Commit 0f843e65 authored by Guoju Fang's avatar Guoju Fang Committed by Jens Axboe
Browse files

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: default avatarGuoju Fang <fangguoju@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarColy Li <colyli@suse.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent f151ba98

drivers/md/bcache/bcache.h

+1 −0
Original line number Diff line number Diff line
@@ -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;

drivers/md/bcache/journal.c

+3 −3
Original line number Diff line number Diff line
@@ -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;

	}

drivers/md/bcache/super.c

+8 −0
Original line number Diff line number Diff line
@@ -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;

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