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author | Trond Myklebust <trond.myklebust@primarydata.com> | 2015-06-04 15:37:10 -0400 |
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committer | Trond Myklebust <trond.myklebust@primarydata.com> | 2015-06-05 11:15:43 -0400 |
commit | 0d2a970d0ae55086520e1e58e572a7acd519429c (patch) | |
tree | b91159e4d38c5c9599cfb7500395729ced35a245 /net/sunrpc/backchannel_rqst.c | |
parent | 1dddda86c056ab4cf49e4206824a9de3e0c4159a (diff) | |
download | linux-0d2a970d0ae55086520e1e58e572a7acd519429c.tar.gz linux-0d2a970d0ae55086520e1e58e572a7acd519429c.tar.bz2 linux-0d2a970d0ae55086520e1e58e572a7acd519429c.zip |
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.c | 37 |
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; |