3.16.62-rc1 review patch. If anyone has any objections, please let me know.
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From: Guoju Fang fangguoju@gmail.com
commit 0f843e65d9eef4936929bb036c5f771fb261eea4 upstream.
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 Signed-off-by: Coly Li colyli@suse.de Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/md/bcache/bcache.h | 1 + drivers/md/bcache/journal.c | 6 +++--- drivers/md/bcache/super.c | 8 ++++++++ 3 files changed, 12 insertions(+), 3 deletions(-)
--- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -898,6 +898,7 @@ void bch_prio_write(struct cache *); void bch_write_bdev_super(struct cached_dev *, struct closure *);
extern struct workqueue_struct *bcache_wq; +extern struct workqueue_struct *bch_journal_wq; extern const char * const bch_cache_modes[]; extern struct mutex bch_register_lock; extern struct list_head bch_cache_sets; --- a/drivers/md/bcache/journal.c +++ b/drivers/md/bcache/journal.c @@ -454,7 +454,7 @@ static void do_journal_discard(struct 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); } }
@@ -559,7 +559,7 @@ static void journal_write_done(struct 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) @@ -592,7 +592,7 @@ static void journal_write_unlocked(struc 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; }
--- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -56,6 +56,7 @@ static int bcache_major; static DEFINE_IDA(bcache_minor); 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)
@@ -2112,6 +2113,9 @@ 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); @@ -2142,6 +2146,10 @@ 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;