Re: [PATCH v13 05/12] bcache: bch_nvmpg_free_pages() of the buddy allocator

Jens Axboe
2021-12-12T20:17:51Z

On 12/12/21 10:05 AM, Coly Li wrote:
> diff --git a/drivers/md/bcache/nvmpg.c b/drivers/md/bcache/nvmpg.c
> index a920779eb548..8ce0c4389b42 100644
> --- a/drivers/md/bcache/nvmpg.c
> +++ b/drivers/md/bcache/nvmpg.c
> @@ -248,6 +248,57 @@ static int init_nvmpg_set_header(struct bch_nvmpg_ns *ns)
> return rc;
> }
>
> +static void __free_space(struct bch_nvmpg_ns *ns, unsigned long nvmpg_offset,
> + int order)
> +{
> + unsigned long add_pages = (1L << order);
> + pgoff_t pgoff;
> + struct page *page;
> + void *va;
> +
> + if (nvmpg_offset == 0) {
> + pr_err("free pages on offset 0\n");
> + return;
> + }
> +
> + page = bch_nvmpg_va_to_pg(bch_nvmpg_offset_to_ptr(nvmpg_offset));
> + WARN_ON((!page) || (page->private != order));
> + pgoff = page->index;
> +
> + while (order < BCH_MAX_ORDER - 1) {
> + struct page *buddy_page;
> +
> + pgoff_t buddy_pgoff = pgoff ^ (1L << order);
> + pgoff_t parent_pgoff = pgoff & ~(1L << order);
> +
> + if ((parent_pgoff + (1L << (order + 1)) > ns->pages_total))
> + break;
> +
> + va = bch_nvmpg_pgoff_to_ptr(ns, buddy_pgoff);
> + buddy_page = bch_nvmpg_va_to_pg(va);
> + WARN_ON(!buddy_page);
> +
> + if (PageBuddy(buddy_page) && (buddy_page->private == order)) {
> + list_del((struct list_head *)&buddy_page->zone_device_data);
> + __ClearPageBuddy(buddy_page);
> + pgoff = parent_pgoff;
> + order++;
> + continue;
> + }
> + break;
> + }
> +
> + va = bch_nvmpg_pgoff_to_ptr(ns, pgoff);
> + page = bch_nvmpg_va_to_pg(va);
> + WARN_ON(!page);
> + list_add((struct list_head *)&page->zone_device_data,
> + &ns->free_area[order]);
> + page->index = pgoff;
> + set_page_private(page, order);
> + __SetPageBuddy(page);
> + ns->free += add_pages;
> +}

There are 3 WARN_ON's in here. If you absolutely must use a WARN_ON,
then make them WARN_ON_ONCE(). Ditto in other spots in this patch.

> +void bch_nvmpg_free_pages(unsigned long nvmpg_offset, int order,
> + const char *uuid)
> +{
> + struct bch_nvmpg_ns *ns;
> + struct bch_nvmpg_head *head;
> + struct bch_nvmpg_recs *recs;
> + int r;
> +
> + mutex_lock(&global_nvmpg_set->lock);
> +
> + ns = global_nvmpg_set->ns_tbl[BCH_NVMPG_GET_NS_ID(nvmpg_offset)];
> + if (!ns) {
> + pr_err("can't find namespace by given kaddr from namespace\n");
> + goto unlock;
> + }
> +
> + head = find_nvmpg_head(uuid, false);
> + if (!head) {
> + pr_err("can't found bch_nvmpg_head by uuid\n");
> + goto unlock;
> + }
> +
> + recs = find_nvmpg_recs(ns, head, false);
> + if (!recs) {
> + pr_err("can't find bch_nvmpg_recs by uuid\n");
> + goto unlock;
> + }
> +
> + r = remove_nvmpg_rec(recs, ns->sb->this_ns, nvmpg_offset, order);
> + if (r < 0) {
> + pr_err("can't find bch_nvmpg_rec\n");
> + goto unlock;
> + }
> +
> + __free_space(ns, nvmpg_offset, order);
> +
> +unlock:
> + mutex_unlock(&global_nvmpg_set->lock);
> +}

Again tons of useless error prints. Make them return a proper error
instad of just making things void...

> @@ -686,6 +835,7 @@ struct bch_nvmpg_ns *bch_register_namespace(const char *dev_path)
> ns->pages_offset = sb->pages_offset;
> ns->pages_total = sb->pages_total;
> ns->sb = sb;
> + /* increase by __free_space() */
> ns->free = 0;
> ns->bdev = bdev;
> ns->set = global_nvmpg_set;

Does that hunk belong in here?

--
Jens Axboe