Re: [PATCH v3] mm/vmalloc: replace BUG_ON to a simple if statement

Hyunmin Lee
2023-02-01T11:41:46Z

On Wed, Feb 01, 2023 at 10:37:19AM +0000, Christophe Leroy wrote:
>
>
> Le 01/02/2023 à 11:11, Hyunmin Lee a écrit :
> > [Vous ne recevez pas souvent de courriers de hn.min.lee@gmail.com. D?couvrez pourquoi ceci est important ? https://aka.ms/LearnAboutSenderIdentification ]
> >
> > As per the coding standards, in the event of an abnormal condition that
> > should not occur under normal circumstances, the kernel should attempt
> > recovery and proceed with execution, rather than halting the machine.
> >
> > Specifically, in the alloc_vmap_area() function, use a simple if()
> > instead of using BUG_ON() halting the machine.
> >
> > Co-Developed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> > Co-Developed-by: Jeungwoo Yoo <casionwoo@gmail.com>
> > Co-Developed-by: Sangyun Kim <sangyun.kim@snu.ac.kr>
> > Signed-off-by: Hyunmin Lee <hn.min.lee@gmail.com>
> > Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> > Signed-off-by: Jeungwoo Yoo <casionwoo@gmail.com>
> > Signed-off-by: Sangyun Kim <sangyun.kim@snu.ac.kr>
> > Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> > ---
> > v1->v2 : Add commit description
> > v2->v3 : Change WARN_ON() to if()
> > ---
> > mm/vmalloc.c | 11 ++++++++---
> > 1 file changed, 8 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 74afa2208558..52a346bc02a1 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -1587,9 +1587,14 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> > int purged = 0;
> > int ret;
> >
> > - BUG_ON(!size);
> > - BUG_ON(offset_in_page(size));
> > - BUG_ON(!is_power_of_2(align));
> > + if (unlikely(!size))
> > + return ERR_PTR(-EINVAL);
> > +
> > + if (unlikely(offset_in_page(size)))
> > + return ERR_PTR(-EINVAL);
> > +
> > + if (unlikely(!is_power_of_2(align)))
> > + return ERR_PTR(-EINVAL);
>
> I would have written it more compact. When using BUG_ON or WARN_ON it is
> interesting to have three separate lines because you get the line number
> in the Oops message, but here you are just returning the exact same
> error code, so it could be:
>
> if (unlikely(!size || offset_in_page(size) || !is_power_of_2(align)))
> return ERR_PTR(-EINVAL);
>
> >
> > if (unlikely(!vmap_initialized))
> > return ERR_PTR(-EBUSY);
> > --
> > 2.25.1
> >
> >
Hi Christophe,

Thanks for your comment.
I will send new patch.

Best,
Min