From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=Ce2X=ZG=lists.ozlabs.org=linux-erofs-bounces+linux-erofs=archiver.kernel.org@kernel.org>
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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED,
	HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,
	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 0E279C432C3
	for <linux-erofs@archiver.kernel.org>; Thu, 14 Nov 2019 22:00:42 +0000 (UTC)
Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2])
	(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 B1EC6206CB
	for <linux-erofs@archiver.kernel.org>; Thu, 14 Nov 2019 22:00:41 +0000 (UTC)
Authentication-Results: mail.kernel.org;
	dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="rLBqMtfq"
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B1EC6206CB
Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org
Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org
Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3])
	by lists.ozlabs.org (Postfix) with ESMTP id 47Db5M0DZHzF83Z
	for <linux-erofs@archiver.kernel.org>; Fri, 15 Nov 2019 09:00:39 +1100 (AEDT)
Authentication-Results: lists.ozlabs.org;
 spf=none (no SPF record) smtp.mailfrom=infradead.org
 (client-ip=2607:7c80:54:e::133; helo=bombadil.infradead.org;
 envelope-from=willy@infradead.org; receiver=<UNKNOWN>)
Authentication-Results: lists.ozlabs.org;
 dmarc=none (p=none dis=none) header.from=infradead.org
Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key;
 unprotected) header.d=infradead.org header.i=@infradead.org
 header.b="rLBqMtfq"; 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 (2048 bits) server-digest SHA256)
 (No client certificate requested)
 by lists.ozlabs.org (Postfix) with ESMTPS id 47Db4y5NXPzF5FT
 for <linux-erofs@lists.ozlabs.org>; Fri, 15 Nov 2019 09:00:18 +1100 (AEDT)
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed;
 d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version
 :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:
 Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date:
 Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:
 List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive;
 bh=R9rapZsPL2Sc4OaIDs6c/5nQ15OuRRZR9anBWrXMzdI=; b=rLBqMtfqNB+uY84vih6nZntUG
 ZnKfo9QJqJ8AcTVXQIqO5nbGL9jANx5BNOJ1UoqG3o46XOYt/bYMv9ksOEQq2KAmjKE3l0u2N/r1q
 8zh9MWZNiZDLDX0UM0aTJcd56XWuoqXq1etH2ib4ShfZM791Y2z0C8JLb9p4GNFXWODKnLws59PJN
 r4PU4/TrQp0qXt+lMbuDfZP+p3WSTbfOj1X0BLeKJn7dgexZdOT/cvwdr81bR8U1vSTl7WqShfzoE
 KkhP6urUSTOpfXa8V6uP8SgbW9kJsdntcNwhZq+Lojj8Z1dr15jWpoMADBDzD/1evAL3+Atyqp2ud
 aaxGeging==;
Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red
 Hat Linux)) id 1iVN9z-0005AF-Gk; Thu, 14 Nov 2019 22:00:15 +0000
Date: Thu, 14 Nov 2019 14:00:15 -0800
From: Matthew Wilcox <willy@infradead.org>
To: Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [bug report] staging: erofs: tidy up decompression frontend
Message-ID: <20191114220015.GA20752@bombadil.infradead.org>
References: <20191114190848.f6tlqpnybagez76g@kili.mountain>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20191114190848.f6tlqpnybagez76g@kili.mountain>
User-Agent: Mutt/1.12.1 (2019-06-15)
X-BeenThere: linux-erofs@lists.ozlabs.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Development of Linux EROFS file system <linux-erofs.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linux-erofs>,
 <mailto:linux-erofs-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linux-erofs/>
List-Post: <mailto:linux-erofs@lists.ozlabs.org>
List-Help: <mailto:linux-erofs-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linux-erofs>,
 <mailto:linux-erofs-request@lists.ozlabs.org?subject=subscribe>
Cc: linux-fsdevel@vger.kernel.org, xiang@kernel.org,
 linux-erofs@lists.ozlabs.org
Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org
Sender: "Linux-erofs"
 <linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org>

On Thu, Nov 14, 2019 at 10:10:03PM +0300, Dan Carpenter wrote:
> 	fs/erofs/zdata.c:443 z_erofs_register_collection()
> 	error: double unlocked 'cl->lock' (orig line 439)
> 
> fs/erofs/zdata.c
>    432          cl = z_erofs_primarycollection(pcl);
>    433          cl->pageofs = map->m_la & ~PAGE_MASK;
>    434  
>    435          /*
>    436           * lock all primary followed works before visible to others
>    437           * and mutex_trylock *never* fails for a new pcluster.
>    438           */
>    439          mutex_trylock(&cl->lock);
>                 ^^^^^^^^^^^^^^^^^^^^^^^^
>    440  
>    441          err = erofs_register_workgroup(inode->i_sb, &pcl->obj, 0);
>    442          if (err) {
>    443                  mutex_unlock(&cl->lock);
>                         ^^^^^^^^^^^^^^^^^^^^^^^
> How can we unlock if we don't know that the trylock succeeded?

The comment says it'll always succeed.  That said, this is an uncommon
pattern -- usually we just mutex_lock().  If there's a good reason to use
mutex_trylock() instead, then I'd prefer it to be guarded with a BUG_ON.