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 X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,URIBL_DBL_ABUSE_MALW,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 596C4C32771 for ; Mon, 27 Jan 2020 10:45:47 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 2BC13207FD for ; Mon, 27 Jan 2020 10:45:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="lwdaXyyi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2BC13207FD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org 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:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=Ha1YO6oaOvnEGq7ds68YzbjOKKarotELOy5CTvjZhmM=; b=lwdaXyyiheGpar o0+vmWkWSsqfw8bMyBdRD0UPAYwiHLed6z5do2KWbNujz4A2lg1c+mkmOAA421SL13bxPZKji/FiW CezQuNuSTLJEGkncqhtyTR1oZn+2R5tIt0kRAILFod1Z9M4Rl91PBll/h1rMyTctVhh7QswtgdttC B+uwbT3lrfIvNu7UXbDBB7mgnzWzWUg2DNH0YHM03+ov6o3cYb/Ep3XHXd2v1ehVvarK9n9K7yw5l ifodip6ijB7+6T7IcKfleaCRzKJCxF5eNP0qBpZw+/pWmUTLQKbUI6z8iA0mIpc8lDmGQzCoywu+G Fz3NFxOtzpaosrYHZS5g==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iw1tb-00067C-W3; Mon, 27 Jan 2020 10:45:31 +0000 Received: from mx2.suse.de ([195.135.220.15]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iw1tY-000669-Rr for linux-mtd@lists.infradead.org; Mon, 27 Jan 2020 10:45:30 +0000 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id AF506ADE0; Mon, 27 Jan 2020 10:45:18 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 492081E0E4E; Mon, 27 Jan 2020 11:45:18 +0100 (CET) Date: Mon, 27 Jan 2020 11:45:18 +0100 From: Jan Kara To: Sascha Hauer Subject: Re: [PATCH 1/8] quota: Allow to pass mount path to quotactl Message-ID: <20200127104518.GC19414@quack2.suse.cz> References: <20200124131323.23885-1-s.hauer@pengutronix.de> <20200124131323.23885-2-s.hauer@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200124131323.23885-2-s.hauer@pengutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200127_024529_184287_0C358B5C X-CRM114-Status: GOOD ( 20.99 ) 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-fsdevel@vger.kernel.org, Richard Weinberger , linux-mtd@lists.infradead.org, kernel@pengutronix.de, Jan Kara Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org On Fri 24-01-20 14:13:16, Sascha Hauer wrote: > This patch introduces the Q_PATH flag to the quotactl cmd argument. > When given, the path given in the special argument to quotactl will > be the mount path where the filesystem is mounted, instead of a path > to the block device. > This is necessary for filesystems which do not have a block device as > backing store. Particularly this is done for upcoming UBIFS support. > > Signed-off-by: Sascha Hauer Thanks for the patch. Some comments are below. > @@ -821,15 +822,20 @@ int kernel_quotactl(unsigned int cmd, const char __user *special, > { > uint cmds, type; > struct super_block *sb = NULL; > - struct path path, *pathp = NULL; > + struct path file_path, *file_pathp = NULL, sb_path; > int ret; > + bool q_path; > > cmds = cmd >> SUBCMDSHIFT; > type = cmd & SUBCMDMASK; > > + Unnecessary empty line added... > if (type >= MAXQUOTAS) > return -EINVAL; > > + q_path = cmds & Q_PATH; > + cmds &= ~Q_PATH; > + > /* > * As a special case Q_SYNC can be called without a specific device. > * It will iterate all superblocks that have quota enabled and call > @@ -847,28 +853,45 @@ int kernel_quotactl(unsigned int cmd, const char __user *special, > * resolution (think about autofs) and thus deadlocks could arise. > */ > if (cmds == Q_QUOTAON) { > - ret = user_path_at(AT_FDCWD, addr, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); > + ret = user_path_at(AT_FDCWD, addr, > + LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT, > + &file_path); > if (ret) > - pathp = ERR_PTR(ret); > + file_pathp = ERR_PTR(ret); > else > - pathp = &path; > + file_pathp = &file_path; > } > > - sb = quotactl_block(special, cmds); > - if (IS_ERR(sb)) { > - ret = PTR_ERR(sb); > - goto out; > + if (q_path) { > + ret = user_path_at(AT_FDCWD, special, > + LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT, > + &sb_path); > + if (ret) > + goto out; > + > + sb = sb_path.mnt->mnt_sb; So I've realized that just looking up superblock with user_path_at() is not enough. Quota code also expects that the superblock will be locked (sb->s_umount) and filesystem will not be frozen (in case the quota operation is going to modify the filesystem). This is needed to serialize e.g. remount and quota operations or quota operations among themselves. So you still need something like following to get superblock from the path: static int quotactl_path(const char __user *special, int cmd, struct path *path) { struct super_block *sb; ret = user_path_at(AT_FDCWD, special, LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT, path); if (ret) return ret; sb = sb_path.mnt->mnt_sb; restart: if (quotactl_cmd_onoff(cmd)) down_write(&sb->s_umount); else down_read(&sb->s_umount); if (quotactl_cmd_write(cmd) && sb->s_writers.frozen != SB_UNFROZEN) { if (quotactl_cmd_onoff(cmd)) up_write(&sb->s_umount); else up_read(&sb->s_umount); wait_event(sb->s_writers.wait_unfrozen, sb->s_writers.frozen == SB_UNFROZEN); goto restart; } return sb; } And then appropriate counterparts when releasing the superblock. Honza -- Jan Kara SUSE Labs, CR ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/