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charset="iso-2022-jp" Content-ID: <0526C214C792514280161EAE42CBE321@jpnprd01.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: nec.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: TY1PR01MB1852.jpnprd01.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0187b92f-08dd-451e-1084-08d8e1fdd4fb X-MS-Exchange-CrossTenant-originalarrivaltime: 08 Mar 2021 06:45:58.7615 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: e67df547-9d0d-4f4d-9161-51c6ed1f7d11 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: U1PWP6mu8kPoyx1O3woeEispJpV51Sjei304CBVph7/qNG1RRLqyZRNZRbWeh/Csn1jEDcvvUeEVVfJmy0m1dg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: TY1PR01MB1868 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 05, 2021 at 02:11:43PM -0800, Luck, Tony wrote: > This whole page table walking patch is trying to work around the > races caused by multiple calls to memory_failure() for the same > page. >=20 > Maybe better to just avoid the races. The comment right above > memory_failure says: >=20 > * Must run in process context (e.g. a work queue) with interrupts > * enabled and no spinlocks hold. >=20 > So it should be safe to grab and hold a mutex. See patch below. The mutex approach looks simpler and safer, so I'm fine with it. >=20 > -Tony >=20 > commit 8dd0dbe7d595e02647e9c2c76c03341a9f6bd7b9 > Author: Tony Luck > Date: Fri Mar 5 10:40:48 2021 -0800 >=20 > Use a mutex to avoid memory_failure() races >=20 > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index 24210c9bd843..c1509f4b565e 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -1381,6 +1381,8 @@ static int memory_failure_dev_pagemap(unsigned long= pfn, int flags, > return rc; > } > =20 > +static DEFINE_MUTEX(mf_mutex); > + > /** > * memory_failure - Handle memory failure of a page. > * @pfn: Page Number of the corrupted page > @@ -1424,12 +1426,18 @@ int memory_failure(unsigned long pfn, int flags) > return -ENXIO; > } > =20 > + mutex_lock(&mf_mutex); Is it better to take mutex before memory_failure_dev_pagemap() block? Or we don't have to protect against race for device memory? Thanks, Naoya Horiguchi=