> +static bool g_nowait = true;
> +module_param_named(nowait, g_nowait, bool, 0444);
> +MODULE_PARM_DESC(virt_boundary, "Set QUEUE_FLAG_NOWAIT irrespective of queue mode. Default: True");
Copy paste error. MODULE_PARM_DESC(nowait,...
> +
> static bool g_virt_boundary = false;
> module_param_named(virt_boundary, g_virt_boundary, bool, 0444);
> MODULE_PARM_DESC(virt_boundary, "Require a virtual boundary for the device. Default: False");
> @@ -983,11 +990,11 @@ static struct nullb_page *null_insert_page(struct nullb *nullb,
>
> spin_unlock_irq(&nullb->lock);
>
> - t_page = null_alloc_page();
> + t_page = null_alloc_page(nullb->dev->nowait ? GFP_NOWAIT : GFP_NOIO);
> if (!t_page)
> goto out_lock;
>
> - if (radix_tree_preload(GFP_NOIO))
> + if (radix_tree_preload(nullb->dev->nowait ? GFP_NOWAIT : GFP_NOIO))
This is not correct. You need to use radix_tree_maybe_preload because
GFP_NOWAIT should not block and this WARN_ON_ONCE flag will trigger in
radix_tree_preload:
/* Warn on non-sensical use... */
WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
I also verified this locally with your patch and while doing a simple fio
write with setting memory_backed=1.
WARNING: CPU: 2 PID: 515 at lib/radix-tree.c:366 radix_tree_preload+0x12/0x20
...
RIP: 0010:radix_tree_preload+0x12/0x20
<snip>
Call Trace:
<TASK>
null_insert_page+0x186/0x4e0 [null_blk]
null_transfer+0x588/0x990 [null_blk]
<snip>
> goto out_freepage;
>
> spin_lock_irq(&nullb->lock);
> @@ -2093,6 +2100,11 @@ static int null_add_dev(struct nullb_device *dev)
> blk_queue_flag_set(QUEUE_FLAG_NONROT, nullb->q);
> blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, nullb->q);
>
> + if (dev->nowait)
> + blk_queue_flag_set(QUEUE_FLAG_NOWAIT, nullb->q);
> + else
> + blk_queue_flag_clear(QUEUE_FLAG_NOWAIT, nullb->q);
> +
> mutex_lock(&lock);
> rv = ida_simple_get(&nullb_indexes, 0, 0, GFP_KERNEL);
> if (rv < 0) {
> diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h
> index eb5972c50be8..1d7af446d728 100644
> --- a/drivers/block/null_blk/null_blk.h
> +++ b/drivers/block/null_blk/null_blk.h
> @@ -107,6 +107,7 @@ struct nullb_device {
> unsigned int index; /* index of the disk, only valid with a disk */
> unsigned int mbps; /* Bandwidth throttle cap (in MB/s) */
> bool blocking; /* blocking blk-mq device */
> + bool nowait; /* to set QUEUE_FLAG_NOWAIT on device queue */
> bool use_per_node_hctx; /* use per-node allocation for hardware context */
> bool power; /* power on/off the device */
> bool memory_backed; /* if data is stored in memory */
> --
> 2.29.0
>
--
Pankaj Raghav
