On Wed, Apr 10, 2013 at 04:54:40PM -0400, Mike Snitzer wrote: > Hey, > > So DM core clearly needs to be more defensive about the possibility for > a NULL return from bio_alloc_bioset() given I'm hitting a NULL pointer > in DM's alloc_tio() because nr_iovecs=512. bio_alloc_bioset()'s call to > bvec_alloc() only supports nr_iovecs up to BIO_MAX_PAGES (256). > > Seems bcache should be using bio_get_nr_vecs() or something else? > > But by using a bcache bucket size of 2MB, with the bcache staged in > Jens' for-next, I've caused bcache to issue bios with nr_iovecs=512: Argh. Why is dm using bi_max_vecs instead of bi_vcnt? I could hack around this in bcache but I think dm is doing the wrong thing here. Unless I've missed something in my testing (and bcache's BIO_MAX_PAGES check isn't quite right, actually) bcache _is_ splitting its bios whenever bio_segments(bio) > BIO_MAX_PAGES, it's only bi_max_vecs that's potentially > BIO_MAX_PAGES. -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
