btrfs: fix dip leak

The btrfs DIO code leaks dip structs when dip->csums allocation
fails; bio->bi_end_io isn't set at the point where the free_ordered
branch is consequently taken, thus bio_endio doesn't call the function
which would free it in the normal case. Fix.

Signed-off-by: Daniel J Blueman <[e-mail]>
Acked-by: Miao Xie <[e-mail]>
Signed-off-by: Chris Mason <[e-mail]>

fs/btrfs/inode.c

···
 	if (!skip_sum) {
 		dip->csums = kmalloc(sizeof(u32) * bio->bi_vcnt, GFP_NOFS);
 		if (!dip->csums) {
+			kfree(dip);
 			ret = -ENOMEM;
 			goto free_ordered;
 		}