Man page 9 : tag_pages_for_writeback

tag_pages_for_writeback - tag pages to be written by write_cache_pages

void tag_pages_for_writeback(struct address_space *  mapping , pgoff_t  start , pgoff_t  end );

mapping
    address space structure to write

start
    starting page index

end
    ending page index (inclusive)

This function scans the page range from start to end (inclusive) and tags all pages that have DIRTY tag set with a special TOWRITE tag. The idea is that write_cache_pages (or whoever calls this function) will then use TOWRITE tag to identify pages eligible for writeback. This mechanism is used to avoid livelocking of writeback by a process steadily creating new dirty pages in the file (thus it is important for this function to be quick so that it can tag pages faster than a dirtying process can create them).