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

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 <>
Signed-off-by: default avatarColy Li <>
Signed-off-by: default avatarJens Axboe <>
parent f151ba98
......@@ -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;
......@@ -485,7 +485,7 @@ static void do_journal_discard(struct cache *ca)
INIT_WORK(&ja->discard_work, journal_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];
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)
continue_at(cl, journal_write, system_wq);
continue_at(cl, journal_write, bch_journal_wq);
......@@ -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)
if (bcache_wq)
if (bch_journal_wq)
if (bcache_major)
unregister_blkdev(bcache_major, "bcache");
......@@ -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;
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment