[PATCH 3/4] io_uring: add warn_once for io_uring_flush()

[Pavel Begunkov <asml.silence@gmail.com>]

files_cancel() should cancel all relevant requests and drop file notes,
so we should never have file notes after that, including on-exit fput
and flush. Add a WARN_ONCE to be sure.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1c931e7a3948..f39671a0d84f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9055,17 +9055,23 @@ void __io_uring_task_cancel(void)
 
 static int io_uring_flush(struct file *file, void *data)
 {
-	if (!current->io_uring)
+	struct io_uring_task *tctx = current->io_uring;
+
+	if (!tctx)
 		return 0;
 
+	/* we should have cancelled and erased it before PF_EXITING */
+	WARN_ON_ONCE((current->flags & PF_EXITING) &&
+		     xa_load(&tctx->xa, (unsigned long)file));
+
 	/*
 	 * fput() is pending, will be 2 if the only other ref is our potential
 	 * task file note. If the task is exiting, drop regardless of count.
 	 */
-	if (fatal_signal_pending(current) || (current->flags & PF_EXITING) ||
-	    atomic_long_read(&file->f_count) == 2)
-		io_uring_del_task_file(file);
+	if (atomic_long_read(&file->f_count) != 2)
+		return 0;
 
+	io_uring_del_task_file(file);
 	return 0;
 }
 
-- 
2.24.0