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=-2.1 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 B0B8CECE58E for ; Fri, 11 Oct 2019 07:51:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8010120679 for ; Fri, 11 Oct 2019 07:51:47 +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="TTiMVoHN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726827AbfJKHvq (ORCPT ); Fri, 11 Oct 2019 03:51:46 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:59148 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726546AbfJKHvp (ORCPT ); Fri, 11 Oct 2019 03:51:45 -0400 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=waqJdP9rJDtEFqbcyOC7uJCMgDCGnjkCl4nSVoSMkIc=; b=TTiMVoHNLa+8q8+e/KY6AvYzp Svhs+EF5AFJfdLyUQQcbonj+z2piAL8I17nA3m2NSRx8J9UFT6qQe7ADrS6DxaboPUrG3W0iDYiKM sK7GDKey21FzA/eJkNAD9934qyDWZ81dJnY9wGQv03kiEMxyBt2ysEUrMH1QNzffL1Lc7rryhyjQD fURZvTo+j6ZxcJD4ZZkl11pVmYPbs4IVmQAo1xT0GFjbtUcKv0OHN8xu4hEhGdHTbOTgukgVkOzlO qup1fUZegCnwmQZmhtJ5qy9aA3SGwSrdahZK73Uos15qM/v5YjYGJXZZZ5DA8QhYmBl7nfCwYlO+5 mf1HtD/JQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1iIpiC-0000PG-SE; Fri, 11 Oct 2019 07:51:44 +0000 Date: Fri, 11 Oct 2019 00:51:44 -0700 From: Christoph Hellwig To: "Darrick J. Wong" Cc: Jens Axboe , Christoph Hellwig , linux-block@vger.kernel.org, linux-fsdevel , xfs Subject: Re: [PATCH] loop: fix no-unmap write-zeroes request behavior Message-ID: <20191011075144.GA26033@infradead.org> References: <20191010170239.GC13098@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191010170239.GC13098@magnolia> User-Agent: Mutt/1.12.1 (2019-06-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Oct 10, 2019 at 10:02:39AM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong > > Currently, if the loop device receives a WRITE_ZEROES request, it asks > the underlying filesystem to punch out the range. This behavior is > correct if unmapping is allowed. However, a NOUNMAP request means that > the caller forbids us from freeing the storage backing the range, so > punching out the range is incorrect behavior. It doesn't really forbid, as most protocols don't have a way for forbid deallocation. It requests not to. Otherwise this looks fine, although I would have implemented it slightly differently: > case REQ_OP_FLUSH: > return lo_req_flush(lo, rq); > case REQ_OP_DISCARD: > - case REQ_OP_WRITE_ZEROES: > return lo_discard(lo, rq, pos); > + case REQ_OP_WRITE_ZEROES: > + return lo_zeroout(lo, rq, pos); This could just become: case REQ_OP_WRITE_ZEROES: if (rq->cmd_flags & REQ_NOUNMAP)) return lo_zeroout(lo, rq, pos); /*FALLTHRU*/ case REQ_OP_DISCARD: return lo_discard(lo, rq, pos);