drivers/scsi/scsi_debug.c: resolve sg buffer const-ness issue

do_device_access() takes a separate parameter to indicate the direction of
data transfer, which it used to use to select the appropriate function out
of sg_pcopy_{to,from}_buffer(). However these two functions now have

So this patch makes it bypass these wrappers and call the underlying
function sg_copy_buffer() directly; this has the same calling style as
do_device_access() i.e. a separate direction-of-transfer parameter and no
pointers-to-const, so skipping the wrappers not only eliminates the
warning, it also make the code simpler :)

[[e-mail]: fix very broken build]
Signed-off-by: Dave Gordon <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>
Cc: James Bottomley <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/scsi/scsi_debug.c

···
 	u64 block, rest = 0;
 	struct scsi_data_buffer *sdb;
 	enum dma_data_direction dir;
-	size_t (*func)(struct scatterlist *, unsigned int, void *, size_t,
-		       off_t);
 
 	if (do_write) {
 		sdb = scsi_out(scmd);
 		dir = DMA_TO_DEVICE;
-		func = sg_pcopy_to_buffer;
 	} else {
 		sdb = scsi_in(scmd);
 		dir = DMA_FROM_DEVICE;
-		func = sg_pcopy_from_buffer;
 	}
 
 	if (!sdb->length)
···
 	if (block + num > sdebug_store_sectors)
 		rest = block + num - sdebug_store_sectors;
 
-	ret = func(sdb->table.sgl, sdb->table.nents,
+	ret = sg_copy_buffer(sdb->table.sgl, sdb->table.nents,
 		   fake_storep + (block * scsi_debug_sector_size),
-		   (num - rest) * scsi_debug_sector_size, 0);
+		   (num - rest) * scsi_debug_sector_size, 0, do_write);
 	if (ret != (num - rest) * scsi_debug_sector_size)
 		return ret;
 
 	if (rest) {
-		ret += func(sdb->table.sgl, sdb->table.nents,
+		ret += sg_copy_buffer(sdb->table.sgl, sdb->table.nents,
 			    fake_storep, rest * scsi_debug_sector_size,
-			    (num - rest) * scsi_debug_sector_size);
+			    (num - rest) * scsi_debug_sector_size, do_write);
 	}
 
 	return ret;

include/linux/scatterlist.h

···
 	unsigned long offset, unsigned long size,
 	gfp_t gfp_mask);
 
+size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
+		      size_t buflen, off_t skip, bool to_buffer);
+
 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 			   const void *buf, size_t buflen);
 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,

lib/scatterlist.c

···
  * Returns the number of copied bytes.
  *
  **/
-static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
-			     void *buf, size_t buflen, off_t skip,
-			     bool to_buffer)
+size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
+		      size_t buflen, off_t skip, bool to_buffer)
 {
 	unsigned int offset = 0;
 	struct sg_mapping_iter miter;
···
 	local_irq_restore(flags);
 	return offset;
 }
+EXPORT_SYMBOL(sg_copy_buffer);
 
 /**
  * sg_copy_from_buffer - Copy from a linear buffer to an SG list