Revert "target/iblock: Convert WRITE_SAME to blkdev_issue_zeroout"

This reverts commit 2237498.

Author: Bryant G. Ly

drivers/target/target_core_device.c

@@ -855,7 +855,7 @@ bool target_configure_unmap_from_queue(struct se_dev_attrib *attrib,
 	attrib->unmap_granularity = q->limits.discard_granularity / block_size;
 	attrib->unmap_granularity_alignment = q->limits.discard_alignment /
 								block_size;
-	attrib->unmap_zeroes_data = (q->limits.max_write_zeroes_sectors);
+	attrib->unmap_zeroes_data = 0;
 	return true;
 }
 EXPORT_SYMBOL(target_configure_unmap_from_queue);

drivers/target/target_core_iblock.c

@@ -86,7 +86,6 @@ static int iblock_configure_device(struct se_device *dev)
 	struct block_device *bd = NULL;
 	struct blk_integrity *bi;
 	fmode_t mode;
-	unsigned int max_write_zeroes_sectors;
 	int ret = -ENOMEM;
 
 	if (!(ib_dev->ibd_flags & IBDF_HAS_UDEV_PATH)) {
@@ -130,11 +129,7 @@ static int iblock_configure_device(struct se_device *dev)
 	 * Enable write same emulation for IBLOCK and use 0xFFFF as
 	 * the smaller WRITE_SAME(10) only has a two-byte block count.
 	 */
-	max_write_zeroes_sectors = bdev_write_zeroes_sectors(bd);
-	if (max_write_zeroes_sectors)
-		dev->dev_attrib.max_write_same_len = max_write_zeroes_sectors;
-	else
-		dev->dev_attrib.max_write_same_len = 0xFFFF;
+	dev->dev_attrib.max_write_same_len = 0xFFFF;
 
 	if (blk_queue_nonrot(q))
 		dev->dev_attrib.is_nonrot = 1;
@@ -423,31 +418,28 @@ iblock_execute_unmap(struct se_cmd *cmd, sector_t lba, sector_t nolb)
 }
 
 static sense_reason_t
-iblock_execute_zero_out(struct block_device *bdev, struct se_cmd *cmd)
+iblock_execute_write_same_direct(struct block_device *bdev, struct se_cmd *cmd)
 {
 	struct se_device *dev = cmd->se_dev;
 	struct scatterlist *sg = &cmd->t_data_sg[0];
-	unsigned char *buf, zero = 0x00, *p = &zero;
-	int rc, ret;
-
-	buf = kmap(sg_page(sg)) + sg->offset;
-	if (!buf)
-		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
-	/*
-	 * Fall back to block_execute_write_same() slow-path if
-	 * incoming WRITE_SAME payload does not contain zeros.
-	 */
-	rc = memcmp(buf, p, cmd->data_length);
-	kunmap(sg_page(sg));
+	struct page *page = NULL;
+	int ret;
 
-	if (rc)
-		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+	if (sg->offset) {
+		page = alloc_page(GFP_KERNEL);
+		if (!page)
+			return TCM_OUT_OF_RESOURCES;
+		sg_copy_to_buffer(sg, cmd->t_data_nents, page_address(page),
+				  dev->dev_attrib.block_size);
+	}
 
-	ret = blkdev_issue_zeroout(bdev,
+	ret = blkdev_issue_write_same(bdev,
 				target_to_linux_sector(dev, cmd->t_task_lba),
 				target_to_linux_sector(dev,
 					sbc_get_write_same_sectors(cmd)),
-				GFP_KERNEL, false);
+				GFP_KERNEL, page ? page : sg_page(sg));
+	if (page)
+		__free_page(page);
 	if (ret)
 		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 
@@ -483,10 +475,8 @@ iblock_execute_write_same(struct se_cmd *cmd)
 		return TCM_INVALID_CDB_FIELD;
 	}
 
-	if (bdev_write_zeroes_sectors(bdev)) {
-		if (!iblock_execute_zero_out(bdev, cmd))
-			return 0;
-	}
+	if (bdev_write_same(bdev))
+		return iblock_execute_write_same_direct(bdev, cmd);
 
 	ibr = kzalloc(sizeof(struct iblock_req), GFP_KERNEL);
 	if (!ibr)