On Thu, 14 Apr 2011 14:48:07 +1000
NeilBrown <neilb@xxxxxxx> wrote:
> > > --- a/mm/huge_memory.c
> > > +++ b/mm/huge_memory.c
> > > @@ -244,24 +244,25 @@ static ssize_t single_flag_show(struct kobject *kobj,
> > > struct kobj_attribute *attr, char *buf,
> > > enum transparent_hugepage_flag flag)
> > > {
> > > - if (test_bit(flag, &transparent_hugepage_flags))
> > > - return sprintf(buf, "[yes] no\n");
> > > - else
> > > - return sprintf(buf, "yes [no]\n");
> > > + return sprintf(buf, "%d\n",
> > > + test_bit(flag, &transparent_hugepage_flags));
>
> It test bit guaranteed to return 0 or 1?
>
> I think the x86 version returns 0 or -1 (that is from reading the code and
> using google to check what 'sbb' does).
Thanks for catching that. One wonders how well-tested the patch was!
Speaking of which...
Here's the current status. Ben, can you please test this soon?
From: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
The conventional format for boolean attributes in sysfs is numeric ("0" or
"1" followed by new-line). Any boolean attribute can then be read and
written using a generic function. Using the strings "yes [no]", "[yes]
no" (read), "yes" and "no" (write) will frustrate this.
[akpm@xxxxxxxxxxxxxxxxxxxx: use kstrtoul()]
[akpm@xxxxxxxxxxxxxxxxxxxx: test_bit() doesn't return 1/0, per Neil]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Johannes Weiner <jweiner@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: NeilBrown <neilb@xxxxxxx>
Cc: <stable@xxxxxxxxxx> [2.6.38.x]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff -puN mm/huge_memory.c~mm-thp-use-conventional-format-for-boolean-attributes mm/huge_memory.c
--- a/mm/huge_memory.c~mm-thp-use-conventional-format-for-boolean-attributes
+++ a/mm/huge_memory.c
@@ -244,24 +244,28 @@ static ssize_t single_flag_show(struct k
struct kobj_attribute *attr, char *buf,
enum transparent_hugepage_flag flag)
{
- if (test_bit(flag, &transparent_hugepage_flags))
- return sprintf(buf, "[yes] no\n");
- else
- return sprintf(buf, "yes [no]\n");
+ return sprintf(buf, "%d\n",
+ !!test_bit(flag, &transparent_hugepage_flags));
}
+
static ssize_t single_flag_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count,
enum transparent_hugepage_flag flag)
{
- if (!memcmp("yes", buf,
- min(sizeof("yes")-1, count))) {
+ unsigned long value;
+ int ret;
+
+ ret = kstrtoul(buf, 10, &value);
+ if (ret < 0)
+ return ret;
+ if (value > 1)
+ return -EINVAL;
+
+ if (value)
set_bit(flag, &transparent_hugepage_flags);
- } else if (!memcmp("no", buf,
- min(sizeof("no")-1, count))) {
+ else
clear_bit(flag, &transparent_hugepage_flags);
- } else
- return -EINVAL;
return count;
}
_
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