Re: [PATCH 1/6] block: Introduce bio_for_each_page()

Zach Brown
2013-09-25T21:17:30Z

> void zero_fill_bio(struct bio *bio)
> {
> - unsigned long flags;
> struct bio_vec bv;
> struct bvec_iter iter;
>
> - bio_for_each_segment(bv, bio, iter) {
> +#if defined(CONFIG_HIGHMEM) || defined(ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE)
> + bio_for_each_page(bv, bio, iter) {
> + unsigned long flags;
> char *data = bvec_kmap_irq(&bv, &flags);
> memset(data, 0, bv.bv_len);
> flush_dcache_page(bv.bv_page);
> bvec_kunmap_irq(data, &flags);
> }
> +#else
> + bio_for_each_segment(bv, bio, iter)
> + memset(page_address(bv.bv_page) + bv.bv_offset,
> + 0, bv.bv_len);
> +#endif

This looks pretty sketchy. I'd expect this to be doable with one loop
and that bvec_kmap_irq() and flush_dcache_page() would fall back to
page_address() and nops when they're not needed.

Where did this come from?

- z