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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Long Li <longli@microsoft.com>,
        Steve French <stfrench@microsoft.com>
Subject: [PATCH 5.4 29/80] cifs: smbd: Only queue work for error recovery on memory registration
Date:   Thu, 19 Dec 2019 19:34:21 +0100
Message-Id: <20191219183103.776965717@linuxfoundation.org>
In-Reply-To: <20191219183031.278083125@linuxfoundation.org>
References: <20191219183031.278083125@linuxfoundation.org>
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From: Long Li <longli@microsoft.com>

commit c21ce58eab1eda4c66507897207e20c82e62a5ac upstream.

It's not necessary to queue invalidated memory registration to work queue, as
all we need to do is to unmap the SG and make it usable again. This can save
CPU cycles in normal data paths as memory registration errors are rare and
normally only happens during reconnection.

Signed-off-by: Long Li <longli@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/cifs/smbdirect.c |   26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

--- a/fs/cifs/smbdirect.c
+++ b/fs/cifs/smbdirect.c
@@ -2269,12 +2269,7 @@ static void smbd_mr_recovery_work(struct
 	int rc;
 
 	list_for_each_entry(smbdirect_mr, &info->mr_list, list) {
-		if (smbdirect_mr->state == MR_INVALIDATED)
-			ib_dma_unmap_sg(
-				info->id->device, smbdirect_mr->sgl,
-				smbdirect_mr->sgl_count,
-				smbdirect_mr->dir);
-		else if (smbdirect_mr->state == MR_ERROR) {
+		if (smbdirect_mr->state == MR_ERROR) {
 
 			/* recover this MR entry */
 			rc = ib_dereg_mr(smbdirect_mr->mr);
@@ -2602,11 +2597,20 @@ int smbd_deregister_mr(struct smbd_mr *s
 		 */
 		smbdirect_mr->state = MR_INVALIDATED;
 
-	/*
-	 * Schedule the work to do MR recovery for future I/Os
-	 * MR recovery is slow and we don't want it to block the current I/O
-	 */
-	queue_work(info->workqueue, &info->mr_recovery_work);
+	if (smbdirect_mr->state == MR_INVALIDATED) {
+		ib_dma_unmap_sg(
+			info->id->device, smbdirect_mr->sgl,
+			smbdirect_mr->sgl_count,
+			smbdirect_mr->dir);
+		smbdirect_mr->state = MR_READY;
+		if (atomic_inc_return(&info->mr_ready_count) == 1)
+			wake_up_interruptible(&info->wait_mr);
+	} else
+		/*
+		 * Schedule the work to do MR recovery for future I/Os MR
+		 * recovery is slow and don't want it to block current I/O
+		 */
+		queue_work(info->workqueue, &info->mr_recovery_work);
 
 done:
 	if (atomic_dec_and_test(&info->mr_used_count))