For multishot mode, there may be cases like:
io_poll_task_func()
-> add_wait_queue()
async_wake()
->io_req_task_work_add()
this one mess up the running task_work list
since req->io_task_work.node is in use.
similar situation for req->io_task_work.fallback_node.
Fix it by set node->next = NULL before we run the tw, so that when we
add req back to the wait queue in middle of tw running, we can safely
re-add it to the tw list.
Fixes: 7cbf1722d5fc ("io_uring: provide FIFO ordering for task_work")
Signed-off-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>
---
fs/io_uring.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 30d959416eba..c16f6be3d46b 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1216,13 +1216,17 @@ static void io_fallback_req_func(struct work_struct *work)
struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx,
fallback_work.work);
struct llist_node *node = llist_del_all(&ctx->fallback_llist);
- struct io_kiocb *req, *tmp;
+ struct io_kiocb *req;
bool locked = false;
percpu_ref_get(&ctx->refs);
- llist_for_each_entry_safe(req, tmp, node, io_task_work.fallback_node)
+ req = llist_entry(node, struct io_kiocb, io_task_work.fallback_node);
+ while (member_address_is_nonnull(req, io_task_work.fallback_node)) {
+ node = req->io_task_work.fallback_node.next;
+ req->io_task_work.fallback_node.next = NULL;
req->io_task_work.func(req, &locked);
-
+ req = llist_entry(node, struct io_kiocb, io_task_work.fallback_node);
+ }
if (locked) {
if (ctx->submit_state.compl_nr)
io_submit_flush_completions(ctx);
@@ -2126,6 +2130,7 @@ static void tctx_task_work(struct callback_head *cb)
locked = mutex_trylock(&ctx->uring_lock);
percpu_ref_get(&ctx->refs);
}
+ node->next = NULL;
req->io_task_work.func(req, &locked);
node = next;
} while (node);
--
2.24.4
