From patchwork Sun Oct 11 17:50:30 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Sterba X-Patchwork-Id: 7369431 Return-Path: X-Original-To: patchwork-linux-btrfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 96A3E9F1B9 for ; Sun, 11 Oct 2015 17:51:46 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id B425D206CD for ; Sun, 11 Oct 2015 17:51:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B3725206CC for ; Sun, 11 Oct 2015 17:51:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751972AbbJKRvk (ORCPT ); Sun, 11 Oct 2015 13:51:40 -0400 Received: from mx2.suse.de ([195.135.220.15]:37047 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751679AbbJKRvj (ORCPT ); Sun, 11 Oct 2015 13:51:39 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 5532BAC66 for ; Sun, 11 Oct 2015 17:51:37 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id BB686DAB45; Sun, 11 Oct 2015 19:50:30 +0200 (CEST) From: David Sterba To: linux-btrfs@vger.kernel.org Cc: David Sterba Subject: [PATCH 4/6] btrfs: add comments to barriers before waitqueue_active Date: Sun, 11 Oct 2015 19:50:30 +0200 Message-Id: X-Mailer: git-send-email 2.1.3 In-Reply-To: References: Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Reduce number of undocumented barriers out there. Signed-off-by: David Sterba --- fs/btrfs/compression.c | 3 +++ fs/btrfs/extent-tree.c | 3 +-- fs/btrfs/locking.c | 3 +++ fs/btrfs/ordered-data.c | 6 ++++++ fs/btrfs/transaction.c | 3 +++ 5 files changed, 16 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 57ee8ca29b06..3a9317ce67f8 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -839,6 +839,9 @@ static void free_workspace(int type, struct list_head *workspace) btrfs_compress_op[idx]->free_workspace(workspace); atomic_dec(alloc_workspace); wake: + /* + * Make sure counter is updated before we wake up waiters. + */ smp_mb(); if (waitqueue_active(workspace_wait)) wake_up(workspace_wait); diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 9f9604201333..59eb92f65c62 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -10363,8 +10363,7 @@ void btrfs_end_write_no_snapshoting(struct btrfs_root *root) { percpu_counter_dec(&root->subv_writers->counter); /* - * Make sure counter is updated before we wake up - * waiters. + * Make sure counter is updated before we wake up waiters. */ smp_mb(); if (waitqueue_active(&root->subv_writers->wait)) diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c index d7e6baf1b205..03f8630dbaf2 100644 --- a/fs/btrfs/locking.c +++ b/fs/btrfs/locking.c @@ -280,6 +280,9 @@ void btrfs_tree_unlock(struct extent_buffer *eb) if (blockers) { WARN_ON(atomic_read(&eb->spinning_writers)); atomic_dec(&eb->blocking_writers); + /* + * Make sure counter is updated before we wake up waiters. + */ smp_mb(); if (waitqueue_active(&eb->write_lock_wq)) wake_up(&eb->write_lock_wq); diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c index 52170cf1757e..071005f008c1 100644 --- a/fs/btrfs/ordered-data.c +++ b/fs/btrfs/ordered-data.c @@ -345,6 +345,9 @@ int btrfs_dec_test_first_ordered_pending(struct inode *inode, if (entry->bytes_left == 0) { ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags); + /* + * Implicit memory barrier after test_and_set_bit + */ if (waitqueue_active(&entry->wait)) wake_up(&entry->wait); } else { @@ -409,6 +412,9 @@ int btrfs_dec_test_ordered_pending(struct inode *inode, if (entry->bytes_left == 0) { ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags); + /* + * Implicit memory barrier after test_and_set_bit + */ if (waitqueue_active(&entry->wait)) wake_up(&entry->wait); } else { diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index e8e5b5a10719..3fd70f797b7d 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -861,6 +861,9 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans, atomic_dec(&cur_trans->num_writers); extwriter_counter_dec(cur_trans, trans->type); + /* + * Make sure counter is updated before we wake up waiters. + */ smp_mb(); if (waitqueue_active(&cur_trans->writer_wait)) wake_up(&cur_trans->writer_wait);