page_cache_async_readahead — file readahead for marked pages
| void page_cache_async_readahead ( | struct address_space * mapping, | 
| struct file_ra_state * ra, | |
| struct file * filp, | |
| struct page * page, | |
| pgoff_t offset, | |
| unsigned long req_size ); | 
mappingaddress_space which holds the pagecache and I/O vectors
rafile_ra_state which holds the readahead state
filp
     passed on to ->readpage and ->readpages
    
page
     the page at offset which has the PG_readahead flag set
    
offset
     start offset into mapping, in pagecache page-sized units
    
req_sizehint: total size of the read which the caller is performing in pagecache pages