From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 269F4C433FE for ; Wed, 1 Dec 2021 16:44:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351613AbhLAQsK convert rfc822-to-8bit (ORCPT ); Wed, 1 Dec 2021 11:48:10 -0500 Received: from frasgout.his.huawei.com ([185.176.79.56]:4187 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351516AbhLAQqr (ORCPT ); Wed, 1 Dec 2021 11:46:47 -0500 Received: from fraeml714-chm.china.huawei.com (unknown [172.18.147.206]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4J44cN5KkYz67sj9; Thu, 2 Dec 2021 00:41:56 +0800 (CST) Received: from fraeml714-chm.china.huawei.com (10.206.15.33) by fraeml714-chm.china.huawei.com (10.206.15.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Wed, 1 Dec 2021 17:43:22 +0100 Received: from fraeml714-chm.china.huawei.com ([10.206.15.33]) by fraeml714-chm.china.huawei.com ([10.206.15.33]) with mapi id 15.01.2308.020; Wed, 1 Dec 2021 17:43:22 +0100 From: Roberto Sassu To: "deven.desai@linux.microsoft.com" , "corbet@lwn.net" , "axboe@kernel.dk" , "agk@redhat.com" , "snitzer@redhat.com" , "ebiggers@kernel.org" , "tytso@mit.edu" , "paul@paul-moore.com" , "eparis@redhat.com" , "jmorris@namei.org" , "serge@hallyn.com" CC: "jannh@google.com" , "dm-devel@redhat.com" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , "linux-fscrypt@vger.kernel.org" , "linux-audit@redhat.com" , "linux-security-module@vger.kernel.org" , "linux-integrity@vger.kernel.org" , "tusharsu@linux.microsoft.com" Subject: RE: [RFC][PATCH] device mapper: Add builtin function dm_get_status() Thread-Topic: [RFC][PATCH] device mapper: Add builtin function dm_get_status() Thread-Index: AQHX5tHI6VSZDPA0J0GM0KIP7fuaeKwd1ttw Date: Wed, 1 Dec 2021 16:43:21 +0000 Message-ID: <69abc43a0cba431ab2411c0442c873d9@huawei.com> References: <81d5e825-1ee2-8f6b-cd9d-07b0f8bd36d3@linux.microsoft.com> <20211201163708.3578176-1-roberto.sassu@huawei.com> In-Reply-To: <20211201163708.3578176-1-roberto.sassu@huawei.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.204.63.33] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Roberto Sassu > Sent: Wednesday, December 1, 2021 5:37 PM > Users of the device mapper driver might want to obtain a device status, > with status types defined in the status_type_t enumerator. > > If a function to get the status is exported by the device mapper, when > compiled as a module, it is not suitable to use by callers compiled builtin > in the kernel. > > Introduce the real function to get the status, _dm_get_status(), in the > device mapper module, and add the stub dm_get_status() in dm-builtin.c, so > that it can be invoked by builtin callers. > > The stub calls the real function if the device mapper is compiled builtin > or the module has been loaded. Calls to the real function are safely > disabled if the module is unloaded. The race condition is avoided by > incrementing the reference count of the module. > > _dm_get_status() invokes the status() method for each device mapper table, > which writes a string to the supplied buffer as output. The buffer might > contain multiple strings concatenated together. If there is not enough > space available, the string is truncated and a termination character is put > at the end. > > Signed-off-by: Roberto Sassu > --- > drivers/md/dm-builtin.c | 13 +++++++ > drivers/md/dm-core.h | 5 +++ > drivers/md/dm.c | 71 +++++++++++++++++++++++++++++++++++ > include/linux/device-mapper.h | 3 ++ > 4 files changed, 92 insertions(+) > > diff --git a/drivers/md/dm-builtin.c b/drivers/md/dm-builtin.c > index 8eb52e425141..cc1e9c27ab41 100644 > --- a/drivers/md/dm-builtin.c > +++ b/drivers/md/dm-builtin.c > @@ -47,3 +47,16 @@ void dm_kobject_release(struct kobject *kobj) > } > > EXPORT_SYMBOL(dm_kobject_release); > + > +dm_get_status_fn status_fn; > +EXPORT_SYMBOL(status_fn); > + > +ssize_t dm_get_status(dev_t dev, status_type_t type, const char > *target_name, > + u8 *buf, size_t buf_len) > +{ > + if (status_fn) > + return status_fn(dev, type, target_name, buf, buf_len); > + > + return -EOPNOTSUPP; > +} > +EXPORT_SYMBOL(dm_get_status); > diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h > index b855fef4f38a..6600ec260558 100644 > --- a/drivers/md/dm-core.h > +++ b/drivers/md/dm-core.h > @@ -259,4 +259,9 @@ extern atomic_t dm_global_event_nr; > extern wait_queue_head_t dm_global_eventq; > void dm_issue_global_event(void); > > +typedef ssize_t (*dm_get_status_fn)(dev_t dev, status_type_t type, > + const char *target_name, u8 *buf, > + size_t buf_len); > + > +extern dm_get_status_fn status_fn; > #endif > diff --git a/drivers/md/dm.c b/drivers/md/dm.c > index 662742a310cb..55e59a4e3661 100644 > --- a/drivers/md/dm.c > +++ b/drivers/md/dm.c > @@ -192,6 +192,74 @@ static unsigned dm_get_numa_node(void) > DM_NUMA_NODE, > num_online_nodes() - 1); > } > > +static ssize_t _dm_get_status(dev_t dev, status_type_t type, > + const char *target_name, u8 *buf, size_t buf_len) > +{ > + struct mapped_device *md; > + struct dm_table *table; > + u8 *buf_ptr = buf; > + ssize_t len, res = 0; > + int srcu_idx, num_targets, i; > + > + if (buf_len > INT_MAX) > + return -EINVAL; > + > + if (!buf_len) > + return buf_len; > + > + if (!try_module_get(THIS_MODULE)) > + return -EBUSY; > + > + md = dm_get_md(dev); > + if (!md) { > + res = -ENOENT; > + goto out_module; > + } > + > + table = dm_get_live_table(md, &srcu_idx); > + if (!table) { > + res = -ENOENT; > + goto out_md; > + } > + > + memset(buf, 0, buf_len); > + > + num_targets = dm_table_get_num_targets(table); > + > + for (i = 0; i < num_targets; i++) { > + struct dm_target *ti = dm_table_get_target(table, i); > + > + if (!ti) > + continue; > + > + if (target_name && strcmp(ti->type->name, target_name)) > + continue; > + > + if (!ti->type->status) > + continue; > + > + ti->type->status(ti, type, 0, buf_ptr, buf + buf_len - buf_ptr); > + > + if (!*buf_ptr) > + continue; > + > + len = strlen(buf_ptr); > + buf_ptr += len + 1; > + > + if (buf_ptr == buf + buf_len) > + break; > + > + res += len + 1; The line above before the check. Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Zhong Ronghua > + } > + > + dm_put_live_table(md, srcu_idx); > +out_md: > + dm_put(md); > +out_module: > + module_put(THIS_MODULE); > + return res; > +} > + > static int __init local_init(void) > { > int r; > @@ -275,6 +343,7 @@ static int __init dm_init(void) > goto bad; > } > > + status_fn = _dm_get_status; > return 0; > bad: > while (i--) > @@ -287,6 +356,8 @@ static void __exit dm_exit(void) > { > int i = ARRAY_SIZE(_exits); > > + status_fn = NULL; > + > while (i--) > _exits[i](); > > diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h > index a7df155ea49b..d97b296d3104 100644 > --- a/include/linux/device-mapper.h > +++ b/include/linux/device-mapper.h > @@ -487,6 +487,9 @@ int dm_report_zones(struct block_device *bdev, > sector_t start, sector_t sector, > struct dm_report_zones_args *args, unsigned int nr_zones); > #endif /* CONFIG_BLK_DEV_ZONED */ > > +ssize_t dm_get_status(dev_t dev, status_type_t type, const char > *target_name, > + u8 *buf, size_t buf_len); > + > /* > * Device mapper functions to parse and create devices specified by the > * parameter "dm-mod.create=" > -- > 2.32.0