[PATCH] io_uring/rw: ensure kiocb_end_write() is always called

[PATCH] io_uring/rw: ensure kiocb_end_write() is always called

[Jens Axboe]

A previous commit moved the notifications and end-write handling, but
it is now missing a few spots where we also want to call both of those.
Without that, we can potentially be missing file notifications, and
more importantly, have an imbalance in the super_block writers sem
accounting.

Fixes: b000145e9907 ("io_uring/rw: defer fsnotify calls to task context")
Reported-by: Dave Chinner <david@fromorbit.com>
Link: https://lore.kernel.org/all/20221010050319.GC2703033@dread.disaster.area/
Signed-off-by: Jens Axboe <axboe@kernel.dk>

---

diff --git a/io_uring/rw.c b/io_uring/rw.c
index 453e0ae92160..100de2626e47 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -234,11 +234,34 @@ static void kiocb_end_write(struct io_kiocb *req)
 	}
 }
 
+/*
+ * Trigger the notifications after having done some IO, and finish the write
+ * accounting, if any.
+ */
+static void io_req_io_end(struct io_kiocb *req)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
+
+	WARN_ON(!in_task());
+
+	if (rw->kiocb.ki_flags & IOCB_WRITE) {
+		kiocb_end_write(req);
+		fsnotify_modify(req->file);
+	} else {
+		fsnotify_access(req->file);
+	}
+}
+
 static bool __io_complete_rw_common(struct io_kiocb *req, long res)
 {
 	if (unlikely(res != req->cqe.res)) {
 		if ((res == -EAGAIN || res == -EOPNOTSUPP) &&
 		    io_rw_should_reissue(req)) {
+			/*
+			 * Reissue will start accounting again, finish the
+			 * current cycle.
+			 */
+			io_req_io_end(req);
 			req->flags |= REQ_F_REISSUE | REQ_F_PARTIAL_IO;
 			return true;
 		}
@@ -264,15 +287,7 @@ static inline int io_fixup_rw_res(struct io_kiocb *req, long res)
 
 static void io_req_rw_complete(struct io_kiocb *req, bool *locked)
 {
-	struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
-
-	if (rw->kiocb.ki_flags & IOCB_WRITE) {
-		kiocb_end_write(req);
-		fsnotify_modify(req->file);
-	} else {
-		fsnotify_access(req->file);
-	}
-
+	io_req_io_end(req);
 	io_req_task_complete(req, locked);
 }
 
@@ -317,6 +332,11 @@ static int kiocb_done(struct io_kiocb *req, ssize_t ret,
 		req->file->f_pos = rw->kiocb.ki_pos;
 	if (ret >= 0 && (rw->kiocb.ki_complete == io_complete_rw)) {
 		if (!__io_complete_rw_common(req, ret)) {
+			/*
+			 * Safe to call io_end from here as we're inline
+			 * from the submission path.
+			 */
+			io_req_io_end(req);
 			io_req_set_res(req, final_ret,
 				       io_put_kbuf(req, issue_flags));
 			return IOU_OK;

-- 
Jens Axboe