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authorSimon Derr <simon.derr@bull.net>2013-06-21 15:32:42 +0200
committerEric Van Hensbergen <ericvh@gmail.com>2013-07-07 22:04:36 -0500
commit1cff33069a4a1ac9ed080756113ecd17ad408282 (patch)
treebc7c5e50fb6ad102b16b93da9263fc36506d5d32 /net/9p
parent2f52d07cb75d96fcbb5b9ab72938590fa9ffb19d (diff)
9P/RDMA: count posted buffers without a pending request
In rdma_request(): If an error occurs between posting the recv and the send, there will be a reply context posted without a pending request. Since there is no way to "un-post" it, we remember it and skip post_recv() for the next request. Signed-off-by: Simon Derr <simon.derr@bull.net> Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Diffstat (limited to 'net/9p')
-rw-r--r--net/9p/client.c6
-rw-r--r--net/9p/trans_rdma.c31
2 files changed, 34 insertions, 3 deletions
diff --git a/net/9p/client.c b/net/9p/client.c
index db5bf2480a33..d18a0b22f62c 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -656,8 +656,10 @@ static int p9_client_flush(struct p9_client *c, struct p9_req_t *oldreq)
return PTR_ERR(req);
- /* if we haven't received a response for oldreq,
- remove it from the list. */
+ /*
+ * if we haven't received a response for oldreq,
+ * remove it from the list.
+ */
spin_lock(&c->lock);
if (oldreq->status == REQ_STATUS_FLSH)
list_del(&oldreq->req_list);
diff --git a/net/9p/trans_rdma.c b/net/9p/trans_rdma.c
index 926e72d00e57..8f68df5d2973 100644
--- a/net/9p/trans_rdma.c
+++ b/net/9p/trans_rdma.c
@@ -74,6 +74,8 @@
* @sq_sem: Semaphore for the SQ
* @rq_depth: The depth of the Receive Queue.
* @rq_sem: Semaphore for the RQ
+ * @excess_rc : Amount of posted Receive Contexts without a pending request.
+ * See rdma_request()
* @addr: The remote peer's address
* @req_lock: Protects the active request list
* @cm_done: Completion event for connection management tracking
@@ -99,6 +101,7 @@ struct p9_trans_rdma {
struct semaphore sq_sem;
int rq_depth;
struct semaphore rq_sem;
+ atomic_t excess_rc;
struct sockaddr_in addr;
spinlock_t req_lock;
@@ -426,6 +429,26 @@ static int rdma_request(struct p9_client *client, struct p9_req_t *req)
struct p9_rdma_context *c = NULL;
struct p9_rdma_context *rpl_context = NULL;
+ /* When an error occurs between posting the recv and the send,
+ * there will be a receive context posted without a pending request.
+ * Since there is no way to "un-post" it, we remember it and skip
+ * post_recv() for the next request.
+ * So here,
+ * see if we are this `next request' and need to absorb an excess rc.
+ * If yes, then drop and free our own, and do not recv_post().
+ **/
+ if (unlikely(atomic_read(&rdma->excess_rc) > 0)) {
+ if ((atomic_sub_return(1, &rdma->excess_rc) >= 0)) {
+ /* Got one ! */
+ kfree(req->rc);
+ req->rc = NULL;
+ goto dont_need_post_recv;
+ } else {
+ /* We raced and lost. */
+ atomic_inc(&rdma->excess_rc);
+ }
+ }
+
/* Allocate an fcall for the reply */
rpl_context = kmalloc(sizeof *rpl_context, GFP_NOFS);
if (!rpl_context) {
@@ -451,10 +474,10 @@ static int rdma_request(struct p9_client *client, struct p9_req_t *req)
p9_debug(P9_DEBUG_FCALL, "POST RECV failed\n");
goto recv_error;
}
-
/* remove posted receive buffer from request structure */
req->rc = NULL;
+dont_need_post_recv:
/* Post the request */
c = kmalloc(sizeof *c, GFP_NOFS);
if (!c) {
@@ -499,6 +522,11 @@ static int rdma_request(struct p9_client *client, struct p9_req_t *req)
send_error:
kfree(c);
p9_debug(P9_DEBUG_ERROR, "Error %d in rdma_request()\n", err);
+
+ /* Ach.
+ * We did recv_post(), but not send. We have one recv_post in excess.
+ */
+ atomic_inc(&rdma->excess_rc);
return err;
/* Handle errors that happened during or while preparing post_recv(): */
@@ -549,6 +577,7 @@ static struct p9_trans_rdma *alloc_rdma(struct p9_rdma_opts *opts)
init_completion(&rdma->cm_done);
sema_init(&rdma->sq_sem, rdma->sq_depth);
sema_init(&rdma->rq_sem, rdma->rq_depth);
+ atomic_set(&rdma->excess_rc, 0);
return rdma;
}

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