On Tue, 30 Aug 2016, Ming Lei wrote: > On Tue, Aug 30, 2016 at 5:57 AM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > > > > On Mon, 29 Aug 2016, Ming Lei wrote: > > > >> On Sat, Aug 27, 2016 at 11:09 PM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > >> > > >> > But this patch won't work for device mapper, blk_bio_segment_split is > >> > called from blk_queue_split and device mapper doesn't use blk_queue_split > >> > (it can't because it frees queue->bio_split). > >> > > >> > We still need these two patches: > >> > https://www.redhat.com/archives/dm-devel/2016-May/msg00211.html > >> > https://www.redhat.com/archives/dm-devel/2016-May/msg00210.html > >> > >> About the 2nd patch, it might not be good enough because in theory > >> a small size bio still may include big bvecs, such as, each bvec points > >> to 512byte buffer, so strictly speaking the bvec number should > >> be checked instead of bio size. > >> > >> Ming Lei > > > > This is not a problem. > > I meant the following code in your 2nd patch: > > + if (unlikely(bio->bi_iter.bi_size > BIO_MAX_SIZE) && > + (bio->bi_rw & (REQ_FLUSH | REQ_DISCARD | REQ_WRITE)) == REQ_WRITE) > + dm_accept_partial_bio(bio, BIO_MAX_SIZE >> SECTOR_SHIFT); > > And the check on .bi_size may not work. kcryptd_crypt_write_convert calls: crypt_alloc_buffer(io, io->base_bio->bi_iter.bi_size) crypt_alloc_buffer does: unsigned int nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; clone = bio_alloc_bioset(GFP_NOIO, nr_iovecs, cc->bs); So, if io->base_bio->bi_iter.bi_size <= BIO_MAX_SIZE, then nr_iovecs will be less or equal than BIO_MAX_PAGES and the function bio_alloc_bioset will succeed. (BTW. BIO_MAX_SIZE was removed in the current kernel, we should use (BIO_MAX_PAGES << PAGE_SHIFT) instead). Mikulas -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
