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Subject[PATCH] cifs: smbd: Check and extend sender credits in interrupt context
Date
From: Long Li <longli@microsoft.com>

When a RDMA packet is received and server is extending send credits, we should
check and unblock senders immediately in IRQ context. Doing it in a worker
queue causes unnecessary delay and doesn't save much CPU on the receive path.

Signed-off-by: Long Li <longli@microsoft.com>
---
fs/cifs/smbdirect.c | 38 +++++++++++++++-----------------------
fs/cifs/smbdirect.h | 1 -
2 files changed, 15 insertions(+), 24 deletions(-)

diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
index a6ae29b3c4e7..8da43a500686 100644
--- a/fs/cifs/smbdirect.c
+++ b/fs/cifs/smbdirect.c
@@ -459,25 +459,6 @@ static void smbd_post_send_credits(struct work_struct *work)
check_and_send_immediate(info);
}

-static void smbd_recv_done_work(struct work_struct *work)
-{
- struct smbd_connection *info =
- container_of(work, struct smbd_connection, recv_done_work);
-
- /*
- * We may have new send credits granted from remote peer
- * If any sender is blcoked on lack of credets, unblock it
- */
- if (atomic_read(&info->send_credits))
- wake_up_interruptible(&info->wait_send_queue);
-
- /*
- * Check if we need to send something to remote peer to
- * grant more credits or respond to KEEP_ALIVE packet
- */
- check_and_send_immediate(info);
-}
-
/* Called from softirq, when recv is done */
static void recv_done(struct ib_cq *cq, struct ib_wc *wc)
{
@@ -546,8 +527,15 @@ static void recv_done(struct ib_cq *cq, struct ib_wc *wc)
atomic_dec(&info->receive_credits);
info->receive_credit_target =
le16_to_cpu(data_transfer->credits_requested);
- atomic_add(le16_to_cpu(data_transfer->credits_granted),
- &info->send_credits);
+ if (le16_to_cpu(data_transfer->credits_granted)) {
+ atomic_add(le16_to_cpu(data_transfer->credits_granted),
+ &info->send_credits);
+ /*
+ * We have new send credits granted from remote peer
+ * If any sender is waiting for credits, unblock it
+ */
+ wake_up_interruptible(&info->wait_send_queue);
+ }

log_incoming(INFO, "data flags %d data_offset %d "
"data_length %d remaining_data_length %d\n",
@@ -563,7 +551,12 @@ static void recv_done(struct ib_cq *cq, struct ib_wc *wc)
info->keep_alive_requested = KEEP_ALIVE_PENDING;
}

- queue_work(info->workqueue, &info->recv_done_work);
+ /*
+ * Check if we need to send something to remote peer to
+ * grant more credits or respond to KEEP_ALIVE packet
+ */
+ check_and_send_immediate(info);
+
return;

default:
@@ -1762,7 +1755,6 @@ static struct smbd_connection *_smbd_get_connection(
atomic_set(&info->send_payload_pending, 0);

INIT_WORK(&info->disconnect_work, smbd_disconnect_rdma_work);
- INIT_WORK(&info->recv_done_work, smbd_recv_done_work);
INIT_WORK(&info->post_send_credits_work, smbd_post_send_credits);
info->new_credits_offered = 0;
spin_lock_init(&info->lock_new_credits_offered);
diff --git a/fs/cifs/smbdirect.h b/fs/cifs/smbdirect.h
index 6ff880a1e186..8ede915f2b24 100644
--- a/fs/cifs/smbdirect.h
+++ b/fs/cifs/smbdirect.h
@@ -67,7 +67,6 @@ struct smbd_connection {
bool negotiate_done;

struct work_struct disconnect_work;
- struct work_struct recv_done_work;
struct work_struct post_send_credits_work;

spinlock_t lock_new_credits_offered;
--
2.17.1
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