Merge tag 'for-linus-20180825' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:
 "A few small fixes for this merge window:

   - Locking imbalance fix for bcache (Shan Hai)

   - A few small fixes for wbt. One is a cleanup/prep, one is a fix for
     an existing issue, and the last two are fixes for changes that went
     into this merge window (me)"

* tag 'for-linus-20180825' of git://git.kernel.dk/linux-block:
  blk-wbt: don't maintain inflight counts if disabled
  blk-wbt: fix has-sleeper queueing check
  blk-wbt: use wq_has_sleeper() for wq active check
  blk-wbt: move disable check into get_limit()
  bcache: release dc->writeback_lock properly in bch_writeback_thread()

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index bb109bb0a055378fb412269d9795b50b629946a4..3772671cf2bc5ad6322786b9531e9eb8bb6c7edd 100644 (file)
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -453,9 +453,26 @@ static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
        else if (val >= 0)
                val *= 1000ULL;
 
-       wbt_set_min_lat(q, val);
+       /*
+        * Ensure that the queue is idled, in case the latency update
+        * ends up either enabling or disabling wbt completely. We can't
+        * have IO inflight if that happens.
+        */
+       if (q->mq_ops) {
+               blk_mq_freeze_queue(q);
+               blk_mq_quiesce_queue(q);
+       } else
+               blk_queue_bypass_start(q);
 
+       wbt_set_min_lat(q, val);
        wbt_update_limits(q);
+
+       if (q->mq_ops) {
+               blk_mq_unquiesce_queue(q);
+               blk_mq_unfreeze_queue(q);
+       } else
+               blk_queue_bypass_end(q);
+
        return count;
 }
 

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index bb93c7c2b182bc8efee456bb64c4da5f05939e3c..84507d3e9a981d5e4888c9b3783f0155f992adba 100644 (file)
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -118,7 +118,7 @@ static void rwb_wake_all(struct rq_wb *rwb)
        for (i = 0; i < WBT_NUM_RWQ; i++) {
                struct rq_wait *rqw = &rwb->rq_wait[i];
 
-               if (waitqueue_active(&rqw->wait))
+               if (wq_has_sleeper(&rqw->wait))
                        wake_up_all(&rqw->wait);
        }
 }
@@ -162,7 +162,7 @@ static void __wbt_done(struct rq_qos *rqos, enum wbt_flags wb_acct)
        if (inflight && inflight >= limit)
                return;
 
-       if (waitqueue_active(&rqw->wait)) {
+       if (wq_has_sleeper(&rqw->wait)) {
                int diff = limit - inflight;
 
                if (!inflight || diff >= rwb->wb_background / 2)
@@ -449,6 +449,13 @@ static inline unsigned int get_limit(struct rq_wb *rwb, unsigned long rw)
 {
        unsigned int limit;
 
+       /*
+        * If we got disabled, just return UINT_MAX. This ensures that
+        * we'll properly inc a new IO, and dec+wakeup at the end.
+        */
+       if (!rwb_enabled(rwb))
+               return UINT_MAX;
+
        if ((rw & REQ_OP_MASK) == REQ_OP_DISCARD)
                return rwb->wb_background;
 
@@ -485,31 +492,17 @@ static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct,
 {
        struct rq_wait *rqw = get_rq_wait(rwb, wb_acct);
        DECLARE_WAITQUEUE(wait, current);
+       bool has_sleeper;
 
-       /*
-       * inc it here even if disabled, since we'll dec it at completion.
-       * this only happens if the task was sleeping in __wbt_wait(),
-       * and someone turned it off at the same time.
-       */
-       if (!rwb_enabled(rwb)) {
-               atomic_inc(&rqw->inflight);
-               return;
-       }
-
-       if (!waitqueue_active(&rqw->wait)
-               && rq_wait_inc_below(rqw, get_limit(rwb, rw)))
+       has_sleeper = wq_has_sleeper(&rqw->wait);
+       if (!has_sleeper && rq_wait_inc_below(rqw, get_limit(rwb, rw)))
                return;
 
        add_wait_queue_exclusive(&rqw->wait, &wait);
        do {
                set_current_state(TASK_UNINTERRUPTIBLE);
 
-               if (!rwb_enabled(rwb)) {
-                       atomic_inc(&rqw->inflight);
-                       break;
-               }
-
-               if (rq_wait_inc_below(rqw, get_limit(rwb, rw)))
+               if (!has_sleeper && rq_wait_inc_below(rqw, get_limit(rwb, rw)))
                        break;
 
                if (lock) {
@@ -518,6 +511,7 @@ static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct,
                        spin_lock_irq(lock);
                } else
                        io_schedule();
+               has_sleeper = false;
        } while (1);
 
        __set_current_state(TASK_RUNNING);
@@ -546,6 +540,9 @@ static enum wbt_flags bio_to_wbt_flags(struct rq_wb *rwb, struct bio *bio)
 {
        enum wbt_flags flags = 0;
 
+       if (!rwb_enabled(rwb))
+               return 0;
+
        if (bio_op(bio) == REQ_OP_READ) {
                flags = WBT_READ;
        } else if (wbt_should_throttle(rwb, bio)) {

diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 6be05bd7ca6711637ac04b57bc5c244caaa95f4b..08c3a9f9676c9e89649b56f765fb378973149a62 100644 (file)
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -685,8 +685,10 @@ static int bch_writeback_thread(void *arg)
                         * data on cache. BCACHE_DEV_DETACHING flag is set in
                         * bch_cached_dev_detach().
                         */
-                       if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
+                       if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
+                               up_write(&dc->writeback_lock);
                                break;
+                       }
                }
 
                up_write(&dc->writeback_lock);