697.248157.1641857025490.JavaMail.zimbra@nod.at> <6f7df7ba-9557-58a3-7978-e5d14a72f234@huawei.com> Subject: Re: [PATCH v6 12/15] ubi: fastmap: Add all fastmap pebs into 'ai->fastmap' when fm->used_blocks>=2 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-Originating-IP: [195.201.40.130] X-Mailer: Zimbra 8.8.12_GA_3807 (ZimbraWebClient - FF95 (Linux)/8.8.12_GA_3809) Thread-Topic: fastmap: Add all fastmap pebs into 'ai->fastmap' when fm->used_blocks>=2 Thread-Index: CDXmZfwm9pTEbBCtB4asuKSA+LK6HQ== Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- Ursprüngliche Mail ----- > Von: "chengzhihao1" > An: "richard" > CC: "Miquel Raynal" , "Vignesh Raghavendra" , "mcoquelin stm32" > , "kirill shutemov" , "Sascha Hauer" > , "linux-mtd" , "linux-kernel" > Gesendet: Dienstag, 11. Januar 2022 03:48:24 > Betreff: Re: [PATCH v6 12/15] ubi: fastmap: Add all fastmap pebs into 'ai->fastmap' when fm->used_blocks>=2 > Hi Richard, >> scan_ai->fastmap may contain also old fastmap PEBs. >> In the area < UBI_FM_MAX_START you can find outdated fastmap PEBs. >> e.g. after power-cut. >> That's why scan_ai->fastmap is copied into ai->fastmap. >> Later in ubi_wl_init() these outdated PEBs will get erased. >> So, you cannot remove this code. > I thought old fastmap PEBs(async erase works in ubi_update_fastmap()) > will be counted into erase PEBs in the next attaching process, because I > saw following code snippet in ubi_write_fastmap(): > 1260 list_for_each_entry(ubi_wrk, &ubi->works, list) { > > 1261 if (ubi_is_erase_work(ubi_wrk)) { > > 1262 wl_e = ubi_wrk->e; > > 1263 ubi_assert(wl_e); > > 1264 > > 1265 fec = (struct ubi_fm_ec *)(fm_raw + > fm_pos); > 1266 > > 1267 fec->pnum = cpu_to_be32(wl_e->pnum); > > 1268 set_seen(ubi, wl_e->pnum, seen_pebs); > > 1269 fec->ec = cpu_to_be32(wl_e->ec); > > 1270 > > 1271 erase_peb_count++; > > 1272 fm_pos += sizeof(*fec); > > 1273 ubi_assert(fm_pos <= ubi->fm_size); > > 1274 } > > 1275 } > > 1276 fmh->erase_peb_count = cpu_to_be32(erase_peb_count); > Half-writing on fastmap will be recognized in scanning, and UBI > fallbacks full scanning, So, I come up with two situations: > 1. power-cut before new fastmap written, the old fastmap is completely > saved until next attaching, and some free PEBs are written with new > fastmap data. Luckly, fastmap anchor PEB's vid header is written first > of all, bad fastmap will be returned by ubi_attach_fastmap() in next > attaching. > 2. power-cut after new fastmap written, the old fastmap PEBs will be > added into 'ai->erase' list in next attaching. > Did I miss other possible circumstances? In ubi_wl_init() there is another corner case documented: /* * The fastmap update code might not find a free PEB for * writing the fastmap anchor to and then reuses the * current fastmap anchor PEB. When this PEB gets erased * and a power cut happens before it is written again we * must make sure that the fastmap attach code doesn't * find any outdated fastmap anchors, hence we erase the * outdated fastmap anchor PEBs synchronously here. */ if (aeb->vol_id == UBI_FM_SB_VOLUME_ID) sync = true; So ubi_wl_init() makes sure that all old fastmap anchors get erased before UBI starts to operate. With your change this is no longer satisfied. Thanks, //richard 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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 33993C433EF for ; Tue, 11 Jan 2022 07:28:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Subject:References: In-Reply-To:Message-ID:Cc:To:From:Date:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=SeWBckmGumOIHLtsQRNDI1hRmMwxmQ4HBJVt0qFuTGQ=; b=jtblvVkvDyC7KECON2+CD2yOgB 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with ESMTP id uuSnmgFaZ1C8; Tue, 11 Jan 2022 08:27:46 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id 46CB0614E2CB; Tue, 11 Jan 2022 08:27:46 +0100 (CET) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id YYWVwdluUz5c; Tue, 11 Jan 2022 08:27:46 +0100 (CET) Received: from lithops.sigma-star.at (lithops.sigma-star.at [195.201.40.130]) by lithops.sigma-star.at (Postfix) with ESMTP id 201D2614E2C4; Tue, 11 Jan 2022 08:27:46 +0100 (CET) Date: Tue, 11 Jan 2022 08:27:46 +0100 (CET) From: Richard Weinberger To: chengzhihao1 Cc: Miquel Raynal , Vignesh Raghavendra , mcoquelin stm32 , kirill shutemov , Sascha Hauer , linux-mtd , linux-kernel Message-ID: <244238061.248369.1641886066066.JavaMail.zimbra@nod.at> In-Reply-To: <6f7df7ba-9557-58a3-7978-e5d14a72f234@huawei.com> References: <20211227032246.2886878-1-chengzhihao1@huawei.com> 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