On Wed, May 15, 2024 at 03:59:43PM +0000, Pankaj Raghav (Samsung) wrote:
> static int __init iomap_init(void)
> {
> + void *addr = kzalloc(16 * PAGE_SIZE, GFP_KERNEL);
Don't use XFS coding style outside XFS.
kzalloc() does not guarantee page alignment much less alignment to
a folio. It happens to work today, but that is an implementation
artefact.
> +
> + if (!addr)
> + return -ENOMEM;
> +
> + zero_fsb_folio = virt_to_folio(addr);
We also don't guarantee that calling kzalloc() gives you a virtual
address that can be converted to a folio. You need to allocate a folio
to be sure that you get a folio.
Of course, you don't actually need a folio. You don't need any of the
folio metadata and can just use raw pages.
> + /*
> + * The zero folio used is 64k.
> + */
> + WARN_ON_ONCE(len > (16 * PAGE_SIZE));
PAGE_SIZE is not necessarily 4KiB.
> + bio = iomap_dio_alloc_bio(iter, dio, BIO_MAX_VECS,
> + REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
The point was that we now only need one biovec, not MAX.
