From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751804AbaHUBxG (ORCPT ); Wed, 20 Aug 2014 21:53:06 -0400 Received: from mail-bn1lp0141.outbound.protection.outlook.com ([207.46.163.141]:8853 "EHLO na01-bn1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750844AbaHUBxE (ORCPT ); Wed, 20 Aug 2014 21:53:04 -0400 Message-ID: <1408585972.4058.95.camel@snotra.buserror.net> Subject: Re: [PATCH] mtd: fsl_ifc_nand: Recover corrupted empty page for preventing read-only mount in UBIFS From: Scott Wood To: CC: , , , Date: Wed, 20 Aug 2014 20:52:52 -0500 In-Reply-To: <26017351.61791396316965998.JavaMail.weblogic@epv6ml06> References: <26017351.61791396316965998.JavaMail.weblogic@epv6ml06> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Originating-IP: [2601:2:5800:3f7:800:984d:d5d4:4421] X-ClientProxiedBy: BLUPR08CA0058.namprd08.prod.outlook.com (10.141.200.38) To DM2PR0301MB0734.namprd03.prod.outlook.com (25.160.97.142) X-Microsoft-Antispam: BCL:0;PCL:0;RULEID:;UriScan:; X-Forefront-PRVS: 0310C78181 X-Forefront-Antispam-Report: SFV:NSPM;SFS:(6009001)(199003)(24454002)(377424004)(189002)(51704005)(85306004)(77096002)(88136002)(103116003)(64706001)(23676002)(102836001)(99396002)(47776003)(104166001)(20776003)(105586002)(95666004)(50466002)(106356001)(21056001)(42186005)(87286001)(87976001)(50226001)(80022001)(77156001)(4396001)(86362001)(46102001)(81542001)(83072002)(89996001)(2351001)(19580395003)(81342001)(83322001)(19580405001)(110136001)(77982001)(107046002)(76176999)(79102001)(92566001)(74502001)(92726001)(50986999)(76482001)(101416001)(93916002)(62966002)(33646002)(31966008)(74662001)(99106002);DIR:OUT;SFP:;SCL:1;SRVR:DM2PR0301MB0734;H:[IPv6:2601:2:5800:3f7:800:984d:d5d4:4421];FPR:;MLV:sfv;PTR:InfoNoRecords;A:1;MX:1;LANG:en; X-OriginatorOrg: freescale.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2014-04-01 at 01:49 +0000, Eunbong Song wrote: > Even if the meaning of EUCLEAN was changed by commit edbc4540. > There is still possibility of read-only mount in UBIFS with ubifs_scan() "corrupt empty space at LEB". > So i made this patch for fix that problem. Please elaborate on the nature of the problem. > This patch do as follow. > - If there are ecc errors which is equal to or less than chip->ecc.strength in page. > - Check that page has how many zero bits, and if zero bits are equal to or less than > chip->ecc.strength then overwrite 1 to zero bits in buf. This is difficult to parse, with no mention in this sentence that you're talking about corrupted empty pages. > ubifs_scan() cannot detect corrupted empty space because buf is recovered by this patch. > And this is safe because ecc controller can correct up to chip->ecc.strength bits. So the concern is that is_blank is failing to report a page that has not been written to but has errors that would have been correctable if the page had been written? Do most drivers handle this? > Signed-off-by: Eunbong Song > --- > drivers/mtd/nand/fsl_ifc_nand.c | 41 +++++++++++++++++++++++++++++++++++++++ > 1 files changed, 41 insertions(+), 0 deletions(-) > > diff --git a/drivers/mtd/nand/fsl_ifc_nand.c b/drivers/mtd/nand/fsl_ifc_nand.c > index 90ca7e7..2129c39 100644 > --- a/drivers/mtd/nand/fsl_ifc_nand.c > +++ b/drivers/mtd/nand/fsl_ifc_nand.c > @@ -277,6 +277,42 @@ static int is_blank(struct mtd_info *mtd, unsigned int bufnum) > return 1; > } > > +static int num_zero_bits(uint8_t val) > +{ > + int i, ret=0; > + > + for(i=7; i>=0 ; i--) > + if(!(0x1 & (val >> i))) > + ret++; Whitespace (here and elsewhere) Also, use hweight8(~val) instead of reimplementing it. Or better, use hweight64() and process the data in larger chunks. > + return ret; > +} > + > +static int is_corrupted_blank(struct mtd_info *mtd, uint8_t * buf) > +{ > + struct nand_chip *chip = mtd->priv; > + int i; > + int zero_bits = 0; > + > + for (i = 0; i < mtd->writesize ; i++) { > + if(buf[i] != 0xff) { > + zero_bits += num_zero_bits(buf[i]); > + } > + } > + > + if(zero_bits && (zero_bits <= chip->ecc.strength)){ > + return 1; > + } > + > + return 0; > +} What if it's a page that legitimately has only a handful of zero bits? You need to count zero bits in the ECC as well. Also, this could be combined with is_blank(). > +static void recover_corrupted_blank(struct mtd_info *mtd, uint8_t * buf) > +{ > + memset(buf, 0xff, mtd->writesize); > + return; > +} > + > /* returns nonzero if entire page is blank */ > static int check_read_ecc(struct mtd_info *mtd, struct fsl_ifc_ctrl *ctrl, > u32 *eccstat, unsigned int bufnum) > @@ -760,6 +796,11 @@ static int fsl_ifc_read_page(struct mtd_info *mtd, struct nand_chip *chip, > if (ctrl->nand_stat != IFC_NAND_EVTER_STAT_OPC) > mtd->ecc_stats.failed++; > > + if(nctrl->max_bitflips && (nctrl->max_bitflips <= chip->ecc.strength)){ > + if(is_corrupted_blank(mtd, buf)) > + recover_corrupted_blank(mtd, buf); > + } If the page is blank except for errors, most likely max_bitflips will be zero because fsl_ifc_run_command() already considered it an uncorrectable error and set ECCER instead. Moving corrupted blank page detection into is_blank() wouldn't have this problem. How did you test this patch? -Scott