From patchwork Thu Mar 9 09:05:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 13167078 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 55110C61DA4 for ; Thu, 9 Mar 2023 09:07:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229683AbjCIJG7 (ORCPT ); Thu, 9 Mar 2023 04:06:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46628 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230180AbjCIJGk (ORCPT ); Thu, 9 Mar 2023 04:06:40 -0500 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 160BDE3A3 for ; Thu, 9 Mar 2023 01:06:00 -0800 (PST) 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=xsGLJqnG0/WyWeWCKXFCMRWvtebfnDs1asDH6FzmiYk=; b=HyXO9MJcmIIfjapFPlzq+DRNtM rxbJ3z98J1ajLKk/zkUQLyqftc4cHWBkt7N/2ul1ylc3zyR5MMRlgEEhUNSEx2trF12Rzlfab+A63 5jq6KvdJ1IDm8LerDCflyObVlpReOl8N3jo+h/4o2fEIxJPx4Ob/Rw8q0Oi719FyqZdqsyEf0rRdH P63Hew4K6wbQvGSTgj63YjqXYwK3aB5OsirPBuEV8h/XMSWeGgTOr2w/NM1GHHayWZUWYmFSx8svF ESLGBaiZl7vNf0Aa/oZdOshWfndiasC4RUfqKdQm39SMs32vDI4B7dcsqcUogfzmSdZ9iGTtA8+Gr PkUf9OBQ==; Received: from [2001:4bb8:190:782d:bc9d:fa49:9fec:5662] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1paCDk-008hcQ-Rx; Thu, 09 Mar 2023 09:05:57 +0000 From: Christoph Hellwig To: Chris Mason , Josef Bacik , David Sterba Cc: linux-btrfs@vger.kernel.org Subject: [PATCH 04/20] btrfs: always read the entire extent_buffer Date: Thu, 9 Mar 2023 10:05:10 +0100 Message-Id: <20230309090526.332550-5-hch@lst.de> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230309090526.332550-1-hch@lst.de> References: <20230309090526.332550-1-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 --- 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 302af9b01bda2a..26d8162bee000d 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4313,7 +4313,6 @@ 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, @@ -4359,10 +4358,8 @@ 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) { @@ -4372,7 +4369,7 @@ 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. @@ -4382,13 +4379,9 @@ 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);