Re: [PATCH 1/3] devmem: remove redundant test on len
From: Andrew Morton
Date: Fri Sep 11 2009 - 20:02:19 EST
On 2009年9月11日 10:23:34 +0800
Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
>
The len test in write_kmem() is always true, so can be reduced.
>
>
CC: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
>
CC: Greg Kroah-Hartman <gregkh@xxxxxxx>
>
CC: Mark Brown <broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
>
CC: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
>
CC: Avi Kivity <avi@xxxxxxxxxxxx>
>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
>
---
>
drivers/char/mem.c | 14 ++++++--------
>
1 file changed, 6 insertions(+), 8 deletions(-)
>
>
--- linux.orig/drivers/char/mem.c
>
+++ linux/drivers/char/mem.c
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@@ -580,18 +580,16 @@ static ssize_t write_kmem(struct file *
>
while (count > 0) {
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int len = count;
>
>
if (len > PAGE_SIZE)
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len = PAGE_SIZE;
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- if (len) {
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- written = copy_from_user(kbuf, buf, len);
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- if (written) {
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- if (wrote + virtr)
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- break;
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- free_page((unsigned long)kbuf);
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- return -EFAULT;
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- }
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+ written = copy_from_user(kbuf, buf, len);
>
+ if (written) {
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+ if (wrote + virtr)
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+ break;
>
+ free_page((unsigned long)kbuf);
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+ return -EFAULT;
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}
>
len = vwrite(kbuf, (char *)p, len);
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count -= len;
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buf += len;
>
virtr += len;
humpf. But take a closer look at what remains.
Local var `written' is unneeded here.
Which makes us look at what `written' _does_ do:
if (written != wrote)
return written;
wrote = written;
lolwhowrotethat?
local var `written' can at least be made local to the first loop.
write_kmem() has a lot of typecasts which indicates that the choices of
types were inappropriate.
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