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Commit cc886c9f authored by Chuck Lever's avatar Chuck Lever Committed by Doug Ledford
Browse files

svcrdma: Improve allocation of struct svc_rdma_op_ctxt 



When the maximum payload size of NFS READ and WRITE was increased
by commit cc9a903d ("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: default avatarChuck Lever <chuck.lever@oracle.com>
Acked-by: default avatarBruce Fields <bfields@fieldses.org>
Signed-off-by: default avatarDoug Ledford <dledford@redhat.com>
parent ced4ac0c

include/linux/sunrpc/svc_rdma.h

+5 −1
Original line number Diff line number Diff line
@@ -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;

net/sunrpc/xprtrdma/svc_rdma_transport.c

+89 −13
Original line number Diff line number Diff line
@@ -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 = 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))