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Tue, 02 Jun 2020 07:49:17 +0000 Received: from b03ledav006.gho.boulder.ibm.com (b03ledav006.gho.boulder.ibm.com [9.17.130.237]) by b03cxnp08025.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0527nFjT17301764 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 2 Jun 2020 07:49:15 GMT Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9B5E9C605B; Tue, 2 Jun 2020 07:49:16 +0000 (GMT) Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3CB78C6057; Tue, 2 Jun 2020 07:49:13 +0000 (GMT) Received: from skywalker.ibmuc.com (unknown [9.199.34.130]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTP; Tue, 2 Jun 2020 07:49:12 +0000 (GMT) From: "Aneesh Kumar K.V" To: linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au, linux-nvdimm@lists.01.org, dan.j.williams@intel.com Subject: [RFC PATCH v2 1/5] libnvdimm/dax: Add a dax flag to control synchronous fault support Date: Tue, 2 Jun 2020 13:19:05 +0530 Message-Id: <20200602074909.36738-1-aneesh.kumar@linux.ibm.com> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216, 18.0.687 definitions=2020-06-02_08:2020-06-01, 2020-06-02 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxscore=0 suspectscore=0 cotscore=-2147483648 mlxlogscore=900 phishscore=0 lowpriorityscore=0 clxscore=1015 bulkscore=0 spamscore=0 adultscore=0 malwarescore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006020043 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jan Kara , Jeff Moyer , msuchanek@suse.de, oohall@gmail.com, "Aneesh Kumar K.V" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" With POWER10, architecture is adding new pmem flush and sync instructions. The kernel should prevent the usage of MAP_SYNC if applications are not using the new instructions on newer hardware This patch adds a dax attribute (/sys/bus/nd/devices/region0/pfn0.1/block/pmem0/dax/sync_fault) which can be used to control this flag. If the device supports synchronous flush then userspace can update this attribute to enable/disable the synchronous fault. The attribute is only visible if there is write cache enabled on the device. Signed-off-by: Aneesh Kumar K.V --- drivers/dax/super.c | 73 ++++++++++++++++++++++++++++++++++++++++++++- mm/Kconfig | 3 ++ 2 files changed, 75 insertions(+), 1 deletion(-) diff --git a/drivers/dax/super.c b/drivers/dax/super.c index 8e32345be0f7..980f7be7e56d 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -198,6 +198,12 @@ enum dax_device_flags { DAXDEV_WRITE_CACHE, /* flag to check if device supports synchronous flush */ DAXDEV_SYNC, + /* + * flag to indicate whether synchronous flush is enabled. + * Some platform may want to disable synchronous flush support + * even though device supports the same. + */ + DAXDEV_SYNC_ENABLED, }; /** @@ -254,6 +260,60 @@ static ssize_t write_cache_store(struct device *dev, } static DEVICE_ATTR_RW(write_cache); +static bool dax_synchronous_enabled(struct dax_device *dax_dev) +{ + return test_bit(DAXDEV_SYNC_ENABLED, &dax_dev->flags); +} + +static void set_dax_synchronous_enable(struct dax_device *dax_dev, bool enable) +{ + if (!test_bit(DAXDEV_SYNC, &dax_dev->flags)) + return; + + if (enable) + set_bit(DAXDEV_SYNC_ENABLED, &dax_dev->flags); + else + clear_bit(DAXDEV_SYNC_ENABLED, &dax_dev->flags); +} + + +static ssize_t sync_fault_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct dax_device *dax_dev = dax_get_by_host(dev_name(dev)); + ssize_t rc; + + WARN_ON_ONCE(!dax_dev); + if (!dax_dev) + return -ENXIO; + + rc = sprintf(buf, "%d\n", !!__dax_synchronous(dax_dev)); + put_dax(dax_dev); + return rc; +} + +static ssize_t sync_fault_store(struct device *dev, + struct device_attribute *attr, const char *buf, size_t len) +{ + bool enable_sync; + int rc = strtobool(buf, &enable_sync); + struct dax_device *dax_dev = dax_get_by_host(dev_name(dev)); + + WARN_ON_ONCE(!dax_dev); + if (!dax_dev) + return -ENXIO; + + if (rc) + len = rc; + else + set_dax_synchronous_enable(dax_dev, enable_sync); + + put_dax(dax_dev); + return len; +} + +static DEVICE_ATTR_RW(sync_fault); + static umode_t dax_visible(struct kobject *kobj, struct attribute *a, int n) { struct device *dev = container_of(kobj, typeof(*dev), kobj); @@ -267,11 +327,18 @@ static umode_t dax_visible(struct kobject *kobj, struct attribute *a, int n) if (a == &dev_attr_write_cache.attr) return 0; #endif + if (a == &dev_attr_sync_fault.attr) { + if (dax_write_cache_enabled(dax_dev)) + return a->mode; + return 0; + } + return a->mode; } static struct attribute *dax_attributes[] = { &dev_attr_write_cache.attr, + &dev_attr_sync_fault.attr, NULL, }; @@ -394,13 +461,17 @@ EXPORT_SYMBOL_GPL(dax_write_cache_enabled); bool __dax_synchronous(struct dax_device *dax_dev) { - return test_bit(DAXDEV_SYNC, &dax_dev->flags); + return test_bit(DAXDEV_SYNC, &dax_dev->flags) && + test_bit(DAXDEV_SYNC_ENABLED, &dax_dev->flags); } EXPORT_SYMBOL_GPL(__dax_synchronous); void __set_dax_synchronous(struct dax_device *dax_dev) { set_bit(DAXDEV_SYNC, &dax_dev->flags); +#ifndef CONFIG_ARCH_MAP_SYNC_DISABLE + set_bit(DAXDEV_SYNC_ENABLED, &dax_dev->flags); +#endif } EXPORT_SYMBOL_GPL(__set_dax_synchronous); diff --git a/mm/Kconfig b/mm/Kconfig index c1acc34c1c35..38fd7cfbfca8 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -867,4 +867,7 @@ config ARCH_HAS_HUGEPD config MAPPING_DIRTY_HELPERS bool +config ARCH_MAP_SYNC_DISABLE + bool + endmenu -- 2.26.2