From de96e9ae69a134c009a6d9a7ca182fa67067ecac Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Fri, 5 Apr 2024 16:50:03 +0100
Subject: [PATCH] io_uring: turn implicit assumptions into a warning
io_req_complete_post() is now io-wq only and shouldn't be used outside
of it, i.e. it relies that io-wq holds a ref for the request as
explained in a comment below. Let's add a warning to enforce the
assumption and make sure nobody would try to do anything weird.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/1013b60c35d431d0698cafbc53c06f5917348c20.1712331455.git.asml.silence@gmail.com
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
io_uring/io_uring.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 8bd5db2056eee..8078d69444111 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -929,6 +929,13 @@ static void io_req_complete_post(struct io_kiocb *req, unsigned issue_flags)
{
struct io_ring_ctx *ctx = req->ctx;
+ /*
+ * All execution paths but io-wq use the deferred completions by
+ * passing IO_URING_F_COMPLETE_DEFER and thus should not end up here.
+ */
+ if (WARN_ON_ONCE(!(issue_flags & IO_URING_F_IOWQ)))
+ return;
+
/*
* Handle special CQ sync cases via task_work. DEFER_TASKRUN requires
* the submitter task context, IOPOLL protects with uring_lock.
@@ -946,7 +953,10 @@ static void io_req_complete_post(struct io_kiocb *req, unsigned issue_flags)
}
io_cq_unlock_post(ctx);
- /* called from io-wq submit work only, the ref won't drop to zero */
+ /*
+ * We don't free the request here because we know it's called from
+ * io-wq only, which holds a reference, so it cannot be the last put.
+ */
req_ref_put(req);
}
--
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