null_blk: Enable modifying 'submit_queues' after an instance has been…

… configured

This patch makes it possible to test blk_mq_update_nr_hw_queues() from
inside a VM.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/null_blk_main.c

@@ -227,7 +227,7 @@ static ssize_t nullb_device_uint_attr_store(unsigned int *val,
  int result;
 
  result = kstrtouint(page, 0, &tmp);
- if (result)
+ if (result < 0)
  return result;
 
  *val = tmp;
@@ -241,7 +241,7 @@ static ssize_t nullb_device_ulong_attr_store(unsigned long *val,
  unsigned long tmp;
 
  result = kstrtoul(page, 0, &tmp);
- if (result)
+ if (result < 0)
  return result;
 
  *val = tmp;
@@ -255,15 +255,15 @@ static ssize_t nullb_device_bool_attr_store(bool *val, const char *page,
  int result;
 
  result = kstrtobool(page, &tmp);
- if (result)
+ if (result < 0)
  return result;
 
  *val = tmp;
  return count;
 }
 
 /* The following macro should only be used with TYPE = {uint, ulong, bool}. */
-#define NULLB_DEVICE_ATTR(NAME, TYPE)  \
+#define NULLB_DEVICE_ATTR(NAME, TYPE, APPLY) \
 static ssize_t \
 nullb_device_##NAME##_show(struct config_item *item, char *page) \
 { \
@@ -274,32 +274,57 @@ static ssize_t \
 nullb_device_##NAME##_store(struct config_item *item, const char *page, \
  size_t count) \
 { \
+ int (*apply_fn)(struct nullb_device *dev, TYPE new_value) = APPLY; \
  struct nullb_device *dev = to_nullb_device(item); \
+ TYPE new_value; \
+ int ret; \
  \
- if (test_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags)) \
- return -EBUSY; \
- return nullb_device_##TYPE##_attr_store(&dev->NAME, page, count); \
+ ret = nullb_device_##TYPE##_attr_store(&new_value, page, count); \
+ if (ret < 0) \
+ return ret; \
+ if (apply_fn) \
+ ret = apply_fn(dev, new_value); \
+ else if (test_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags)) \
+ ret = -EBUSY; \
+ if (ret < 0) \
+ return ret; \
+ dev->NAME = new_value; \
+ return count; \
 } \
 CONFIGFS_ATTR(nullb_device_, NAME);
 
-NULLB_DEVICE_ATTR(size, ulong);
-NULLB_DEVICE_ATTR(completion_nsec, ulong);
-NULLB_DEVICE_ATTR(submit_queues, uint);
-NULLB_DEVICE_ATTR(home_node, uint);
-NULLB_DEVICE_ATTR(queue_mode, uint);
-NULLB_DEVICE_ATTR(blocksize, uint);
-NULLB_DEVICE_ATTR(irqmode, uint);
-NULLB_DEVICE_ATTR(hw_queue_depth, uint);
-NULLB_DEVICE_ATTR(index, uint);
-NULLB_DEVICE_ATTR(blocking, bool);
-NULLB_DEVICE_ATTR(use_per_node_hctx, bool);
-NULLB_DEVICE_ATTR(memory_backed, bool);
-NULLB_DEVICE_ATTR(discard, bool);
-NULLB_DEVICE_ATTR(mbps, uint);
-NULLB_DEVICE_ATTR(cache_size, ulong);
-NULLB_DEVICE_ATTR(zoned, bool);
-NULLB_DEVICE_ATTR(zone_size, ulong);
-NULLB_DEVICE_ATTR(zone_nr_conv, uint);
+static int nullb_apply_submit_queues(struct nullb_device *dev,
+ unsigned int submit_queues)
+{
+ struct nullb *nullb = dev->nullb;
+ struct blk_mq_tag_set *set;
+
+ if (!nullb)
+ return 0;
+
+ set = nullb->tag_set;
+ blk_mq_update_nr_hw_queues(set, submit_queues);
+ return set->nr_hw_queues == submit_queues ? 0 : -ENOMEM;
+}
+
+NULLB_DEVICE_ATTR(size, ulong, NULL);
+NULLB_DEVICE_ATTR(completion_nsec, ulong, NULL);
+NULLB_DEVICE_ATTR(submit_queues, uint, nullb_apply_submit_queues);
+NULLB_DEVICE_ATTR(home_node, uint, NULL);
+NULLB_DEVICE_ATTR(queue_mode, uint, NULL);
+NULLB_DEVICE_ATTR(blocksize, uint, NULL);
+NULLB_DEVICE_ATTR(irqmode, uint, NULL);
+NULLB_DEVICE_ATTR(hw_queue_depth, uint, NULL);
+NULLB_DEVICE_ATTR(index, uint, NULL);
+NULLB_DEVICE_ATTR(blocking, bool, NULL);
+NULLB_DEVICE_ATTR(use_per_node_hctx, bool, NULL);
+NULLB_DEVICE_ATTR(memory_backed, bool, NULL);
+NULLB_DEVICE_ATTR(discard, bool, NULL);
+NULLB_DEVICE_ATTR(mbps, uint, NULL);
+NULLB_DEVICE_ATTR(cache_size, ulong, NULL);
+NULLB_DEVICE_ATTR(zoned, bool, NULL);
+NULLB_DEVICE_ATTR(zone_size, ulong, NULL);
+NULLB_DEVICE_ATTR(zone_nr_conv, uint, NULL);
 
 static ssize_t nullb_device_power_show(struct config_item *item, char *page)
 {