From patchwork Wed Feb 19 21:01:02 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 11392621 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 637CA138D for ; Wed, 19 Feb 2020 21:02:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3A4AA24654 for ; Wed, 19 Feb 2020 21:02:35 +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="Rr0Isn6K" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727780AbgBSVBG (ORCPT ); Wed, 19 Feb 2020 16:01:06 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:35922 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727648AbgBSVBF (ORCPT ); Wed, 19 Feb 2020 16:01:05 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=8zYEi4IG7gzAvMHdDHY3fStOc4dh5wVqKWm99G/lD2Q=; b=Rr0Isn6KV0yiQsuTepKXa8KVhx +JyO+IlvzFzA0z8sV2iMvtsm9Pv6cgJBZMIpSg1cP4Tx/ZMk08ueKIw29L1ptgphnFq+2Q+86II+5 PJNKMmaiCDdBTTJcDI/iXmLXg84N2WswF5/urdiVm5BTv6ykoK2n3od2eyCx5s1P6nY1KF4YFoSKI volIkWq8cBw6eiWFrgoZdNhCO9tAL9ZiLKXZMPI9znsj3s/nMwWW9pTQdBxelt0H9avPXVOec5UVz t7L9I6CkSyQomfI4fzLa6hPYbkKOJATGVMcI+Zu0LuHW7aFhXW23e3VE3cpt3VyFwn6ldkAqvOfZV bM3ipe0w==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1j4WSv-0008VZ-JM; Wed, 19 Feb 2020 21:01:05 +0000 From: Matthew Wilcox To: linux-fsdevel@vger.kernel.org Cc: "Matthew Wilcox (Oracle)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, ocfs2-devel@oss.oracle.com, linux-xfs@vger.kernel.org Subject: [PATCH v7 23/24] mm: Document why we don't set PageReadahead Date: Wed, 19 Feb 2020 13:01:02 -0800 Message-Id: <20200219210103.32400-24-willy@infradead.org> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20200219210103.32400-1-willy@infradead.org> References: <20200219210103.32400-1-willy@infradead.org> MIME-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: "Matthew Wilcox (Oracle)" If the page is already in cache, we don't set PageReadahead on it. Signed-off-by: Matthew Wilcox (Oracle) --- mm/readahead.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/mm/readahead.c b/mm/readahead.c index 453ef146de83..bbe7208fcc2d 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -196,9 +196,12 @@ void page_cache_readahead_unbounded(struct address_space *mapping, if (page && !xa_is_value(page)) { /* - * Page already present? Kick off the current batch of - * contiguous pages before continuing with the next - * batch. + * Page already present? Kick off the current batch + * of contiguous pages before continuing with the + * next batch. This page may be the one we would + * have intended to mark as Readahead, but we don't + * have a stable reference to this page, and it's + * not worth getting one just for that. */ read_pages(&rac, &page_pool); continue;