From patchwork Tue Mar 14 06:16:39 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 13173722 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 78414C74A44 for ; Tue, 14 Mar 2023 06:17:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229866AbjCNGRU (ORCPT ); Tue, 14 Mar 2023 02:17:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51508 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229832AbjCNGRR (ORCPT ); Tue, 14 Mar 2023 02:17:17 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2048B77E11 for ; Mon, 13 Mar 2023 23:17:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; 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=ouQi74ztiIsf1g9BY5UKzOb5A3asYmZ5/EMg4AbvHgQ=; b=kwwZFK9yGri+ZPsDAPhcaY8VXw l08YKhu2vhaIy8+Odn5b8vHWSRABhevKrMv+o7vHRfipbwK5RI93S9DcY9mBPkfEkUpXynmSxMEDk y3dGbu4yVA1YP1F+VegtTRSv7VY321AsPecxrr9m4m1F+aGAG21NPmOej40F3xu/qyk6toy3jvFFB Y8YYMCaTriSHIyzakLp80rh7VJpwSRPGEJ+NHO+Dozy5pQ702FiobFxGOQClN28AQz5Ivg+noNsxh ahgKlozmOlSyQDI+4wGCa0JdtMV9QQlZ3D8EmCO1691JVLZ4+cDmcJOQllmMUqZmhjvc16TSRks9F ar1iil+g==; Received: from 2a02-8389-2341-5b80-39d3-4735-9a3c-88d8.cable.dynamic.v6.surfer.at ([2a02:8389:2341:5b80:39d3:4735:9a3c:88d8] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1pbxyD-009Ai8-7F; Tue, 14 Mar 2023 06:17:13 +0000 From: Christoph Hellwig To: Chris Mason , Josef Bacik , David Sterba Cc: linux-btrfs@vger.kernel.org, Qu Wenruo Subject: [PATCH 05/21] btrfs: always read the entire extent_buffer Date: Tue, 14 Mar 2023 07:16:39 +0100 Message-Id: <20230314061655.245340-6-hch@lst.de> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230314061655.245340-1-hch@lst.de> References: <20230314061655.245340-1-hch@lst.de> MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Currently read_extent_buffer_pages skips pages that are already uptodate when reading in an extent_buffer. While this reduces the amount of data read, it increases the number of I/O operations as we now need to do multiple I/Os when reading an extent buffer with one or more uptodate pages in the middle of it. On any modern storage device, be that hard drives or SSDs this actually decreases I/O performance. Fortunately this case is pretty rare as the pages are always initially read together and then aged the same way. Besides simplifying the code a bit as-is this will allow for major simplifications to the I/O completion handler later on. Note that the case where all pages are uptodate is still handled by an optimized fast path that does not read any data from disk. Signed-off-by: Christoph Hellwig Reviewed-by: Qu Wenruo Reviewed-by: Johannes Thumshirn --- fs/btrfs/extent_io.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 2bc141b3f3bc4b..e7a0ef6d70bfe1 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4314,7 +4314,6 @@ int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num, int locked_pages = 0; int all_uptodate = 1; int num_pages; - unsigned long num_reads = 0; struct btrfs_bio_ctrl bio_ctrl = { .opf = REQ_OP_READ, .mirror_num = mirror_num, @@ -4360,10 +4359,8 @@ int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num, */ for (i = 0; i < num_pages; i++) { page = eb->pages[i]; - if (!PageUptodate(page)) { - num_reads++; + if (!PageUptodate(page)) all_uptodate = 0; - } } if (all_uptodate) { @@ -4373,7 +4370,7 @@ int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num, clear_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags); eb->read_mirror = 0; - atomic_set(&eb->io_pages, num_reads); + atomic_set(&eb->io_pages, num_pages); /* * It is possible for release_folio to clear the TREE_REF bit before we * set io_pages. See check_buffer_tree_ref for a more detailed comment. @@ -4383,13 +4380,9 @@ int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num, for (i = 0; i < num_pages; i++) { page = eb->pages[i]; - if (!PageUptodate(page)) { - ClearPageError(page); - submit_extent_page(&bio_ctrl, page_offset(page), page, - PAGE_SIZE, 0); - } else { - unlock_page(page); - } + ClearPageError(page); + submit_extent_page(&bio_ctrl, page_offset(page), page, + PAGE_SIZE, 0); } submit_one_bio(&bio_ctrl);