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    SubjectRe: [PATCH 2/3] devmem: handle partial kmem write/read
    On Tue, Sep 15, 2009 at 05:01:30PM +0800, Wu Fengguang wrote:
    > On Tue, Sep 15, 2009 at 10:38:11AM +0800, KAMEZAWA Hiroyuki wrote:
    > > On Tue, 15 Sep 2009 10:18:53 +0800
    > > Wu Fengguang <fengguang.wu@intel.com> wrote:
    > >
    > > > Return early on partial read/write, which may happen in future.
    > > > (eg. hit hwpoison pages)
    > > >
    > > Hmm, please modify vread() as you did in vwrite() and
    > >
    > > ==
    > > kbuf = (char *)__get_free_page(GFP_KERNEL);
    > > if (!kbuf)
    > > return -ENOMEM;
    > > ==
    > > Add __GFP_ZERO to kbuf allocation, and just ignore vread()'s return value.
    > > Then, this will be much simpler.
    >
    > Thanks, here is the updated patch, which
    > - updates vread/vwrite prototype to return 0 (or error code in future).
    > - do zero fill in the callers
    > Comment updates are ignored for now.

    This patch also makes it trivial to add your
    is_vmalloc_or_module_addr() fixes, like this :)

    ---
    From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

    Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
    ---
    drivers/char/mem.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    --- linux-mm.orig/drivers/char/mem.c 2009-09-15 16:58:06.000000000 +0800
    +++ linux-mm/drivers/char/mem.c 2009-09-15 16:58:12.000000000 +0800
    @@ -446,6 +446,10 @@ static ssize_t read_kmem(struct file *fi
    return -ENOMEM;
    while (count > 0) {
    sz = size_inside_page(p, count);
    + if (!is_vmalloc_or_module_addr((void*)p)) {
    + ret = -EFAULT;
    + break;
    + }
    ret = vread(kbuf, (char *)p, sz);
    if (ret)
    break;
    @@ -546,6 +550,10 @@ static ssize_t write_kmem(struct file *
    unsigned long sz = size_inside_page(p, count);
    unsigned long n;

    + if (!is_vmalloc_or_module_addr((void*)p)) {
    + ret = -EFAULT;
    + break;
    + }
    n = copy_from_user(kbuf, buf, sz);
    if (n) {
    if (wrote + virtr)

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