lkml.org 
[lkml]   [2009]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/3] devmem: handle partial kmem write/read
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,
-Kame

> CC: Greg KH <greg@kroah.com>
> CC: Andi Kleen <andi@firstfloor.org>
> CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> ---
> drivers/char/mem.c | 30 ++++++++++++++++++------------
> mm/vmalloc.c | 10 +---------
> 2 files changed, 19 insertions(+), 21 deletions(-)
>
> --- linux-mm.orig/drivers/char/mem.c 2009-09-15 09:44:49.000000000 +0800
> +++ linux-mm/drivers/char/mem.c 2009-09-15 09:44:55.000000000 +0800
> @@ -444,18 +444,22 @@ static ssize_t read_kmem(struct file *fi
> if (!kbuf)
> return -ENOMEM;
> while (count > 0) {
> + unsigned long n;
> +
> sz = size_inside_page(p, count);
> - sz = vread(kbuf, (char *)p, sz);
> - if (!sz)
> + n = vread(kbuf, (char *)p, sz);
> + if (!n)
> break;
> - if (copy_to_user(buf, kbuf, sz)) {
> + if (copy_to_user(buf, kbuf, n)) {
> free_page((unsigned long)kbuf);
> return -EFAULT;
> }
> - count -= sz;
> - buf += sz;
> - read += sz;
> - p += sz;
> + count -= n;
> + buf += n;
> + read += n;
> + p += n;
> + if (n < sz)
> + break;
> }
> free_page((unsigned long)kbuf);
> }
> @@ -551,11 +555,13 @@ static ssize_t write_kmem(struct file *
> free_page((unsigned long)kbuf);
> return -EFAULT;
> }
> - sz = vwrite(kbuf, (char *)p, sz);
> - count -= sz;
> - buf += sz;
> - virtr += sz;
> - p += sz;
> + n = vwrite(kbuf, (char *)p, sz);
> + count -= n;
> + buf += n;
> + virtr += n;
> + p += n;
> + if (n < sz)
> + break;
> }
> free_page((unsigned long)kbuf);
> }
>
> --
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>



\
 
 \ /
  Last update: 2009-09-15 04:43    [from the cache]
©2003-2011 Jasper Spaans