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SubjectRe: [PATCH] devres: zero the memory in devm_krealloc() if needed
On Fri, Oct 30, 2020 at 12:57:06PM +0200, Andy Shevchenko wrote:
> On Fri, Oct 30, 2020 at 10:03:50AM +0100, Bartosz Golaszewski wrote:
> > On Thu, Oct 29, 2020 at 9:05 PM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> > >
> > > On Mon, Oct 26, 2020 at 01:27:28PM +0100, Bartosz Golaszewski wrote:
> > > > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> > > >
> > > > If we're returning the same pointer (when new size is smaller or equal
> > > > to the old size) we need to check if the user wants the memory zeroed
> > > > and memset() it manually if so.
> > >
> > > Any use case? Because to me it sounds contradictory to the whole idea of [k]realloc().
> >
> > This is kind of a gray area in original krealloc() too and I want to
> > submit a patch for mm too. Right now krealloc ignores the __GFP_ZERO
> > flag if new_size <= old_size but zeroes the memory if new_size >
> > old_size.
>
> > This should be consistent - either ignore __GFP_ZERO or
> > don't ignore it in both cases. I think that not ignoring it is better
> > - if user passes it then it's for a reason.
>
> Sorry, but I consider in these two choices the best is the former one, i.e.
> ignoring, because non-ignoring for sizes less than current is counter the
> REalloc() by definition.
>
> Reading realloc(3):
>
> "If the new size is larger than the old size, the added memory will not be
> initialized."
>
> So, supports my choice over yours.

Two notes:
- perhaps kzrealloc() for what you want
- there is a library call reallocarray() which supports your idea about
krealloc_array() API in kernel.


--
With Best Regards,
Andy Shevchenko


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