On 11/14/22 4:24 PM, Jinpu Wang wrote:
On Mon, Nov 14, 2022 at 9:00 AM Guoqing Jiang <guoqing.jiang@xxxxxxxxx> wrote:
Hi Jinpu,
On 11/14/22 3:39 PM, Jinpu Wang wrote:
Hi Guoqing,
Thx for the patch, see comments below.
On Sun, Nov 13, 2022 at 2:08 AM Guoqing Jiang <guoqing.jiang@xxxxxxxxx> wrote:
The ib_dev_count is supposed to track the number of added ib devices
which is only used in rtrs_srv_{add,remove}_one.
However we only trigger rtrs_srv_add_one from rnbd_srv_init_module
-> rtrs_srv_open -> ib_register_client -> client->add which should
happen only once.
client->add is call per ib_device, eg:
jwang@xxxxxxxxxxxx:~$ ls -l /sys/class/infiniband/mlx5_*
lrwxrwxrwx 1 root root 0 Nov 8 13:49 /sys/class/infiniband/mlx5_0 ->
../../devices/pci0000:ae/0000:ae:00.0/0000:af:00.0/infiniband/mlx5_0
lrwxrwxrwx 1 root root 0 Nov 8 13:49 /sys/class/infiniband/mlx5_1 ->
../../devices/pci0000:ae/0000:ae:00.0/0000:af:00.1/infiniband/mlx5_1
rtrs will be call twice for mlx5_0 and mlx5_1 devices
Ah, yes.
But still we can only load/unload module once, I guess it was used to avoid
racy condition (concurrent loading/unloading module?), could you elaborate
why it is needed?
The change was introduced due to a bug report, you can follow the
discussion here for the history and reason:
https://lore.kernel.org/linux-rdma/20200617103732.10356-1-haris.iqbal@xxxxxxxxxxxxxxx/
Thanks for the link.
I probably missed something but I don't know how rnbd_server module can be
initialized before cma module since we have the dependency chain as
follows.
INFINIBAND_RTRS_SERVER depends on INFINIBAND_ADDR_TRANS
BLK_DEV_RNBD_SERVER depends on INFINIBAND_RTRS_SERVER
But commit 558d52b2976b ("RDMA/rtrs-srv: Incorporate ib_register_client into
rtrs server init") did mention this.
"and if the rnbd_server module is initialized before RDMA cma module, a
null ptr
dereference occurs during the RDMA bind operation."
Thanks,
Guoqing
