Re: [PATCH 1/1] mm: change inlined allocation helpers to account at the call site

Andrew Morton
2024-04-04T22:41:52Z

On Thu, 4 Apr 2024 18:38:39 -0400 Kent Overstreet <kent.overstreet@linux.dev> wrote:

> On Thu, Apr 04, 2024 at 11:33:22PM +0100, Matthew Wilcox wrote:
> > On Thu, Apr 04, 2024 at 03:17:43PM -0700, Suren Baghdasaryan wrote:
> > > Ironically, checkpatch generates warnings for these type casts:
> > >
> > > WARNING: unnecessary cast may hide bugs, see
> > > http://c-faq.com/malloc/mallocnocast.html
> > > #425: FILE: include/linux/dma-fence-chain.h:90:
> > > + ((struct dma_fence_chain *)kmalloc(sizeof(struct dma_fence_chain),
> > > GFP_KERNEL))
> > >
> > > I guess I can safely ignore them in this case (since we cast to the
> > > expected type)?
> >
> > I find ignoring checkpatch to be a solid move 99% of the time.
> >
> > I really don't like the codetags. This is so much churn, and it could
> > all be avoided by just passing in _RET_IP_ or _THIS_IP_ depending on
> > whether we wanted to profile this function or its caller. vmalloc
> > has done it this way since 2008 (OK, using __builtin_return_address())
> > and lockdep has used _THIS_IP_ / _RET_IP_ since 2006.
>
> Except you can't. We've been over this; using that approach for tracing
> is one thing, using it for actual accounting isn't workable.

I missed that. There have been many emails. Please remind us of the
reasoning here.