[PATCH] bdi: add check before create debugfs dir or files

[weiping zhang <zhangweiping@didichuxing.com>]

we should make sure parents directory exist, and then create dir or
files under that.

Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>
---
 mm/backing-dev.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 74b52dfd5852..81f4a86ebbed 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -115,9 +115,11 @@ static const struct file_operations bdi_debug_stats_fops = {
 
 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
 {
-	bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
-	bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
-					       bdi, &bdi_debug_stats_fops);
+	if (bdi_debug_root)
+		bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
+	if (bdi->debug_dir)
+		bdi->debug_stats = debugfs_create_file("stats", 0444,
+				bdi->debug_dir, bdi, &bdi_debug_stats_fops);
 }
 
 static void bdi_debug_unregister(struct backing_dev_info *bdi)
-- 
2.14.2

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