From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from iad1-shared-relay2.dreamhost.com ([208.113.157.41]:45114 "EHLO iad1-shared-relay2.dreamhost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752445AbdF3KVT (ORCPT ); Fri, 30 Jun 2017 06:21:19 -0400 Received: from iad1-shared-relay1.dreamhost.com (iad1-shared-relay1.dreamhost.com [208.113.157.50]) by iad1-shared-relay2.dreamhost.com (Postfix) with ESMTP id B28B93E56B5 for ; Thu, 29 Jun 2017 15:21:09 -0700 (PDT) Received: from ware.dreamhost.com (ware.dreamhost.com [64.111.127.160]) by iad1-shared-relay1.dreamhost.com (Postfix) with ESMTP id 56CEDB400CF for ; Thu, 29 Jun 2017 15:21:08 -0700 (PDT) In-Reply-To: <20170629134510.GA32385@infradead.org> References: <20170629134510.GA32385@infradead.org> From: Tang Junhui Date: Tue, 27 Jun 2017 17:41:35 -0700 Subject: [PATCH 17/19] bcache: fix for gc and write-back race To: linux-block@vger.kernel.org Message-Id: <20170629222108.4362D100130@ware.dreamhost.com> Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org gc and write-back get raced (see the email "bcache get stucked" I sended before): gc thread write-back thread | |bch_writeback_thread() |bch_gc_thread() | | |==>read_dirty() |==>bch_btree_gc() | |==>btree_root() //get btree root | | node write locker | |==>bch_btree_gc_root() | | |==>read_dirty_submit() | |==>write_dirty() | |==>continue_at(cl, write_dirty_finish, system_wq); | |==>write_dirty_finish()//excute in system_wq | |==>bch_btree_insert() | |==>bch_btree_map_leaf_nodes() | |==>__bch_btree_map_nodes() | |==>btree_root //try to get btree root node read lock | |-----stuck here |==>bch_btree_set_root() | |==>bch_journal_meta() | |==>bch_journal() | |==>journal_try_write() | |==>journal_write_unlocked() //journal_full(&c->journal) condition satisfied |==>continue_at(cl, journal_write, system_wq); //try to excute journal_write in system_wq | //but work queue is excuting write_dirty_finish() |==>closure_sync(); //wait journal_write execute over and wake up gc, | --stuck here |==>release root node write locker This patch alloc a separate work-queue for write-back thread to avoid such race. Signed-off-by: Tang Junhui Cc: stable@vger.kernel.org --- drivers/md/bcache/bcache.h | 1 + drivers/md/bcache/super.c | 2 ++ drivers/md/bcache/writeback.c | 8 ++++++-- 3 files changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index 44123e4..deb0a6c 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -333,6 +333,7 @@ struct cached_dev { /* Limit number of writeback bios in flight */ struct semaphore in_flight; struct task_struct *writeback_thread; + struct workqueue_struct *writeback_write_wq; struct keybuf writeback_keys; diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index e06641e..24cb9b7 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -1063,6 +1063,8 @@ static void cached_dev_free(struct closure *cl) cancel_delayed_work_sync(&dc->writeback_rate_update); if (!IS_ERR_OR_NULL(dc->writeback_thread)) kthread_stop(dc->writeback_thread); + if (dc->writeback_write_wq) + destroy_workqueue(dc->writeback_write_wq); mutex_lock(&bch_register_lock); diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c index 4104eaa..4bc5daa 100644 --- a/drivers/md/bcache/writeback.c +++ b/drivers/md/bcache/writeback.c @@ -189,7 +189,7 @@ static void write_dirty(struct closure *cl) closure_bio_submit(&io->bio, cl); - continue_at(cl, write_dirty_finish, system_wq); + continue_at(cl, write_dirty_finish, io->dc->writeback_write_wq); } static void read_dirty_endio(struct bio *bio) @@ -209,7 +209,7 @@ static void read_dirty_submit(struct closure *cl) closure_bio_submit(&io->bio, cl); - continue_at(cl, write_dirty, system_wq); + continue_at(cl, write_dirty, io->dc->writeback_write_wq); } static void read_dirty(struct cached_dev *dc) @@ -527,6 +527,10 @@ void bch_cached_dev_writeback_init(struct cached_dev *dc) int bch_cached_dev_writeback_start(struct cached_dev *dc) { + dc->writeback_write_wq = alloc_workqueue("bcache_writeback_wq", WQ_MEM_RECLAIM, 0); + if (!dc->writeback_write_wq) + return -ENOMEM; + dc->writeback_thread = kthread_create(bch_writeback_thread, dc, "bcache_writeback"); if (IS_ERR(dc->writeback_thread)) -- 1.8.3.1