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Wed, 17 Feb 2021 09:18:37 +0000 From: Johannes Thumshirn To: Damien Le Moal , Michal Hocko CC: Dan Carpenter , "linux-scsi@vger.kernel.org" Subject: Re: [bug report] scsi: sd_zbc: emulate ZONE_APPEND commands Thread-Topic: [bug report] scsi: sd_zbc: emulate ZONE_APPEND commands Thread-Index: AQHXBJuZNMPC4HbBMEOENoattX2qog== Date: Wed, 17 Feb 2021 09:18:37 +0000 Message-ID: References: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: wdc.com; dkim=none (message not signed) header.d=none;wdc.com; dmarc=none action=none header.from=wdc.com; x-originating-ip: [2001:a62:1542:e101:1923:7af3:ae74:5873] x-ms-publictraffictype: Email x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 5b3d4648-4ede-4ad8-df80-08d8d325021b x-ms-traffictypediagnostic: SN6PR04MB3808: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:10000; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SN4PR0401MB3598.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5b3d4648-4ede-4ad8-df80-08d8d325021b X-MS-Exchange-CrossTenant-originalarrivaltime: 17 Feb 2021 09:18:37.4737 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: l0C8Sq/C5u2t2UIplR/QyuyEIpn+99Bkg0gzcbc9fUKMx89SBD1vx/+m6GNgXqBT95VA6IxteghXEYQoFK0mNmJCM1robFQPZxBi9JMQK+8= X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN6PR04MB3808 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On 17/02/2021 10:13, Damien Le Moal wrote:=0A= > On 2021/02/17 17:03, Michal Hocko wrote:=0A= >> On Wed 17-02-21 06:42:37, Johannes Thumshirn wrote:=0A= >>> On 17/02/2021 00:33, Damien Le Moal wrote:=0A= >>>> On 2021/02/17 4:42, Dan Carpenter wrote:=0A= >>>>> Hello Johannes Thumshirn,=0A= >>>>>=0A= >>>>> The patch 5795eb443060: "scsi: sd_zbc: emulate ZONE_APPEND commands"= =0A= >>>>> from May 12, 2020, leads to the following static checker warning:=0A= >>>>>=0A= >>>>> drivers/scsi/sd_zbc.c:741 sd_zbc_revalidate_zones()=0A= >>>>> error: kvmalloc() only makes sense with GFP_KERNEL=0A= >>>>>=0A= >>>>> drivers/scsi/sd_zbc.c=0A= >>>>> 721 /*=0A= >>>>> 722 * There is nothing to do for regular disks, includin= g host-aware disks=0A= >>>>> 723 * that have partitions.=0A= >>>>> 724 */=0A= >>>>> 725 if (!blk_queue_is_zoned(q))=0A= >>>>> 726 return 0;=0A= >>>>> 727 =0A= >>>>> 728 /*=0A= >>>>> 729 * Make sure revalidate zones are serialized to ensur= e exclusive=0A= >>>>> 730 * updates of the scsi disk data.=0A= >>>>> 731 */=0A= >>>>> 732 mutex_lock(&sdkp->rev_mutex);=0A= >>>>> 733 =0A= >>>>> 734 if (sdkp->zone_blocks =3D=3D zone_blocks &&=0A= >>>>> 735 sdkp->nr_zones =3D=3D nr_zones &&=0A= >>>>> 736 disk->queue->nr_zones =3D=3D nr_zones)=0A= >>>>> 737 goto unlock;=0A= >>>>> 738 =0A= >>>>> 739 sdkp->zone_blocks =3D zone_blocks;=0A= >>>>> 740 sdkp->nr_zones =3D nr_zones;=0A= >>>>> 741 sdkp->rev_wp_offset =3D kvcalloc(nr_zones, sizeof(u32= ), GFP_NOIO);=0A= >>>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^= ^^^^^^^^^^=0A= >>>>> We're passing GFP_NOIO here so it just defaults to kcalloc() and will= =0A= >>>>> not vmalloc() the memory.=0A= >>>>=0A= >>>> Indeed... And the allocation can get a little too big for kmalloc().= =0A= >>>>=0A= >>>> Johannes, I think we need to move that allocation before the rev_mutex= locking,=0A= >>>> using a local var for the allocated address, and then using GFP_KERNEL= should be=0A= >>>> safe... But not entirely sure. Using kmalloc would be simpler but on l= arge SMR=0A= >>>> drives, that allocation will soon need to be 400K or so (i.e. 100,000 = zones or=0A= >>>> even more), too large for kmalloc to succeed reliably.=0A= >>>>=0A= >>>=0A= >>>=0A= >>> No I don't think so. A mutex isn't a spinlock so we can sleep on the al= location.=0A= >>> We can't use GFP_KERNEL as we're about to do I/O. blk_revalidate_disk_z= ones() called=0A= >>> a few line below also does the memalloc_noio_{save,restore}() dance.=0A= >>=0A= >> You should be extending noio scope then if this allocation falls into=0A= >> the same category. Ideally the scope should start at the recursion place= =0A= >> and end where the scope really ened.=0A= > =0A= > But it does not look like __vmalloc_node() (fallback in kvmalloc_node() i= f=0A= > kmalloc() fails) cares about the context allocation flags... I can't see= =0A= > if/where the context allocation flags are taken into account. It looks li= ke only=0A= > the gfp_mask argument is used. Am I missing something ?=0A= =0A= =0A= It does here:=0A= =0A= void *kvmalloc_node(size_t size, gfp_t flags, int node) = = =0A= { = = =0A= gfp_t kmalloc_flags =3D flags; = = =0A= void *ret; = = =0A= = = =0A= /* = = =0A= * vmalloc uses GFP_KERNEL for some internal allocations (e.g page = tables) = =0A= * so the given set of flags has to be compatible. = = =0A= */ = = =0A= if ((flags & GFP_KERNEL) !=3D GFP_KERNEL) = = =0A= return kmalloc_node(size, flags, node);=0A= =0A= /* [...] */=0A= =0A= return __vmalloc_node(size, 1, flags, node, = = =0A= __builtin_return_address(0)); = = =0A= } = = =0A= EXPORT_SYMBOL(kvmalloc_node);=0A= =0A= We're not reaching __vmalloc_node() if GFP_KERNEL isn't set. Also, from the= , function's=0A= documentation:=0A= =0A= * @flags: gfp mask for the allocation - must be compatible (superset) with= GFP_KERNEL. = =0A= =0A= So yeah, we should've read that before calling kvcalloc(..., GFP_NOIO).=0A=