From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f196.google.com ([209.85.216.196]:37768 "EHLO mail-qt0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753545AbeBBRxd (ORCPT ); Fri, 2 Feb 2018 12:53:33 -0500 Date: Fri, 2 Feb 2018 09:53:28 -0800 From: Tejun Heo To: Jens Axboe , Miklos Szeredi Cc: Joshua Miller , kernel-team@fb.com, Johannes Weiner , Jan Kara , stable@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH 1/2] bdi: make sure congestion states are clear on free Message-ID: <20180202175328.GL1121507@devbig577.frc2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org List-ID: FUSE has a bug where it fails to clear congestion states if a connection gets aborted while congested, which can leave nr_wb_congested[] stuck until reboot causing wait_iff_congested() to wait spuriously. While the bdi owner, FUSE, is primarily responsible for clearing congestion states before destroying bdi_writebacks, bdi layer can ensure that congestion states are not leaked beyond bdi_writeback lifecycle. Signed-off-by: Tejun Heo Reported-by: Joshua Miller Cc: Johannes Weiner Cc: Jan Kara Cc: stable@vger.kernel.org --- include/linux/backing-dev.h | 14 +++++++++++++- mm/backing-dev.c | 2 +- 2 files changed, 14 insertions(+), 2 deletions(-) --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -220,6 +220,18 @@ static inline int bdi_sched_wait(void *w return 0; } +static inline void __wb_congested_free(struct bdi_writeback_congested *congested) +{ + /* + * Make sure congestion states are cleared before freeing to avoid + * nr_wb_congested() corruption which can lead to misbehaving + * wait_iff_congested(). + */ + clear_wb_congested(congested, BLK_RW_SYNC); + clear_wb_congested(congested, BLK_RW_ASYNC); + kfree(congested); +} + #ifdef CONFIG_CGROUP_WRITEBACK struct bdi_writeback_congested * @@ -409,7 +421,7 @@ wb_congested_get_create(struct backing_d static inline void wb_congested_put(struct bdi_writeback_congested *congested) { if (atomic_dec_and_test(&congested->refcnt)) - kfree(congested); + __wb_congested_free(congested); } static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi) --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -509,7 +509,7 @@ void wb_congested_put(struct bdi_writeba } spin_unlock_irqrestore(&cgwb_lock, flags); - kfree(congested); + __wb_congested_free(congested); } static void cgwb_release_workfn(struct work_struct *work)