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);
fscrypt_set_bio_crypt_ctx(bio, inode,
pos >> inode->i_blkbits, GFP_KERNEL);
(or even better the folio version)
