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

Pull block fixes from Jens Axboe:
 "A smaller collection of fixes for the block core that would be nice to
  have in -rc2.  This pull request contains:

   - Fixes for races in the wait/wakeup logic used in blk-mq from
     Alexander.  No issues have been observed, but it is definitely a
     bit flakey currently.  Alternatively, we may drop the cyclic
     wakeups going forward, but that needs more testing.

   - Some cleanups from Christoph.

   - Fix for an oops in null_blk if queue_mode=1 and softirq completions
     are used.  From me.

   - A fix for a regression caused by the chunk size setting.  It
     inadvertently used max_hw_sectors instead of max_sectors, which is
     incorrect, and causes hangs on btrfs multi-disk setups (where hw
     sectors apparently isn't set).  From me.

   - Removal of WQ_POWER_EFFICIENT in the kblockd creation.  This was a
     recent addition as well, but it actually breaks blk-mq which relies
     on strict scheduling.  If the workqueue power_efficient mode is
     turned on, this breaks blk-mq.  From Matias.

   - null_blk module parameter description fix from Mike"

* 'for-linus' of git://git.kernel.dk/linux-block:
  blk-mq: bitmap tag: fix races in bt_get() function
  blk-mq: bitmap tag: fix race on blk_mq_bitmap_tags::wake_cnt
  blk-mq: bitmap tag: fix races on shared ::wake_index fields
  block: blk_max_size_offset() should check ->max_sectors
  null_blk: fix softirq completions for queue_mode == 1
  blk-mq: merge blk_mq_drain_queue and __blk_mq_drain_queue
  blk-mq: properly drain stopped queues
  block: remove WQ_POWER_EFFICIENT from kblockd
  null_blk: fix name and description of 'queue_mode' module parameter
  block: remove elv_abort_queue and blk_abort_flushes

11 files changed, 50 insertions, 96 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index f6f6b9af3e3f..6f8dba161bfe 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -3312,8 +3312,7 @@ int __init blk_dev_init(void)
 
         /* used for unplugging and affects IO latency/throughput - HIGHPRI */
         kblockd_workqueue = alloc_workqueue("kblockd",
-                                            WQ_MEM_RECLAIM | WQ_HIGHPRI |
-                                            WQ_POWER_EFFICIENT, 0);
+                                            WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
         if (!kblockd_workqueue)
                 panic("Failed to create kblockd\n");
 
diff --git a/block/blk-flush.c b/block/blk-flush.c
index 8ffee4b5f93d..3cb5e9e7108a 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -422,44 +422,6 @@ void blk_insert_flush(struct request *rq)
 }
 
 /**
- * blk_abort_flushes - @q is being aborted, abort flush requests
- * @q: request_queue being aborted
- *
- * To be called from elv_abort_queue().  @q is being aborted.  Prepare all
- * FLUSH/FUA requests for abortion.
- *
- * CONTEXT:
- * spin_lock_irq(q->queue_lock)
- */
-void blk_abort_flushes(struct request_queue *q)
-{
-        struct request *rq, *n;
-        int i;
-
-        /*
-         * Requests in flight for data are already owned by the dispatch
-         * queue or the device driver.  Just restore for normal completion.
-         */
-        list_for_each_entry_safe(rq, n, &q->flush_data_in_flight, flush.list) {
-                list_del_init(&rq->flush.list);
-                blk_flush_restore_request(rq);
-        }
-
-        /*
-         * We need to give away requests on flush queues.  Restore for
-         * normal completion and put them on the dispatch queue.
-         */
-        for (i = 0; i < ARRAY_SIZE(q->flush_queue); i++) {
-                list_for_each_entry_safe(rq, n, &q->flush_queue[i],
-                                         flush.list) {
-                        list_del_init(&rq->flush.list);
-                        blk_flush_restore_request(rq);
-                        list_add_tail(&rq->queuelist, &q->queue_head);
-                }
-        }
-}
-
-/**
  * blkdev_issue_flush - queue a flush
  * @bdev:       blockdev to issue flush for
  * @gfp_mask:   memory allocation flags (for bio_alloc)
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 1aab39f71d95..c1b92426c95e 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -43,9 +43,16 @@ bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
         return bt_has_free_tags(&tags->bitmap_tags);
 }
 
-static inline void bt_index_inc(unsigned int *index)
+static inline int bt_index_inc(int index)
 {
-        *index = (*index + 1) & (BT_WAIT_QUEUES - 1);
+        return (index + 1) & (BT_WAIT_QUEUES - 1);
+}
+
+static inline void bt_index_atomic_inc(atomic_t *index)
+{
+        int old = atomic_read(index);
+        int new = bt_index_inc(old);
+        atomic_cmpxchg(index, old, new);
 }
 
 /*
@@ -69,14 +76,14 @@ static void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags)
         int i, wake_index;
 
         bt = &tags->bitmap_tags;
-        wake_index = bt->wake_index;
+        wake_index = atomic_read(&bt->wake_index);
         for (i = 0; i < BT_WAIT_QUEUES; i++) {
                 struct bt_wait_state *bs = &bt->bs[wake_index];
 
                 if (waitqueue_active(&bs->wait))
                         wake_up(&bs->wait);
 
-                bt_index_inc(&wake_index);
+                wake_index = bt_index_inc(wake_index);
         }
 }
 
@@ -212,12 +219,14 @@ static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt,
                                          struct blk_mq_hw_ctx *hctx)
 {
         struct bt_wait_state *bs;
+        int wait_index;
 
         if (!hctx)
                 return &bt->bs[0];
 
-        bs = &bt->bs[hctx->wait_index];
-        bt_index_inc(&hctx->wait_index);
+        wait_index = atomic_read(&hctx->wait_index);
+        bs = &bt->bs[wait_index];
+        bt_index_atomic_inc(&hctx->wait_index);
         return bs;
 }
 
@@ -239,18 +248,12 @@ static int bt_get(struct blk_mq_alloc_data *data,
 
         bs = bt_wait_ptr(bt, hctx);
         do {
-                bool was_empty;
-
-                was_empty = list_empty(&wait.task_list);
                 prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE);
 
                 tag = __bt_get(hctx, bt, last_tag);
                 if (tag != -1)
                         break;
 
-                if (was_empty)
-                        atomic_set(&bs->wait_cnt, bt->wake_cnt);
-
                 blk_mq_put_ctx(data->ctx);
 
                 io_schedule();
@@ -313,18 +316,19 @@ static struct bt_wait_state *bt_wake_ptr(struct blk_mq_bitmap_tags *bt)
 {
         int i, wake_index;
 
-        wake_index = bt->wake_index;
+        wake_index = atomic_read(&bt->wake_index);
         for (i = 0; i < BT_WAIT_QUEUES; i++) {
                 struct bt_wait_state *bs = &bt->bs[wake_index];
 
                 if (waitqueue_active(&bs->wait)) {
-                        if (wake_index != bt->wake_index)
-                                bt->wake_index = wake_index;
+                        int o = atomic_read(&bt->wake_index);
+                        if (wake_index != o)
+                                atomic_cmpxchg(&bt->wake_index, o, wake_index);
 
                         return bs;
                 }
 
-                bt_index_inc(&wake_index);
+                wake_index = bt_index_inc(wake_index);
         }
 
         return NULL;
@@ -334,6 +338,7 @@ static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag)
 {
         const int index = TAG_TO_INDEX(bt, tag);
         struct bt_wait_state *bs;
+        int wait_cnt;
 
         /*
          * The unlock memory barrier need to order access to req in free
@@ -342,10 +347,19 @@ static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag)
         clear_bit_unlock(TAG_TO_BIT(bt, tag), &bt->map[index].word);
 
         bs = bt_wake_ptr(bt);
-        if (bs && atomic_dec_and_test(&bs->wait_cnt)) {
-                atomic_set(&bs->wait_cnt, bt->wake_cnt);
-                bt_index_inc(&bt->wake_index);
+        if (!bs)
+                return;
+
+        wait_cnt = atomic_dec_return(&bs->wait_cnt);
+        if (wait_cnt == 0) {
+wake:
+                atomic_add(bt->wake_cnt, &bs->wait_cnt);
+                bt_index_atomic_inc(&bt->wake_index);
                 wake_up(&bs->wait);
+        } else if (wait_cnt < 0) {
+                wait_cnt = atomic_inc_return(&bs->wait_cnt);
+                if (!wait_cnt)
+                        goto wake;
         }
 }
 
@@ -499,10 +513,13 @@ static int bt_alloc(struct blk_mq_bitmap_tags *bt, unsigned int depth,
                 return -ENOMEM;
         }
 
-        for (i = 0; i < BT_WAIT_QUEUES; i++)
+        bt_update_count(bt, depth);
+
+        for (i = 0; i < BT_WAIT_QUEUES; i++) {
                 init_waitqueue_head(&bt->bs[i].wait);
+                atomic_set(&bt->bs[i].wait_cnt, bt->wake_cnt);
+        }
 
-        bt_update_count(bt, depth);
         return 0;
 }
 
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index 98696a65d4d4..6206ed17ef76 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -24,7 +24,7 @@ struct blk_mq_bitmap_tags {
         unsigned int map_nr;
         struct blk_align_bitmap *map;
 
-        unsigned int wake_index;
+        atomic_t wake_index;
         struct bt_wait_state *bs;
 };
 
diff --git a/block/blk-mq.c b/block/blk-mq.c
index e11f5f8e0313..0ef2dc7f01bf 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -109,7 +109,7 @@ static void blk_mq_queue_exit(struct request_queue *q)
         __percpu_counter_add(&q->mq_usage_counter, -1, 1000000);
 }
 
-static void __blk_mq_drain_queue(struct request_queue *q)
+void blk_mq_drain_queue(struct request_queue *q)
 {
         while (true) {
                 s64 count;
@@ -120,7 +120,7 @@ static void __blk_mq_drain_queue(struct request_queue *q)
 
                 if (count == 0)
                         break;
-                blk_mq_run_queues(q, false);
+                blk_mq_start_hw_queues(q);
                 msleep(10);
         }
 }
@@ -139,12 +139,7 @@ static void blk_mq_freeze_queue(struct request_queue *q)
         spin_unlock_irq(q->queue_lock);
 
         if (drain)
-                __blk_mq_drain_queue(q);
-}
-
-void blk_mq_drain_queue(struct request_queue *q)
-{
-        __blk_mq_drain_queue(q);
+                blk_mq_drain_queue(q);
 }
 
 static void blk_mq_unfreeze_queue(struct request_queue *q)
diff --git a/block/blk.h b/block/blk.h
index 45385e9abf6f..6748c4f8d7a1 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -84,7 +84,6 @@ static inline void blk_clear_rq_complete(struct request *rq)
 #define ELV_ON_HASH(rq) ((rq)->cmd_flags & REQ_HASHED)
 
 void blk_insert_flush(struct request *rq);
-void blk_abort_flushes(struct request_queue *q);
 
 static inline struct request *__elv_next_request(struct request_queue *q)
 {
diff --git a/block/elevator.c b/block/elevator.c
index f35edddfe9b5..34bded18910e 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -729,26 +729,6 @@ int elv_may_queue(struct request_queue *q, int rw)
         return ELV_MQUEUE_MAY;
 }
 
-void elv_abort_queue(struct request_queue *q)
-{
-        struct request *rq;
-
-        blk_abort_flushes(q);
-
-        while (!list_empty(&q->queue_head)) {
-                rq = list_entry_rq(q->queue_head.next);
-                rq->cmd_flags |= REQ_QUIET;
-                trace_block_rq_abort(q, rq);
-                /*
-                 * Mark this request as started so we don't trigger
-                 * any debug logic in the end I/O path.
-                 */
-                blk_start_request(rq);
-                __blk_end_request_all(rq, -EIO);
-        }
-}
-EXPORT_SYMBOL(elv_abort_queue);
-
 void elv_completed_request(struct request_queue *q, struct request *rq)
 {
         struct elevator_queue *e = q->elevator;
diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 77087a29b127..a3b042c4d448 100644
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -79,7 +79,7 @@ MODULE_PARM_DESC(home_node, "Home node for the device");
 
 static int queue_mode = NULL_Q_MQ;
 module_param(queue_mode, int, S_IRUGO);
-MODULE_PARM_DESC(use_mq, "Use blk-mq interface (0=bio,1=rq,2=multiqueue)");
+MODULE_PARM_DESC(queue_mode, "Block interface to use (0=bio,1=rq,2=multiqueue)");
 
 static int gb = 250;
 module_param(gb, int, S_IRUGO);
@@ -227,7 +227,10 @@ static void null_cmd_end_timer(struct nullb_cmd *cmd)
 
 static void null_softirq_done_fn(struct request *rq)
 {
-        end_cmd(blk_mq_rq_to_pdu(rq));
+        if (queue_mode == NULL_Q_MQ)
+                end_cmd(blk_mq_rq_to_pdu(rq));
+        else
+                end_cmd(rq->special);
 }
 
 static inline void null_handle_cmd(struct nullb_cmd *cmd)
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index a002cf191427..eb726b9c5762 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -42,7 +42,7 @@ struct blk_mq_hw_ctx {
         unsigned int            nr_ctx;
         struct blk_mq_ctx       **ctxs;
 
-        unsigned int            wait_index;
+        atomic_t                wait_index;
 
         struct blk_mq_tags      *tags;
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 31e11051f1ba..713f8b62b435 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -920,7 +920,7 @@ static inline unsigned int blk_max_size_offset(struct request_queue *q,
                                                sector_t offset)
 {
         if (!q->limits.chunk_sectors)
-                return q->limits.max_hw_sectors;
+                return q->limits.max_sectors;
 
         return q->limits.chunk_sectors -
                         (offset & (q->limits.chunk_sectors - 1));
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 4ff262e2bf37..e2a6bd7fb133 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -133,7 +133,6 @@ extern struct request *elv_latter_request(struct request_queue *, struct request
 extern int elv_register_queue(struct request_queue *q);
 extern void elv_unregister_queue(struct request_queue *q);
 extern int elv_may_queue(struct request_queue *, int);
-extern void elv_abort_queue(struct request_queue *);
 extern void elv_completed_request(struct request_queue *, struct request *);
 extern int elv_set_request(struct request_queue *q, struct request *rq,
                            struct bio *bio, gfp_t gfp_mask);