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SubjectRe: [PATCH] slab: deal with NULL pointers passed to kmem_cache_free
On Mon, 19 Mar 2007 15:49:46 -0500
Matt Mackall <mpm@selenic.com> wrote:

> On Mon, Mar 19, 2007 at 10:08:03AM -0700, Christoph Lameter wrote:
> > On Mon, 19 Mar 2007, Pekka J Enberg wrote:
> >
> > > This changes kmem_cache_free() to deal with NULL objects passed to it. The
> > > current behavior is inconsistent with kfree() so there are callers
> > > passing NULL to kmem_cache_free().
> >
> > Hmmm.. kmem_cache_free is significantly different. One also needs to
> > specify the slab cache.
>
> I think this sort of thing should work:
>
> a = kmalloc(...)
> b = kmem_cache_alloc(..)
> c = allocate_some_id(...)
> if (!a || !b || !c) {
> free_some_id(c)
> kmem_cache_free(c)
> kfree(a);
> return -ENOMEM;
> }

Would prefer to do:

static inline void kmem_cache_free_if_not_null(struct kmem_cache *cachep,
void *objp)
{
if (objp)
kmem_cache_free(cachep, objp);
}

so that we don't add extra overhead to all the thousands of existing,
well-behaved callsites.

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