A flex array can be used to reduce the allocation to 1.

And actually mtdconcat was using the pointer + 1 trick to point to the
overallocated area. Better alternatives exist.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 drivers/mtd/mtd_virt_concat.c | 8 +-------
 drivers/mtd/mtdconcat.c       | 5 +----
 include/linux/mtd/concat.h    | 2 +-
 3 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/drivers/mtd/mtd_virt_concat.c b/drivers/mtd/mtd_virt_concat.c
index 33f9a63dd450..b56f2431974b 100644
--- a/drivers/mtd/mtd_virt_concat.c
+++ b/drivers/mtd/mtd_virt_concat.c
@@ -182,18 +182,12 @@ static int mtd_virt_concat_create_item(struct device_node *parts,
 	for (i = 1; i < count; i++)
 		item->nodes[i] = of_parse_phandle(parts, CONCAT_PROP, (i - 1));
 
-	concat = kzalloc(sizeof(*concat), GFP_KERNEL);
+	concat = kzalloc_flex(*concat, subdev, count, GFP_KERNEL);
 	if (!concat) {
 		kfree(item);
 		return -ENOMEM;
 	}
 
-	concat->subdev = kcalloc(count, sizeof(*concat->subdev), GFP_KERNEL);
-	if (!concat->subdev) {
-		kfree(item);
-		kfree(concat);
-		return -ENOMEM;
-	}
 	item->concat = concat;
 
 	list_add_tail(&item->head, &concat_node_list);
diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
index 241d15235d01..c97167d51fe2 100644
--- a/drivers/mtd/mtdconcat.c
+++ b/drivers/mtd/mtdconcat.c
@@ -627,7 +627,6 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],	/* subdevices to c
 				   const char *name)
 {				/* name for the new device   */
 	int i;
-	size_t size;
 	struct mtd_concat *concat;
 	struct mtd_info *subdev_master = NULL;
 	uint32_t max_erasesize, curr_erasesize;
@@ -640,15 +639,13 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],	/* subdevices to c
 	printk(KERN_NOTICE "into device \"%s\"\n", name);
 
 	/* allocate the device structure */
-	size = SIZEOF_STRUCT_MTD_CONCAT(num_devs);
-	concat = kzalloc(size, GFP_KERNEL);
+	concat = kzalloc_flex(*concat, subdev, num_devs, GFP_KERNEL);
 	if (!concat) {
 		printk
 		    ("memory allocation error while creating concatenated device \"%s\"\n",
 		     name);
 		return NULL;
 	}
-	concat->subdev = (struct mtd_info **) (concat + 1);
 
 	/*
 	 * Set up the new "super" device's MTD object structure, check for
diff --git a/include/linux/mtd/concat.h b/include/linux/mtd/concat.h
index 2cd9d48958a8..f8d4d6ac1fc1 100644
--- a/include/linux/mtd/concat.h
+++ b/include/linux/mtd/concat.h
@@ -18,7 +18,7 @@
 struct mtd_concat {
 	struct mtd_info mtd;
 	int num_subdev;
-	struct mtd_info **subdev;
+	struct mtd_info *subdev[];
 };
 
 struct mtd_info *mtd_concat_create(
-- 
2.53.0