Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.38 as permitted sender) client-ip=23.128.96.38;
From:   Daniel Gomez <da.gomez@samsung.com>
To:     Matthew Wilcox <willy@infradead.org>
CC:     "minchan@kernel.org" <minchan@kernel.org>,
        "senozhatsky@chromium.org" <senozhatsky@chromium.org>,
        "axboe@kernel.dk" <axboe@kernel.dk>,
        "djwong@kernel.org" <djwong@kernel.org>,
        "hughd@google.com" <hughd@google.com>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "mcgrof@kernel.org" <mcgrof@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "gost.dev@samsung.com" <gost.dev@samsung.com>,
        Pankaj Raghav <p.raghav@samsung.com>
Subject: Re: [RFC PATCH 01/11] XArray: add cmpxchg order test
Thread-Topic: [RFC PATCH 01/11] XArray: add cmpxchg order test
Thread-Index: AQHaCePk2/Onfe3eA0ia1dQGCoKrA7BhNHAAgAgOVAA=
Date:   Fri, 3 Nov 2023 23:12:58 +0000
Message-ID: <20231103231254.bytltpzsc2qojlbw@sarkhan>
In-Reply-To: <ZT68dBiJKNLXLRZA@casper.infradead.org>
Accept-Language: en-US, en-GB
Content-Language: en-US
x-ms-exchange-messagesentrepresentingtype: 1
x-ms-exchange-transport-fromentityheader: Hosted
x-originating-ip: [106.110.32.103]
Content-Type: text/plain; charset="us-ascii"
Content-ID: <BE63A8201D5D3541A51BCEF17F33D0F1@scsc.local>
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrKKsWRmVeSWpSXmKPExsWy7djP87o1da6pBtNnW1nMWb+GzWL13X42
        i8tP+Cyefupjsdh7S9tiz96TLBaXd81hs7i35j+rxa4/O9gtbkx4ymix7Ot7dovdGxexWfz+
        MYfNgddjdsNFFo8Fm0o9Nq/Q8rh8ttRj06pONo9Nnyaxe5yY8ZvF4/MmuQCOKC6blNSczLLU
        In27BK6MzUd3Mxac5anY13GcsYFxJVcXIyeHhICJxInn79i6GLk4hARWMErs3HedBcL5wijR
        On8KE4TzmVHi9IJnLDAtzy/1MYLYQgLLGSXObGWCsIGKjn2Og2g4zShx99p9Jri5M+/sYwOp
        YhPQlNh3chN7FyMHh4iAhsSbLUYgNcwCR1kllqzdBLZBWMBWYv3WOcwgtoiAncTDWy/ZIWwr
        iVdfroPVsAioSLzY/hOshlfAVGLOtMVgNZxA1y3d/gnsIkYBWYlHK3+BxZkFxCVuPZnPBPGB
        oMSi2XuYIWwxiX+7HrJB2DoSZ68/YYSwDSS2Lt0H9bGSxJ+OhYwQc3QkFuz+xAZhW0o0nPwM
        FdeWWLbwNdQ9ghInZz4Bh6OEwFQuibVL50Etc5E4enA31BHCEq+Ob2GfwKgzC8l9s5DsmIVk
        xywkO2Yh2bGAkXUVo3hqaXFuemqxYV5quV5xYm5xaV66XnJ+7iZGYMo7/e/4px2Mc1991DvE
        yMTBeIhRgoNZSYTX0dslVYg3JbGyKrUoP76oNCe1+BCjNAeLkjivaop8qpBAemJJanZqakFq
        EUyWiYNTqoFJe/1Fy0W1vvNvn9m0sGwBX8O6OKlXSb+bhBRXbS+r/nhon/n38A1qr2PWCq1w
        eZuqWvJZVkc5+YTPWhuJW29FvPzu5ZWuUZ/7mn8Jr9wRjYfFfZpF7y8d61ycv1xqwS82xlVz
        jncdVwnd28jsLML86kjEG8t/ouK1z2P1RduT7Hu8czIPHV/049J81uW+HaumKMYkLryRa5hl
        XRY2WTX7Zvz6M/6X1/1o6blpXft3Y07ywstBt1bf+v00jvlIzIJ1c580/5K2O+Gw+XBbtoCu
        3by/b489++N7XzzMb4pkRY7AlLNp0Ukv2kzTbY0Odl5TK4z89vTJrh3FJrPbPl2Rtd21s8N5
        55sfMV3MPB5cSizFGYmGWsxFxYkAjGb8Z+gDAAA=
X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrPKsWRmVeSWpSXmKPExsVy+t/xe7rVda6pBj1ztCzmrF/DZrH6bj+b
        xeUnfBZPP/WxWOy9pW2xZ+9JFovLu+awWdxb85/VYtefHewWNyY8ZbRY9vU9u8XujYvYLH7/
        mMPmwOsxu+Eii8eCTaUem1doeVw+W+qxaVUnm8emT5PYPU7M+M3i8XmTXABHlJ5NUX5pSapC
        Rn5xia1StKGFkZ6hpYWekYmlnqGxeayVkamSvp1NSmpOZllqkb5dgl7G5qO7GQvO8lTs6zjO
        2MC4kquLkZNDQsBE4vmlPsYuRi4OIYGljBInzsxjhEjISGz8cpUVwhaW+HOtiw2i6COjxPPJ
        21kgnNOMErP/XYPKrGCU6J/+kR2khU1AU2LfyU1ANgeHiICGxJstRiA1zAJHWSWWrN3EAlIj
        LGArsX7rHGYQW0TATuLhrZfsELaVxKsv18FqWARUJF5s/wlWwytgKjFn2mJ2iGVzmSTu/V4D
        luAEemLp9k9MIDajgKzEo5W/wAYxC4hL3HoynwniBwGJJXvOM0PYohIvH/+D+k1H4uz1J1A/
        G0hsXbqPBcJWkvjTsZARYo6OxILdn9ggbEuJhpOfoeLaEssWvoY6TlDi5MwnLBMYZWYhWT0L
        SfssJO2zkLTPQtK+gJF1FaNIamlxbnpusaFecWJucWleul5yfu4mRmBK23bs5+YdjPNefdQ7
        xMjEwXiIUYKDWUmE19HbJVWINyWxsiq1KD++qDQntfgQoykw8CYyS4km5wOTal5JvKGZgamh
        iZmlgamlmbGSOK9nQUeikEB6YklqdmpqQWoRTB8TB6dUA1O6tFrHju1ue1rd91ewfJFm2DIr
        SUL3Qctk7RUJ995WNb3ewfrr8O1eg/pEftWEjzqnNzUb3lVbJGAoeVv4yimVgs+tZWVb/299
        uZVhIvOnDse8ZGmfZRMDG0PzL8+M0d9+89ix+SzvGUqjmK6efXHmynkP2XkCW97HBDh2Seuf
        cv9o9Tn2/6xnZ5/X/Jv2Rscq+U2b4ZHlCxy3as/2MZp5V+HGXVMedpvPujeUilremL5k/HBH
        aYbB/ijmMw6zI61Y3IMqWe5Gsr2M2sJQnXjEvGF52AG7Nyfs3ef9NeXdvG1DduusvZ2sUtfj
        75Z6frBnenpb7Emiwdsz7Rb9J3st3v5b/jC7O2uZFrPo70dKLMUZiYZazEXFiQChzl1/8gMA
        AA==
X-CMS-MailID: 20231103231259eucas1p18e529693e4b47b5e0623271bf319a25f
X-Msg-Generator: CA
X-RootMTR: 20231028211538eucas1p186e33f92dbea7030f14f7f79aa1b8d54
X-EPHeader: CA
CMS-TYPE: 201P
X-CMS-RootMailID: 20231028211538eucas1p186e33f92dbea7030f14f7f79aa1b8d54
References: <20230919135536.2165715-1-da.gomez@samsung.com>
        <20231028211518.3424020-1-da.gomez@samsung.com>
        <CGME20231028211538eucas1p186e33f92dbea7030f14f7f79aa1b8d54@eucas1p1.samsung.com>
        <20231028211518.3424020-2-da.gomez@samsung.com>
        <ZT68dBiJKNLXLRZA@casper.infradead.org>
X-Spam-Status: No, score=-1.3 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE
	autolearn=unavailable autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on fry.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (fry.vger.email [0.0.0.0]); Fri, 03 Nov 2023 16:13:30 -0700 (PDT)

On Sun, Oct 29, 2023 at 08:11:32PM +0000, Matthew Wilcox wrote:
> On Sat, Oct 28, 2023 at 09:15:35PM +0000, Daniel Gomez wrote:
> > +static noinline void check_cmpxchg_order(struct xarray *xa)
> > +{
> > +	void *FIVE =3D xa_mk_value(5);
> > +	unsigned int order =3D IS_ENABLED(CONFIG_XARRAY_MULTI) ? 15 : 1;
>
> ... have you tried this with CONFIG_XARRAY_MULTI deselected?
> I suspect it will BUG() because orders greater than 0 are not allowed.
>
> > +	XA_BUG_ON(xa, !xa_empty(xa));
> > +	XA_BUG_ON(xa, xa_store_index(xa, 5, GFP_KERNEL) !=3D NULL);
> > +	XA_BUG_ON(xa, xa_insert(xa, 5, FIVE, GFP_KERNEL) !=3D -EBUSY);
> > +	XA_BUG_ON(xa, xa_store_order(xa, 5, order, FIVE, GFP_KERNEL));
> > +	XA_BUG_ON(xa, xa_get_order(xa, 5) !=3D order);
> > +	XA_BUG_ON(xa, xa_get_order(xa, xa_to_value(FIVE)) !=3D order);
> > +	old =3D xa_cmpxchg(xa, 5, FIVE, NULL, GFP_KERNEL);
> > +	XA_BUG_ON(xa, old !=3D FIVE);
> > +	XA_BUG_ON(xa, xa_get_order(xa, 5) !=3D 0);
> > +	XA_BUG_ON(xa, xa_get_order(xa, xa_to_value(FIVE)) !=3D 0);
> > +	XA_BUG_ON(xa, xa_get_order(xa, xa_to_value(old)) !=3D 0);
> > +	XA_BUG_ON(xa, !xa_empty(xa));
>
> I'm not sure this is a great test.  It definitely does do what you claim
> it will, but for example, it's possible that we might keep that
> information for other orders.  So maybe we should have another entry at
> (1 << order) that keeps the node around and could theoretically keep
> the order information around for the now-NULL entry?

Thanks Matthew for the review. I'm sending a separate patch with the
fixes and improvements on the XArray cmpxchg test.=