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Date:      Tue, 27 Aug 2024 22:09:31 +0100
From:      Jessica Clarke <jrtc27@freebsd.org>
To:        Mark Johnston <markj@FreeBSD.org>
Cc:        "src-committers@freebsd.org" <src-committers@FreeBSD.org>, "dev-commits-src-all@freebsd.org" <dev-commits-src-all@FreeBSD.org>, "dev-commits-src-main@freebsd.org" <dev-commits-src-main@FreeBSD.org>
Subject:   Re: git: fe66e4caf456 - main - rangelock: Disable cheat mode by default
Message-ID:  <9CF133C9-42AD-41EE-961E-FBD76DD5F592@freebsd.org>
In-Reply-To: <202408272038.47RKc6Ga049071@gitrepo.freebsd.org>
References:  <202408272038.47RKc6Ga049071@gitrepo.freebsd.org>

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On 27 Aug 2024, at 21:38, Mark Johnston <markj@FreeBSD.org> wrote:
>=20
> The branch main has been updated by markj:
>=20
> URL: =
https://cgit.FreeBSD.org/src/commit/?id=3Dfe66e4caf4561ee3349ad7a29cc99761=
08c3b04f
>=20
> commit fe66e4caf4561ee3349ad7a29cc9976108c3b04f
> Author:     Mark Johnston <markj@FreeBSD.org>
> AuthorDate: 2024-08-27 20:31:25 +0000
> Commit:     Mark Johnston <markj@FreeBSD.org>
> CommitDate: 2024-08-27 20:36:31 +0000
>=20
>    rangelock: Disable cheat mode by default
>=20
>    Cheat mode is incompatible with code which locks multiple ranges in =
the
>    same vnode, with at least one range being write-locked.  This can =
arise
>    in kern_copy_file_range().  Until that's handled somehow, avoid the
>    problem to make the fusefs tests stable.
>=20
>    PR:             281073
>    Fixes:          9ef425e560a9 ("rangelocks: add fast cheating mode")
>    Reviewed by:    kib
>    Differential Revision:  https://reviews.freebsd.org/D46457
> ---
> sys/kern/kern_rangelock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/sys/kern/kern_rangelock.c b/sys/kern/kern_rangelock.c
> index 14163dd1c782..38449f71a8b7 100644
> --- a/sys/kern/kern_rangelock.c
> +++ b/sys/kern/kern_rangelock.c
> @@ -66,7 +66,7 @@
>  * trylocks are same as normal locks but do not drain.
>  */
>=20
> -static int rangelock_cheat =3D 1;
> +static int rangelock_cheat =3D 0;

This probably deserves a comment for why it=E2=80=99s disabled/the risks =
of
enabling it, and/or some text in the sysctl description?

Jess

> SYSCTL_INT(_debug, OID_AUTO, rangelock_cheat, CTLFLAG_RWTUN,
>     &rangelock_cheat, 0,
>     "");




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