f2fs: invalidate inmemory page

If user truncates file's data, we should truncate inmemory pages too.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 9d4a7ab..902c4c3 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -203,6 +203,22 @@
 	mutex_unlock(&fi->inmem_lock);
 }
 
+void invalidate_inmem_page(struct inode *inode, struct page *page)
+{
+	struct f2fs_inode_info *fi = F2FS_I(inode);
+	struct inmem_pages *cur;
+
+	mutex_lock(&fi->inmem_lock);
+	cur = radix_tree_lookup(&fi->inmem_root, page->index);
+	if (cur) {
+		radix_tree_delete(&fi->inmem_root, cur->page->index);
+		f2fs_put_page(cur->page, 0);
+		list_del(&cur->list);
+		kmem_cache_free(inmem_entry_slab, cur);
+	}
+	mutex_unlock(&fi->inmem_lock);
+}
+
 void commit_inmem_pages(struct inode *inode, bool abort)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);