From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EAC8C21370 for ; Wed, 13 Mar 2024 19:17:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710357472; cv=none; b=FrmstpiXFjmWcW3whWGkzel8SL+zdiXbTNL91KjniD2FfB6UkInl090OXnQnISb8bMJTIN2WPNCziYvhXcKLQCIxGqVw+xDiOdrCECogcwNzFbo+q06kSLCeB6KDGeZ0eVxr6VZki6KVmSBDfoPWg5G0T4+SKNXo3KCYtMgFBqo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710357472; c=relaxed/simple; bh=NmfEK6L5+fopktxibmRTDPM9F2T+mchbo4YQ1kT1Blc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lH5lS8l1peoA1C81+Hrok9r03OaEcooAvTTzQJHoHRLm+n5HWYxckLSENxRItX1O98ofvzq92y3QzKr74JG3bm1VCt2GEVy2wmAiR5uXv2MX/A2P8DDaPWYyzEe7J0AgILWCNlLhn0kDzm7E8JPvFZK2Dg8uX7dy6JOIEpCeSfs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=PhmX1chm; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="PhmX1chm" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=Y7No5BwSBcNxAZE4T0od85sb/fUSBA4xSBUxPEwP8vU=; b=PhmX1chmLgkAVW3std5UqfdxDP rwyCiSKjNl7ij3pV6kGYxMnljYFyCvXcI4tslQ2y88inn3vZJ1G13rc9rD9IFsIn37Mlhko44St52 8GOs/9TtkekpiUW5IupsRk+0m0r/wFZiFyOMLOA8yt9r6ktHwHEii+kleCKf0+LNwS5bPlQlBMN9I 9rq/GrjWGE3IPje6ExSR4G0BDf46vpMPcIUujVUq2VvHBftHGZ7nfDM2fvWYlljDOD7fOEwmOBzHn 4mesg1rIM7BGM5Q0vPwsfLa29GFYNlTXxiR25H3tH0Hj/1WyRRXViXRO9VdZtReSnCEx5Fi/LOsGb PYa4WUCw==; Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rkU6m-000000064wa-18LU; Wed, 13 Mar 2024 19:17:48 +0000 Date: Wed, 13 Mar 2024 19:17:48 +0000 From: Matthew Wilcox To: Pankaj Raghav Cc: Jens Axboe , Christoph Hellwig , linux-block@vger.kernel.org, Tetsuo Handa , Hannes Reinecke Subject: Re: brd in a memdesc world Message-ID: References: <4605ebb7-2fcf-4570-b849-7aaa80a21954@samsung.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4605ebb7-2fcf-4570-b849-7aaa80a21954@samsung.com> On Wed, Mar 13, 2024 at 07:36:01PM +0100, Pankaj Raghav wrote: > Got it! Probably moving to folios just for the sake of retaining the > debugging checks is not enough. That would be my assessment, but maybe Jens has a different preference. > > None of those things are needed for brd's uses. All brd needs is to > > be able to allocate, kmap and free chunks of memory. Unless there are > > plans to do more than this. > > I remember he mentioned he wanted to support bigger logical block sizes > in brd, in which case moving to folios might be justified. Using folios (or some other data structure that embedded the order of the allocation) would be justified if there was a proposal on the table to support variable sized allocations in the brd XArray. Hannes wasn't suggesting that; his patch series used a fixed size per block device (which honestly makes sense; I don't see the advantage to supporting variable sized allocations).