[PATCH v2 14/16] writeback: segregated allocation and free of writeback contexts

[Kundan Kumar <kundan.kumar@samsung.com>]

The independent functions of alloc and free will be used while changing
the number of writeback contexts.

Signed-off-by: Kundan Kumar <kundan.kumar@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
 mm/backing-dev.c | 72 ++++++++++++++++++++++++++++++++----------------
 1 file changed, 49 insertions(+), 23 deletions(-)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 0a3204a3a3a3..2a8f3b683b2d 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -1038,8 +1038,46 @@ static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
 
 #endif	/* CONFIG_CGROUP_WRITEBACK */
 
+static struct bdi_writeback_ctx **wb_ctx_alloc(struct backing_dev_info *bdi,
+					       int num_ctxs)
+{
+	struct bdi_writeback_ctx **wb_ctx;
+
+	wb_ctx = kcalloc(num_ctxs, sizeof(struct bdi_writeback_ctx *),
+			     GFP_KERNEL);
+	if (!wb_ctx)
+		return NULL;
+
+	for (int i = 0; i < num_ctxs; i++) {
+		wb_ctx[i] = (struct bdi_writeback_ctx *)
+			kzalloc(sizeof(struct bdi_writeback_ctx), GFP_KERNEL);
+		if (!wb_ctx[i]) {
+			pr_err("Failed to allocate %d", i);
+			while (--i >= 0)
+				kfree(wb_ctx[i]);
+			kfree(wb_ctx);
+			return NULL;
+		}
+		INIT_LIST_HEAD(&wb_ctx[i]->wb_list);
+		init_waitqueue_head(&wb_ctx[i]->wb_waitq);
+	}
+	return wb_ctx;
+}
+
+static void wb_ctx_free(struct backing_dev_info *bdi)
+{
+	struct bdi_writeback_ctx *bdi_wb_ctx;
+
+	for_each_bdi_wb_ctx(bdi, bdi_wb_ctx) {
+		kfree(bdi_wb_ctx);
+	}
+	kfree(bdi->wb_ctx);
+}
+
 int bdi_init(struct backing_dev_info *bdi)
 {
+	int ret;
+
 	bdi->dev = NULL;
 
 	kref_init(&bdi->refcnt);
@@ -1047,48 +1085,36 @@ int bdi_init(struct backing_dev_info *bdi)
 	bdi->max_ratio = 100 * BDI_RATIO_SCALE;
 	bdi->max_prop_frac = FPROP_FRAC_BASE;
 
+	INIT_LIST_HEAD(&bdi->bdi_list);
+
 	/*
 	 * User can configure nr_wb_ctx using the newly introduced sysfs knob.
 	 * echo N > /sys/class/bdi/<maj>:<min>/nwritebacks
 	 * Filesystem can also increase same during mount.
 	 */
 	bdi->nr_wb_ctx = 1;
-	bdi->wb_ctx = kcalloc(bdi->nr_wb_ctx,
-				  sizeof(struct bdi_writeback_ctx *),
-				  GFP_KERNEL);
-	INIT_LIST_HEAD(&bdi->bdi_list);
-	for (int i = 0; i < bdi->nr_wb_ctx; i++) {
-		bdi->wb_ctx[i] = (struct bdi_writeback_ctx *)
-			 kzalloc(sizeof(struct bdi_writeback_ctx), GFP_KERNEL);
-		if (!bdi->wb_ctx[i]) {
-			pr_err("Failed to allocate %d", i);
-			while (--i >= 0)
-				kfree(bdi->wb_ctx[i]);
-			kfree(bdi->wb_ctx);
-			return -ENOMEM;
-		}
-		INIT_LIST_HEAD(&bdi->wb_ctx[i]->wb_list);
-		init_waitqueue_head(&bdi->wb_ctx[i]->wb_waitq);
-	}
+
+	bdi->wb_ctx = wb_ctx_alloc(bdi, bdi->nr_wb_ctx);
+	if (!bdi->wb_ctx)
+		return -ENOMEM;
+
 	bdi->last_bdp_sleep = jiffies;
 
-	return cgwb_bdi_init(bdi);
+	ret = cgwb_bdi_init(bdi);
+	if (ret)
+		wb_ctx_free(bdi);
+	return ret;
 }
 
 struct backing_dev_info *bdi_alloc(int node_id)
 {
 	struct backing_dev_info *bdi;
-	struct bdi_writeback_ctx *bdi_wb_ctx;
 
 	bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
 	if (!bdi)
 		return NULL;
 
 	if (bdi_init(bdi)) {
-		for_each_bdi_wb_ctx(bdi, bdi_wb_ctx) {
-			kfree(bdi_wb_ctx);
-		}
-		kfree(bdi->wb_ctx);
 		kfree(bdi);
 		return NULL;
 	}
-- 
2.25.1