mmc: bcm2835: Avoid possible races on data requests

There are two accesses on the data requests which are not protected by
the mutex. So fix this accordingly.
Signed-off-by: NStefan Wahren <stefan.wahren@i2se.com>
Acked-by: NEric Anholt <eric@anholt.net>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/bcm2835.c

@@ -1053,10 +1053,12 @@ static void bcm2835_dma_complete_work(struct work_struct *work)
 {
 	struct bcm2835_host *host =
 		container_of(work, struct bcm2835_host, dma_work);
-	struct mmc_data *data = host->data;
+	struct mmc_data *data;
 
 	mutex_lock(&host->mutex);
 
+	data = host->data;
+
 	if (host->dma_chan) {
 		dma_unmap_sg(host->dma_chan->device->dev,
 			     data->sg, data->sg_len,
@@ -1181,9 +1183,6 @@ static void bcm2835_request(struct mmc_host *mmc, struct mmc_request *mrq)
 		return;
 	}
 
-	if (host->use_dma && mrq->data && (mrq->data->blocks > PIO_THRESHOLD))
-		bcm2835_prepare_dma(host, mrq->data);
-
 	mutex_lock(&host->mutex);
 
 	WARN_ON(host->mrq);
@@ -1207,6 +1206,9 @@ static void bcm2835_request(struct mmc_host *mmc, struct mmc_request *mrq)
 		return;
 	}
 
+	if (host->use_dma && mrq->data && (mrq->data->blocks > PIO_THRESHOLD))
+		bcm2835_prepare_dma(host, mrq->data);
+
 	host->use_sbc = !!mrq->sbc && host->mrq->data &&
 			(host->mrq->data->flags & MMC_DATA_READ);
 	if (host->use_sbc) {