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

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Date:   Tue, 18 Feb 2020 20:54:23 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.5 02/80] io_uring: retry raw bdev writes if we hit -EOPNOTSUPP

From: Jens Axboe <axboe@...nel.dk>

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@...r.kernel.org # 5.5
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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 {