On Tue, May 07, 2024 at 09:10:15AM -0700, Christoph Hellwig wrote:
> On Tue, May 07, 2024 at 05:00:28PM +0100, Matthew Wilcox wrote:
> > If the len is more than PAGE_SIZE * BIO_MAX_VECS, __bio_add_page()
> > will fail silently. I hate this interface.
>
> No, it won't. You can pass an arbitray len to it.
>
> >
> > You should be doing something like ...
> >
> > while (len) {
> > unsigned int io_len = min_t(unsigned int, len, PAGE_SIZE);
> >
> > while (!bio || bio_add_page() < io_len) {
> > if (bio)
> > iomap_dio_submit_bio(iter, dio, bio, pos);
> > bio = iomap_dio_alloc_bio(iter, dio, BIO_MAX_VECS,
> > REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
> > fscrypt_set_bio_crypt_ctx(bio, inode,
> > pos >> inode->i_blkbits, GFP_KERNEL);
> > }
> > }
>
> Wee, no. The right way is:
>
> bio = iomap_dio_alloc_bio(iter, dio, 1,
> REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
> __bio_add_page(bio, page, len, 0);
no? len can be > PAGE_SIZE. and that can be true in the folio version
too, because we won't necessarily be able to allocate the THP.
> fscrypt_set_bio_crypt_ctx(bio, inode,
> pos >> inode->i_blkbits, GFP_KERNEL);
>
> (or even better the folio version)
