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 <chuck.lever@xxxxxxxxxx>
---
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 0783f6e..58ed9f2 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_ON_ONCE("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))
--
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