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>

diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index f5747cf..f5e0dff 100644 (file)
--- a/drivers/block/null_blk_main.c
+++ b/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;
@@ -255,7 +255,7 @@ 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;
@@ -263,7 +263,7 @@ static ssize_t nullb_device_bool_attr_store(bool *val, const char *page,
 }
 
 /* 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)
 {