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xprtrdma: Backchannel can use GFP_KERNEL allocations 

The Receive handler runs in process context, thus can use on-demand
GFP_KERNEL allocations instead of pre-allocation.

This makes the xprtrdma backchannel independent of the number of
backchannel session slots provisioned by the Upper Layer protocol.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Chuck Lever 2019-04-24 09:39:37 -04:00 committed by Anna Schumaker
parent d2832af38d
commit 3f9c7e7693
1 changed files with 40 additions and 64 deletions
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104
net/sunrpc/xprtrdma/backchannel.c
View File

@ -19,35 +19,6 @@
#undef RPCRDMA_BACKCHANNEL_DEBUG
static int rpcrdma_bc_setup_reqs(struct rpcrdma_xprt *r_xprt,
unsigned int count)
{
struct rpc_xprt *xprt = &r_xprt->rx_xprt;
struct rpcrdma_req *req;
struct rpc_rqst *rqst;
unsigned int i;
for (i = 0; i < (count << 1); i++) {
size_t size;
size = min_t(size_t, r_xprt->rx_data.inline_rsize, PAGE_SIZE);
req = rpcrdma_req_create(r_xprt, size, GFP_KERNEL);
if (!req)
return -ENOMEM;
rqst = &req->rl_slot;
rqst->rq_xprt = xprt;
INIT_LIST_HEAD(&rqst->rq_bc_list);
__set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
spin_lock(&xprt->bc_pa_lock);
list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
spin_unlock(&xprt->bc_pa_lock);
xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf),
size);
}
return 0;
}
/**
* xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
* @xprt: transport associated with these backchannel resources
@ -58,34 +29,10 @@ static int rpcrdma_bc_setup_reqs(struct rpcrdma_xprt *r_xprt,
int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
{
struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
int rc;
/* The backchannel reply path returns each rpc_rqst to the
* bc_pa_list _after_ the reply is sent. If the server is
* faster than the client, it can send another backward
* direction request before the rpc_rqst is returned to the
* list. The client rejects the request in this case.
*
* Twice as many rpc_rqsts are prepared to ensure there is
* always an rpc_rqst available as soon as a reply is sent.
*/
if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
goto out_err;
rc = rpcrdma_bc_setup_reqs(r_xprt, reqs);
if (rc)
goto out_free;
r_xprt->rx_buf.rb_bc_srv_max_requests = reqs;
r_xprt->rx_buf.rb_bc_srv_max_requests = RPCRDMA_BACKWARD_WRS >> 1;
trace_xprtrdma_cb_setup(r_xprt, reqs);
return 0;
out_free:
xprt_rdma_bc_destroy(xprt, reqs);
out_err:
pr_err("RPC: %s: setup backchannel transport failed\n", __func__);
return -ENOMEM;
}
/**
@ -213,6 +160,43 @@ void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
spin_unlock(&xprt->bc_pa_lock);
}
static struct rpc_rqst *rpcrdma_bc_rqst_get(struct rpcrdma_xprt *r_xprt)
{
struct rpc_xprt *xprt = &r_xprt->rx_xprt;
struct rpcrdma_req *req;
struct rpc_rqst *rqst;
size_t size;
spin_lock(&xprt->bc_pa_lock);
rqst = list_first_entry_or_null(&xprt->bc_pa_list, struct rpc_rqst,
rq_bc_pa_list);
if (!rqst)
goto create_req;
list_del(&rqst->rq_bc_pa_list);
spin_unlock(&xprt->bc_pa_lock);
return rqst;
create_req:
spin_unlock(&xprt->bc_pa_lock);
/* Set a limit to prevent a remote from overrunning our resources.
*/
if (xprt->bc_alloc_count >= RPCRDMA_BACKWARD_WRS)
return NULL;
size = min_t(size_t, r_xprt->rx_data.inline_rsize, PAGE_SIZE);
req = rpcrdma_req_create(r_xprt, size, GFP_KERNEL);
if (!req)
return NULL;
xprt->bc_alloc_count++;
rqst = &req->rl_slot;
rqst->rq_xprt = xprt;
__set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf), size);
return rqst;
}
/**
* rpcrdma_bc_receive_call - Handle a backward direction call
* @r_xprt: transport receiving the call
@ -244,18 +228,10 @@ void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
pr_info("RPC: %s: %*ph\n", __func__, size, p);
#endif
/* Grab a free bc rqst */
spin_lock(&xprt->bc_pa_lock);
if (list_empty(&xprt->bc_pa_list)) {
spin_unlock(&xprt->bc_pa_lock);
rqst = rpcrdma_bc_rqst_get(r_xprt);
if (!rqst)
goto out_overflow;
}
rqst = list_first_entry(&xprt->bc_pa_list,
struct rpc_rqst, rq_bc_pa_list);
list_del(&rqst->rq_bc_pa_list);
spin_unlock(&xprt->bc_pa_lock);
/* Prepare rqst */
rqst->rq_reply_bytes_recvd = 0;
rqst->rq_xid = *p;