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    [PATCH] unpaged: anon in VM_UNPAGED · ee498ed7
    Hugh Dickins 提交于
    copy_one_pte needs to copy the anonymous COWed pages in a VM_UNPAGED area,
    zap_pte_range needs to free them, do_wp_page needs to COW them: just like
    ordinary pages, not like the unpaged.
    
    But recognizing them is a little subtle: because PageReserved is no longer a
    condition for remap_pfn_range, we can now mmap all of /dev/mem (whether the
    distro permits, and whether it's advisable on this or that architecture, is
    another matter).  So if we can see a PageAnon, it may not be ours to mess with
    (or may be ours from elsewhere in the address space).  I suspect there's an
    entertaining insoluble self-referential problem here, but the page_is_anon
    function does a good practical job, and MAP_PRIVATE PROT_WRITE VM_UNPAGED will
    always be an odd choice.
    
    In updating the comment on page_address_in_vma, noticed a potential NULL
    dereference, in a path we don't actually take, but fixed it.
    Signed-off-by: NHugh Dickins <hugh@veritas.com>
    Signed-off-by: NAndrew Morton <akpm@osdl.org>
    Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
    ee498ed7
memory.c 60.2 KB