From patchwork Thu Jul 6 11:21:15 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Damien Le Moal X-Patchwork-Id: 9828049 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id C689F602BD for ; Thu, 6 Jul 2017 11:21:56 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B84122861A for ; Thu, 6 Jul 2017 11:21:56 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id ACD7728627; Thu, 6 Jul 2017 11:21:56 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E650228619 for ; Thu, 6 Jul 2017 11:21:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751865AbdGFLVz (ORCPT ); Thu, 6 Jul 2017 07:21:55 -0400 Received: from esa2.hgst.iphmx.com ([68.232.143.124]:55052 "EHLO esa2.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750977AbdGFLVy (ORCPT ); Thu, 6 Jul 2017 07:21:54 -0400 X-IronPort-AV: E=Sophos;i="5.40,317,1496073600"; d="scan'208";a="128340020" Received: from sjappemgw12.hgst.com (HELO sjappemgw11.hgst.com) ([199.255.44.66]) by ob1.hgst.iphmx.com with ESMTP; 06 Jul 2017 19:36:11 +0800 Received: from washi.fujisawa.hgst.com ([10.80.170.19]) by sjappemgw11.hgst.com with ESMTP; 06 Jul 2017 04:21:16 -0700 From: Damien Le Moal To: linux-block@vger.kernel.org, Jens Axboe Cc: Christoph Hellwig Subject: [PATCH v3] block: Fix __blkdev_issue_zeroout loop Date: Thu, 6 Jul 2017 20:21:15 +0900 Message-Id: <20170706112115.616-1-damien.lemoal@wdc.com> X-Mailer: git-send-email 2.9.4 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The BIO issuing loop in __blkdev_issue_zeroout() is allocating BIOs with a maximum number of bvec (pages) equal to min(nr_sects, (sector_t)BIO_MAX_PAGES) This works since the requested number of bvecs will always be limited to the absolute maximum number supported (BIO_MAX_PAGES), but this is ineficient as too many bvec entries may be requested due to the different units being used in the min() operation (number of sectors vs number of pages). To fix this, introduce the helper __blkdev_sectors_to_bio_pages() to correctly calculate the number of bvecs for zeroout BIOs as the issuing loop progresses. The calculation is done using consistent units and makes sure that the number of pages return is at least 1 (for cases where the number of sectors is less that the number of sectors in a page). Also remove a trailing space after the bit shift in the internal loop min() call. Signed-off-by: Damien Le Moal Reviewed-by: Christoph Hellwig --- block/blk-lib.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/block/blk-lib.c b/block/blk-lib.c index e8caecd..3fe0aec 100644 --- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -261,6 +261,19 @@ static int __blkdev_issue_write_zeroes(struct block_device *bdev, return 0; } +/* + * Convert a number of 512B sectors to a number of pages. + * The result is limited to a number of pages that can fit into a BIO. + * Also make sure that the result is always at least 1 (page) for the cases + * where nr_sects is lower than the number of sectors in a page. + */ +static unsigned int __blkdev_sectors_to_bio_pages(sector_t nr_sects) +{ + sector_t bytes = (nr_sects << 9) + PAGE_SIZE - 1; + + return min(bytes >> PAGE_SHIFT, (sector_t)BIO_MAX_PAGES); +} + /** * __blkdev_issue_zeroout - generate number of zero filed write bios * @bdev: blockdev to issue @@ -307,18 +320,18 @@ int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector, ret = 0; while (nr_sects != 0) { - bio = next_bio(bio, min(nr_sects, (sector_t)BIO_MAX_PAGES), - gfp_mask); + bio = next_bio(bio, __blkdev_sectors_to_bio_pages(nr_sects), + gfp_mask); bio->bi_iter.bi_sector = sector; bio->bi_bdev = bdev; bio_set_op_attrs(bio, REQ_OP_WRITE, 0); while (nr_sects != 0) { - sz = min((sector_t) PAGE_SIZE >> 9 , nr_sects); - bi_size = bio_add_page(bio, ZERO_PAGE(0), sz << 9, 0); + sz = min((sector_t) PAGE_SIZE, nr_sects << 9); + bi_size = bio_add_page(bio, ZERO_PAGE(0), sz, 0); nr_sects -= bi_size >> 9; sector += bi_size >> 9; - if (bi_size < (sz << 9)) + if (bi_size < sz) break; } cond_resched();