From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nate Dailey , Coly Li , Shaohua Li Subject: [PATCH 4.14 128/193] raid1: prevent freeze_array/wait_all_barriers deadlock Date: Tue, 28 Nov 2017 11:26:15 +0100 Message-Id: <20171128100619.303923847@linuxfoundation.org> In-Reply-To: <20171128100613.638270407@linuxfoundation.org> References: <20171128100613.638270407@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nate Dailey commit f6eca2d43ed694ab8124dd24c88277f7eca93b7d upstream. If freeze_array is attempted in the middle of close_sync/ wait_all_barriers, deadlock can occur. freeze_array will wait for nr_pending and nr_queued to line up. wait_all_barriers increments nr_pending for each barrier bucket, one at a time, but doesn't actually issue IO that could be counted in nr_queued. So freeze_array is blocked until wait_all_barriers completes and allow_all_barriers runs. At the same time, when _wait_barrier sees array_frozen == 1, it stops and waits for freeze_array to complete. Prevent the deadlock by making close_sync call _wait_barrier and _allow_barrier for one bucket at a time, instead of deferring the _allow_barrier calls until after all _wait_barriers are complete. Signed-off-by: Nate Dailey Fix: fd76863e37fe(RAID1: a new I/O barrier implementation to remove resync window) Reviewed-by: Coly Li Signed-off-by: Shaohua Li Signed-off-by: Greg Kroah-Hartman --- drivers/md/raid1.c | 24 ++++++------------------ 1 file changed, 6 insertions(+), 18 deletions(-) --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -990,14 +990,6 @@ static void wait_barrier(struct r1conf * _wait_barrier(conf, idx); } -static void wait_all_barriers(struct r1conf *conf) -{ - int idx; - - for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++) - _wait_barrier(conf, idx); -} - static void _allow_barrier(struct r1conf *conf, int idx) { atomic_dec(&conf->nr_pending[idx]); @@ -1011,14 +1003,6 @@ static void allow_barrier(struct r1conf _allow_barrier(conf, idx); } -static void allow_all_barriers(struct r1conf *conf) -{ - int idx; - - for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++) - _allow_barrier(conf, idx); -} - /* conf->resync_lock should be held */ static int get_unqueued_pending(struct r1conf *conf) { @@ -1654,8 +1638,12 @@ static void print_conf(struct r1conf *co static void close_sync(struct r1conf *conf) { - wait_all_barriers(conf); - allow_all_barriers(conf); + int idx; + + for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++) { + _wait_barrier(conf, idx); + _allow_barrier(conf, idx); + } mempool_destroy(conf->r1buf_pool); conf->r1buf_pool = NULL;