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>
diff --git a/io_uring/notif.c b/io_uring/notif.c
index e6d98dc..c5179e5 100644
--- a/io_uring/notif.c
+++ b/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;