Hi Danilo, Thanks for the review! On Tue, Sep 10, 2024 at 12:06:05PM +0200, Danilo Krummrich wrote: > On Mon, Sep 09, 2024 at 09:29:56AM +0800, Feng Tang wrote: > > For current krealloc(), one problem is its caller doesn't know what's > > the actual request size, say the object is 64 bytes kmalloc one, but > > the original caller may only requested 48 bytes. And when krealloc() > > shrinks or grows in the same object, or allocate a new bigger object, > > it lacks this 'original size' information to do accurate data preserving > > or zeroing (when __GFP_ZERO is set). > > > > And when some slub debug option is enabled, kmalloc caches do have this > > 'orig_size' feature. So utilize it to do more accurate data handling, > > as well as enforce the kmalloc-redzone sanity check. > > > > The krealloc() related code is moved from slab_common.c to slub.c for > > more efficient function calling. > > I think it would be good to do this in a separate commit, for a better diff and > history. Agreed. will do. > > > > Suggested-by: Vlastimil Babka <vbabka@xxxxxxx> > > Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx> > > --- > > mm/slab_common.c | 84 ------------------------------------- > > mm/slub.c | 106 +++++++++++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 106 insertions(+), 84 deletions(-) [...] > > + > > +/** > > + * krealloc - reallocate memory. The contents will remain unchanged. > > + * @p: object to reallocate memory for. > > + * @new_size: how many bytes of memory are required. > > + * @flags: the type of memory to allocate. > > + * > > + * If @p is %NULL, krealloc() behaves exactly like kmalloc(). If @new_size > > + * is 0 and @p is not a %NULL pointer, the object pointed to is freed. > > + * > > + * If __GFP_ZERO logic is requested, callers must ensure that, starting with the > > + * initial memory allocation, every subsequent call to this API for the same > > + * memory allocation is flagged with __GFP_ZERO. Otherwise, it is possible that > > + * __GFP_ZERO is not fully honored by this API. > > + * > > + * When slub_debug_orig_size() is off, since krealloc() only knows about the > > I think you want to remove ' since ' here. Yes! :) > > + * bucket size of an allocation (but not the exact size it was allocated with) > > + * and hence implements the following semantics for shrinking and growing > > + * buffers with __GFP_ZERO. > > + * > > + * new bucket > > + * 0 size size > > + * |--------|----------------| > > + * | keep | zero | > > + * > > + * Otherwize, the original allocation size 'orig_size' could be used to > > Typo in 'otherwise'. Will fix. Thanks, Feng
