6.8-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jens Axboe <axboe@xxxxxxxxx>
commit 2a975d426c82ff05ec1f0b773798d909fe4a3105 upstream.
Supporting multishot reads requires support for NOWAIT, as the
alternative would be always having io-wq execute the work item whenever
the poll readiness triggered. Any fast file type will have NOWAIT
support (eg it understands both O_NONBLOCK and IOCB_NOWAIT). If the
given file type does not, then simply resort to single shot execution.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: fc68fcda04910 ("io_uring/rw: add support for IORING_OP_READ_MULTISHOT")
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
io_uring/rw.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -938,6 +938,13 @@ int io_read_mshot(struct io_kiocb *req,
ret = __io_read(req, issue_flags);
/*
+ * If the file doesn't support proper NOWAIT, then disable multishot
+ * and stay in single shot mode.
+ */
+ if (!io_file_supports_nowait(req))
+ req->flags &= ~REQ_F_APOLL_MULTISHOT;
+
+ /*
* If we get -EAGAIN, recycle our buffer and just let normal poll
* handling arm it.
*/
@@ -956,7 +963,7 @@ int io_read_mshot(struct io_kiocb *req,
/*
* Any successful return value will keep the multishot read armed.
*/
- if (ret > 0) {
+ if (ret > 0 && req->flags & REQ_F_APOLL_MULTISHOT) {
/*
* Put our buffer and post a CQE. If we fail to post a CQE, then
* jump to the termination path. This request is then done.
