IB/hfi1: Fix user SDMA racy user request claim

The user SDMA in-use claim bit is in the structure that gets zeroed out
once the claim is made.  Move the request in-use flag into its own bit
array and use that for atomic claims.  This cleans up the claim code and
removes any race possibility.

Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

diff --git a/drivers/infiniband/hw/hfi1/user_sdma.c b/drivers/infiniband/hw/hfi1/user_sdma.c
index 5c13224..e88d555 100644 (file)
--- a/drivers/infiniband/hw/hfi1/user_sdma.c
+++ b/drivers/infiniband/hw/hfi1/user_sdma.c
@@ -145,7 +145,7 @@ MODULE_PARM_DESC(sdma_comp_size, "Size of User SDMA completion ring. Default: 12
 /* Last packet in the request */
 #define TXREQ_FLAGS_REQ_LAST_PKT BIT(0)
 
-#define SDMA_REQ_IN_USE     0
+/* SDMA request flag bits */
 #define SDMA_REQ_FOR_THREAD 1
 #define SDMA_REQ_SEND_DONE  2
 #define SDMA_REQ_HAVE_AHG   3
@@ -397,6 +397,11 @@ int hfi1_user_sdma_alloc_queues(struct hfi1_ctxtdata *uctxt, struct file *fp)
        if (!pq->reqs)
                goto pq_reqs_nomem;
 
+       memsize = BITS_TO_LONGS(hfi1_sdma_comp_ring_size) * sizeof(long);
+       pq->req_in_use = kzalloc(memsize, GFP_KERNEL);
+       if (!pq->req_in_use)
+               goto pq_reqs_no_in_use;
+
        INIT_LIST_HEAD(&pq->list);
        pq->dd = dd;
        pq->ctxt = uctxt->ctxt;
@@ -453,6 +458,8 @@ cq_comps_nomem:
 cq_nomem:
        kmem_cache_destroy(pq->txreq_cache);
 pq_txreq_nomem:
+       kfree(pq->req_in_use);
+pq_reqs_no_in_use:
        kfree(pq->reqs);
 pq_reqs_nomem:
        kfree(pq);
@@ -484,6 +491,7 @@ int hfi1_user_sdma_free_queues(struct hfi1_filedata *fd)
                        pq->wait,
                        (ACCESS_ONCE(pq->state) == SDMA_PKT_Q_INACTIVE));
                kfree(pq->reqs);
+               kfree(pq->req_in_use);
                kmem_cache_destroy(pq->txreq_cache);
                kfree(pq);
                fd->pq = NULL;
@@ -572,29 +580,27 @@ int hfi1_user_sdma_process_request(struct file *fp, struct iovec *iovec,
                return -EINVAL;
        }
 
-       if (cq->comps[info.comp_idx].status == QUEUED ||
-           test_bit(SDMA_REQ_IN_USE, &pq->reqs[info.comp_idx].flags)) {
-               hfi1_cdbg(SDMA, "[%u:%u:%u] Entry %u is in QUEUED state",
-                         dd->unit, uctxt->ctxt, fd->subctxt,
-                         info.comp_idx);
-               return -EBADSLT;
-       }
        if (!info.fragsize) {
                hfi1_cdbg(SDMA,
                          "[%u:%u:%u:%u] Request does not specify fragsize",
                          dd->unit, uctxt->ctxt, fd->subctxt, info.comp_idx);
                return -EINVAL;
        }
+
+       /* Try to claim the request. */
+       if (test_and_set_bit(info.comp_idx, pq->req_in_use)) {
+               hfi1_cdbg(SDMA, "[%u:%u:%u] Entry %u is in use",
+                         dd->unit, uctxt->ctxt, fd->subctxt,
+                         info.comp_idx);
+               return -EBADSLT;
+       }
        /*
-        * We've done all the safety checks that we can up to this point,
-        * "allocate" the request entry.
+        * All safety checks have been done and this request has been claimed.
         */
        hfi1_cdbg(SDMA, "[%u:%u:%u] Using req/comp entry %u\n", dd->unit,
                  uctxt->ctxt, fd->subctxt, info.comp_idx);
        req = pq->reqs + info.comp_idx;
        memset(req, 0, sizeof(*req));
-       /* Mark the request as IN_USE before we start filling it in. */
-       set_bit(SDMA_REQ_IN_USE, &req->flags);
        req->data_iovs = req_iovcnt(info.ctrl) - 1; /* subtract header vector */
        req->pq = pq;
        req->cq = cq;
@@ -1612,7 +1618,7 @@ static void user_sdma_free_request(struct user_sdma_request *req, bool unpin)
                }
        }
        kfree(req->tids);
-       clear_bit(SDMA_REQ_IN_USE, &req->flags);
+       clear_bit(req->info.comp_idx, req->pq->req_in_use);
 }
 
 static inline void set_comp_state(struct hfi1_user_sdma_pkt_q *pq,

diff --git a/drivers/infiniband/hw/hfi1/user_sdma.h b/drivers/infiniband/hw/hfi1/user_sdma.h
index b9240e3..20ff846 100644 (file)
--- a/drivers/infiniband/hw/hfi1/user_sdma.h
+++ b/drivers/infiniband/hw/hfi1/user_sdma.h
@@ -63,6 +63,7 @@ struct hfi1_user_sdma_pkt_q {
        struct hfi1_devdata *dd;
        struct kmem_cache *txreq_cache;
        struct user_sdma_request *reqs;
+       unsigned long *req_in_use;
        struct iowait busy;
        unsigned state;
        wait_queue_head_t wait;