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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 B7669C433DB for ; Tue, 9 Feb 2021 07:52:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 87FEA64EAA for ; Tue, 9 Feb 2021 07:52:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229503AbhBIHwH (ORCPT ); Tue, 9 Feb 2021 02:52:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40572 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229611AbhBIHwF (ORCPT ); Tue, 9 Feb 2021 02:52:05 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 45783C061788 for ; Mon, 8 Feb 2021 23:51:25 -0800 (PST) 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=EM9ebD6T3YZ87BljQm1u4zKY1Qrjyi/gchis3HgKbnk=; b=YGzn4qrByn1VVeMq+/1eaeN9Bn uXSEv/OlTWPm/BeEW/Kdhl/HT4f3R2hEMOrm0KZbsVggbBQT2XTHY1LJJY/kgK/4Xge7Ix39IvtyE vtM7hvsEnqZyAqbQPQQxZ4SqWmZdd/X16PB4/Xvjsq4e6Ltx2kjixVl9TYr3KfGjz81Z5hYInRh66 49gPC/oC4Cn8J1ommGY/szMCvKXH/We41B4v7Z2WqOPtR7aHkopBzuj6lvjUn6jdIkqZHWwt2dkPL ynISjv/1nWkjiPs1Xeo10zf0Ju/iiawOK2TOcGS7RwT7MWixnxJj2HfxwG7f1ko1kuwawzTf3j0Dk qu0TPG4g==; Received: from hch by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1l9Nnr-0077sW-Us; Tue, 09 Feb 2021 07:51:21 +0000 Date: Tue, 9 Feb 2021 07:51:19 +0000 From: Christoph Hellwig To: Jens Axboe Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, hch@infradead.org, akpm@linux-foundation.org Subject: Re: [PATCH 3/3] iomap: use filemap_range_needs_writeback() for O_DIRECT reads Message-ID: <20210209075119.GC1696555@infradead.org> References: <20210209023008.76263-1-axboe@kernel.dk> <20210209023008.76263-4-axboe@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210209023008.76263-4-axboe@kernel.dk> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Feb 08, 2021 at 07:30:08PM -0700, Jens Axboe wrote: > + if (iocb->ki_flags & IOCB_NOWAIT) { > + if (filemap_range_needs_writeback(mapping, pos, end)) { > + ret = -EAGAIN; > + goto out_free_dio; > + } > + flags |= IOMAP_NOWAIT; > + } > if (iter_is_iovec(iter)) > dio->flags |= IOMAP_DIO_DIRTY; > } else { > + if (iocb->ki_flags & IOCB_NOWAIT) { > + if (filemap_range_has_page(mapping, pos, end)) { > + ret = -EAGAIN; > + goto out_free_dio; > + } > + flags |= IOMAP_NOWAIT; > + } > + > flags |= IOMAP_WRITE; > dio->flags |= IOMAP_DIO_WRITE; > > @@ -478,14 +493,6 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, > dio->flags |= IOMAP_DIO_WRITE_FUA; > } > > - if (iocb->ki_flags & IOCB_NOWAIT) { > - if (filemap_range_has_page(mapping, pos, end)) { > - ret = -EAGAIN; > - goto out_free_dio; > - } > - flags |= IOMAP_NOWAIT; > - } looking at this I really hate the scheme with the potential racyness and duplicated page looksups. Why can't we pass a nonblock flag to filemap_write_and_wait_range and invalidate_inode_pages2_range that makes them return -EAGAIN when they would block to clean this whole mess up?