[PATCH v4 10/21] xprtrdma: Properly handle exhaustion of the rb_mws list

Chuck Lever
2014-07-22T14:52:25Z

If the rb_mws list is exhausted, clean up and return NULL so that
call_allocate() will delay and try again.

Signed-off-by: Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
Tested-by: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
Tested-by: Shirley Ma <shirley.ma-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
Tested-by: Devesh Sharma <devesh.sharma-laKkSmNT4hbQT0dZR+AlfA@public.gmane.org>
---
net/sunrpc/xprtrdma/verbs.c | 103 ++++++++++++++++++++++++++++++-------------
1 file changed, 71 insertions(+), 32 deletions(-)

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index abac484..cdea6ff 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1256,6 +1256,67 @@ rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf)
kfree(buf->rb_pool);
}

+/* "*mw" can be NULL when rpcrdma_buffer_get_mrs() fails, leaving
+ * some req segments uninitialized.
+ */
+static void
+rpcrdma_buffer_put_mr(struct rpcrdma_mw **mw, struct rpcrdma_buffer *buf)
+{
+ if (*mw) {
+ list_add_tail(&(*mw)->mw_list, &buf->rb_mws);
+ *mw = NULL;
+ }
+}
+
+/* Cycle mw's back in reverse order, and "spin" them.
+ * This delays and scrambles reuse as much as possible.
+ */
+static void
+rpcrdma_buffer_put_mrs(struct rpcrdma_req *req, struct rpcrdma_buffer *buf)
+{
+ struct rpcrdma_mr_seg *seg = req->rl_segments;
+ struct rpcrdma_mr_seg *seg1 = seg;
+ int i;
+
+ for (i = 1, seg++; i < RPCRDMA_MAX_SEGS; seg++, i++)
+ rpcrdma_buffer_put_mr(&seg->mr_chunk.rl_mw, buf);
+ rpcrdma_buffer_put_mr(&seg1->mr_chunk.rl_mw, buf);
+}
+
+static void
+rpcrdma_buffer_put_sendbuf(struct rpcrdma_req *req, struct rpcrdma_buffer *buf)
+{
+ buf->rb_send_bufs[--buf->rb_send_index] = req;
+ req->rl_niovs = 0;
+ if (req->rl_reply) {
+ buf->rb_recv_bufs[--buf->rb_recv_index] = req->rl_reply;
+ req->rl_reply->rr_func = NULL;
+ req->rl_reply = NULL;
+ }
+}
+
+static struct rpcrdma_req *
+rpcrdma_buffer_get_mrs(struct rpcrdma_req *req, struct rpcrdma_buffer *buf)
+{
+ struct rpcrdma_mw *r;
+ int i;
+
+ i = RPCRDMA_MAX_SEGS - 1;
+ while (!list_empty(&buf->rb_mws)) {
+ r = list_entry(buf->rb_mws.next,
+ struct rpcrdma_mw, mw_list);
+ list_del(&r->mw_list);
+ req->rl_segments[i].mr_chunk.rl_mw = r;
+ if (unlikely(i-- == 0))
+ return req; /* Success */
+ }
+
+ /* Not enough entries on rb_mws for this req */
+ rpcrdma_buffer_put_sendbuf(req, buf);
+ rpcrdma_buffer_put_mrs(req, buf);
+ return NULL;
+}
+
/*
* Get a set of request/reply buffers.
*
@@ -1268,10 +1329,9 @@ rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf)
struct rpcrdma_req *
rpcrdma_buffer_get(struct rpcrdma_buffer *buffers)
{
+ struct rpcrdma_ia *ia = rdmab_to_ia(buffers);
struct rpcrdma_req *req;
unsigned long flags;
- int i;
- struct rpcrdma_mw *r;

spin_lock_irqsave(&buffers->rb_lock, flags);
if (buffers->rb_send_index == buffers->rb_max_requests) {
@@ -1291,14 +1351,13 @@ rpcrdma_buffer_get(struct rpcrdma_buffer *buffers)
buffers->rb_recv_bufs[buffers->rb_recv_index++] = NULL;
}
buffers->rb_send_bufs[buffers->rb_send_index++] = NULL;
- if (!list_empty(&buffers->rb_mws)) {
- i = RPCRDMA_MAX_SEGS - 1;
- do {
- r = list_entry(buffers->rb_mws.next,
- struct rpcrdma_mw, mw_list);
- list_del(&r->mw_list);
- req->rl_segments[i].mr_chunk.rl_mw = r;
- } while (--i >= 0);
+ switch (ia->ri_memreg_strategy) {
+ case RPCRDMA_FRMR:
+ case RPCRDMA_MTHCAFMR:
+ req = rpcrdma_buffer_get_mrs(req, buffers);
+ break;
+ default:
+ break;
}
spin_unlock_irqrestore(&buffers->rb_lock, flags);
return req;
@@ -1313,34 +1372,14 @@ rpcrdma_buffer_put(struct rpcrdma_req *req)
{
struct rpcrdma_buffer *buffers = req->rl_buffer;
struct rpcrdma_ia *ia = rdmab_to_ia(buffers);
- int i;
unsigned long flags;

spin_lock_irqsave(&buffers->rb_lock, flags);
- buffers->rb_send_bufs[--buffers->rb_send_index] = req;
- req->rl_niovs = 0;
- if (req->rl_reply) {
- buffers->rb_recv_bufs[--buffers->rb_recv_index] = req->rl_reply;
- req->rl_reply->rr_func = NULL;
- req->rl_reply = NULL;
- }
+ rpcrdma_buffer_put_sendbuf(req, buffers);
switch (ia->ri_memreg_strategy) {
case RPCRDMA_FRMR:
case RPCRDMA_MTHCAFMR:
- /*
- * Cycle mw's back in reverse order, and "spin" them.
- * This delays and scrambles reuse as much as possible.
- */
- i = 1;
- do {
- struct rpcrdma_mw **mw;
- mw = &req->rl_segments[i].mr_chunk.rl_mw;
- list_add_tail(&(*mw)->mw_list, &buffers->rb_mws);
- *mw = NULL;
- } while (++i < RPCRDMA_MAX_SEGS);
- list_add_tail(&req->rl_segments[0].mr_chunk.rl_mw->mw_list,
- &buffers->rb_mws);
- req->rl_segments[0].mr_chunk.rl_mw = NULL;
+ rpcrdma_buffer_put_mrs(req, buffers);
break;
default:
break;