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authorTrond Myklebust <trond.myklebust@primarydata.com>2015-06-04 15:37:10 -0400
committerTrond Myklebust <trond.myklebust@primarydata.com>2015-06-05 11:15:43 -0400
commit0d2a970d0ae55086520e1e58e572a7acd519429c (patch)
treeb91159e4d38c5c9599cfb7500395729ced35a245 /net/sunrpc/backchannel_rqst.c
parent1dddda86c056ab4cf49e4206824a9de3e0c4159a (diff)
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SUNRPC: Fix a backchannel race
We need to allow the server to send a new request immediately after we've replied to the previous one. Right now, there is a window between the send and the release of the old request in rpc_put_task(), where the server could send us a new backchannel RPC call, and we have no request to service it. Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Diffstat (limited to 'net/sunrpc/backchannel_rqst.c')
-rw-r--r--net/sunrpc/backchannel_rqst.c37
1 files changed, 24 insertions, 13 deletions
diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
index 1baa41099469..9825ff0f91d6 100644
--- a/net/sunrpc/backchannel_rqst.c
+++ b/net/sunrpc/backchannel_rqst.c
@@ -37,16 +37,18 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
static inline int xprt_need_to_requeue(struct rpc_xprt *xprt)
{
- return xprt->bc_alloc_count > 0;
+ return xprt->bc_alloc_count < atomic_read(&xprt->bc_free_slots);
}
static inline void xprt_inc_alloc_count(struct rpc_xprt *xprt, unsigned int n)
{
+ atomic_add(n, &xprt->bc_free_slots);
xprt->bc_alloc_count += n;
}
static inline int xprt_dec_alloc_count(struct rpc_xprt *xprt, unsigned int n)
{
+ atomic_sub(n, &xprt->bc_free_slots);
return xprt->bc_alloc_count -= n;
}
@@ -232,9 +234,15 @@ static struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt, __be32 xid)
struct rpc_rqst *req = NULL;
dprintk("RPC: allocate a backchannel request\n");
- if (list_empty(&xprt->bc_pa_list))
+ if (atomic_read(&xprt->bc_free_slots) <= 0)
goto not_found;
-
+ if (list_empty(&xprt->bc_pa_list)) {
+ req = xprt_alloc_bc_req(xprt, GFP_ATOMIC);
+ if (!req)
+ goto not_found;
+ /* Note: this 'free' request adds it to xprt->bc_pa_list */
+ xprt_free_bc_request(req);
+ }
req = list_first_entry(&xprt->bc_pa_list, struct rpc_rqst,
rq_bc_pa_list);
req->rq_reply_bytes_recvd = 0;
@@ -260,11 +268,21 @@ void xprt_free_bc_request(struct rpc_rqst *req)
req->rq_connect_cookie = xprt->connect_cookie - 1;
smp_mb__before_atomic();
- WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state));
clear_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
smp_mb__after_atomic();
- if (!xprt_need_to_requeue(xprt)) {
+ /*
+ * Return it to the list of preallocations so that it
+ * may be reused by a new callback request.
+ */
+ spin_lock_bh(&xprt->bc_pa_lock);
+ if (xprt_need_to_requeue(xprt)) {
+ list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
+ xprt->bc_alloc_count++;
+ req = NULL;
+ }
+ spin_unlock_bh(&xprt->bc_pa_lock);
+ if (req != NULL) {
/*
* The last remaining session was destroyed while this
* entry was in use. Free the entry and don't attempt
@@ -275,14 +293,6 @@ void xprt_free_bc_request(struct rpc_rqst *req)
xprt_free_allocation(req);
return;
}
-
- /*
- * Return it to the list of preallocations so that it
- * may be reused by a new callback request.
- */
- spin_lock_bh(&xprt->bc_pa_lock);
- list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
- spin_unlock_bh(&xprt->bc_pa_lock);
}
/*
@@ -326,6 +336,7 @@ void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
spin_lock(&xprt->bc_pa_lock);
list_del(&req->rq_bc_pa_list);
+ xprt->bc_alloc_count--;
spin_unlock(&xprt->bc_pa_lock);
req->rq_private_buf.len = copied;