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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 9DC8FC433E7 for ; Thu, 15 Oct 2020 16:43:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B799C22255 for ; Thu, 15 Oct 2020 16:43:43 +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="bQaSzufp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B799C22255 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 17A476B005D; Thu, 15 Oct 2020 12:43:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 151046B0068; Thu, 15 Oct 2020 12:43:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 08E1B6B006E; Thu, 15 Oct 2020 12:43:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0124.hostedemail.com [216.40.44.124]) by kanga.kvack.org (Postfix) with ESMTP id D067F6B005D for ; Thu, 15 Oct 2020 12:43:42 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 71C72180AD807 for ; Thu, 15 Oct 2020 16:43:42 +0000 (UTC) X-FDA: 77374731084.27.bells23_3315d2527216 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 3562C3D669 for ; Thu, 15 Oct 2020 16:43:42 +0000 (UTC) X-HE-Tag: bells23_3315d2527216 X-Filterd-Recvd-Size: 4836 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Thu, 15 Oct 2020 16:43:38 +0000 (UTC) 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> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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.