Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block into for-3.18

This is to receive 0a30288da1ae ("blk-mq, percpu_ref: implement a
kludge for SCSI blk-mq stall during probe") which implements
__percpu_ref_kill_expedited() to work around SCSI blk-mq stall.  The
commit reverted and patches to implement proper fix will be added.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>

1 files changed, 119 insertions, 43 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 702df07b980d..255d79c14dc1 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -112,18 +112,31 @@ static void blk_mq_usage_counter_release(struct percpu_ref *ref)
  */
 void blk_mq_freeze_queue(struct request_queue *q)
 {
+        bool freeze;
+
         spin_lock_irq(q->queue_lock);
-        q->mq_freeze_depth++;
+        freeze = !q->mq_freeze_depth++;
         spin_unlock_irq(q->queue_lock);
 
-        percpu_ref_kill(&q->mq_usage_counter);
-        blk_mq_run_queues(q, false);
+        if (freeze) {
+                /*
+                 * XXX: Temporary kludge to work around SCSI blk-mq stall.
+                 * SCSI synchronously creates and destroys many queues
+                 * back-to-back during probe leading to lengthy stalls.
+                 * This will be fixed by keeping ->mq_usage_counter in
+                 * atomic mode until genhd registration, but, for now,
+                 * let's work around using expedited synchronization.
+                 */
+                __percpu_ref_kill_expedited(&q->mq_usage_counter);
+
+                blk_mq_run_queues(q, false);
+        }
         wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter));
 }
 
 static void blk_mq_unfreeze_queue(struct request_queue *q)
 {
-        bool wake = false;
+        bool wake;
 
         spin_lock_irq(q->queue_lock);
         wake = !--q->mq_freeze_depth;
@@ -172,6 +185,8 @@ static void blk_mq_rq_ctx_init(struct request_queue *q, struct blk_mq_ctx *ctx,
         /* tag was already set */
         rq->errors = 0;
 
+        rq->cmd = rq->__cmd;
+
         rq->extra_len = 0;
         rq->sense_len = 0;
         rq->resid_len = 0;
@@ -197,7 +212,6 @@ __blk_mq_alloc_request(struct blk_mq_alloc_data *data, int rw)
         if (tag != BLK_MQ_TAG_FAIL) {
                 rq = data->hctx->tags->rqs[tag];
 
-                rq->cmd_flags = 0;
                 if (blk_mq_tag_busy(data->hctx)) {
                         rq->cmd_flags = REQ_MQ_INFLIGHT;
                         atomic_inc(&data->hctx->nr_active);
@@ -252,6 +266,7 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx,
 
         if (rq->cmd_flags & REQ_MQ_INFLIGHT)
                 atomic_dec(&hctx->nr_active);
+        rq->cmd_flags = 0;
 
         clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
         blk_mq_put_tag(hctx, tag, &ctx->last_tag);
@@ -387,6 +402,12 @@ static void blk_mq_start_request(struct request *rq, bool last)
         blk_add_timer(rq);
 
         /*
+         * Ensure that ->deadline is visible before set the started
+         * flag and clear the completed flag.
+         */
+        smp_mb__before_atomic();
+
+        /*
          * Mark us as started and clear complete. Complete might have been
          * set if requeue raced with timeout, which then marked it as
          * complete. So be sure to clear complete again when we start
@@ -467,7 +488,11 @@ static void blk_mq_requeue_work(struct work_struct *work)
                 blk_mq_insert_request(rq, false, false, false);
         }
 
-        blk_mq_run_queues(q, false);
+        /*
+         * Use the start variant of queue running here, so that running
+         * the requeue work will kick stopped queues.
+         */
+        blk_mq_start_hw_queues(q);
 }
 
 void blk_mq_add_to_requeue_list(struct request *rq, bool at_head)
@@ -951,14 +976,9 @@ void blk_mq_insert_request(struct request *rq, bool at_head, bool run_queue,
 
         hctx = q->mq_ops->map_queue(q, ctx->cpu);
 
-        if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA) &&
-            !(rq->cmd_flags & (REQ_FLUSH_SEQ))) {
-                blk_insert_flush(rq);
-        } else {
-                spin_lock(&ctx->lock);
-                __blk_mq_insert_request(hctx, rq, at_head);
-                spin_unlock(&ctx->lock);
-        }
+        spin_lock(&ctx->lock);
+        __blk_mq_insert_request(hctx, rq, at_head);
+        spin_unlock(&ctx->lock);
 
         if (run_queue)
                 blk_mq_run_hw_queue(hctx, async);
@@ -1068,13 +1088,17 @@ static void blk_mq_bio_to_request(struct request *rq, struct bio *bio)
                 blk_account_io_start(rq, 1);
 }
 
+static inline bool hctx_allow_merges(struct blk_mq_hw_ctx *hctx)
+{
+        return (hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
+                !blk_queue_nomerges(hctx->queue);
+}
+
 static inline bool blk_mq_merge_queue_io(struct blk_mq_hw_ctx *hctx,
                                          struct blk_mq_ctx *ctx,
                                          struct request *rq, struct bio *bio)
 {
-        struct request_queue *q = hctx->queue;
-
-        if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE)) {
+        if (!hctx_allow_merges(hctx)) {
                 blk_mq_bio_to_request(rq, bio);
                 spin_lock(&ctx->lock);
 insert_rq:
@@ -1082,6 +1106,8 @@ insert_rq:
                 spin_unlock(&ctx->lock);
                 return false;
         } else {
+                struct request_queue *q = hctx->queue;
+
                 spin_lock(&ctx->lock);
                 if (!blk_mq_attempt_merge(q, ctx, bio)) {
                         blk_mq_bio_to_request(rq, bio);
@@ -1309,6 +1335,7 @@ static void blk_mq_free_rq_map(struct blk_mq_tag_set *set,
                                 continue;
                         set->ops->exit_request(set->driver_data, tags->rqs[i],
                                                 hctx_idx, i);
+                        tags->rqs[i] = NULL;
                 }
         }
 
@@ -1342,8 +1369,9 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
 
         INIT_LIST_HEAD(&tags->page_list);
 
-        tags->rqs = kmalloc_node(set->queue_depth * sizeof(struct request *),
-                                        GFP_KERNEL, set->numa_node);
+        tags->rqs = kzalloc_node(set->queue_depth * sizeof(struct request *),
+                                 GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY,
+                                 set->numa_node);
         if (!tags->rqs) {
                 blk_mq_free_tags(tags);
                 return NULL;
@@ -1367,8 +1395,9 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
                         this_order--;
 
                 do {
-                        page = alloc_pages_node(set->numa_node, GFP_KERNEL,
-                                                this_order);
+                        page = alloc_pages_node(set->numa_node,
+                                GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY,
+                                this_order);
                         if (page)
                                 break;
                         if (!this_order--)
@@ -1389,11 +1418,15 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
                 left -= to_do * rq_size;
                 for (j = 0; j < to_do; j++) {
                         tags->rqs[i] = p;
+                        tags->rqs[i]->atomic_flags = 0;
+                        tags->rqs[i]->cmd_flags = 0;
                         if (set->ops->init_request) {
                                 if (set->ops->init_request(set->driver_data,
                                                 tags->rqs[i], hctx_idx, i,
-                                                set->numa_node))
+                                                set->numa_node)) {
+                                        tags->rqs[i] = NULL;
                                         goto fail;
+                                }
                         }
 
                         p += rq_size;
@@ -1404,7 +1437,6 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
         return tags;
 
 fail:
-        pr_warn("%s: failed to allocate requests\n", __func__);
         blk_mq_free_rq_map(set, tags, hctx_idx);
         return NULL;
 }
@@ -1574,7 +1606,7 @@ static int blk_mq_init_hw_queues(struct request_queue *q,
                 hctx->tags = set->tags[i];
 
                 /*
-                 * Allocate space for all possible cpus to avoid allocation in
+                 * Allocate space for all possible cpus to avoid allocation at
                  * runtime
                  */
                 hctx->ctxs = kmalloc_node(nr_cpu_ids * sizeof(void *),
@@ -1662,8 +1694,8 @@ static void blk_mq_map_swqueue(struct request_queue *q)
 
         queue_for_each_hw_ctx(q, hctx, i) {
                 /*
-                 * If not software queues are mapped to this hardware queue,
-                 * disable it and free the request entries
+                 * If no software queues are mapped to this hardware queue,
+                 * disable it and free the request entries.
                  */
                 if (!hctx->nr_ctx) {
                         struct blk_mq_tag_set *set = q->tag_set;
@@ -1713,14 +1745,10 @@ static void blk_mq_del_queue_tag_set(struct request_queue *q)
 {
         struct blk_mq_tag_set *set = q->tag_set;
 
-        blk_mq_freeze_queue(q);
-
         mutex_lock(&set->tag_list_lock);
         list_del_init(&q->tag_set_list);
         blk_mq_update_tag_set_depth(set);
         mutex_unlock(&set->tag_list_lock);
-
-        blk_mq_unfreeze_queue(q);
 }
 
 static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
@@ -1929,6 +1957,60 @@ static int blk_mq_queue_reinit_notify(struct notifier_block *nb,
         return NOTIFY_OK;
 }
 
+static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
+{
+        int i;
+
+        for (i = 0; i < set->nr_hw_queues; i++) {
+                set->tags[i] = blk_mq_init_rq_map(set, i);
+                if (!set->tags[i])
+                        goto out_unwind;
+        }
+
+        return 0;
+
+out_unwind:
+        while (--i >= 0)
+                blk_mq_free_rq_map(set, set->tags[i], i);
+
+        return -ENOMEM;
+}
+
+/*
+ * Allocate the request maps associated with this tag_set. Note that this
+ * may reduce the depth asked for, if memory is tight. set->queue_depth
+ * will be updated to reflect the allocated depth.
+ */
+static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
+{
+        unsigned int depth;
+        int err;
+
+        depth = set->queue_depth;
+        do {
+                err = __blk_mq_alloc_rq_maps(set);
+                if (!err)
+                        break;
+
+                set->queue_depth >>= 1;
+                if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN) {
+                        err = -ENOMEM;
+                        break;
+                }
+        } while (set->queue_depth);
+
+        if (!set->queue_depth || err) {
+                pr_err("blk-mq: failed to allocate request map\n");
+                return -ENOMEM;
+        }
+
+        if (depth != set->queue_depth)
+                pr_info("blk-mq: reduced tag depth (%u -> %u)\n",
+                                                depth, set->queue_depth);
+
+        return 0;
+}
+
 /*
  * Alloc a tag set to be associated with one or more request queues.
  * May fail with EINVAL for various error conditions. May adjust the
@@ -1937,8 +2019,6 @@ static int blk_mq_queue_reinit_notify(struct notifier_block *nb,
  */
 int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 {
-        int i;
-
         if (!set->nr_hw_queues)
                 return -EINVAL;
         if (!set->queue_depth)
@@ -1959,23 +2039,18 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
                                  sizeof(struct blk_mq_tags *),
                                  GFP_KERNEL, set->numa_node);
         if (!set->tags)
-                goto out;
+                return -ENOMEM;
 
-        for (i = 0; i < set->nr_hw_queues; i++) {
-                set->tags[i] = blk_mq_init_rq_map(set, i);
-                if (!set->tags[i])
-                        goto out_unwind;
-        }
+        if (blk_mq_alloc_rq_maps(set))
+                goto enomem;
 
         mutex_init(&set->tag_list_lock);
         INIT_LIST_HEAD(&set->tag_list);
 
         return 0;
-
-out_unwind:
-        while (--i >= 0)
-                blk_mq_free_rq_map(set, set->tags[i], i);
-out:
+enomem:
+        kfree(set->tags);
+        set->tags = NULL;
         return -ENOMEM;
 }
 EXPORT_SYMBOL(blk_mq_alloc_tag_set);
@@ -1990,6 +2065,7 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
         }
 
         kfree(set->tags);
+        set->tags = NULL;
 }
 EXPORT_SYMBOL(blk_mq_free_tag_set);