blk-mq: make the sysfs mq/ layout reflect current mappings

Currently blk-mq registers all the hardware queues in sysfs,
regardless of whether it uses them (e.g. they have CPU mappings)
or not. The unused hardware queues lack the cpux/ directories,
and the other sysfs entries (like active, pending, etc) are all
zeroes.

Change this so that sysfs correctly reflects the current mappings
of the hardware queues.

Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 83 insertions, 19 deletions

diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 99a60a829e69..e5f575ff0bf9 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -327,6 +327,42 @@ static struct kobj_type blk_mq_hw_ktype = {
         .release        = blk_mq_sysfs_release,
 };
 
+void blk_mq_unregister_hctx(struct blk_mq_hw_ctx *hctx)
+{
+        struct blk_mq_ctx *ctx;
+        int i;
+
+        if (!hctx->nr_ctx || !(hctx->flags & BLK_MQ_F_SYSFS_UP))
+                return;
+
+        hctx_for_each_ctx(hctx, ctx, i)
+                kobject_del(&ctx->kobj);
+
+        kobject_del(&hctx->kobj);
+}
+
+int blk_mq_register_hctx(struct blk_mq_hw_ctx *hctx)
+{
+        struct request_queue *q = hctx->queue;
+        struct blk_mq_ctx *ctx;
+        int i, ret;
+
+        if (!hctx->nr_ctx || !(hctx->flags & BLK_MQ_F_SYSFS_UP))
+                return 0;
+
+        ret = kobject_add(&hctx->kobj, &q->mq_kobj, "%u", hctx->queue_num);
+        if (ret)
+                return ret;
+
+        hctx_for_each_ctx(hctx, ctx, i) {
+                ret = kobject_add(&ctx->kobj, &hctx->kobj, "cpu%u", ctx->cpu);
+                if (ret)
+                        break;
+        }
+
+        return ret;
+}
+
 void blk_mq_unregister_disk(struct gendisk *disk)
 {
         struct request_queue *q = disk->queue;
@@ -335,11 +371,11 @@ void blk_mq_unregister_disk(struct gendisk *disk)
         int i, j;
 
         queue_for_each_hw_ctx(q, hctx, i) {
-                hctx_for_each_ctx(hctx, ctx, j) {
-                        kobject_del(&ctx->kobj);
+                blk_mq_unregister_hctx(hctx);
+
+                hctx_for_each_ctx(hctx, ctx, j)
                         kobject_put(&ctx->kobj);
-                }
-                kobject_del(&hctx->kobj);
+
                 kobject_put(&hctx->kobj);
         }
 
@@ -350,15 +386,30 @@ void blk_mq_unregister_disk(struct gendisk *disk)
         kobject_put(&disk_to_dev(disk)->kobj);
 }
 
+static void blk_mq_sysfs_init(struct request_queue *q)
+{
+        struct blk_mq_hw_ctx *hctx;
+        struct blk_mq_ctx *ctx;
+        int i, j;
+
+        kobject_init(&q->mq_kobj, &blk_mq_ktype);
+
+        queue_for_each_hw_ctx(q, hctx, i) {
+                kobject_init(&hctx->kobj, &blk_mq_hw_ktype);
+
+                hctx_for_each_ctx(hctx, ctx, j)
+                        kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);
+        }
+}
+
 int blk_mq_register_disk(struct gendisk *disk)
 {
         struct device *dev = disk_to_dev(disk);
         struct request_queue *q = disk->queue;
         struct blk_mq_hw_ctx *hctx;
-        struct blk_mq_ctx *ctx;
-        int ret, i, j;
+        int ret, i;
 
-        kobject_init(&q->mq_kobj, &blk_mq_ktype);
+        blk_mq_sysfs_init(q);
 
         ret = kobject_add(&q->mq_kobj, kobject_get(&dev->kobj), "%s", "mq");
         if (ret < 0)
@@ -367,20 +418,10 @@ int blk_mq_register_disk(struct gendisk *disk)
         kobject_uevent(&q->mq_kobj, KOBJ_ADD);
 
         queue_for_each_hw_ctx(q, hctx, i) {
-                kobject_init(&hctx->kobj, &blk_mq_hw_ktype);
-                ret = kobject_add(&hctx->kobj, &q->mq_kobj, "%u", i);
+                hctx->flags |= BLK_MQ_F_SYSFS_UP;
+                ret = blk_mq_register_hctx(hctx);
                 if (ret)
                         break;
-
-                if (!hctx->nr_ctx)
-                        continue;
-
-                hctx_for_each_ctx(hctx, ctx, j) {
-                        kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);
-                        ret = kobject_add(&ctx->kobj, &hctx->kobj, "cpu%u", ctx->cpu);
-                        if (ret)
-                                break;
-                }
         }
 
         if (ret) {
@@ -390,3 +431,26 @@ int blk_mq_register_disk(struct gendisk *disk)
 
         return 0;
 }
+
+void blk_mq_sysfs_unregister(struct request_queue *q)
+{
+        struct blk_mq_hw_ctx *hctx;
+        int i;
+
+        queue_for_each_hw_ctx(q, hctx, i)
+                blk_mq_unregister_hctx(hctx);
+}
+
+int blk_mq_sysfs_register(struct request_queue *q)
+{
+        struct blk_mq_hw_ctx *hctx;
+        int i, ret = 0;
+
+        queue_for_each_hw_ctx(q, hctx, i) {
+                ret = blk_mq_register_hctx(hctx);
+                if (ret)
+                        break;
+        }
+
+        return ret;
+}