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

Suren Baghdasaryan
2024-04-04T22:17:58Z

On Thu, Apr 4, 2024 at 10:08 AM Suren Baghdasaryan <surenb@google.com> wrote:
>
> On Thu, Apr 4, 2024 at 10:04 AM Matthew Wilcox <willy@infradead.org> wrote:
> >
> > On Thu, Apr 04, 2024 at 09:54:04AM -0700, Suren Baghdasaryan wrote:
> > > +++ b/include/linux/dma-fence-chain.h
> > > @@ -86,10 +86,7 @@ dma_fence_chain_contained(struct dma_fence *fence)
> > > *
> > > * Returns a new struct dma_fence_chain object or NULL on failure.
> > > */
> > > -static inline struct dma_fence_chain *dma_fence_chain_alloc(void)
> > > -{
> > > - return kmalloc(sizeof(struct dma_fence_chain), GFP_KERNEL);
> > > -};
> > > +#define dma_fence_chain_alloc() kmalloc(sizeof(struct dma_fence_chain), GFP_KERNEL)
> >
> > You've removed some typesafety here. Before, if I wrote:
> >
> > struct page *page = dma_fence_chain_alloc();
> >
> > the compiler would warn me that I've done something stupid. Now it
> > can't tell. Suggest perhaps:
> >
> > #define dma_fence_chain_alloc() \
> > (struct dma_fence_chain *)kmalloc(sizeof(struct dma_fence_chain), \
> > GFP_KERNEL)
> >
> > but maybe there's a better way of doing that. There are a few other
> > occurrences of the same problem in this monster patch.
>
> Got your point.

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)?

>
> >
> > > +++ b/include/linux/hid_bpf.h
> > > @@ -149,10 +149,7 @@ static inline int hid_bpf_connect_device(struct hid_device *hdev) { return 0; }
> > > static inline void hid_bpf_disconnect_device(struct hid_device *hdev) {}
> > > static inline void hid_bpf_destroy_device(struct hid_device *hid) {}
> > > static inline void hid_bpf_device_init(struct hid_device *hid) {}
> > > -static inline u8 *call_hid_bpf_rdesc_fixup(struct hid_device *hdev, u8 *rdesc, unsigned int *size)
> > > -{
> > > - return kmemdup(rdesc, *size, GFP_KERNEL);
> > > -}
> > > +#define call_hid_bpf_rdesc_fixup(_hdev, _rdesc, _size) kmemdup(_rdesc, *(_size), GFP_KERNEL)
> >
> > here
> >
> > > -static inline handle_t *jbd2_alloc_handle(gfp_t gfp_flags)
> > > -{
> > > - return kmem_cache_zalloc(jbd2_handle_cache, gfp_flags);
> > > -}
> > > +#define jbd2_alloc_handle(_gfp_flags) kmem_cache_zalloc(jbd2_handle_cache, _gfp_flags)
> >
> > here
> >
> > > +++ b/include/linux/skmsg.h
> > > @@ -410,11 +410,8 @@ void sk_psock_stop_verdict(struct sock *sk, struct sk_psock *psock);
> > > int sk_psock_msg_verdict(struct sock *sk, struct sk_psock *psock,
> > > struct sk_msg *msg);
> > >
> > > -static inline struct sk_psock_link *sk_psock_init_link(void)
> > > -{
> > > - return kzalloc(sizeof(struct sk_psock_link),
> > > - GFP_ATOMIC | __GFP_NOWARN);
> > > -}
> > > +#define sk_psock_init_link() \
> > > + kzalloc(sizeof(struct sk_psock_link), GFP_ATOMIC | __GFP_NOWARN)
> >
> > here
> >
> > ... I kind of gave up at this point. You'll want to audit for yourself
> > anyway ;-)
>
> Yes, I'll go over it and will make the required changes. Thanks for
> looking into it!
> Suren.