[PATCH 5.8 012/148] io_uring: find and cancel head link async work on files exit

Greg Kroah-Hartman
2020-08-24T08:32:18Z

From: Jens Axboe <axboe@kernel.dk>

commit b711d4eaf0c408a811311ee3e94d6e9e5a230a9a upstream.

Commit f254ac04c874 ("io_uring: enable lookup of links holding inflight files")
only handled 2 out of the three head link cases we have, we also need to
lookup and cancel work that is blocked in io-wq if that work has a link
that's holding a reference to the files structure.

Put the "cancel head links that hold this request pending" logic into
io_attempt_cancel(), which will to through the motions of finding and
canceling head links that hold the current inflight files stable request
pending.

Cc: stable@vger.kernel.org
Reported-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/io_uring.c | 33 +++++++++++++++++++++++++++++----
1 file changed, 29 insertions(+), 4 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7609,6 +7609,33 @@ static bool io_timeout_remove_link(struc
return found;
}

+static bool io_cancel_link_cb(struct io_wq_work *work, void *data)
+{
+ return io_match_link(container_of(work, struct io_kiocb, work), data);
+}
+
+static void io_attempt_cancel(struct io_ring_ctx *ctx, struct io_kiocb *req)
+{
+ enum io_wq_cancel cret;
+
+ /* cancel this particular work, if it's running */
+ cret = io_wq_cancel_work(ctx->io_wq, &req->work);
+ if (cret != IO_WQ_CANCEL_NOTFOUND)
+ return;
+
+ /* find links that hold this pending, cancel those */
+ cret = io_wq_cancel_cb(ctx->io_wq, io_cancel_link_cb, req, true);
+ if (cret != IO_WQ_CANCEL_NOTFOUND)
+ return;
+
+ /* if we have a poll link holding this pending, cancel that */
+ if (io_poll_remove_link(ctx, req))
+ return;
+
+ /* final option, timeout link is holding this req pending */
+ io_timeout_remove_link(ctx, req);
+}
+
static void io_uring_cancel_files(struct io_ring_ctx *ctx,
struct files_struct *files)
{
@@ -7665,10 +7692,8 @@ static void io_uring_cancel_files(struct
continue;
}
} else {
- io_wq_cancel_work(ctx->io_wq, &cancel_req->work);
- /* could be a link, check and remove if it is */
- if (!io_poll_remove_link(ctx, cancel_req))
- io_timeout_remove_link(ctx, cancel_req);
+ /* cancel this request, or head link requests */
+ io_attempt_cancel(ctx, cancel_req);
io_put_req(cancel_req);
}