[PATCH] inode: don't memset the inode address space twice

[Dave Chinner <david@fromorbit.com>]

From: Dave Chinner <dchinner@redhat.com>

Noticed when looking at why cycling 600k inodes/s through the inode
cache was taking a total of 8% cpu in memset() during inode
initialisation.  There is no need to zero the inode.i_data structure
twice.

This increases single threaded bulkstat throughput from ~200,000
inodes/s to ~220,000 inodes/s, so we save a substantial amount of
CPU time per inode init by doing this.

Signed-Off-By: Dave Chinner <dchinner@redhat.com>
---
 fs/inode.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 6295f1415761..b153aeaa61ea 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -346,9 +346,8 @@ void inc_nlink(struct inode *inode)
 }
 EXPORT_SYMBOL(inc_nlink);
 
-void address_space_init_once(struct address_space *mapping)
+static void __address_space_init_once(struct address_space *mapping)
 {
-	memset(mapping, 0, sizeof(*mapping));
 	INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC | __GFP_ACCOUNT);
 	spin_lock_init(&mapping->tree_lock);
 	init_rwsem(&mapping->i_mmap_rwsem);
@@ -356,6 +355,12 @@ void address_space_init_once(struct address_space *mapping)
 	spin_lock_init(&mapping->private_lock);
 	mapping->i_mmap = RB_ROOT_CACHED;
 }
+
+void address_space_init_once(struct address_space *mapping)
+{
+	memset(mapping, 0, sizeof(*mapping));
+	__address_space_init_once(mapping);
+}
 EXPORT_SYMBOL(address_space_init_once);
 
 /*
@@ -371,7 +376,7 @@ void inode_init_once(struct inode *inode)
 	INIT_LIST_HEAD(&inode->i_io_list);
 	INIT_LIST_HEAD(&inode->i_wb_list);
 	INIT_LIST_HEAD(&inode->i_lru);
-	address_space_init_once(&inode->i_data);
+	__address_space_init_once(&inode->i_data);
 	i_size_ordered_init(inode);
 }
 EXPORT_SYMBOL(inode_init_once);
-- 
2.16.1