From cc886c9ff1607eda04062bdcec963e2f8e6a3eb1 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Thu, 7 Jan 2016 14:49:12 -0500 Subject: [PATCH] svcrdma: Improve allocation of struct svc_rdma_op_ctxt When the maximum payload size of NFS READ and WRITE was increased by commit cc9a903d915c ("svcrdma: Change maximum server payload back to RPCSVC_MAXPAYLOAD"), the size of struct svc_rdma_op_ctxt increased to over 6KB (on x86_64). That makes allocating one of these from a kmem_cache more likely to fail in situations when system memory is exhausted. Since I'm about to add a caller where this allocation must always work _and_ it cannot sleep, pre-allocate ctxts for each connection. Another motivation for this change is that NFSv4.x servers are required by specification not to drop NFS requests. Pre-allocating memory resources reduces the likelihood of a drop. Signed-off-by: Chuck Lever Acked-by: Bruce Fields Signed-off-by: Doug Ledford --- include/linux/sunrpc/svc_rdma.h | 6 +- net/sunrpc/xprtrdma/svc_rdma_transport.c | 102 +++++++++++++++++++++++++++---- 2 files changed, 94 insertions(+), 14 deletions(-) diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h index f869807..be2804b 100644 --- a/include/linux/sunrpc/svc_rdma.h +++ b/include/linux/sunrpc/svc_rdma.h @@ -69,6 +69,7 @@ extern atomic_t rdma_stat_sq_prod; * completes. */ struct svc_rdma_op_ctxt { + struct list_head free; struct svc_rdma_op_ctxt *read_hdr; struct svc_rdma_fastreg_mr *frmr; int hdr_count; @@ -141,7 +142,10 @@ struct svcxprt_rdma { struct ib_pd *sc_pd; atomic_t sc_dma_used; - atomic_t sc_ctxt_used; + spinlock_t sc_ctxt_lock; + struct list_head sc_ctxts; + int sc_ctxt_used; + struct list_head sc_rq_dto_q; spinlock_t sc_rq_dto_lock; struct ib_qp *sc_qp; diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c index a100d56..9801115 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c @@ -153,18 +153,76 @@ static void svc_rdma_bc_free(struct svc_xprt *xprt) } #endif /* CONFIG_SUNRPC_BACKCHANNEL */ -struct svc_rdma_op_ctxt *svc_rdma_get_context(struct svcxprt_rdma *xprt) +static struct svc_rdma_op_ctxt *alloc_ctxt(struct svcxprt_rdma *xprt, + gfp_t flags) { struct svc_rdma_op_ctxt *ctxt; - ctxt = kmem_cache_alloc(svc_rdma_ctxt_cachep, - GFP_KERNEL | __GFP_NOFAIL); - ctxt->xprt = xprt; - INIT_LIST_HEAD(&ctxt->dto_q); + ctxt = kmalloc(sizeof(*ctxt), flags); + if (ctxt) { + ctxt->xprt = xprt; + INIT_LIST_HEAD(&ctxt->free); + INIT_LIST_HEAD(&ctxt->dto_q); + } + return ctxt; +} + +static bool svc_rdma_prealloc_ctxts(struct svcxprt_rdma *xprt) +{ + int i; + + /* Each RPC/RDMA credit can consume a number of send + * and receive WQEs. One ctxt is allocated for each. + */ + i = xprt->sc_sq_depth + xprt->sc_max_requests; + + while (i--) { + struct svc_rdma_op_ctxt *ctxt; + + ctxt = alloc_ctxt(xprt, GFP_KERNEL); + if (!ctxt) { + dprintk("svcrdma: No memory for RDMA ctxt\n"); + return false; + } + list_add(&ctxt->free, &xprt->sc_ctxts); + } + return true; +} + +struct svc_rdma_op_ctxt *svc_rdma_get_context(struct svcxprt_rdma *xprt) +{ + struct svc_rdma_op_ctxt *ctxt = NULL; + + spin_lock_bh(&xprt->sc_ctxt_lock); + xprt->sc_ctxt_used++; + if (list_empty(&xprt->sc_ctxts)) + goto out_empty; + + ctxt = list_first_entry(&xprt->sc_ctxts, + struct svc_rdma_op_ctxt, free); + list_del_init(&ctxt->free); + spin_unlock_bh(&xprt->sc_ctxt_lock); + +out: ctxt->count = 0; ctxt->frmr = NULL; - atomic_inc(&xprt->sc_ctxt_used); return ctxt; + +out_empty: + /* Either pre-allocation missed the mark, or send + * queue accounting is broken. + */ + spin_unlock_bh(&xprt->sc_ctxt_lock); + + ctxt = alloc_ctxt(xprt, GFP_NOIO); + if (ctxt) + goto out; + + spin_lock_bh(&xprt->sc_ctxt_lock); + xprt->sc_ctxt_used--; + spin_unlock_bh(&xprt->sc_ctxt_lock); + WARN_ONCE(1, "svcrdma: empty RDMA ctxt list?\n"); + return NULL; } void svc_rdma_unmap_dma(struct svc_rdma_op_ctxt *ctxt) @@ -190,16 +248,29 @@ void svc_rdma_unmap_dma(struct svc_rdma_op_ctxt *ctxt) void svc_rdma_put_context(struct svc_rdma_op_ctxt *ctxt, int free_pages) { - struct svcxprt_rdma *xprt; + struct svcxprt_rdma *xprt = ctxt->xprt; int i; - xprt = ctxt->xprt; if (free_pages) for (i = 0; i < ctxt->count; i++) put_page(ctxt->pages[i]); - kmem_cache_free(svc_rdma_ctxt_cachep, ctxt); - atomic_dec(&xprt->sc_ctxt_used); + spin_lock_bh(&xprt->sc_ctxt_lock); + xprt->sc_ctxt_used--; + list_add(&ctxt->free, &xprt->sc_ctxts); + spin_unlock_bh(&xprt->sc_ctxt_lock); +} + +static void svc_rdma_destroy_ctxts(struct svcxprt_rdma *xprt) +{ + while (!list_empty(&xprt->sc_ctxts)) { + struct svc_rdma_op_ctxt *ctxt; + + ctxt = list_first_entry(&xprt->sc_ctxts, + struct svc_rdma_op_ctxt, free); + list_del(&ctxt->free); + kfree(ctxt); + } } /* @@ -521,11 +592,13 @@ static struct svcxprt_rdma *rdma_create_xprt(struct svc_serv *serv, INIT_LIST_HEAD(&cma_xprt->sc_rq_dto_q); INIT_LIST_HEAD(&cma_xprt->sc_read_complete_q); INIT_LIST_HEAD(&cma_xprt->sc_frmr_q); + INIT_LIST_HEAD(&cma_xprt->sc_ctxts); init_waitqueue_head(&cma_xprt->sc_send_wait); spin_lock_init(&cma_xprt->sc_lock); spin_lock_init(&cma_xprt->sc_rq_dto_lock); spin_lock_init(&cma_xprt->sc_frmr_q_lock); + spin_lock_init(&cma_xprt->sc_ctxt_lock); if (listener) set_bit(XPT_LISTENER, &cma_xprt->sc_xprt.xpt_flags); @@ -913,6 +986,9 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt) (size_t)svcrdma_max_requests); newxprt->sc_sq_depth = RPCRDMA_SQ_DEPTH_MULT * newxprt->sc_max_requests; + if (!svc_rdma_prealloc_ctxts(newxprt)) + goto errout; + /* * Limit ORD based on client limit, local device limit, and * configured svcrdma limit. @@ -1174,15 +1250,15 @@ static void __svc_rdma_free(struct work_struct *work) } /* Warn if we leaked a resource or under-referenced */ - if (atomic_read(&rdma->sc_ctxt_used) != 0) + if (rdma->sc_ctxt_used != 0) pr_err("svcrdma: ctxt still in use? (%d)\n", - atomic_read(&rdma->sc_ctxt_used)); + rdma->sc_ctxt_used); if (atomic_read(&rdma->sc_dma_used) != 0) pr_err("svcrdma: dma still in use? (%d)\n", atomic_read(&rdma->sc_dma_used)); - /* De-allocate fastreg mr */ rdma_dealloc_frmr_q(rdma); + svc_rdma_destroy_ctxts(rdma); /* Destroy the QP if present (not a listener) */ if (rdma->sc_qp && !IS_ERR(rdma->sc_qp)) -- 2.7.4