Re: [PATCH] mm: check the function kmalloc_slab return value

[tury]

在 2022年06月14日 16:48, Vlastimil Babka 写道:
> On 6/14/22 10:39, Ren Yu wrote:
> > As the possible failure of the kmalloc_slab,
> > it should be better to check it.
> AFAIK failure is not possible, kmalloc_slab() is not an allocation function,
> it just returns a member of kmalloc_caches array, which is initialized
> elsewhere and shouldn't contain NULLs. So the patch seems unnecessary to me.
>
> > Signed-off-by: Ren Yu <renyu@xxxxxxxxxxxx>
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > ---
> > v2:
> > - fix build waring integer from pointer without a cast
> > ---
> > ---
> >   mm/slab.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/mm/slab.c b/mm/slab.c
> > index f8cd00f4ba13..72135e555827 100644
> > --- a/mm/slab.c
> > +++ b/mm/slab.c
> > @@ -2064,6 +2064,8 @@ int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
> >   	if (OFF_SLAB(cachep)) {
> >   		cachep->freelist_cache =
> >   			kmalloc_slab(cachep->freelist_size, 0u);
> > +		if (unlikely(ZERO_OR_NULL_PTR(cachep->freelist_cache)))
> The usual way is "if (!cachep->freelist_cache)". Not sure why check for ZERO.
>
> > +			return cachep->freelist_cache;
> So in case of NULL this would return NULL, thus 0, but __kmem_cache_create()
> return 0 on success, so it's wrong. You would have to return e.g. -ENOMEM.
Thanks for the advice ,I'll be re-patching
> >   	}
> >   
> >   	err = setup_cpu_cache(cachep, gfp);