On 06/27/18 16:21, Ming Lei wrote:

What we need to do is to only copy the 1st bvec for WRITE_SAME, your patch
changes to copy (bio->bi_iter.bi_size / block size) bvecs, then memory corruption
may be triggered. So bio_for_each_segment() can't be used here.

Has it been considered to use memcpy() to copy the bi_vcnt bio_vecs 
instead of using bio_for_each_segment() in bio_clone_bioset()? That will 
in this context probably be even faster than using bio_for_each_segment().

Bart.