2020-08-11 00:49:31

by Jens Axboe

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 <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

---

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

2020-08-11 06:16:30

by Dave Chinner

Subject: Re: [PATCH] fs: RWF_NOWAIT should imply IOCB_NOIO

On Mon, Aug 10, 2020 at 06:48:19PM -0600, Jens Axboe wrote:
> 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 <[email protected]>
> Signed-off-by: Jens Axboe <[email protected]>
>
> ---
>
> 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;

Looks good.

Reviewed-by: Dave Chinner <[email protected]>

--
Dave Chinner
[email protected]