From patchwork Fri Sep 7 14:55:22 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Sterba X-Patchwork-Id: 10592261 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 62590921 for ; Fri, 7 Sep 2018 14:55:42 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 461A22B560 for ; Fri, 7 Sep 2018 14:55:42 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3A6322B5A9; Fri, 7 Sep 2018 14:55:42 +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=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, 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 C47332B560 for ; Fri, 7 Sep 2018 14:55:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730047AbeIGTg5 (ORCPT ); Fri, 7 Sep 2018 15:36:57 -0400 Received: from mx2.suse.de ([195.135.220.15]:50666 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727856AbeIGTg5 (ORCPT ); Fri, 7 Sep 2018 15:36:57 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id D64F1ACBB for ; Fri, 7 Sep 2018 14:55:38 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id EE3FBDAD81; Fri, 7 Sep 2018 16:55:22 +0200 (CEST) From: David Sterba To: linux-btrfs@vger.kernel.org Cc: David Sterba Subject: [PATCH 10/11] btrfs: dev-replace: remove custom read/write blocking scheme Date: Fri, 7 Sep 2018 16:55:22 +0200 Message-Id: X-Mailer: git-send-email 2.18.0 In-Reply-To: References: Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP After the rw semaphore has been added, the custom blocking using ::blocking_readers and ::read_lock_wq is redundant. The blocking logic in __btrfs_map_block is replaced by extending the time the semaphore is held, that has the same blocking effect on writes as the previous custom scheme that waited until ::blocking_readers was zero. Signed-off-by: David Sterba --- fs/btrfs/ctree.h | 2 -- fs/btrfs/dev-replace.c | 16 ---------------- fs/btrfs/dev-replace.h | 1 - fs/btrfs/disk-io.c | 2 -- fs/btrfs/volumes.c | 13 ++++++------- 5 files changed, 6 insertions(+), 28 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 02b5372a42d7..2a255d5897f8 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -367,8 +367,6 @@ struct btrfs_dev_replace { struct mutex lock_finishing_cancel_unmount; struct rw_semaphore rwsem; - atomic_t blocking_readers; - wait_queue_head_t read_lock_wq; struct btrfs_scrub_progress scrub_progress; diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index ddaa9dcf8284..e8c2f418b2d7 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -965,14 +965,7 @@ void btrfs_dev_replace_read_unlock(struct btrfs_dev_replace *dev_replace) void btrfs_dev_replace_write_lock(struct btrfs_dev_replace *dev_replace) { -again: - wait_event(dev_replace->read_lock_wq, - atomic_read(&dev_replace->blocking_readers) == 0); down_write(&dev_replace->rwsem); - if (atomic_read(&dev_replace->blocking_readers)) { - up_write(&dev_replace->rwsem); - goto again; - } } void btrfs_dev_replace_write_unlock(struct btrfs_dev_replace *dev_replace) @@ -980,15 +973,6 @@ void btrfs_dev_replace_write_unlock(struct btrfs_dev_replace *dev_replace) up_write(&dev_replace->rwsem); } -/* inc blocking cnt and release read lock */ -void btrfs_dev_replace_set_lock_blocking( - struct btrfs_dev_replace *dev_replace) -{ - /* only set blocking for read lock */ - atomic_inc(&dev_replace->blocking_readers); - up_read(&dev_replace->rwsem); -} - void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info) { percpu_counter_inc(&fs_info->dev_replace.bio_counter); diff --git a/fs/btrfs/dev-replace.h b/fs/btrfs/dev-replace.h index 795c551f5b5e..eec7289c2618 100644 --- a/fs/btrfs/dev-replace.h +++ b/fs/btrfs/dev-replace.h @@ -26,6 +26,5 @@ void btrfs_dev_replace_read_lock(struct btrfs_dev_replace *dev_replace); void btrfs_dev_replace_read_unlock(struct btrfs_dev_replace *dev_replace); void btrfs_dev_replace_write_lock(struct btrfs_dev_replace *dev_replace); void btrfs_dev_replace_write_unlock(struct btrfs_dev_replace *dev_replace); -void btrfs_dev_replace_set_lock_blocking(struct btrfs_dev_replace *dev_replace); #endif diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 3f73f2a3d67b..520b1d6f615f 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -2155,9 +2155,7 @@ static void btrfs_init_dev_replace_locks(struct btrfs_fs_info *fs_info) { mutex_init(&fs_info->dev_replace.lock_finishing_cancel_unmount); init_rwsem(&fs_info->dev_replace.rwsem); - atomic_set(&fs_info->dev_replace.blocking_readers, 0); init_waitqueue_head(&fs_info->dev_replace.replace_wait); - init_waitqueue_head(&fs_info->dev_replace.read_lock_wq); } static void btrfs_init_qgroup(struct btrfs_fs_info *fs_info) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 762a4499d00a..d1f83529ac80 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -5706,10 +5706,12 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, btrfs_dev_replace_read_lock(dev_replace); dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(dev_replace); + /* + * Hold the semaphore for read during the whole operation, write is + * requested at commit time but must wait. + */ if (!dev_replace_is_ongoing) btrfs_dev_replace_read_unlock(dev_replace); - else - btrfs_dev_replace_set_lock_blocking(dev_replace); if (dev_replace_is_ongoing && mirror_num == map->num_stripes + 1 && !need_full_stripe(op) && dev_replace->tgtdev != NULL) { @@ -5904,11 +5906,8 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, } out: if (dev_replace_is_ongoing) { - ASSERT(atomic_read(&dev_replace->blocking_readers) > 0); - btrfs_dev_replace_read_lock(dev_replace); - /* Barrier implied by atomic_dec_and_test */ - if (atomic_dec_and_test(&dev_replace->blocking_readers)) - cond_wake_up_nomb(&dev_replace->read_lock_wq); + lockdep_assert_held(&dev_replace->rwsem); + /* Unlock and let waiting writers proceed */ btrfs_dev_replace_read_unlock(dev_replace); } free_extent_map(em);