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Subject[PATCH 4.14 172/183] RDMA/core: Reduce poll batch for direct cq polling
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Max Gurtovoy <maxg@mellanox.com>


[ Upstream commit d3b9e8ad425cfd5b9116732e057f1b48e4d3bcb8 ]

Fix warning limit for kernel stack consumption:

drivers/infiniband/core/cq.c: In function 'ib_process_cq_direct':
drivers/infiniband/core/cq.c:78:1: error: the frame size of 1032 bytes
is larger than 1024 bytes [-Werror=frame-larger-than=]

Using smaller ib_wc array on the stack brings us comfortably below that
limit again.

Fixes: 246d8b184c10 ("IB/cq: Don't force IB_POLL_DIRECT poll context for ib_process_cq_direct")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Sergey Gorenko <sergeygo@mellanox.com>
Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/infiniband/core/cq.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)

--- a/drivers/infiniband/core/cq.c
+++ b/drivers/infiniband/core/cq.c
@@ -17,6 +17,7 @@

/* # of WCs to poll for with a single call to ib_poll_cq */
#define IB_POLL_BATCH 16
+#define IB_POLL_BATCH_DIRECT 8

/* # of WCs to iterate over before yielding */
#define IB_POLL_BUDGET_IRQ 256
@@ -25,18 +26,18 @@
#define IB_POLL_FLAGS \
(IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS)

-static int __ib_process_cq(struct ib_cq *cq, int budget, struct ib_wc *poll_wc)
+static int __ib_process_cq(struct ib_cq *cq, int budget, struct ib_wc *wcs,
+ int batch)
{
int i, n, completed = 0;
- struct ib_wc *wcs = poll_wc ? : cq->wc;

/*
* budget might be (-1) if the caller does not
* want to bound this call, thus we need unsigned
* minimum here.
*/
- while ((n = ib_poll_cq(cq, min_t(u32, IB_POLL_BATCH,
- budget - completed), wcs)) > 0) {
+ while ((n = ib_poll_cq(cq, min_t(u32, batch,
+ budget - completed), wcs)) > 0) {
for (i = 0; i < n; i++) {
struct ib_wc *wc = &wcs[i];

@@ -48,8 +49,7 @@ static int __ib_process_cq(struct ib_cq

completed += n;

- if (n != IB_POLL_BATCH ||
- (budget != -1 && completed >= budget))
+ if (n != batch || (budget != -1 && completed >= budget))
break;
}

@@ -72,9 +72,9 @@ static int __ib_process_cq(struct ib_cq
*/
int ib_process_cq_direct(struct ib_cq *cq, int budget)
{
- struct ib_wc wcs[IB_POLL_BATCH];
+ struct ib_wc wcs[IB_POLL_BATCH_DIRECT];

- return __ib_process_cq(cq, budget, wcs);
+ return __ib_process_cq(cq, budget, wcs, IB_POLL_BATCH_DIRECT);
}
EXPORT_SYMBOL(ib_process_cq_direct);

@@ -88,7 +88,7 @@ static int ib_poll_handler(struct irq_po
struct ib_cq *cq = container_of(iop, struct ib_cq, iop);
int completed;

- completed = __ib_process_cq(cq, budget, NULL);
+ completed = __ib_process_cq(cq, budget, cq->wc, IB_POLL_BATCH);
if (completed < budget) {
irq_poll_complete(&cq->iop);
if (ib_req_notify_cq(cq, IB_POLL_FLAGS) > 0)
@@ -108,7 +108,8 @@ static void ib_cq_poll_work(struct work_
struct ib_cq *cq = container_of(work, struct ib_cq, work);
int completed;

- completed = __ib_process_cq(cq, IB_POLL_BUDGET_WORKQUEUE, NULL);
+ completed = __ib_process_cq(cq, IB_POLL_BUDGET_WORKQUEUE, cq->wc,
+ IB_POLL_BATCH);
if (completed >= IB_POLL_BUDGET_WORKQUEUE ||
ib_req_notify_cq(cq, IB_POLL_FLAGS) > 0)
queue_work(ib_comp_wq, &cq->work);

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