On Wed, 28 Aug 2024 00:20:23 -0700 Mina Almasry wrote:

quoted

On Sun, 25 Aug 2024 04:15:02 +0000 Mina Almasry wrote:  

quoted

+void net_devmem_free_dmabuf(struct net_iov *niov)
+{
+     struct net_devmem_dmabuf_binding *binding = net_iov_binding(niov);
+     unsigned long dma_addr = net_devmem_get_dma_addr(niov);
+
+     if (gen_pool_has_addr(binding->chunk_pool, dma_addr, PAGE_SIZE))
+             gen_pool_free(binding->chunk_pool, dma_addr, PAGE_SIZE);  

Is the check necessary for correctness? Should it perhaps be a WARN
under DEBUG_NET instead? The rest LGTM:
 

Not really necessary for correctness per se, but if we try to free a
dma_addr that is not in a gen_pool (due to some other bug in the
code), then gen_pool_free ends up BUG_ON, crashing the kernel.

Arguably gen_pool_free should not BUG_ON, but I think that's an old
API, and existing call sites have worked around the BUG_ON by doing a
gen_pool_has_addr check like I do here, for example kernel/dma/pool.c.
So I did not seek to change this established behavior.

I think WARN seems fine to me, but maybe not under DEBUG_NET. I don't
want production code crashing due to this error, if it's OK with you.

Unless I hear otherwise I'll add a WARN without debug here.

WARN makes sense, I didn't know about the BUG_ON() hiding inside
gen_pool :(