target: rewrite fd_execute_write_same

With the new bio_vec backed iov_iter helpers we can simply set up
on bio_vec per LBA, all pointing to the same initiator-supplied
buffer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_file.c

@@ -433,59 +433,17 @@ fd_execute_sync_cache(struct se_cmd *cmd)
 	return 0;
 }
 
-static unsigned char *
-fd_setup_write_same_buf(struct se_cmd *cmd, struct scatterlist *sg,
-		    unsigned int len)
-{
-	struct se_device *se_dev = cmd->se_dev;
-	unsigned int block_size = se_dev->dev_attrib.block_size;
-	unsigned int i = 0, end;
-	unsigned char *buf, *p, *kmap_buf;
-
-	buf = kzalloc(min_t(unsigned int, len, PAGE_SIZE), GFP_KERNEL);
-	if (!buf) {
-		pr_err("Unable to allocate fd_execute_write_same buf\n");
-		return NULL;
-	}
-
-	kmap_buf = kmap(sg_page(sg)) + sg->offset;
-	if (!kmap_buf) {
-		pr_err("kmap() failed in fd_setup_write_same\n");
-		kfree(buf);
-		return NULL;
-	}
-	/*
-	 * Fill local *buf to contain multiple WRITE_SAME blocks up to
-	 * min(len, PAGE_SIZE)
-	 */
-	p = buf;
-	end = min_t(unsigned int, len, PAGE_SIZE);
-
-	while (i < end) {
-		memcpy(p, kmap_buf, block_size);
-
-		i += block_size;
-		p += block_size;
-	}
-	kunmap(sg_page(sg));
-
-	return buf;
-}
-
 static sense_reason_t
 fd_execute_write_same(struct se_cmd *cmd)
 {
 	struct se_device *se_dev = cmd->se_dev;
 	struct fd_dev *fd_dev = FD_DEV(se_dev);
-	struct file *f = fd_dev->fd_file;
-	struct scatterlist *sg;
-	struct iovec *iov;
-	mm_segment_t old_fs;
-	sector_t nolb = sbc_get_write_same_sectors(cmd);
 	loff_t pos = cmd->t_task_lba * se_dev->dev_attrib.block_size;
-	unsigned int len, len_tmp, iov_num;
-	int i, rc;
-	unsigned char *buf;
+	sector_t nolb = sbc_get_write_same_sectors(cmd);
+	struct iov_iter iter;
+	struct bio_vec *bvec;
+	unsigned int len = 0, i;
+	ssize_t ret;
 
 	if (!nolb) {
 		target_complete_cmd(cmd, SAM_STAT_GOOD);
@@ -496,49 +454,35 @@ fd_execute_write_same(struct se_cmd *cmd)
 		       " backends not supported\n");
 		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 	}
-	sg = &cmd->t_data_sg[0];
 
 	if (cmd->t_data_nents > 1 ||
-	    sg->length != cmd->se_dev->dev_attrib.block_size) {
+	    cmd->t_data_sg[0].length != cmd->se_dev->dev_attrib.block_size) {
 		pr_err("WRITE_SAME: Illegal SGL t_data_nents: %u length: %u"
-			" block_size: %u\n", cmd->t_data_nents, sg->length,
+			" block_size: %u\n",
+			cmd->t_data_nents,
+			cmd->t_data_sg[0].length,
 			cmd->se_dev->dev_attrib.block_size);
 		return TCM_INVALID_CDB_FIELD;
 	}
 
-	len = len_tmp = nolb * se_dev->dev_attrib.block_size;
-	iov_num = DIV_ROUND_UP(len, PAGE_SIZE);
-
-	buf = fd_setup_write_same_buf(cmd, sg, len);
-	if (!buf)
+	bvec = kcalloc(nolb, sizeof(struct bio_vec), GFP_KERNEL);
+	if (!bvec)
 		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 
-	iov = vzalloc(sizeof(struct iovec) * iov_num);
-	if (!iov) {
-		pr_err("Unable to allocate fd_execute_write_same iovecs\n");
-		kfree(buf);
-		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
-	}
-	/*
-	 * Map the single fabric received scatterlist block now populated
-	 * in *buf into each iovec for I/O submission.
-	 */
-	for (i = 0; i < iov_num; i++) {
-		iov[i].iov_base = buf;
-		iov[i].iov_len = min_t(unsigned int, len_tmp, PAGE_SIZE);
-		len_tmp -= iov[i].iov_len;
-	}
+	for (i = 0; i < nolb; i++) {
+		bvec[i].bv_page = sg_page(&cmd->t_data_sg[0]);
+		bvec[i].bv_len = cmd->t_data_sg[0].length;
+		bvec[i].bv_offset = cmd->t_data_sg[0].offset;
 
-	old_fs = get_fs();
-	set_fs(get_ds());
-	rc = vfs_writev(f, &iov[0], iov_num, &pos);
-	set_fs(old_fs);
+		len += se_dev->dev_attrib.block_size;
+	}
 
-	vfree(iov);
-	kfree(buf);
+	iov_iter_bvec(&iter, ITER_BVEC, bvec, nolb, len);
+	ret = vfs_iter_write(fd_dev->fd_file, &iter, &pos);
 
-	if (rc < 0 || rc != len) {
-		pr_err("vfs_writev() returned %d for write same\n", rc);
+	kfree(bvec);
+	if (ret < 0 || ret != len) {
+		pr_err("vfs_iter_write() returned %zd for write same\n", ret);
 		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 	}