[PATCH 5.5 02/80] io_uring: retry raw bdev writes if we hit -EOPNOTSUPP

[Greg Kroah-Hartman]

From: Jens Axboe <axboe@xxxxxxxxx>

commit faac996ccd5da95bc56b91aa80f2643c2d0a1c56 upstream.

For non-blocking issue, we set IOCB_NOWAIT in the kiocb. However, on a
raw block device, this yields an -EOPNOTSUPP return, as non-blocking
writes aren't supported. Turn this -EOPNOTSUPP into -EAGAIN, so we retry
from blocking context with IOCB_NOWAIT cleared.

Cc: stable@xxxxxxxxxxxxxxx # 5.5
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/io_uring.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1978,6 +1978,12 @@ static int io_write(struct io_kiocb *req
 			ret2 = call_write_iter(req->file, kiocb, &iter);
 		else
 			ret2 = loop_rw_iter(WRITE, req->file, kiocb, &iter);
+		/*
+		 * Raw bdev writes will -EOPNOTSUPP for IOCB_NOWAIT. Just
+		 * retry them without IOCB_NOWAIT.
+		 */
+		if (ret2 == -EOPNOTSUPP && (kiocb->ki_flags & IOCB_NOWAIT))
+			ret2 = -EAGAIN;
 		if (!force_nonblock || ret2 != -EAGAIN) {
 			kiocb_done(kiocb, ret2, nxt, req->in_async);
 		} else {