btrfs: Replace kmalloc with kmalloc_array

Replace kmalloc(size * nr, ) with kmalloc_array(nr, size), thus making
it easier to check is that the calculation doesn't wrap or return a smaller allocation

Signed-off-by: Dulshani Gunawardhana <dulshani.gunawardhana89@gmail.com>
Reviewed-by: Zach Brown <zab@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

fs/btrfs/delayed-inode.c

@@ -770,13 +770,13 @@ static int btrfs_batch_insert_items(struct btrfs_root *root,
 	 */
 	btrfs_set_path_blocking(path);
 
-	keys = kmalloc(sizeof(struct btrfs_key) * nitems, GFP_NOFS);
+	keys = kmalloc_array(nitems, sizeof(struct btrfs_key), GFP_NOFS);
 	if (!keys) {
 		ret = -ENOMEM;
 		goto out;
 	}
 
-	data_size = kmalloc(sizeof(u32) * nitems, GFP_NOFS);
+	data_size = kmalloc_array(nitems, sizeof(u32), GFP_NOFS);
 	if (!data_size) {
 		ret = -ENOMEM;
 		goto error;

fs/btrfs/ioctl.c

@@ -1198,7 +1198,7 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 		ra = &file->f_ra;
 	}
 
-	pages = kmalloc(sizeof(struct page *) * max_cluster,
+	pages = kmalloc_array(max_cluster, sizeof(struct page *),
 			GFP_NOFS);
 	if (!pages) {
 		ret = -ENOMEM;

fs/btrfs/super.c

@@ -1470,7 +1470,7 @@ static int btrfs_calc_avail_data_space(struct btrfs_root *root, u64 *free_bytes)
 	nr_devices = fs_info->fs_devices->open_devices;
 	BUG_ON(!nr_devices);
 
-	devices_info = kmalloc(sizeof(*devices_info) * nr_devices,
+	devices_info = kmalloc_array(nr_devices, sizeof(*devices_info),
 			       GFP_NOFS);
 	if (!devices_info)
 		return -ENOMEM;

fs/btrfs/volumes.c

@@ -4901,7 +4901,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
 			num_stripes = map->num_stripes;
 			max_errors = nr_parity_stripes(map);
 
-			raid_map = kmalloc(sizeof(u64) * num_stripes,
+			raid_map = kmalloc_array(num_stripes, sizeof(u64),
 					   GFP_NOFS);
 			if (!raid_map) {
 				ret = -ENOMEM;