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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 AA3D7C433DF for ; Thu, 15 Oct 2020 16:43:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3ECB12226B for ; Thu, 15 Oct 2020 16:43:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="bQaSzufp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389918AbgJOQng (ORCPT ); Thu, 15 Oct 2020 12:43:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49876 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388946AbgJOQng (ORCPT ); Thu, 15 Oct 2020 12:43:36 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E7E28C061755; Thu, 15 Oct 2020 09:43:35 -0700 (PDT) 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=Hz/6L/k6/ZOdJL5HZTqoNr1Jk2Qpg013UruFF7Ew+Ak=; b=bQaSzufpfmAGrd9FrqRwxr4T5m X84DxXuyxdBxVSzNhwLsBArjvcHS/mpvQPMZpafZ2TFdCdqgJ61ukuXQ8z1+fRqIJN4wmquqbdjwb WlC/CzV4Pp78jUv25MprLTjKe1dtz28Q/PktQvYy7zVnE/E3avpBrh5UWPXm2Fgae7v6OeA7rDMq4 7iaqZGguIxyTRBXcyx5J0Q4M03apjgSaI7oKJVb+jf6v9ttPIG3pGr5Dj6oOGRgd2VxNiwCBRvGTx qATN08w9wjnLNiSCe1bkXvj5OwbEQdtYQ+VNCBA2TlI4A8jt7rVLQHJzG1ZvNjQL68Fr4DnKbAIwu E1bjNH9Q==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kT6Lm-0005af-0i; Thu, 15 Oct 2020 16:43:34 +0000 Date: Thu, 15 Oct 2020 17:43:33 +0100 From: Matthew Wilcox To: Christoph Hellwig Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, v9fs-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-afs@lists.infradead.org, ceph-devel@vger.kernel.org, linux-cifs@vger.kernel.org, ecryptfs@vger.kernel.org, linux-um@lists.infradead.org, linux-mtd@lists.infradead.org, Richard Weinberger , linux-xfs@vger.kernel.org Subject: Re: [PATCH v2 16/16] iomap: Make readpage synchronous Message-ID: <20201015164333.GA20115@casper.infradead.org> References: <20201009143104.22673-1-willy@infradead.org> <20201009143104.22673-17-willy@infradead.org> <20201015094203.GA21420@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201015094203.GA21420@infradead.org> Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Thu, Oct 15, 2020 at 10:42:03AM +0100, Christoph Hellwig wrote: > > +static void iomap_read_page_end_io(struct bio_vec *bvec, > > + struct completion *done, bool error) > > I really don't like the parameters here. Part of the problem is > that ctx is only assigned to bi_private conditionally, which can > easily be fixed. The other part is the strange bool error when > we can just pass on bi_stats. See the patch at the end of what > I'd do intead. I prefer assigning ctx conditionally to propagating the knowledge that !rac means synchronous. I've gone with this: static void iomap_read_page_end_io(struct bio_vec *bvec, - struct completion *done, bool error) + struct iomap_readpage_ctx *ctx, blk_status_t status) { struct page *page = bvec->bv_page; struct iomap_page *iop = to_iomap_page(page); - if (!error) + if (status == BLK_STS_OK) { iomap_set_range_uptodate(page, bvec->bv_offset, bvec->bv_len); + } else if (ctx && ctx->status == BLK_STS_OK) { + ctx->status = status; + } if (!iop || atomic_sub_and_test(bvec->bv_len, &iop->read_bytes_pending)) { - if (done) - complete(done); + if (ctx) + complete(&ctx->done); else unlock_page(page); } > > } else { > > WARN_ON_ONCE(ctx.cur_page_in_bio); > > - unlock_page(page); > > + complete(&ctx.done); > > } > > > > + wait_for_completion(&ctx.done); > > I don't think we need the complete / wait_for_completion dance in > this case. > > > + if (ret >= 0) > > + ret = blk_status_to_errno(ctx.status); > > + if (ret == 0) > > + return AOP_UPDATED_PAGE; > > + unlock_page(page); > > + return ret; > > Nipick, but I'd rather have a goto out_unlock for both error case > and have the AOP_UPDATED_PAGE for the normal path straight in line. > > Here is an untested patch with my suggestions: I think we can go a little further here: @@ -340,16 +335,12 @@ iomap_readpage(struct page *page, const struct iomap_ops * ops) if (ctx.bio) { submit_bio(ctx.bio); - WARN_ON_ONCE(!ctx.cur_page_in_bio); - } else { - WARN_ON_ONCE(ctx.cur_page_in_bio); - complete(&ctx.done); + wait_for_completion(&ctx.done); + if (ret > 0) + ret = blk_status_to_errno(ctx.status); } - wait_for_completion(&ctx.done); if (ret >= 0) - ret = blk_status_to_errno(ctx.status); - if (ret == 0) return AOP_UPDATED_PAGE; unlock_page(page); return ret; ... there's no need to call blk_status_to_errno if we never submitted a bio.