linux-kernel - [PATCH] fs: RWF_NOWAIT should imply IOCB

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Message-ID: <e8325bef-7e91-5fd4-fa25-74cfa169ffd2@kernel.dk>
Date:   Mon, 10 Aug 2020 18:48:19 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     linux-fsdevel <linux-fsdevel@...r.kernel.org>
Cc:     Dave Chinner <david@...morbit.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] fs: RWF_NOWAIT should imply IOCB_NOIO

With the change allowing read-ahead for IOCB_NOWAIT, we changed the
RWF_NOWAIT semantics of only doing cached reads. Since we know have
IOCB_NOIO to manage that specific side of it, just make RWF_NOWAIT
imply IOCB_NOIO as well to restore the previous behavior.

Fixes: 2e85abf053b9 ("mm: allow read-ahead with IOCB_NOWAIT set")
Reported-by: Dave Chinner <david@...morbit.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>

---

This was a known change with the buffered async read change, but we
didn't have IOCB_NOIO until late in 5.8. Now that bases are synced,
make the change to make RWF_NOWAIT behave like past kernels.

diff --git a/include/linux/fs.h b/include/linux/fs.h
index bd7ec3eaeed0..f1cca4bfdd7b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3293,7 +3293,7 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags)
 	if (flags & RWF_NOWAIT) {
 		if (!(ki->ki_filp->f_mode & FMODE_NOWAIT))
 			return -EOPNOTSUPP;
-		kiocb_flags |= IOCB_NOWAIT;
+		kiocb_flags |= IOCB_NOWAIT | IOCB_NOIO;
 	}
 	if (flags & RWF_HIPRI)
 		kiocb_flags |= IOCB_HIPRI;

-- 
Jens Axboe