[PATCHv3, RFC 02/34] block: implement add_bdi_stat()

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

We're going to add/remove a number of page cache entries at once. This
patch implements add_bdi_stat() which adjusts bdi stats by arbitrary
amount. It's required for batched page cache manipulations.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 include/linux/backing-dev.h |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 3504599..b05d961 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -167,6 +167,16 @@ static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
 	__add_bdi_stat(bdi, item, -1);
 }
 
+static inline void add_bdi_stat(struct backing_dev_info *bdi,
+		enum bdi_stat_item item, s64 amount)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	__add_bdi_stat(bdi, item, amount);
+	local_irq_restore(flags);
+}
+
 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
 		enum bdi_stat_item item)
 {
-- 
1.7.10.4