Re: [PATCH rdma-next v1 2/3] RDMA/uverbs: Use kernel API to allocate uverbs indexes

[Leon Romanovsky <leon@xxxxxxxxxx>]

On Wed, Oct 03, 2018 at 11:17:39AM -0400, Dennis Dalessandro wrote:
> On 10/2/2018 4:13 AM, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@xxxxxxxxxxxx>
> >
> > Replace custom code to allocate indexes to generic kernel API.
> >
> > Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
> > ---
> >   drivers/infiniband/core/uverbs_main.c | 12 ++++++------
> >   1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
> > index 12d8f8097574..74a420eba04f 100644
> > --- a/drivers/infiniband/core/uverbs_main.c
> > +++ b/drivers/infiniband/core/uverbs_main.c
> > @@ -73,7 +73,7 @@ enum {
> >   static dev_t dynamic_uverbs_dev;
> >   static struct class *uverbs_class;
> > -static DECLARE_BITMAP(dev_map, IB_UVERBS_MAX_DEVICES);
> > +static DEFINE_IDA(uverbs_ida);
> >   static ssize_t (*uverbs_cmd_table[])(struct ib_uverbs_file *file,
> >   				     const char __user *buf, int in_len,
> > @@ -1267,11 +1267,11 @@ static void ib_uverbs_add_one(struct ib_device *device)
> >   	rcu_assign_pointer(uverbs_dev->ib_dev, device);
> >   	uverbs_dev->num_comp_vectors = device->num_comp_vectors;
> > -	devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
> > -	if (devnum >= IB_UVERBS_MAX_DEVICES)
> > +	devnum = ida_alloc_max(&uverbs_ida, IB_UVERBS_MAX_DEVICES - 1,
> > +			       GFP_KERNEL);
> > +	if (devnum < 0)
>
> So is it OK if the value we get back is 0?

find_first_zero_bit() returns 0 for "first uverbs" too, so no change here.

diff --git a/drivers/infiniband/core/uverbs_main.c
b/drivers/infiniband/core/uverbs_main.c
index 50152c1b1004..3c41e975b572 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -1038,6 +1038,7 @@ static void ib_uverbs_add_one(struct ib_device *device)
        INIT_LIST_HEAD(&uverbs_dev->uverbs_events_file_list);

	devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
+       printk(KERN_ERR "LR: %d\n", devnum);
        if (devnum >= IB_UVERBS_MAX_DEVICES)
                 goto err;
        uverbs_dev->devnum = devnum;

And the corresponding dmesg:
[   29.726666] mlx5_ib: Mellanox Connect-IB Infiniband driver v5.0-0
[   29.727389] mlx5_ib: Mellanox Connect-IB Infiniband driver v5.0-0
[   30.081904] LR: 0
[   30.545240] LR: 1

Thanks

>
> -Denny

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