Man page 9 : read_cache_page

read_cache_page - read into page cache, fill it if needed

struct page * read_cache_page(struct address_space *  mapping , pgoff_t  index , int (* filler ) (void *, struct page *), void *  data );

mapping
    the pageAqs address_space

index
    the page index

filler
    function to perform the read

data
    first arg to filler(data, page) function, often left as NULL

Read into the page cache. If a page already exists, and PageUptodate is not set, try to fill the page then wait for it to become unlocked.

If the page does not get brought uptodate, return -EIO.