On Tue, Jun 23, 2020 at 7:54 PM Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > On Tue, Jun 23, 2020 at 07:15:03PM +0530, Haris Iqbal wrote: > > On Tue, Jun 23, 2020 at 5:47 PM Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > > > > > On Tue, Jun 23, 2020 at 03:20:27PM +0530, Haris Iqbal wrote: > > > > Hi Jason and Leon, > > > > > > > > Did you get a chance to look into my previous email? > > > > > > Was there a question? > > > > Multiple actually :) > > > > > > > > Jason > > > > In response to your emails, > > > > > Somehow nvme-rdma works: > > > > I think that's because the callchain during the nvme_rdma_init_module > > initialization stops at "nvmf_register_transport()". Here only the > > "struct nvmf_transport_ops nvme_rdma_transport" is registered, which > > contains the function "nvme_rdma_create_ctrl()". I tested this in my > > local setup and during kernel boot, that's the extent of the > > callchain. > > The ".create_ctrl"; which now points to "nvme_rdma_create_ctrl()" is > > called later from "nvmf_dev_write()". I am not sure when this is > > called, probably when the "discover" happens from the client side or > > during the server config. > > > > It seems that the "rdma_bind_addr()" is called by the nvme rdma > > module; but during the following events > > 1) When a discover happens from the client side. Call trace for that looks like, > > [ 1098.409398] nvmf_dev_write > > [ 1098.409403] nvmf_create_ctrl > > [ 1098.414568] nvme_rdma_create_ctrl > > [ 1098.415009] nvme_rdma_setup_ctrl > > [ 1098.415010] nvme_rdma_configure_admin_queue > > [ 1098.415010] nvme_rdma_alloc_queue > > [ 1098.415032] rdma_resolve_addr > > [ 1098.415032] cma_bind_addr > > [ 1098.415033] rdma_bind_addr > > > > 2) When a connect happens from the client side. Call trace is the same > > as above, plus "nvme_rdma_alloc_queue()" is called n number of times; > > n being the number of IO queues being created. > > > > On the server side, when an nvmf port is enabled, that also triggers a > > call to "rdma_bind_addr()", but that is not from the nvme rdma module. > > may be nvme target rdma? (not sure). > > > > Does this make sense or am I missing something here? > > It make sense, delaying creating and CM ID's until user space starts > will solve this init time problme Right, and the patch is trying to achieve the delay by changing the init level to "late_initcall()" > > > > > > If the rdma_create_id() is not on a callchain from module_init then you don't have a problem. > > > > I am a little confused. I thought the problem occurs from a call to > > either "rdma_resolve_addr()" which calls "rdma_bind_addr()", > > or a direct call to "rdma_bind_addr()" as in rtrs case. > > In both the cases, a call to "rdma_create_id()" is needed before this. > > Right rdma_create_id() must precede anything that has problems, and it > should not be done from module_init. I understand this, but I am not sure why that is; as in why it should not be done from module_init? Also, about one of your previous statements, > It is not OK to create RDMA CM IDs outside > a client - CM IDs are supposed to be cleaned up when the client is > removed. > > Similarly they are supposed to be created from the client attachment. This again is a little confusing to me, since what I've observed in nvmt is, when a server port is created, the "rdma_bind_addr()" function is called. And this goes well with the server/target and client/initiator model, where the server has to get ready and start listening before a client can initiate a connection. What am I missing here? > > Jason -- Regards -Haris
