Re: [PATCH v2 05/12] nbd: Enable lock context analysis

On 7/31/26 1:28 AM, Bart Van Assche wrote:
> Add __must_hold() annotations where these are missing. Document which mutex
> protects nbd_index_idr.
> 
> Signed-off-by: Bart Van Assche <[email protected]>
> ---
>   drivers/block/nbd.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 8f10762e90ef..751449d362b0 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -49,8 +49,8 @@
>   #define CREATE_TRACE_POINTS
>   #include <trace/events/nbd.h>
>   
> -static DEFINE_IDR(nbd_index_idr);
>   static DEFINE_MUTEX(nbd_index_mutex);
> +static __guarded_by(&nbd_index_mutex) DEFINE_IDR(nbd_index_idr);

Maybe we should replace this with DEFINE_IDR_GUARDED() as I mentioned
in previous email.

>   static struct workqueue_struct *nbd_del_wq;
>   static int nbd_total_devices = 0;
>   
> @@ -1506,6 +1506,7 @@ static void nbd_config_put(struct nbd_device *nbd)
>   }
>   
>   static int nbd_start_device(struct nbd_device *nbd)
> +	__must_hold(&nbd->config_lock)
>   {
>   	struct nbd_config *config = nbd->config;
>   	int num_connections = config->num_connections;
> @@ -1578,6 +1579,7 @@ static int nbd_start_device(struct nbd_device *nbd)
>   }
>   
>   static int nbd_start_device_ioctl(struct nbd_device *nbd)
> +	__must_hold(&nbd->config_lock)
>   {
>   	struct nbd_config *config = nbd->config;
>   	int ret;
> @@ -1629,6 +1631,7 @@ static void nbd_set_cmd_timeout(struct nbd_device *nbd, u64 timeout)
>   /* Must be called with config_lock held */
>   static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
>   		       unsigned int cmd, unsigned long arg)
> +	__must_hold(&nbd->config_lock)
>   {
>   	struct nbd_config *config = nbd->config;
>   	loff_t bytesize;
> @@ -2773,7 +2776,11 @@ static void __exit nbd_cleanup(void)
>   	/* Also wait for nbd_dev_remove_work() completes */
>   	destroy_workqueue(nbd_del_wq);
>   
> -	idr_destroy(&nbd_index_idr);
> +	{
> +		__assume_ctx_lock(&nbd_index_mutex);
> +		idr_destroy(&nbd_index_idr);
> +	}
> +

Could we instead introduce a scoped __assume_ctx_lock() helper so we don't need the
explicit scope here? Alternatively, would annotating nbd_cleanup() with __context_unsafe
be a better fit?

Thanks,
--Nilay