Mike Marshall <hubcap@xxxxxxxxxxxx> wrote:
> /* allocate an array of bio_vecs. */
> bvs = kzalloc(npages * (sizeof(struct bio_vec)), GFP_KERNEL);
>
Better to use kcalloc() here as it has overflow checking.
> /* hook the bio_vecs to the pages. */
> for (i = 0; i < npages; i++) {
> bvs[i].bv_page = pages[i];
> bvs[i].bv_len = PAGE_SIZE;
> bvs[i].bv_offset = 0;
> }
>
> iov_iter_bvec(&iter, READ, bvs, npages, npages * PAGE_SIZE);
>
> /* read in the pages. */
> ret = wait_for_direct_io(ORANGEFS_IO_READ, inode, &offset, &iter,
> npages * PAGE_SIZE, inode->i_size, NULL, NULL, file);
>
> /* clean up. */
> for (i = 0; i < npages; i++) {
> SetPageUptodate(bvs[i].bv_page);
> unlock_page(bvs[i].bv_page);
> put_page(bvs[i].bv_page);
> }
> kfree(pages);
> kfree(bvs);
> }
Could you try ITER_XARRAY instead of ITER_BVEC:
https://lore.kernel.org/linux-fsdevel/161653786033.2770958.14154191921867463240.stgit@xxxxxxxxxxxxxxxxxxxxxx/T/#u
Setting the iterator looks like:
iov_iter_xarray(&iter, READ, &mapping->i_pages,
offset, npages * PAGE_SIZE);
The xarray iterator will handle THPs, but I'm not sure if bvecs will.
Cleanup afterwards would look something like:
static void afs_file_read_done(struct afs_read *req)
{
struct afs_vnode *vnode = req->vnode;
struct page *page;
pgoff_t index = req->pos >> PAGE_SHIFT;
pgoff_t last = index + req->nr_pages - 1;
XA_STATE(xas, &vnode->vfs_inode.i_mapping->i_pages, index);
if (iov_iter_count(req->iter) > 0) {
/* The read was short - clear the excess buffer. */
_debug("afterclear %zx %zx %llx/%llx",
req->iter->iov_offset,
iov_iter_count(req->iter),
req->actual_len, req->len);
iov_iter_zero(iov_iter_count(req->iter), req->iter);
}
rcu_read_lock();
xas_for_each(&xas, page, last) {
page_endio(page, false, 0);
put_page(page);
}
rcu_read_unlock();
task_io_account_read(req->len);
req->cleanup = NULL;
}
David
