On Tue, 22 Mar 2011, Ben Hutchings wrote:
> 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.
>
> Cc'd to stable in order to change this before many scripts depend on
> the current strings.
>
I agree with this in general, it's certainly the standard way of altering
a boolean tunable throughout the kernel so it would be nice to use the
same userspace libraries with THP.
Let's cc Andrew on this since it will go through the -mm tree if it's
merged.
> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxx [2.6.38]
> ---
> mm/huge_memory.c | 21 +++++++++++----------
> 1 files changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 113e35c..dc0b3f0 100644
> --- 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));
> }
> 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;
> + char *endp;
> +
> + value = simple_strtoul(buf, &endp, 0);
> + if (endp == buf || 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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