linux-kernel - [PATCH V2] dmaengine: Fix client_count is countered one more incorrectly.

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Message-Id: <20220930173652.1251349-1-koba.ko@canonical.com>
Date:   Sat,  1 Oct 2022 01:36:52 +0800
From:   Koba Ko <koba.ko@...onical.com>
To:     Vinod Koul <vkoul@...nel.org>, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Jie Hai <haijie1@...wei.com>, Dave Jiang <dave.jiang@...el.com>
Subject: [PATCH V2] dmaengine: Fix client_count is countered one more incorrectly.

If the passed client_count is 0,
it would be incremented by balance_ref_count first
then increment one more.
This would cause client_count to 2.

cat /sys/class/dma/dma0chan*/in_use
2
2
2

Fixes: d2f4f99db3e9 ("dmaengine: Rework dma_chan_get")
Signed-off-by: Koba Ko <koba.ko@...onical.com>
Reviewed-by: Jie Hai <haijie1@...wei.com>
Test-by: Jie Hai <haijie1@...wei.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>
Reviewed-by: Dave Jiang <dave.jiang@...el.com>

---
V2: Remove [3/3] on subject.
---
 drivers/dma/dmaengine.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 2cfa8458b51be..78f8a9f3ad825 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -451,7 +451,8 @@ static int dma_chan_get(struct dma_chan *chan)
 	/* The channel is already in use, update client count */
 	if (chan->client_count) {
 		__module_get(owner);
-		goto out;
+		chan->client_count++;
+		return 0;
 	}
 
 	if (!try_module_get(owner))
@@ -470,11 +471,11 @@ static int dma_chan_get(struct dma_chan *chan)
 			goto err_out;
 	}
 
+	chan->client_count++;
+
 	if (!dma_has_cap(DMA_PRIVATE, chan->device->cap_mask))
 		balance_ref_count(chan);
 
-out:
-	chan->client_count++;
 	return 0;
 
 err_out:
-- 
2.25.1