dax: dirty inode only if required

Signed-off-by: NDmitry Monakhov <dmonakhov@openvz.org>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/dax.c

@@ -358,7 +358,8 @@ static int dax_radix_entry(struct address_space *mapping, pgoff_t index,
 	void *entry;
 
 	WARN_ON_ONCE(pmd_entry && !dirty);
-	__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
+	if (dirty)
+		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 
 	spin_lock_irq(&mapping->tree_lock);