unmap_mapping_range — unmap the portion of all mmaps in the specified address_space corresponding to the specified page range in the underlying file.
| void unmap_mapping_range ( | struct address_space * mapping, | 
| loff_t const holebegin, | |
| loff_t const holelen, | |
| int even_cows ); | 
mappingthe address space containing mmaps to be unmapped.
holebegin
     byte in first page to unmap, relative to the start of
     the underlying file.  This will be rounded down to a PAGE_SIZE
     boundary.  Note that this is different from truncate_pagecache, which
     must keep the partial page.  In contrast, we must get rid of
     partial pages.
    
holelensize of prospective hole in bytes. This will be rounded up to a PAGE_SIZE boundary. A holelen of zero truncates to the end of the file.
even_cows1 when truncating a file, unmap even private COWed pages; but 0 when invalidating pagecache, don't throw away private data.