mapping
index
gfp_mask
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.