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bcache: add separate workqueue for journal_write to avoid deadlock 

After write SSD completed, bcache schedules journal_write work to
system_wq, which is a public workqueue in system, without WQ_MEM_RECLAIM
flag. system_wq is also a bound wq, and there may be no idle kworker on
current processor. Creating a new kworker may unfortunately need to
reclaim memory first, by shrinking cache and slab used by vfs, which
depends on bcache device. That's a deadlock.

This patch create a new workqueue for journal_write with WQ_MEM_RECLAIM
flag. It's rescuer thread will work to avoid the deadlock.

Signed-off-by: Guoju Fang <fangguoju@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Guoju Fang 2018-09-27 23:41:46 +08:00 committed by Jens Axboe
parent f151ba989d
commit 0f843e65d9
3 changed files with 12 additions and 3 deletions
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1
drivers/md/bcache/bcache.h
View File

@ -965,6 +965,7 @@ void bch_prio_write(struct cache *ca);
void bch_write_bdev_super(struct cached_dev *dc, struct closure *parent);
extern struct workqueue_struct *bcache_wq;
extern struct workqueue_struct *bch_journal_wq;
extern struct mutex bch_register_lock;
extern struct list_head bch_cache_sets;

6
drivers/md/bcache/journal.c
View File

@ -485,7 +485,7 @@ static void do_journal_discard(struct cache *ca)
closure_get(&ca->set->cl);
INIT_WORK(&ja->discard_work, journal_discard_work);
schedule_work(&ja->discard_work);
queue_work(bch_journal_wq, &ja->discard_work);
}
}
@ -592,7 +592,7 @@ static void journal_write_done(struct closure *cl)
: &j->w[0];
__closure_wake_up(&w->wait);
continue_at_nobarrier(cl, journal_write, system_wq);
continue_at_nobarrier(cl, journal_write, bch_journal_wq);
}
static void journal_write_unlock(struct closure *cl)
@ -627,7 +627,7 @@ static void journal_write_unlocked(struct closure *cl)
spin_unlock(&c->journal.lock);
btree_flush_write(c);
continue_at(cl, journal_write, system_wq);
continue_at(cl, journal_write, bch_journal_wq);
return;
}

8
drivers/md/bcache/super.c
View File

@ -47,6 +47,7 @@ static int bcache_major;
static DEFINE_IDA(bcache_device_idx);
static wait_queue_head_t unregister_wait;
struct workqueue_struct *bcache_wq;
struct workqueue_struct *bch_journal_wq;
#define BTREE_MAX_PAGES (256 * 1024 / PAGE_SIZE)
/* limitation of partitions number on single bcache device */
@ -2341,6 +2342,9 @@ static void bcache_exit(void)
kobject_put(bcache_kobj);
if (bcache_wq)
destroy_workqueue(bcache_wq);
if (bch_journal_wq)
destroy_workqueue(bch_journal_wq);
if (bcache_major)
unregister_blkdev(bcache_major, "bcache");
unregister_reboot_notifier(&reboot);
@ -2370,6 +2374,10 @@ static int __init bcache_init(void)
if (!bcache_wq)
goto err;
bch_journal_wq = alloc_workqueue("bch_journal", WQ_MEM_RECLAIM, 0);
if (!bch_journal_wq)
goto err;
bcache_kobj = kobject_create_and_add("bcache", fs_kobj);
if (!bcache_kobj)
goto err;