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    SubjectRe: [RFC][PATCH] Cross Memory Attach
    On Tue, Sep 14, 2010 at 6:18 PM, Christopher Yeoh <cyeoh@au1.ibm.com> wrote:
    > +
    > +               if (copy_to) {
    > +                       ret = copy_from_user(target_kaddr,
    > +                                            user_buf + *bytes_copied,
    > +                                            bytes_to_copy);
    > +                       if (ret) {
    > +                               kunmap(process_pages[i]);
    > +                               goto end;
    > +                       }
    > +               } else {
    > +                       ret = copy_to_user(user_buf + *bytes_copied,
    > +                                          target_kaddr, bytes_to_copy);
    > +                       if (ret) {
    > +                               kunmap(process_pages[i]);
    > +                               goto end;
    > +                       }
    > +               }
    > +               kunmap(process_pages[i]);

    Btw, please just do this as

    if (copy_to)
    ret = copy_from_user(..);
    else
    ret = copy_to_user(..);
    kunmap(process_pages[i]);
    if (ret)
    goto out;

    (and also, I think you should probably use a real variable for
    *bytes_copied, rather than update things behind the pointer. Update
    the pointer just once at the end instead, or preferably just change
    the calling convention to just return the number of bytes copied, and
    let the caller do the page counting).

    Linus
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