diff options
| author | Tang Junhui <tang.junhui@zte.com.cn> | 2017-09-06 14:25:59 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-09-27 11:00:17 +0200 |
| commit | f522051a84e566b5552b3ba6127184d9cba54120 (patch) | |
| tree | 505404eb7f7630db7739d3af772ec7750da1feb0 | |
| parent | a6c5e7a0cd0184d3cf4fe29b598931329b237569 (diff) | |
| download | linux-stable-f522051a84e566b5552b3ba6127184d9cba54120.tar.gz linux-stable-f522051a84e566b5552b3ba6127184d9cba54120.tar.bz2 linux-stable-f522051a84e566b5552b3ba6127184d9cba54120.zip | |
bcache: fix for gc and write-back race
commit 9baf30972b5568d8b5bc8b3c46a6ec5b58100463 upstream.
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.
(Commit log re-organized by Coly Li to pass checkpatch.pl checking)
Signed-off-by: Tang Junhui <tang.junhui@zte.com.cn>
Acked-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/md/bcache/bcache.h | 1 | ||||
| -rw-r--r-- | drivers/md/bcache/super.c | 2 | ||||
| -rw-r--r-- | drivers/md/bcache/writeback.c | 9 |
3 files changed, 10 insertions, 2 deletions
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index c3ea03c9a1a8..02619cabda8b 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 46f4c7ee5560..c5ceea9222ff 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -1056,6 +1056,8 @@ 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 8513c5e43458..bbb1dc9e1639 100644 --- a/drivers/md/bcache/writeback.c +++ b/drivers/md/bcache/writeback.c @@ -191,7 +191,7 @@ 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) @@ -211,7 +211,7 @@ 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) @@ -523,6 +523,11 @@ 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)) |