On 1/6/23 5:34 PM, David Howells wrote: > Convert the block layer's bio code to use iov_iter_extract_pages() instead > of iov_iter_get_pages(). This will pin pages or leave them unaltered > rather than getting a ref on them as appropriate to the source iterator. > > A field, bi_cleanup_mode, is added to the bio struct that gets set by > iov_iter_extract_pages() with FOLL_* flags indicating what cleanup is > necessary. FOLL_GET -> put_page(), FOLL_PIN -> unpin_user_page(). Other > flags could also be used in future. > > Newly allocated bio structs have bi_cleanup_mode set to FOLL_GET to > indicate that attached pages are ref'd by default. Cloning sets it to 0. > __bio_iov_iter_get_pages() overrides it to what iov_iter_extract_pages() > indicates. What's the motivation for this change? It's growing struct bio, which we can have a lot of in the system. I read the cover letter too and I can tell what the change does, but there's no justification really for the change. So unless there's a good reason to do this, then that's a NAK in terms of just the addition to struct bio alone. -- Jens Axboe
