nfs: Ignore kmemleak false positive in nfs_readdir_make_qstr

Strings allocated via kmemdup() in nfs_readdir_make_qstr() are
referenced from the nfs_cache_array which is stored in a page cache
page. Kmemleak does not scan such pages and it reports several false
positives. This patch annotates the string->name pointer so that
kmemleak does not consider it a real leak.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Bryan Schumaker <bjschuma@netapp.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/dir.c

@@ -34,6 +34,7 @@
 #include <linux/mount.h>
 #include <linux/sched.h>
 #include <linux/vmalloc.h>
+#include <linux/kmemleak.h>
 
 #include "delegation.h"
 #include "iostat.h"
@@ -238,6 +239,11 @@ int nfs_readdir_make_qstr(struct qstr *string, const char *name, unsigned int le
 	string->name = kmemdup(name, len, GFP_KERNEL);
 	if (string->name == NULL)
 		return -ENOMEM;
+	/*
+	 * Avoid a kmemleak false positive. The pointer to the name is stored
+	 * in a page cache page which kmemleak does not scan.
+	 */
+	kmemleak_not_leak(string->name);
 	string->hash = full_name_hash(name, len);
 	return 0;
 }