+ * Allocates a new inode for given superblock. The default gfp_mask
+ * for allocations related to inode->i_mapping is GFP_HIGHUSER_PAGECACHE.
+ * If HIGHMEM pages are unsuitable or it is known that pages allocated
+ * for the page cache are not reclaimable or migratable,
+ * mapping_set_gfp_mask() must be called with suitable flags on the
+ * newly created inode's mapping
+ *