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SubjectRe: [PATCH V4 2/2] ptr_ring: try vmalloc() when kmalloc() fails
On Fri, Feb 09, 2018 at 05:45:50PM +0800, Jason Wang wrote:
> This patch switch to use kvmalloc_array() for using a vmalloc()
> fallback to help in case kmalloc() fails.

Above isn't really saying anything about the motivation, it
just explains what kvmalloc_array does.

How about:

Switch ptr_ring from kmalloc to kvmalloc. This way it can support larger
ring sizes.

>
> Reported-by: syzbot+e4d4f9ddd4295539735d@syzkaller.appspotmail.com
> Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")

I don't see this as a bugfix - it's more of an enhancement.

Do we need this in net or can we defer this to net-next?

I'm not sure myself. For now

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> Signed-off-by: Jason Wang <jasowang@redhat.com>


> ---
> include/linux/ptr_ring.h | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
> index 6051a5f..b884b77 100644
> --- a/include/linux/ptr_ring.h
> +++ b/include/linux/ptr_ring.h
> @@ -464,11 +464,14 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
> __PTR_RING_PEEK_CALL_v; \
> })
>
> +/* Not all gfp_t flags (besides GFP_KERNEL) are allowed. See
> + * documentation for vmalloc for which of them are legal.
> + */
> static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
> {
> if (size * sizeof(void *) > KMALLOC_MAX_SIZE)
> return NULL;
> - return kcalloc(size, sizeof(void *), gfp);
> + return kvmalloc_array(size, sizeof(void *), gfp | __GFP_ZERO);
> }
>
> static inline void __ptr_ring_set_size(struct ptr_ring *r, int size)
> @@ -603,7 +606,7 @@ static inline int ptr_ring_resize(struct ptr_ring *r, int size, gfp_t gfp,
> spin_unlock(&(r)->producer_lock);
> spin_unlock_irqrestore(&(r)->consumer_lock, flags);
>
> - kfree(old);
> + kvfree(old);
>
> return 0;
> }
> @@ -643,7 +646,7 @@ static inline int ptr_ring_resize_multiple(struct ptr_ring **rings,
> }
>
> for (i = 0; i < nrings; ++i)
> - kfree(queues[i]);
> + kvfree(queues[i]);
>
> kfree(queues);
>
> @@ -651,7 +654,7 @@ static inline int ptr_ring_resize_multiple(struct ptr_ring **rings,
>
> nomem:
> while (--i >= 0)
> - kfree(queues[i]);
> + kvfree(queues[i]);
>
> kfree(queues);
>
> @@ -666,7 +669,7 @@ static inline void ptr_ring_cleanup(struct ptr_ring *r, void (*destroy)(void *))
> if (destroy)
> while ((ptr = ptr_ring_consume(r)))
> destroy(ptr);
> - kfree(r->queue);
> + kvfree(r->queue);
> }
>
> #endif /* _LINUX_PTR_RING_H */
> --
> 2.7.4

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