Messages in this thread | | | Date | Thu, 9 Feb 2012 15:05:34 +0200 | Subject | Re: [PATCH RFC] slab: introduce knalloc/kxnalloc | From | Pekka Enberg <> |
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On Thu, Feb 9, 2012 at 2:41 PM, Xi Wang <xi.wang@gmail.com> wrote: > This patch introduces knalloc/kxnalloc wrappers that perform integer > overflow checks without zeroing the memory. > > knalloc(n, size, flags) is the non-zeroing version of kcalloc(), > which allocates n * size bytes. > > kxnalloc(xsize, n, size, flags) allocates xsize + n * size bytes. > It is useful to allocate a structure ending with a zero-length array, > which is a commonly used pattern. For example, in posix_acl_alloc() > to allocate a posix_acl object one could call > > kxnalloc(sizeof(struct posix_acl), > count, sizeof(struct posix_acl_entry), flags); > > to avoid overflowing the allocation size. > > Suggested-by: Andrew Morton <akpm@linux-foundation.org> > Signed-off-by: Xi Wang <xi.wang@gmail.com>
Are there really enough potential users to justify adding both?
> --- > I coined the name knalloc() for Andrew's wtf_do_i_call_this() in the > previous email. A better name is welcome. > > I additionally added kxnalloc() since it's a common idiom. > --- > include/linux/slab.h | 31 +++++++++++++++++++++++++++---- > 1 files changed, 27 insertions(+), 4 deletions(-) > > diff --git a/include/linux/slab.h b/include/linux/slab.h > index 573c809..e3a1e81 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -190,7 +190,8 @@ size_t ksize(const void *); > #endif > > /** > - * kcalloc - allocate memory for an array. The memory is set to zero. > + * kxnalloc - allocate memory for an array with an extra header. > + * @xsize: extra header size. > * @n: number of elements. > * @size: element size. > * @flags: the type of memory to allocate. > @@ -240,11 +241,33 @@ size_t ksize(const void *); > * for general use, and so are not documented here. For a full list of > * potential flags, always refer to linux/gfp.h. > */ > -static inline void *kcalloc(size_t n, size_t size, gfp_t flags) > +static inline void *kxnalloc(size_t xsize, size_t n, size_t size, gfp_t flags) > { > - if (size != 0 && n > ULONG_MAX / size) > + if (size != 0 && n > (ULONG_MAX - xsize) / size) > return NULL; > - return __kmalloc(n * size, flags | __GFP_ZERO); > + return __kmalloc(xsize + n * size, flags); > +} > + > +/** > + * knalloc - allocate memory for an array. > + * @n: number of elements. > + * @size: element size. > + * @flags: the type of memory to allocate (see kmalloc). > + */ > +static inline void *knalloc(size_t n, size_t size, gfp_t flags) > +{ > + return kxnalloc(0, n, size, flags); > +}
> +/** > + * kcalloc - allocate memory for an array. The memory is set to zero. > + * @n: number of elements. > + * @size: element size. > + * @flags: the type of memory to allocate (see kmalloc). > + */ > +static inline void *kcalloc(size_t n, size_t size, gfp_t flags) > +{ > + return knalloc(n, size, flags | __GFP_ZERO); > } > > #if !defined(CONFIG_NUMA) && !defined(CONFIG_SLOB) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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