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

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On 12/13/21 4:16 AM, Jens Axboe wrote:
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...

Copied. It will be improved as you suggested.


@@ -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?


Could you please give me more detailed explanation of the above question? Do you mention the bch_register_namespace() function, or the code block which initializes members of ns?

Thank you.

Coly Li




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