[PATCH] backing: silence compiler warning using __printf

[Mathieu Malaterre]

__printf marker was added in commit d2cc4dde9206 ("bdi_register: add
__printf verification, fix arg mismatch") for function `bdi_register`
since it is useful to verify format and arguments. Apply equivalent gcc
attribute to `bdi_register_va`.

Remove warning triggered with W=1:

  mm/backing-dev.c:881:2: warning: function might be possible candidate for âgnu_printfâ format attribute [-Wsuggest-attribute=format]

Signed-off-by: Mathieu Malaterre <malat@xxxxxxxxxx>
---
 include/linux/backing-dev.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 3e4ce54d84ab..0e9c0f71f726 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -28,6 +28,7 @@ void bdi_put(struct backing_dev_info *bdi);
 
 __printf(2, 3)
 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...);
+__printf(2, 0)
 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt,
 		    va_list args);
 int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner);
-- 
2.11.0