ublk: rewrite ublk_ctrl_get_queue_affinity to not rely on hctx->cpumask

Looking at the hctxs and cpumap is not safe without at very last a RCU
reference.  It also requires the queue to be set up before starting the
device, which leads to rather awkward life time rules.

Instead rewrite ublk_ctrl_get_queue_affinity to just build the cpumask
directly from the mq_map in the tag set, similar to hctx->cpumask is
built.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220721130916.1869719-8-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index b8ac7b5..748247c 100644 (file)
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1245,26 +1245,15 @@ out_unlock:
        return ret;
 }
 
-static struct blk_mq_hw_ctx *ublk_get_hw_queue(struct ublk_device *ub,
-               unsigned int index)
-{
-       struct blk_mq_hw_ctx *hctx;
-       unsigned long i;
-
-       queue_for_each_hw_ctx(ub->ub_queue, hctx, i)
-               if (hctx->queue_num == index)
-                       return hctx;
-       return NULL;
-}
-
 static int ublk_ctrl_get_queue_affinity(struct io_uring_cmd *cmd)
 {
        struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
        void __user *argp = (void __user *)(unsigned long)header->addr;
-       struct blk_mq_hw_ctx *hctx;
        struct ublk_device *ub;
+       cpumask_var_t cpumask;
        unsigned long queue;
        unsigned int retlen;
+       unsigned int i;
        int ret = -EINVAL;
        
        if (header->len * BITS_PER_BYTE < nr_cpu_ids)
@@ -1276,30 +1265,34 @@ static int ublk_ctrl_get_queue_affinity(struct io_uring_cmd *cmd)
 
        ub = ublk_get_device_from_id(header->dev_id);
        if (!ub)
-               goto out;
+               return -EINVAL;
 
        queue = header->data[0];
        if (queue >= ub->dev_info.nr_hw_queues)
-               goto out;
-       hctx = ublk_get_hw_queue(ub, queue);
-       if (!hctx)
-               goto out;
+               goto out_put_device;
 
-       retlen = min_t(unsigned short, header->len, cpumask_size());
-       if (copy_to_user(argp, hctx->cpumask, retlen)) {
-               ret = -EFAULT;
-               goto out;
-       }
-       if (retlen != header->len) {
-               if (clear_user(argp + retlen, header->len - retlen)) {
-                       ret = -EFAULT;
-                       goto out;
-               }
+       ret = -ENOMEM;
+       if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
+               goto out_put_device;
+
+       for_each_possible_cpu(i) {
+               if (ub->tag_set.map[HCTX_TYPE_DEFAULT].mq_map[i] == queue)
+                       cpumask_set_cpu(i, cpumask);
        }
+
+       ret = -EFAULT;
+       retlen = min_t(unsigned short, header->len, cpumask_size());
+       if (copy_to_user(argp, cpumask, retlen))
+               goto out_free_cpumask;
+       if (retlen != header->len &&
+           clear_user(argp + retlen, header->len - retlen))
+               goto out_free_cpumask;
+
        ret = 0;
- out:
-       if (ub)
-               ublk_put_device(ub);
+out_free_cpumask:
+       free_cpumask_var(cpumask);
+out_put_device:
+       ublk_put_device(ub);
        return ret;
 }