struct page * find_or_create_page (struct address_space * mapping, unsigned long index, unsigned int gfp_mask);
mapping - the page's address_space index - the page's index into the mapping gfp_mask - page allocation mode
Locates a page in the pagecache. If the page is not present, a new page is allocated using gfp_mask and is added to the pagecache and to the VM's LRU list. The returned page is locked and has its reference count incremented.
find_or_create_page may sleep, even if gfp_flags specifies an atomic allocation!
find_or_create_page returns the desired page's address, or zero on memory exhaustion.