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=-10.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 5129AC43441 for ; Thu, 22 Nov 2018 10:17:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1266D20866 for ; Thu, 22 Nov 2018 10:17:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="hCeSDnKk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1266D20866 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2394123AbeKVU4D (ORCPT ); Thu, 22 Nov 2018 15:56:03 -0500 Received: from mail.kernel.org ([198.145.29.99]:51796 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388046AbeKVU4C (ORCPT ); Thu, 22 Nov 2018 15:56:02 -0500 Received: from localhost (unknown [95.99.132.93]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CE9FB20684; Thu, 22 Nov 2018 10:17:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1542881835; bh=4qEpFH3jL3XoPlqUH+hNrkZzqtVYQsVVcZTCBxHiqT4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hCeSDnKkpCmUOVAbhKmcBZtWMzKxTUP//b0sIR+oaD7l17adobcY6wE0vgEvYY4VH fLxoKMIZEUhRQNA5LHXCiDsdDVENo9HBL6mFhYkmB7bjf6i2gAlRjT82EaYVAYk8Wx 6Thkq4EWlzd2mxF78q/XCEFsqigiZaOFuJqulVDM= Date: Thu, 22 Nov 2018 11:17:11 +0100 From: Greg Kroah-Hartman To: Gao Xiang Cc: devel@driverdev.osuosl.org, linux-erofs@lists.ozlabs.org, Chao Yu , LKML , weidu.du@huawei.com, Miao Xie Subject: Re: [PATCH 02/10] staging: erofs: fix race when the managed cache is enabled Message-ID: <20181122101711.GA3189@kroah.com> References: <20181120143425.43637-1-gaoxiang25@huawei.com> <20181120143425.43637-3-gaoxiang25@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181120143425.43637-3-gaoxiang25@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 20, 2018 at 10:34:17PM +0800, Gao Xiang wrote: > When the managed cache is enabled, the last reference count > of a workgroup must be used for its workstation. > > Otherwise, it could lead to incorrect (un)freezes in > the reclaim path, and it would be harmful. > > A typical race as follows: > > Thread 1 (In the reclaim path) Thread 2 > workgroup_freeze(grp, 1) refcnt = 1 > ... > workgroup_unfreeze(grp, 1) refcnt = 1 > workgroup_get(grp) refcnt = 2 (x) > workgroup_put(grp) refcnt = 1 (x) > ...unexpected behaviors > > * grp is detached but still used, which violates cache-managed > freeze constraint. > > Reviewed-by: Chao Yu > Signed-off-by: Gao Xiang > --- > drivers/staging/erofs/internal.h | 1 + > drivers/staging/erofs/utils.c | 131 +++++++++++++++++++++++++++------------ > 2 files changed, 93 insertions(+), 39 deletions(-) > > diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h > index 57575c7f5635..89dbd0888e53 100644 > --- a/drivers/staging/erofs/internal.h > +++ b/drivers/staging/erofs/internal.h > @@ -250,6 +250,7 @@ static inline bool erofs_workgroup_get(struct erofs_workgroup *grp, int *ocnt) > } > > #define __erofs_workgroup_get(grp) atomic_inc(&(grp)->refcount) > +#define __erofs_workgroup_put(grp) atomic_dec(&(grp)->refcount) Any specific reason why you are not using the refcount.h api instead of "doing it yourself" with atomic_inc/dec()? I'm not rejecting this, just curious. thanks, greg k-h From mboxrd@z Thu Jan 1 00:00:00 1970 From: gregkh@linuxfoundation.org (Greg Kroah-Hartman) Date: Thu, 22 Nov 2018 11:17:11 +0100 Subject: [PATCH 02/10] staging: erofs: fix race when the managed cache is enabled In-Reply-To: <20181120143425.43637-3-gaoxiang25@huawei.com> References: <20181120143425.43637-1-gaoxiang25@huawei.com> <20181120143425.43637-3-gaoxiang25@huawei.com> Message-ID: <20181122101711.GA3189@kroah.com> On Tue, Nov 20, 2018@10:34:17PM +0800, Gao Xiang wrote: > When the managed cache is enabled, the last reference count > of a workgroup must be used for its workstation. > > Otherwise, it could lead to incorrect (un)freezes in > the reclaim path, and it would be harmful. > > A typical race as follows: > > Thread 1 (In the reclaim path) Thread 2 > workgroup_freeze(grp, 1) refcnt = 1 > ... > workgroup_unfreeze(grp, 1) refcnt = 1 > workgroup_get(grp) refcnt = 2 (x) > workgroup_put(grp) refcnt = 1 (x) > ...unexpected behaviors > > * grp is detached but still used, which violates cache-managed > freeze constraint. > > Reviewed-by: Chao Yu > Signed-off-by: Gao Xiang > --- > drivers/staging/erofs/internal.h | 1 + > drivers/staging/erofs/utils.c | 131 +++++++++++++++++++++++++++------------ > 2 files changed, 93 insertions(+), 39 deletions(-) > > diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h > index 57575c7f5635..89dbd0888e53 100644 > --- a/drivers/staging/erofs/internal.h > +++ b/drivers/staging/erofs/internal.h > @@ -250,6 +250,7 @@ static inline bool erofs_workgroup_get(struct erofs_workgroup *grp, int *ocnt) > } > > #define __erofs_workgroup_get(grp) atomic_inc(&(grp)->refcount) > +#define __erofs_workgroup_put(grp) atomic_dec(&(grp)->refcount) Any specific reason why you are not using the refcount.h api instead of "doing it yourself" with atomic_inc/dec()? I'm not rejecting this, just curious. thanks, greg k-h