On Wed, Apr 28, 2021 at 10:58:44AM -0600, Jens Axboe wrote: > On 4/28/21 10:50 AM, Matthew Wilcox wrote: > > bio_add_page() has its arguments in the wrong order: > > > > extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int); > > > > Oh, right, and the prototype commits the cardinal sin of just giving you > > a pair of unsigned ints and doesn't bother to tell you what they mean. > > I'll send a patch for that ... anyway: > > > > int bio_add_page(struct bio *bio, struct page *page, > > unsigned int len, unsigned int offset) > > > > This fails to follow #4: https://ozlabs.org/~rusty/index.cgi/tech/2008-03-30.html > > > > Here's what I want to do for the folio equivalent: > > > > size_t bio_add_folio(struct bio *bio, struct folio *folio, size_t off, > > size_t len) > > > > This will make the transition more painful, but it does remove an irritant > > for the future. Any objections? > > What's the point in shuffling len and offset around? That almost everything else does (off, len). Grepping include, here's the (object, len, off) examples I found (will miss multi-line examples, tried to use my best judgement, tried to exclude loff_t): bio_add_zone_append_page __bio_try_merge_page __bio_add_page bio_integrity_add_page fscrypt_encrypt_block_inplace fscrypt_decrypt_block_inplace sg_set_page sg_copy_buffer sg_pcopy_from_buffer sg_pcopy_to_buffer sg_zero_buffer copy_linear_skb versus (object, off, len): bpf_ctx_copy_t ->is_partially_uptodate memcpy_from_page memcpy_to_page memzero_page (basically all of the iomap functions) kvm_write_guest_page kvm_vcpu_write_guest_page skb_gro_remcsum_process nf_checksum_partial perf_copy_f read_module_eeprom skb_frag_foreach_page skb_to_sgvec_nomark skb_to_sgvec skb_send_sock various skb_checksum_ops sk_msg_clone various gss_krb functions xdr_process_buf usercopy_warn various network getfrag functions Not _quite_ as one-sided as I thought, but there are basically three families of functions (bio, fscrypt, sg) that are len-first (plus copy_linear_skb() is out-of-family), then networking, filesystems, highmem, perf, bpf, kvm are off-first. So, you're the maintainer, it's your call ... do you want bio_add_folio() to resemble the bio_add_page() calls as much as possible, or do you want to migrate towards how the rest of the world works?
