io_uring/rw: treat -EOPNOTSUPP for IOCB_NOWAIT like -EAGAIN

Some file systems, ocfs2 in this case, will return -EOPNOTSUPP for
an IOCB_NOWAIT read/write attempt. While this can be argued to be
correct, the usual return value for something that requires blocking
issue is -EAGAIN.

A refactoring io_uring commit dropped calling kiocb_done() for
negative return values, which is otherwise where we already do that
transformation. To ensure we catch it in both spots, check it in
__io_read() itself as well.

Reported-by: Robert Sander <r.sander@heinlein-support.de>
Link: https://fosstodon.org/@gurubert@mastodon.gurubert.de/113112431889638440
Cc: stable@vger.kernel.org
Fixes: a08d195b586a ("io_uring/rw: split io_read() into a helper")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/rw.c b/io_uring/rw.c
index f5e0694..f4d885b 100644 (file)
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -855,6 +855,14 @@ static int __io_read(struct io_kiocb *req, unsigned int issue_flags)
 
        ret = io_iter_do_read(rw, &io->iter);
 
+       /*
+        * Some file systems like to return -EOPNOTSUPP for an IOCB_NOWAIT
+        * issue, even though they should be returning -EAGAIN. To be safe,
+        * retry from blocking context for either.
+        */
+       if (ret == -EOPNOTSUPP && force_nonblock)
+               ret = -EAGAIN;
+
        if (ret == -EAGAIN || (req->flags & REQ_F_REISSUE)) {
                req->flags &= ~REQ_F_REISSUE;
                /* If we can poll, just do that. */