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    SubjectRe: [PATCH 3/4] copyfile: sendfile_loop
    The new loop patch.  Tested on my machine, appears to work.

    Jörn

    --
    But this is not to say that the main benefit of Linux and other GPL
    software is lower-cost. Control is the main benefit--cost is secondary.
    -- Bruce Perens

    Linus and Andrew are rightfully concerned about local DoS via a large
    file->file sendfile(). This patch turns large sendfile() calls into a
    loop of 4k chunks. After each chunk, it adds a cond_resched for
    interactivity and a signal check to allow aborts etc. after the user
    found out what a bad idea this may be.

    Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de>
    ---

    read_write.c | 31 ++++++++++++++++++++++++++++++-
    1 files changed, 30 insertions(+), 1 deletion(-)


    --- linux-2.6.8cow/fs/read_write.c~sendfile_loop 2004-09-05 12:06:39.000000000 +0200
    +++ linux-2.6.8cow/fs/read_write.c 2004-09-07 13:27:30.000000000 +0200
    @@ -561,6 +561,35 @@
    return ret;
    }

    +/**
    + * sendfile() of a 2GB file over usb1-attached hard drives can take a moment.
    + * This little loop is supposed to stop now and then to check for signals,
    + * reschedule and generally play nice with others.
    + */
    +ssize_t inline __vfs_sendfile(struct file *in_file, loff_t *ppos, size_t count,
    + read_actor_t actor, struct file *out_file)
    +{
    + ssize_t done = 0, ret;
    + while (count) {
    + size_t n = min(count, (size_t)4096);
    + ret = in_file->f_op->sendfile(in_file, ppos, n, actor,out_file);
    + if (ret < 0) {
    + if (done)
    + return done;
    + else
    + return ret;
    + }
    +
    + done += ret;
    + count -= ret;
    +
    + if ((ret == 0) || signal_pending(current))
    + break;
    + cond_resched();
    + }
    + return done;
    +}
    +
    ssize_t vfs_sendfile(struct file *out_file, struct file *in_file, loff_t *ppos,
    size_t count, loff_t max)
    {
    @@ -608,7 +637,7 @@
    count = max - pos;
    }

    - ret = in_file->f_op->sendfile(in_file, ppos, count, file_send_actor, out_file);
    + ret = __vfs_sendfile(in_file, ppos, count, file_send_actor, out_file);

    if (*ppos > max)
    return -EOVERFLOW;
    -
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