From patchwork Mon Feb 17 18:45:46 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 11387373 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 7937917F0 for ; Mon, 17 Feb 2020 18:48:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 597BB22525 for ; Mon, 17 Feb 2020 18:48:27 +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="l7hv3PdT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729280AbgBQSsJ (ORCPT ); Mon, 17 Feb 2020 13:48:09 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:48162 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729898AbgBQSqW (ORCPT ); Mon, 17 Feb 2020 13:46:22 -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=f6e1vXABPDL0rMBXcPDUicTcSHShodWe/Rf26ms+MIM=; b=l7hv3PdTD5FlyDvtWj7UIPyYIh pFC/dM1GbjDjHpQBTch+Ju7Tj6oFrw59IcILNGPJj2pRhPguzUqywp4ihcqCujOiORMcLauMi6++M kn6iUgpEid7/AdCzyF06VM+n6zhEa4s9iKGvJ120z70Va5ZAEKt7ybAjLiNO1ZRtcnYM7cRhfYHny FViLwoiNRNq0gdWXh6D6fvopIONeuQBtk3up9M2TW0Ly/0YrIA1GEBuqfD5GflLHZuRNw8q2V6UNg AioV/Bgo3ETArbEHNGlWf/KkKm7VWOmabymzPwLel4x8sURqCjyXn6tWcxXkHiaNRugSbhMboBXBa CMyA7Qyw==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1j3lPL-00058v-ER; Mon, 17 Feb 2020 18:46:15 +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 v6 04/16] mm: Tweak readahead loop slightly Date: Mon, 17 Feb 2020 10:45:46 -0800 Message-Id: <20200217184613.19668-6-willy@infradead.org> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20200217184613.19668-1-willy@infradead.org> References: <20200217184613.19668-1-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)" Eliminate the page_offset variable which was just confusing; record the start of each consecutive run of pages in the readahead_control, and move the 'kick off a fresh batch' code to the end of the function for easier use in the next patch. Signed-off-by: Matthew Wilcox (Oracle) --- mm/readahead.c | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-) diff --git a/mm/readahead.c b/mm/readahead.c index 15329309231f..74791b96013f 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -154,7 +154,6 @@ void __do_page_cache_readahead(struct address_space *mapping, unsigned long lookahead_size) { struct inode *inode = mapping->host; - struct page *page; unsigned long end_index; /* The last page we want to read */ LIST_HEAD(page_pool); int page_idx; @@ -163,6 +162,7 @@ void __do_page_cache_readahead(struct address_space *mapping, struct readahead_control rac = { .mapping = mapping, .file = filp, + ._start = offset, ._nr_pages = 0, }; @@ -175,32 +175,39 @@ void __do_page_cache_readahead(struct address_space *mapping, * Preallocate as many pages as we will need. */ for (page_idx = 0; page_idx < nr_to_read; page_idx++) { - pgoff_t page_offset = offset + page_idx; + struct page *page; - if (page_offset > end_index) + if (offset > end_index) break; - page = xa_load(&mapping->i_pages, page_offset); + page = xa_load(&mapping->i_pages, offset); 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. */ - if (readahead_count(&rac)) - read_pages(&rac, &page_pool, gfp_mask); - rac._nr_pages = 0; - continue; + goto read; } page = __page_cache_alloc(gfp_mask); if (!page) break; - page->index = page_offset; + page->index = offset; list_add(&page->lru, &page_pool); if (page_idx == nr_to_read - lookahead_size) SetPageReadahead(page); rac._nr_pages++; + offset++; + continue; +read: + if (readahead_count(&rac)) + read_pages(&rac, &page_pool, gfp_mask); + rac._nr_pages = 0; + rac._start = ++offset; } /*