2023-10-19 15:01 GMT+09:00, Kangjing (Chaser) Huang <huangkangjing@xxxxxxxxx>:
> Thank you for the review. Also thanks a lot to Namjae for submitting
> this patch on my behalf.
>
>
> On Tue, Oct 17, 2023 at 10:07 AM Tom Talpey <tom@xxxxxxxxxx> wrote:
>>
>> On 10/15/2023 10:45 AM, Namjae Jeon wrote:
>> > From: Kangjing Huang <huangkangjing@xxxxxxxxx>
>> >
>> > Physical ib_device does not have an underlying net_device, thus its
>> > association with IPoIB net_device cannot be retrieved via
>> > ops.get_netdev() or ib_device_get_by_netdev(). ksmbd reads physical
>> > ib_device port GUID from the lower 16 bytes of the hardware addresses
>> > on
>> > IPoIB net_device and match its underlying ib_device using ib_find_gid()
>> >
>> > Signed-off-by: Kangjing Huang <huangkangjing@xxxxxxxxx>
>> > Acked-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
>> > ---
>> > fs/smb/server/transport_rdma.c | 39
>> > +++++++++++++++++++++++++---------
>> > 1 file changed, 29 insertions(+), 10 deletions(-)
>> >
>> > diff --git a/fs/smb/server/transport_rdma.c
>> > b/fs/smb/server/transport_rdma.c
>> > index 3b269e1f523a..a82131f7dd83 100644
>> > --- a/fs/smb/server/transport_rdma.c
>> > +++ b/fs/smb/server/transport_rdma.c
>> > @@ -2140,8 +2140,7 @@ static int smb_direct_ib_client_add(struct
>> > ib_device *ib_dev)
>> > if (ib_dev->node_type != RDMA_NODE_IB_CA)
>> > smb_direct_port = SMB_DIRECT_PORT_IWARP;
>> >
>> > - if (!ib_dev->ops.get_netdev ||
>> > - !rdma_frwr_is_supported(&ib_dev->attrs))
>> > + if (!rdma_frwr_is_supported(&ib_dev->attrs))
>> > return 0;
>> >
>> > smb_dev = kzalloc(sizeof(*smb_dev), GFP_KERNEL);
>> > @@ -2241,17 +2240,37 @@ bool ksmbd_rdma_capable_netdev(struct net_device
>> > *netdev)
>> > for (i = 0; i < smb_dev->ib_dev->phys_port_cnt; i++) {
>> > struct net_device *ndev;
>> >
>> > - ndev =
>> > smb_dev->ib_dev->ops.get_netdev(smb_dev->ib_dev,
>> > - i + 1);
>> > - if (!ndev)
>> > - continue;
>> > + /* RoCE and iWRAP ib_dev is backed by a netdev */
>> > + if (smb_dev->ib_dev->ops.get_netdev) {
>>
>> The "IWRAP" is a typo, but IMO the comment is misleading. This is simply
>> looking up the target netdev, it's not limited to these two rdma types.
>> I suggest deleting the comment.
>>
>
> I agree with this point and will update this comment in version 2 of the
> patch.
>
>> > + ndev = smb_dev->ib_dev->ops.get_netdev(
>> > + smb_dev->ib_dev, i + 1);
>> > + if (!ndev)
>> > + continue;
>> >
>> > - if (ndev == netdev) {
>> > + if (ndev == netdev) {
>> > + dev_put(ndev);
>> > + rdma_capable = true;
>> > + goto out;
>> > + }
>> > dev_put(ndev);
>>
>> Why not move this dev_put up above the if (ndev == netdev) test? It's
>> needed in both cases, so it's confusing to have two copies.
>
> I do agree that these two puts are very confusing. However, this code
> structure comes from the original ksmbd_rdma_capable_netdev() and
> this patch only indents it one more level and puts it in the if test for
> get_netdev.
>
> Also, while two puts look very weird, IMO putting it before the if
> statement
> is equally unintuitive as well since that would be testing the pointer after
> its
> reference is released. Although since no de-reference is happening here, it
> might be fine. Please confirm this is good coding-style-wise and I will
> include
> this change in v2 of the patch.
There is no need to update code that does not have problems.
>
>>
>> > - rdma_capable = true;
>> > - goto out;
>> > + /* match physical ib_dev with IPoIB netdev by GUID
>> > */
>>
>> Add more information to this comment, perhaps:
>>
>> /* if no exact netdev match, check for matching Infiniband GUID */
>>
>
> Fair point, will update this comment in v2.
>
>> > + } else if (netdev->type == ARPHRD_INFINIBAND) {
>> > + struct netdev_hw_addr *ha;
>> > + union ib_gid gid;
>> > + u32 port_num;
>> > + int ret;
>> > +
>> > + netdev_hw_addr_list_for_each(
>> > + ha, &netdev->dev_addrs) {
>> > + memcpy(&gid, ha->addr + 4,
>> > sizeof(gid));
>> > + ret = ib_find_gid(smb_dev->ib_dev,
>> > &gid,
>> > + &port_num,
>> > NULL);
>> > + if (!ret) {
>> > + rdma_capable = true;
>> > + goto out;
>>
>> Won't this leak the ndev? It needs a dev_put(ndev) before breaking
>> the loop, too, right?
>>
>
> This will not leak the ndev. Please look closer, this else branch matches
> with
> the if test on the existence of ops.get_netdev of the current ib_dev. And
> ndev
> is acquired only through that op. In the else branch, ndev is just not
> acquired.
> The original code was indented one more level here so the patch might look
> a bit confusing, but one of the if before this block is a deleted(-) line.
You're right.
Please send v2 patch after adding comments that Tom pointed out.
Thanks!
>
>> > + }
>> > + }
>> > }
>> > - dev_put(ndev);
>> > }
>> > }
>> > out:
>
>
>
> --
> Kangjing "Chaser" Huang
>
