[PATCH v5 4/4] io_uring: remove ring quiesce for io_uring_register

Usama Arif
2022-02-03T23:34:57Z

Ring quiesce is currently only used for 2 opcodes
IORING_REGISTER_ENABLE_RINGS and IORING_REGISTER_RESTRICTIONS.
IORING_SETUP_R_DISABLED prevents submitting requests and
so there will be no requests until IORING_REGISTER_ENABLE_RINGS
is called. And IORING_REGISTER_RESTRICTIONS works only before
IORING_REGISTER_ENABLE_RINGS is called. Hence ring quiesce is
not needed for these opcodes and therefore io_uring_register.

Signed-off-by: Usama Arif <usama.arif@bytedance.com>
---
fs/io_uring.c | 69 ---------------------------------------------------
1 file changed, 69 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 5ae51ea12f0f..89e4dd7e8995 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -11022,64 +11022,6 @@ static __cold int io_register_iowq_max_workers(struct io_ring_ctx *ctx,
return ret;
}

-static bool io_register_op_must_quiesce(int op)
-{
- switch (op) {
- case IORING_REGISTER_BUFFERS:
- case IORING_UNREGISTER_BUFFERS:
- case IORING_REGISTER_FILES:
- case IORING_UNREGISTER_FILES:
- case IORING_REGISTER_FILES_UPDATE:
- case IORING_REGISTER_EVENTFD:
- case IORING_REGISTER_EVENTFD_ASYNC:
- case IORING_UNREGISTER_EVENTFD:
- case IORING_REGISTER_PROBE:
- case IORING_REGISTER_PERSONALITY:
- case IORING_UNREGISTER_PERSONALITY:
- case IORING_REGISTER_FILES2:
- case IORING_REGISTER_FILES_UPDATE2:
- case IORING_REGISTER_BUFFERS2:
- case IORING_REGISTER_BUFFERS_UPDATE:
- case IORING_REGISTER_IOWQ_AFF:
- case IORING_UNREGISTER_IOWQ_AFF:
- case IORING_REGISTER_IOWQ_MAX_WORKERS:
- return false;
- default:
- return true;
- }
-}
-
-static __cold int io_ctx_quiesce(struct io_ring_ctx *ctx)
-{
- long ret;
-
- percpu_ref_kill(&ctx->refs);
-
- /*
- * Drop uring mutex before waiting for references to exit. If another
- * thread is currently inside io_uring_enter() it might need to grab the
- * uring_lock to make progress. If we hold it here across the drain
- * wait, then we can deadlock. It's safe to drop the mutex here, since
- * no new references will come in after we've killed the percpu ref.
- */
- mutex_unlock(&ctx->uring_lock);
- do {
- ret = wait_for_completion_interruptible_timeout(&ctx->ref_comp, HZ);
- if (ret) {
- ret = min(0L, ret);
- break;
- }
-
- ret = io_run_task_work_sig();
- io_req_caches_free(ctx);
- } while (ret >= 0);
- mutex_lock(&ctx->uring_lock);
-
- if (ret)
- io_refs_resurrect(&ctx->refs, &ctx->ref_comp);
- return ret;
-}
-
static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
void __user *arg, unsigned nr_args)
__releases(ctx->uring_lock)
@@ -11103,12 +11045,6 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
return -EACCES;
}

- if (io_register_op_must_quiesce(opcode)) {
- ret = io_ctx_quiesce(ctx);
- if (ret)
- return ret;
- }
-
switch (opcode) {
case IORING_REGISTER_BUFFERS:
ret = io_sqe_buffers_register(ctx, arg, nr_args, NULL);
@@ -11213,11 +11149,6 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
break;
}

- if (io_register_op_must_quiesce(opcode)) {
- /* bring the ctx back to life */
- percpu_ref_reinit(&ctx->refs);
- reinit_completion(&ctx->ref_comp);
- }
return ret;
}

--
2.25.1