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    SubjectRe: [RFC][PATCH] kmemdup_from_user(): introduce
    Andrew Morton wrote:
    > On Fri, 06 Mar 2009 16:27:53 +0800 Li Zefan <lizf@cn.fujitsu.com> wrote:
    >
    >>> Let's not add wrapper for every two lines that happen to be used
    >>> together.
    >>>
    >> Why not if we have good reasons? And I don't think we can call this
    >> "happen to" if there are 250+ of them?
    >
    > The change is a good one. If a reviewer (me) sees it then you know the
    > code's all right and the review effort becomes less - all you need to check
    > is that the call site is using IS_ERR/PTR_ERR and isn't testing for
    > NULL. Less code, less chance for bugs.
    >
    > Plus it makes kernel text smaller.
    >
    > Yes, the name is a bit cumbersome.
    >

    How about memdup_user()? like kstrndup() vs strndup_user().

    Here is the statistics when using 5 kmemdup_from_user() in btrfs:

    $ diffstat
    ioctl.c | 49 ++++++++++++-------------------------------------
    super.c | 13 ++++---------
    2 files changed, 16 insertions(+), 46 deletions(-)

    the kernel size on i386:

    text data bss dec hex filename
    288339 1924 508 290771 46fd3 fs/btrfs/btrfs.o.orig
    text data bss dec hex filename
    288255 1924 508 290687 46f7f fs/btrfs/btrfs.o

    so saves 84 bytes.

    the kernel size on IA64:

    text data bss dec hex filename
    898752 3736 109 902597 dc5c5 fs/btrfs/btrfs.o.orig
    text data bss dec hex filename
    898176 3712 109 901997 dc36d fs/btrfs/btrfs.o

    so saves 576 bytes.


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