io_uring: account locked pages for non-fixed zc

Fixed buffers are RLIMIT_MEMLOCK accounted, however it doesn't cover iovec
based zerocopy sends. Do the accounting on the io_uring side.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/19b6e3975440f59f1f6199c7ee7acf977b4eecdc.1657643355.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/net.c

@@ -906,6 +906,7 @@ int io_sendzc(struct io_kiocb *req, unsigned int issue_flags)
 	ret = import_single_range(WRITE, zc->buf, zc->len, &iov, &msg.msg_iter);
 	if (unlikely(ret))
 		return ret;
+	mm_account_pinned_pages(&notif->uarg.mmp, zc->len);
 
 	msg_flags = zc->msg_flags | MSG_ZEROCOPY;
 	if (issue_flags & IO_URING_F_NONBLOCK)

io_uring/notif.c

@@ -14,7 +14,13 @@ static void __io_notif_complete_tw(struct callback_head *cb)
 	struct io_notif *notif = container_of(cb, struct io_notif, task_work);
 	struct io_rsrc_node *rsrc_node = notif->rsrc_node;
 	struct io_ring_ctx *ctx = notif->ctx;
+	struct mmpin *mmp = &notif->uarg.mmp;
 
+	if (mmp->user) {
+		atomic_long_sub(mmp->num_pg, &mmp->user->locked_vm);
+		free_uid(mmp->user);
+		mmp->user = NULL;
+	}
 	if (likely(notif->task)) {
 		io_put_task(notif->task, 1);
 		notif->task = NULL;