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Subject[PATCH 2/3] devmem: handle partial kmem write/read
Return early on partial read/write, which may happen in future.
(eg. hit hwpoison pages)

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);
}
--



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