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 DD225EB64DD for ; Thu, 27 Jul 2023 06:19:41 +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:References:In-Reply-To: Message-ID:Subject: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=AOx+j6suBkDIUcJtl1KqgIklptEB7o+QC1+AyXskCew=; b=xBjTQv8ibSGjpP 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h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qskc8UL7HpZtZS2sXdp6DAYX33Iw0SkA6UUJwMFN1pc=; b=MQ0XLEXe41fjTls2Ua+EtFbn5ci6ACukYOsA5oI8CXGsqok8uG8giYHxAruqtu7zDUPPux nSQuSUKMgQLcH2Eiy/Uh8gd0/SYBhgXC+61KeB1mQUMz42yetKDk8Hos1WrFB6y/Jkqin9 T7krT175sF10KnPzoxC9sp2OHE5iPgYvnqFUZPd2kNeS8tr/5EeJbEg7GKAEUXW/PtVfm4 tHn6XncNABpQORtDSCONGiZMHqvgA7YsARmbNRo+un8syOWAgts7U3wohC38L+SPFSCO/r vmjWsCUXPi5CfftItyX2o8PWcZMLB8L36WlK93cuXAQRN0HPqoZyIL8gDV1xeQ== Date: Thu, 27 Jul 2023 08:19:14 +0200 From: Miquel Raynal To: "Usyskin, Alexander" Cc: Fabrizio Castro , Richard Weinberger , Vignesh Raghavendra , "linux-mtd@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "Winkler, Tomas" , "Lubart, Vitaly" , Andy Shevchenko , Geert Uytterhoeven , Biju Das , "linux-renesas-soc@vger.kernel.org" , Chris Paterson Subject: Re: [PATCH 1/2] mtd: use refcount to prevent corruption Message-ID: <20230727081914.03e44b96@xps-13> In-Reply-To: References: <20230620131905.648089-1-alexander.usyskin@intel.com> <20230620131905.648089-2-alexander.usyskin@intel.com> <20230715174112.3909e43f@xps-13> <20230716153926.5e975231@xps-13> <20230724135118.54e39faf@xps-13> Organization: Bootlin X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-GND-Sasl: miquel.raynal@bootlin.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230726_231924_287601_17299169 X-CRM114-Status: GOOD ( 34.06 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-mtd" Errors-To: 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t=1690438758; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qskc8UL7HpZtZS2sXdp6DAYX33Iw0SkA6UUJwMFN1pc=; b=MQ0XLEXe41fjTls2Ua+EtFbn5ci6ACukYOsA5oI8CXGsqok8uG8giYHxAruqtu7zDUPPux nSQuSUKMgQLcH2Eiy/Uh8gd0/SYBhgXC+61KeB1mQUMz42yetKDk8Hos1WrFB6y/Jkqin9 T7krT175sF10KnPzoxC9sp2OHE5iPgYvnqFUZPd2kNeS8tr/5EeJbEg7GKAEUXW/PtVfm4 tHn6XncNABpQORtDSCONGiZMHqvgA7YsARmbNRo+un8syOWAgts7U3wohC38L+SPFSCO/r vmjWsCUXPi5CfftItyX2o8PWcZMLB8L36WlK93cuXAQRN0HPqoZyIL8gDV1xeQ== Date: Thu, 27 Jul 2023 08:19:14 +0200 From: Miquel Raynal To: "Usyskin, Alexander" Cc: Fabrizio Castro , Richard Weinberger , Vignesh Raghavendra , "linux-mtd@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "Winkler, Tomas" , "Lubart, Vitaly" , Andy Shevchenko , Geert Uytterhoeven , Biju Das , "linux-renesas-soc@vger.kernel.org" , Chris Paterson Subject: Re: [PATCH 1/2] mtd: use refcount to prevent corruption Message-ID: <20230727081914.03e44b96@xps-13> In-Reply-To: References: <20230620131905.648089-1-alexander.usyskin@intel.com> <20230620131905.648089-2-alexander.usyskin@intel.com> <20230715174112.3909e43f@xps-13> <20230716153926.5e975231@xps-13> <20230724135118.54e39faf@xps-13> Organization: Bootlin X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-GND-Sasl: miquel.raynal@bootlin.com Precedence: bulk List-ID: X-Mailing-List: linux-renesas-soc@vger.kernel.org Hi Alexander, alexander.usyskin@intel.com wrote on Tue, 25 Jul 2023 12:50:04 +0000: > Hi > >=20 > > Hi Miquel, =20 > > > > > > Hi Alexander, > > > > > > alexander.usyskin@intel.com wrote on Mon, 24 Jul 2023 11:43:59 +0000: > > > =20 > > > > > > > > With this patch applied, when I load up the module, I get t= he same 3 > > > > > > > > devices: > > > > > > > > /dev/mtd0 > > > > > > > > /dev/mtd0ro > > > > > > > > /dev/mtdblock0 > > > > > > > > > > > > > > > > Upon removal, the below 2 devices still hang around: > > > > > > > > /dev/mtd0 > > > > > > > > /dev/mtd0ro =20 > > > > > > > =20 > > > > > > Our use-case do not produce mtdblock, maybe there are some =20 > > > imbalances =20 > > > > > of get/put? =20 > > > > > > I have somewhere version with pr_debug after every kref_get/put= . That =20 > > > may =20 > > > > > help to catch where =20 > > > > > > it missed, I hope. =20 > > > > > > > > > > I believe mtdblock is the good citizen here. Just disable > > > > > CONFIG_MTD_BLOCK from your configuration and you will likely obse= rve > > > > > the same issue, just a bit narrowed, perhaps. Indeed, if you mana= ge to > > > > > follow all the get/put calls it can help to find an imbalance. > > > > > > > > > > Thanks, > > > > > Miqu=C3=A8l =20 > > > > > > > > Miquel, do you have CONFIG_MTD_PARTITIONED_MASTER set in your =20 > > > config? > > > > > > Not sure I get your question. You can enable or disable it, it should > > > work in both cases (yet, the handling is of course a bit different as > > > the top level device will be retained/not retained). > > > > > > Thanks, > > > Miqu=C3=A8l =20 > >=20 > > I'm trying to understand why I can't reproduce the problem in my scenar= io. > > I found an important difference in upstreamed patch and internal versio= n: > > The IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER) check around > > kref_get/put does not exists in the internal tree. > > The code before my patch do not have such check, so I tend to assume th= at > > this check should be removed. > > If you reproduce happens with CONFIG_MTD_PARTITIONED_MASTER > > disabled that may explain problems that you see. > >=20 > > -- > > Thanks, > > Sasha > > =20 >=20 > I've tried to reproduce this with latest Linux 6.5-rc1 and my two patches. > The manual modprobe mtdblock creates mtdblock0 over my partitions too. > I can't reproduce problem neither with MTD_PARTITIONED_MASTER nor without. >=20 > Let's try to debug on your system, can you enable dynamic debug for mtd s= ubsystem, > reproduce and publish dmesg? >=20 > The prints for kref get/put can be added as below: >=20 > diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c > index 2466ea466466..374835831428 100644 > --- a/drivers/mtd/mtdcore.c > +++ b/drivers/mtd/mtdcore.c > @@ -1242,10 +1242,13 @@ int __get_mtd_device(struct mtd_info *mtd) > } >=20 > kref_get(&mtd->refcnt); > + pr_debug("get mtd %s %d\n", mtd->name, kref_read(&mtd->refcnt)); >=20 > while (mtd->parent) { > - if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER) || mtd->par= ent !=3D master) > + if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER) || mtd->par= ent !=3D master) { > kref_get(&mtd->parent->refcnt); > + pr_debug("get mtd %s %d\n", mtd->parent->name, kr= ef_read(&mtd->parent->refcnt)); > + } > mtd =3D mtd->parent; > } >=20 > @@ -1335,12 +1338,15 @@ void __put_mtd_device(struct mtd_info *mtd) > while (mtd !=3D master) { > struct mtd_info *parent =3D mtd->parent; >=20 > + pr_debug("put mtd %s %d\n", mtd->name, kref_read(&mtd->re= fcnt)); > kref_put(&mtd->refcnt, mtd_device_release); > mtd =3D parent; > } >=20 > - if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER)) > + if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER)) { > + pr_debug("put mtd %s %d\n", master->name, kref_read(&mast= er->refcnt)); > kref_put(&master->refcnt, mtd_device_release); > + } >=20 > module_put(master->owner); >=20 >=20 Could this be helpful? https://lore.kernel.org/all/20230725215539.3135304-1-zhangxiaoxu5@huawei.co= m/ If you successfully test it, please send your Tested-by. Thanks, Miqu=C3=A8l