drivers: rkflash: Using kmap_atomic to build page address mapping

The virtual address of allocated __GFP_HIGHMEM pages is not mapped
in large memeory aarch32 system, Using kmap to build it, or it will
failed like:

    Unable to handle kernel NULL pointer dereference at virtual address 00000000
    pgd = 50ec00c8
    [00000000] *pgd=00000000
    Internal error: Oops: 817 [#1] PREEMPT SMP ARM
    Modules linked in:
    CPU: 3 PID: 67 Comm: rkflash Not tainted 4.19.111 rockchip-linux#67
    Hardware name: Generic DT based system
    PC is at memcpy+0x50/0x330
    LR is at 0x61640a68

Change-Id: I0cde9012d29e49d9ba751cb019ccfa784c01b7c7
Signed-off-by: Jon Lin <jon.lin@rock-chips.com>

drivers/rkflash/rkflash_blk.c

@@ -245,20 +245,26 @@ static int rkflash_blk_xfer(struct flash_blk_dev *dev,
 static int rkflash_blk_check_buffer_align(struct request *req, char **pbuf)
 {
 	int nr_vec = 0;
-	struct bio_vec bvec;
+	struct bio_vec bv;
 	struct req_iterator iter;
 	char *buffer;
 	void *firstbuf = 0;
 	char *nextbuffer = 0;
 
-	rq_for_each_segment(bvec, req, iter) {
-		buffer = page_address(bvec.bv_page) + bvec.bv_offset;
+	rq_for_each_segment(bv, req, iter) {
+		/* high mem return 0 and using kernel buffer */
+		if (PageHighMem(bv.bv_page))
+			return 0;
+
+		buffer = page_address(bv.bv_page) + bv.bv_offset;
+		if (!buffer)
+			return 0;
 		if (!firstbuf)
 			firstbuf = buffer;
 		nr_vec++;
 		if (nextbuffer && nextbuffer != buffer)
 			return 0;
-		nextbuffer = buffer + bvec.bv_len;
+		nextbuffer = buffer + bv.bv_len;
 	}
 	*pbuf = firstbuf;
 	return 1;
@@ -269,12 +275,11 @@ static int rkflash_blktrans_thread(void *arg)
 	struct flash_blk_ops *blk_ops = arg;
 	struct request_queue *rq = blk_ops->rq;
 	struct request *req = NULL;
-	char *buf;
+	char *buf, *page_buf;
 	struct req_iterator rq_iter;
 	struct bio_vec bvec;
 	unsigned long long sector_index = ULLONG_MAX;
 	unsigned long totle_nsect;
-	unsigned long rq_len = 0;
 	int rw_flag = 0;
 
 	spin_lock_irq(rq->queue_lock);
@@ -305,7 +310,6 @@ static int rkflash_blktrans_thread(void *arg)
 		dev = req->rq_disk->private_data;
 		totle_nsect = (req->__data_len) >> 9;
 		sector_index = blk_rq_pos(req);
-		rq_len = 0;
 		buf = 0;
 		res = 0;
 		rw_flag = req_op(req);
@@ -322,7 +326,7 @@ static int rkflash_blktrans_thread(void *arg)
 			if (!__blk_end_request_cur(req, res))
 				req = NULL;
 			continue;
-		} else if (rw_flag == REQ_OP_READ && mtd_read_temp_buffer) {
+		} else if (rw_flag == REQ_OP_READ) {
 			buf = mtd_read_temp_buffer;
 			rkflash_blk_check_buffer_align(req, &buf);
 			spin_unlock_irq(rq->queue_lock);
@@ -337,46 +341,39 @@ static int rkflash_blktrans_thread(void *arg)
 				char *p = buf;
 
 				rq_for_each_segment(bvec, req, rq_iter) {
-					memcpy(page_address(bvec.bv_page) +
+					page_buf = kmap_atomic(bvec.bv_page);
+					memcpy(page_buf +
 					       bvec.bv_offset,
 					       p,
 					       bvec.bv_len);
 					p += bvec.bv_len;
+					kunmap_atomic(page_buf);
 				}
 			}
 		} else if (rw_flag == REQ_OP_WRITE){
-			rq_for_each_segment(bvec, req, rq_iter) {
-				if ((page_address(bvec.bv_page)
-					+ bvec.bv_offset)
-					== (buf + rq_len)) {
-					rq_len += bvec.bv_len;
-				} else {
-					if (rq_len) {
-						spin_unlock_irq(rq->queue_lock);
-						res = rkflash_blk_xfer(dev,
-								       sector_index,
-								       rq_len >> 9,
-								       buf,
-								       rw_flag,
-								       totle_nsect);
-						spin_lock_irq(rq->queue_lock);
-					}
-					sector_index += rq_len >> 9;
-					buf = (page_address(bvec.bv_page) +
-						bvec.bv_offset);
-					rq_len = bvec.bv_len;
+			buf = mtd_read_temp_buffer;
+			rkflash_blk_check_buffer_align(req, &buf);
+			if (buf == mtd_read_temp_buffer) {
+				char *p = buf;
+
+				rq_for_each_segment(bvec, req, rq_iter) {
+					page_buf = kmap_atomic(bvec.bv_page);
+					memcpy(p,
+					       page_buf +
+					       bvec.bv_offset,
+					       bvec.bv_len);
+					p += bvec.bv_len;
+					kunmap_atomic(page_buf);
 				}
 			}
-			if (rq_len) {
-				spin_unlock_irq(rq->queue_lock);
-				res = rkflash_blk_xfer(dev,
-						       sector_index,
-						       rq_len >> 9,
-						       buf,
-						       rw_flag,
-						       totle_nsect);
-				spin_lock_irq(rq->queue_lock);
-			}
+			spin_unlock_irq(rq->queue_lock);
+			res = rkflash_blk_xfer(dev,
+					       sector_index,
+					       totle_nsect,
+					       buf,
+					       rw_flag,
+					       totle_nsect);
+			spin_lock_irq(rq->queue_lock);
 		} else {
 			pr_err("%s error req flag\n", __func__);
 		}