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authorTang Junhui <tang.junhui@zte.com.cn>2017-09-06 14:25:59 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-09-27 10:57:21 +0200
commit50aee960b0d1f55c2fb682ab54262bcceaf558aa (patch)
treefbce2d0fa51d833554e34e7bf0af94bd6e3077f5
parentc04dc907e590c85d84f252c1de390da1cfd5e3dc (diff)
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.h1
-rw-r--r--drivers/md/bcache/super.c2
-rw-r--r--drivers/md/bcache/writeback.c9
3 files changed, 10 insertions, 2 deletions
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 04f7bc28ef83..dfdd1908641c 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -348,6 +348,7 @@ 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 38522cc6b26d..8e5666ac8a6a 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1087,6 +1087,8 @@ 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 43dc9cb14d28..b0667b321a3f 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, &io->dc->disk);
- 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, int error)
@@ -211,7 +211,7 @@ static void read_dirty_submit(struct closure *cl)
closure_bio_submit(&io->bio, cl, &io->dc->disk);
- 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))