udmabuf: Ensure to perform cache synchronisation in begin_cpu_udmabuf()

The message of commit 504e2b4ab97a ("dma-buf/udmabuf: skip redundant cpu sync to
fix cacheline EEXIST warning") says:

> The CPU sync at map/unmap time is also redundant for udmabuf:
> begin_cpu_udmabuf() and end_cpu_udmabuf() already perform explicit
> cache synchronization via dma_sync_sgtable_for_cpu/device() when CPU
> access is requested through the dma-buf interface.

This, however, does not apply to the first time begin_cpu_udmabuf() is
called on an udmabuf, in which case the implementation previously relied on
get_sg_table() to perform the cache synchronisation.

Ensure to call dma_sync_sgtable_for_cpu() in that case as well.

Fixes: 504e2b4ab97a ("dma-buf/udmabuf: skip redundant cpu sync to fix cacheline EEXIST warning")
Signed-off-by: Robert Mader <robert.mader@collabora.com>
Reviewed-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Link: https://patch.msgid.link/20260627105725.9083-1-robert.mader@collabora.com

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index bced421c0d658964cc5dc7ed3a46cc311144ac78..08f57bc1294df4bfbc3560ebd7977cce84495282 100644 (file)
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -224,21 +224,22 @@ static int begin_cpu_udmabuf(struct dma_buf *buf,
 {
        struct udmabuf *ubuf = buf->priv;
        struct device *dev = ubuf->device->this_device;
-       int ret = 0;
 
        if (!ubuf->sg) {
                ubuf->sg = get_sg_table(dev, buf, direction);
                if (IS_ERR(ubuf->sg)) {
+                       int ret;
+
                        ret = PTR_ERR(ubuf->sg);
                        ubuf->sg = NULL;
+                       return ret;
                } else {
                        ubuf->sg_dir = direction;
                }
-       } else {
-               dma_sync_sgtable_for_cpu(dev, ubuf->sg, direction);
        }
 
-       return ret;
+       dma_sync_sgtable_for_cpu(dev, ubuf->sg, direction);
+       return 0;
 }
 
 static int end_cpu_udmabuf(struct dma_buf *buf,