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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91FA5C433EF for ; Mon, 4 Oct 2021 18:41:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6DE106140D for ; Mon, 4 Oct 2021 18:41:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235233AbhJDSnV (ORCPT ); Mon, 4 Oct 2021 14:43:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53980 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233311AbhJDSnU (ORCPT ); Mon, 4 Oct 2021 14:43:20 -0400 Received: from mail-ed1-x533.google.com (mail-ed1-x533.google.com [IPv6:2a00:1450:4864:20::533]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92726C061745 for ; Mon, 4 Oct 2021 11:41:31 -0700 (PDT) Received: by mail-ed1-x533.google.com with SMTP id p13so40517061edw.0 for ; Mon, 04 Oct 2021 11:41:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=56z64RfaxhBPHKBxrKpIeCmw/JUaEkC5bctLSO4zbPw=; b=TeduhA16QD2I64VEL8/9gJBRrib/Wz2GZLhomm/YNweUBFDosOQiR+aEnQJnaC/TEW rWsreaFR7KDYuJkO4zUwgtEpOzn0aWtEK98XFefnumwNRlaJWh40mZStymnEvzxnk88j zDo4oOfjR9VHkw/c9lvbymAKvxfNTxpPsFq1WjxD2EJQn7uAHEXlvxUE0ZDh8ArzT3S3 IN7GxnAFJHJscNHTl/7O5IHo/wjzjI6qPDHcjl38P3ERDrNyZmRb+PV0I2QJFQEEbjmb Rl2RjOVG0xNzpAGCG8S4/Ttiouc5c/C40giJRPxQDoKP3cpZSlQL13Qvzm3tYuWW3oDN pVMA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=56z64RfaxhBPHKBxrKpIeCmw/JUaEkC5bctLSO4zbPw=; b=my8nPcSQL/oC7w4jpu5wLQ5B9o1RoVJ+y9jGqUpv7R4DSXDU4MRoLfgkz9CJ0qZwgy WQKkYwoor1i4fCz7Npzpt35W9Bgb3Fp/tzIE6Iey4gFH22Y4mfX2IFwoPo7GhRtszTyZ liJz4zDOlM09KnGsA+zGDH//0nNXsjCelQPUySBB9vJJsPPTlZ5ryMuvhmrRQrTIGkuR 4SrBdAHPc1Fuh3FsNJPauEALocq568B/OVW/6KpcB0idVkZqUXERcA4E5CvslCXRtrfK XLi+M+rsnBt8Rt6Riosvxzmhz6Z+yXEhecdR0PdB8W1egDgc2BjjSB7vSrvmFrcCIiuP /uXA== X-Gm-Message-State: AOAM530thlAHgF2FsfpMAO6ExePAU2BHZYa9DoF3ctkDtsMYakYKlZnS dEJ7aLZ83F8fX7c8Njfarz3i+VtFoo/OxnfLivfu/A== X-Google-Smtp-Source: ABdhPJz2rknpyNQ8MGXFJG1LnJpKskoos7OkxWt2/J14Md3TpbhY+emzD05svJEHbtaRNGKVB9WKg4SX3f/nTp+xnhM= X-Received: by 2002:a17:906:b098:: with SMTP id x24mr19388219ejy.88.1633372888755; Mon, 04 Oct 2021 11:41:28 -0700 (PDT) MIME-Version: 1.0 References: <20211001181627.394921-1-bgeffon@google.com> In-Reply-To: From: Brian Geffon Date: Mon, 4 Oct 2021 14:40:52 -0400 Message-ID: Subject: Re: [PATCH] zram: Allow backing device to be assigned after init To: Minchan Kim Cc: Andrew Morton , Nitin Gupta , Sergey Senozhatsky , Jonathan Corbet , LKML , linux-doc@vger.kernel.org, linux-block@vger.kernel.org, Suleiman Souhlal , Jesse Barnes Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Oct 4, 2021 at 2:29 PM Minchan Kim wrote: > > On Fri, Oct 01, 2021 at 11:16:27AM -0700, Brian Geffon wrote: > > There does not appear to be a technical reason to not > > allow the zram backing device to be assigned after the > > zram device is initialized. > > > > This change will allow for the backing device to be assigned > > as long as no backing device is already assigned. In that > > event backing_dev would return -EEXIST. > > > > Signed-off-by: Brian Geffon > > --- > > drivers/block/zram/zram_drv.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > > index fcaf2750f68f..12b4555ee079 100644 > > --- a/drivers/block/zram/zram_drv.c > > +++ b/drivers/block/zram/zram_drv.c > > @@ -462,9 +462,9 @@ static ssize_t backing_dev_store(struct device *dev, > > return -ENOMEM; > > > > down_write(&zram->init_lock); > > - if (init_done(zram)) { > > - pr_info("Can't setup backing device for initialized device\n"); > > - err = -EBUSY; > > + if (zram->backing_dev) { > > + pr_info("Backing device is already assigned\n"); > > + err = -EEXIST; > > goto out; > > Hi Brian, > Hi Minchan, > I am worry about the inconsistency with other interface of current zram > set up. They were supposed to set it up before zram disksize setting > because it makes code more simple/maintainalbe in that we don't need > to check some feature on the fly. > > Let's think about when zram extends the writeback of incompressible > page on demand. The write path will need the backing_dev under > down_read(&zarm->init_lock) or other conditional variable to check > whether the feature is enabled or not on the fly. I don't follow what you mean by that, writeback_store already holds down_read(&zarm->init_lock). Brian