Re: [RFC PATCH 06/10] net: add SO_DEVMEM_DONTNEED setsockopt to release RX pages

On 7/10/23 15:32, Mina Almasry wrote:

Add an interface for the user to notify the kernel that it is done reading
the NET_RX dmabuf pages returned as cmsg. The kernel will drop the
reference on the NET_RX pages to make them available for re-use.

Signed-off-by: Mina Almasry <redacted>
---

+		for (i = 0; i < num_tokens; i++) {
+			for (j = 0; j < tokens[i].token_count; j++) {
+				struct page *pg = xa_erase(&sk->sk_pagepool,
+							   tokens[i].token_start + j);
+
+				if (pg)
+					put_page(pg);
+				else
+					/* -EINTR here notifies the userspace
+					 * that not all tokens passed to it have
+					 * been freed.
+					 */
+					ret = -EINTR;

Unless I'm missing something, this type of error reporting is 
unrecoverable -- userspace doesn't know how many tokens have been freed.

I think you should either make it explicitly unrecoverable (somehow shut 
down dmabuf handling entirely) or tell userspace how many tokens were 
successfully freed.

--Andy