io_uring: add helper to free all request caches

We have three different ones, put it in a helper for easy calling. This
is in preparation for doing it outside of ring freeing as well. With
that in mind, also ensure that we do the proper locking for safe calling
from a context where the ring it still live.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -8693,10 +8693,27 @@ static void io_req_cache_free(struct list_head *list, struct task_struct *tsk)
 	}
 }
 
-static void io_ring_ctx_free(struct io_ring_ctx *ctx)
+static void io_req_caches_free(struct io_ring_ctx *ctx, struct task_struct *tsk)
 {
 	struct io_submit_state *submit_state = &ctx->submit_state;
 
+	mutex_lock(&ctx->uring_lock);
+
+	if (submit_state->free_reqs)
+		kmem_cache_free_bulk(req_cachep, submit_state->free_reqs,
+				     submit_state->reqs);
+
+	io_req_cache_free(&submit_state->comp.free_list, NULL);
+
+	spin_lock_irq(&ctx->completion_lock);
+	io_req_cache_free(&submit_state->comp.locked_free_list, NULL);
+	spin_unlock_irq(&ctx->completion_lock);
+
+	mutex_unlock(&ctx->uring_lock);
+}
+
+static void io_ring_ctx_free(struct io_ring_ctx *ctx)
+{
 	/*
 	 * Some may use context even when all refs and requests have been put,
 	 * and they are free to do so while still holding uring_lock, see
@@ -8715,10 +8732,6 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
 		ctx->mm_account = NULL;
 	}
 
-	if (submit_state->free_reqs)
-		kmem_cache_free_bulk(req_cachep, submit_state->free_reqs,
-				     submit_state->reqs);
-
 #ifdef CONFIG_BLK_CGROUP
 	if (ctx->sqo_blkcg_css)
 		css_put(ctx->sqo_blkcg_css);
@@ -8742,9 +8755,8 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
 	percpu_ref_exit(&ctx->refs);
 	free_uid(ctx->user);
 	put_cred(ctx->creds);
+	io_req_caches_free(ctx, NULL);
 	kfree(ctx->cancel_hash);
-	io_req_cache_free(&ctx->submit_state.comp.free_list, NULL);
-	io_req_cache_free(&ctx->submit_state.comp.locked_free_list, NULL);
 	kfree(ctx);
 }