From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A6ED08F70 for ; Sun, 16 Jul 2023 19:55:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A87AC433C7; Sun, 16 Jul 2023 19:55:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689537314; bh=dSJV2Pt02hqcoAgLSATVio9w1Ze7tmF/AomDT8ytcm4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jZWQkHgdtuJeXXj1UJrpd91V4QNTZseLg9LniBP3aGNIR5CAhV9jCAeU85zJpu9my mGTljCZgaEgPFycgaQ5ozQ9MUV7i0ju6RYgiosLMibmjfF/rP4NuekuVK76u2SVKld ZdWwayklaBGBTX1Z2EQAGgnuIOmmYYrmllhelzuA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Johannes Thumshirn , Qu Wenruo , Christoph Hellwig , David Sterba , Sasha Levin Subject: [PATCH 6.4 051/800] btrfs: always read the entire extent_buffer Date: Sun, 16 Jul 2023 21:38:24 +0200 Message-ID: <20230716194950.276988598@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230716194949.099592437@linuxfoundation.org> References: <20230716194949.099592437@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Christoph Hellwig [ Upstream commit e95382834cf885b478dbe14a66451b863eb35c94 ] 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. Reviewed-by: Johannes Thumshirn Reviewed-by: Qu Wenruo Signed-off-by: Christoph Hellwig Reviewed-by: David Sterba Signed-off-by: David Sterba Stable-dep-of: 7027f87108ce ("btrfs: don't treat zoned writeback as being from an async helper thread") Signed-off-by: Sasha Levin --- 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 a1adadd5d25dd..d1a635f237688 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); -- 2.39.2