On Mon, Nov 09, 2020 at 05:26:37PM -0800, Tom Rix wrote:
>
> On 11/8/20 11:11 PM, Lukas Bulwahn wrote:
> > make clang-analyzer caught my attention with:
> >
> > kernel/sysctl.c:1511:4: warning: Value stored to 'first' is never read \
> > [clang-analyzer-deadcode.DeadStores]
> > first = 0;
> > ^
> >
> > Commit 9f977fb7ae9d ("sysctl: add proc_do_large_bitmap") introduced
> > proc_do_large_bitmap(), where the variable first is only effectively used
> > when write is false; when write is true, the variable first is only used in
> > a dead assignment.
> >
> > So, simply remove this dead assignment and put the variable in local scope.
> >
> > As compilers will detect this unneeded assignment and optimize this anyway,
> > the resulting object code is identical before and after this change.
> >
> > No functional change. No change to object code.
> >
> > Signed-off-by: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
> > ---
> > applies cleanly on v5.10-rc3 and next-20201106
> >
> > Luis, Kees, Iurii, please pick this minor non-urgent clean-up patch.
> >
> > kernel/sysctl.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> > index ce75c67572b9..cc274a431d91 100644
> > --- a/kernel/sysctl.c
> > +++ b/kernel/sysctl.c
> > @@ -1423,7 +1423,6 @@ int proc_do_large_bitmap(struct ctl_table *table, int write,
> > void *buffer, size_t *lenp, loff_t *ppos)
> > {
> > int err = 0;
> > - bool first = 1;
> > size_t left = *lenp;
> > unsigned long bitmap_len = table->maxlen;
> > unsigned long *bitmap = *(unsigned long **) table->data;
> > @@ -1508,12 +1507,12 @@ int proc_do_large_bitmap(struct ctl_table *table, int write,
> > }
> >
> > bitmap_set(tmp_bitmap, val_a, val_b - val_a + 1);
> > - first = 0;
> > proc_skip_char(&p, &left, '\n');
> > }
> > left += skipped;
> > } else {
> > unsigned long bit_a, bit_b = 0;
> > + bool first = 1;
>
> This looks fine, but while you are here how about setting, to match the type
>
> first = true
>
> And then only clearing first once
>
> if (!first)
> proc_put_char(&buffer, &left, ',');
>
> else
>
> first = false
>
> Instead of at every loop iteraction
Thanks for your patch Lukas!
Agreed, please resend with that change as requested by Tom. And also
please add Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> to your To address.
Luis
