io_uring: unlock if __io_run_local_work locked inside

It is possible for tw to lock the ring, and this was not propogated out to
io_run_local_work. This can cause an unlock to be missed.

Instead pass a pointer to locked into __io_run_local_work.

Fixes: 8ac5d85a89b4 ("io_uring: add local task_work run helper that is entered locked")
Signed-off-by: Dylan Yudaken <dylany@meta.com>
Link: https://lore.kernel.org/r/20221027144429.3971400-3-dylany@meta.com
[axboe: WARN_ON() -> WARN_ON_ONCE() and add a minor comment]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 8a0ce7379e89751b75ffcebc16e3ecd35f70acac..ac8c488e3077d9e1fb88cb9fd91063a4dc1c4b52 100644 (file)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1173,7 +1173,7 @@ static void __cold io_move_task_work_from_local(struct io_ring_ctx *ctx)
        }
 }
 
-int __io_run_local_work(struct io_ring_ctx *ctx, bool locked)
+int __io_run_local_work(struct io_ring_ctx *ctx, bool *locked)
 {
        struct llist_node *node;
        struct llist_node fake;
@@ -1192,7 +1192,7 @@ again:
                struct io_kiocb *req = container_of(node, struct io_kiocb,
                                                    io_task_work.node);
                prefetch(container_of(next, struct io_kiocb, io_task_work.node));
-               req->io_task_work.func(req, &locked);
+               req->io_task_work.func(req, locked);
                ret++;
                node = next;
        }
@@ -1208,7 +1208,7 @@ again:
                goto again;
        }
 
-       if (locked)
+       if (*locked)
                io_submit_flush_completions(ctx);
        trace_io_uring_local_work_run(ctx, ret, loops);
        return ret;
@@ -1225,7 +1225,7 @@ int io_run_local_work(struct io_ring_ctx *ctx)
 
        __set_current_state(TASK_RUNNING);
        locked = mutex_trylock(&ctx->uring_lock);
-       ret = __io_run_local_work(ctx, locked);
+       ret = __io_run_local_work(ctx, &locked);
        if (locked)
                mutex_unlock(&ctx->uring_lock);
 

diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index ef77d2aa3172ca470a7364af92abf57232ddbc8b..e99a79f2df9b18365559d6623133f77fdb60e3a6 100644 (file)
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -27,7 +27,7 @@ enum {
 struct io_uring_cqe *__io_get_cqe(struct io_ring_ctx *ctx, bool overflow);
 bool io_req_cqe_overflow(struct io_kiocb *req);
 int io_run_task_work_sig(struct io_ring_ctx *ctx);
-int __io_run_local_work(struct io_ring_ctx *ctx, bool locked);
+int __io_run_local_work(struct io_ring_ctx *ctx, bool *locked);
 int io_run_local_work(struct io_ring_ctx *ctx);
 void io_req_complete_failed(struct io_kiocb *req, s32 res);
 void __io_req_complete(struct io_kiocb *req, unsigned issue_flags);
@@ -277,9 +277,18 @@ static inline int io_run_task_work_ctx(struct io_ring_ctx *ctx)
 
 static inline int io_run_local_work_locked(struct io_ring_ctx *ctx)
 {
+       bool locked;
+       int ret;
+
        if (llist_empty(&ctx->work_llist))
                return 0;
-       return __io_run_local_work(ctx, true);
+
+       locked = true;
+       ret = __io_run_local_work(ctx, &locked);
+       /* shouldn't happen! */
+       if (WARN_ON_ONCE(!locked))
+               mutex_lock(&ctx->uring_lock);
+       return ret;
 }
 
 static inline void io_tw_lock(struct io_ring_ctx *ctx, bool *locked)