From patchwork Tue Apr 14 15:02:22 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Matthew Wilcox (Oracle)" X-Patchwork-Id: 11488109 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 455BB15AB for ; Tue, 14 Apr 2020 15:04:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2D5CC2076D for ; Tue, 14 Apr 2020 15:04:47 +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="mVT1NSNp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407161AbgDNPEN (ORCPT ); Tue, 14 Apr 2020 11:04:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43558 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405635AbgDNPCq (ORCPT ); Tue, 14 Apr 2020 11:02:46 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C226C03C1AD; Tue, 14 Apr 2020 08:02:41 -0700 (PDT) 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=wgHaMQ5NgsDKhTvfEwz+JAE6nlgMEKsX9P0uFTq8za0=; b=mVT1NSNp4+99ljtt8f5ensst1H BVN9ODww8/c4MKOX1APGFzeneBVLRxMFCc2GXaB3wFMrQtvT87NSC0nLVH4Ir7GVIADnlHy7ruhV9 d0vpxR70DyLbIhoPTYtmPAAb4YTMvpBUjtmFpAZmFQrAYzrbrHiUMmBebE8LE0QtToKrgBWhXWfl8 M57DLAhccVC9xC6vdxATVRnAzCSBZFBKkDZNxwlXvmpf9HutyUjq74veM+s5TR2/B6rIxfZiksWyV O6La15VtrLxkSJi6lyVR/jl/kkIIbv8f+Le7ZaSJJYx1c3rjAki3fFnbvWkmdr0RyHnInKmW1seFo OiLMGEOw==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jON5A-0006Ox-73; Tue, 14 Apr 2020 15:02:36 +0000 From: Matthew Wilcox To: Andrew Morton Cc: "Matthew Wilcox (Oracle)" , linux-fsdevel@vger.kernel.org, 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, Christoph Hellwig , William Kucharski Subject: [PATCH v11 14/25] mm: Document why we don't set PageReadahead Date: Tue, 14 Apr 2020 08:02:22 -0700 Message-Id: <20200414150233.24495-15-willy@infradead.org> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20200414150233.24495-1-willy@infradead.org> References: <20200414150233.24495-1-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) Reviewed-by: Christoph Hellwig Reviewed-by: William Kucharski --- mm/readahead.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/mm/readahead.c b/mm/readahead.c index ae231a5312cb..73cb59ed5cff 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -195,9 +195,12 @@ 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, true); continue;