[PATCH] dm-crypt end_io bv_offset fix

From: Christophe Saout <christophe@saout.de>

We should copy the bvec array for read requests so that we still
have the unmodified bvec array to decrypt the data afterwards.

(as discussed earlier this day for highmem bounces)

drivers/md/dm-crypt.c

@@ -593,8 +593,21 @@ crypt_clone(struct crypt_config *cc, struct crypt_io *io, struct bio *bio,
 				return NULL;
 			}
 		}
-	} else
-		clone = bio_clone(bio, GFP_NOIO);
+	} else {
+		/*
+		 * The block layer might modify the bvec array, so always
+		 * copy the required bvecs because we need the original
+		 * one in order to decrypt the whole bio data *afterwards*.
+		 */
+		clone = bio_alloc(GFP_NOIO, bio_segments(bio));
+		if (clone) {
+			clone->bi_idx = 0;
+			clone->bi_vcnt = bio_segments(bio);
+			clone->bi_size = bio->bi_size;
+			memcpy(clone->bi_io_vec, bio_iovec(bio),
+			       sizeof(struct bio_vec) * clone->bi_vcnt);
+		}
+	}
 
 	if (!clone)
 		return NULL;