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Wed, 17 Nov 2021 10:15:43 +0000 Message-ID: <70f49eba-c1d9-817c-057f-501f58fb90a4@oracle.com> Date: Wed, 17 Nov 2021 11:15:31 +0100 Subject: Re: [PATCH v5 7/8] device-dax: ensure dev_dax->pgmap is valid for dynamic devices Content-Language: en-US To: Christoph Hellwig Cc: linux-mm@kvack.org, Dan Williams , Vishal Verma , Dave Jiang , Naoya Horiguchi , Matthew Wilcox , Jason Gunthorpe , John Hubbard , Jane Chu , Muchun Song , Mike Kravetz , Andrew Morton , Jonathan Corbet , nvdimm@lists.linux.dev, linux-doc@vger.kernel.org References: <20211112150824.11028-1-joao.m.martins@oracle.com> <20211112150824.11028-8-joao.m.martins@oracle.com> <20211117093733.GB8429@lst.de> From: Joao Martins In-Reply-To: <20211117093733.GB8429@lst.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AM0PR10CA0013.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:208:17c::23) To BLAPR10MB4835.namprd10.prod.outlook.com (2603:10b6:208:331::11) MIME-Version: 1.0 Received: from [10.175.34.134] (138.3.203.6) by AM0PR10CA0013.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:208:17c::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4713.20 via Frontend Transport; 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dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=S+CV3bqc; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=AmNgFPK3; dmarc=pass (policy=none) header.from=oracle.com; spf=none (imf27.hostedemail.com: domain of joao.m.martins@oracle.com has no SPF policy when checking 205.220.177.32) smtp.mailfrom=joao.m.martins@oracle.com X-HE-Tag: 1637144149-784583 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 11/17/21 10:37, Christoph Hellwig wrote: >> +bool static_dev_dax(struct dev_dax *dev_dax) >> +{ >> + return is_static(dev_dax->region); >> +} >> +EXPORT_SYMBOL_GPL(static_dev_dax); > > This function would massively benefit from documentic what a static > DAX region is and why someone would want to care. Because even as > someone occasionally dabbling with the DAX code I have no idea at all > what that means. > Good idea. Maybe something like this: diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c index 19dd83d3f3ea..8be6ec1ba193 100644 --- a/drivers/dax/bus.c +++ b/drivers/dax/bus.c @@ -129,6 +129,19 @@ ATTRIBUTE_GROUPS(dax_drv); static int dax_bus_match(struct device *dev, struct device_driver *drv); +/* + * Static dax regions (PMEM) are regions partitioned by an external entity like + * nvdimm where a single range is assigned and which boundaries are + * defined by NVDIMM Namespace boundaries (e.g. need to be contiguous). + * Dynamic dax regions (HMEM), the assigned region can be subdivided by dax + * core into multiple devices (i.e. "partitions") which are composed with 1 or + * more discontiguous ranges. + * When allocating a dax region, drivers must set whether it's static. + * On static dax devices, the @pgmap is pre-assigned to dax when calling + * devm_create_dev_dax(), whereas in dynamic dax devices it is allocated + * on device ->probe(). Care is needed to make sure that non static devices + * are killed with a cleared @pgmap field (see kill_dev_dax()). + */ static bool is_static(struct dax_region *dax_region) { return (dax_region->res.flags & IORESOURCE_DAX_STATIC) != 0;