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Subject: [PATCH 1/2] device-dax/kmem: Fix resource release
From:   Dan Williams <dan.j.williams@intel.com>
To:     linux-kernel@vger.kernel.org
Cc:     David Hildenbrand <david@redhat.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Pavel Tatashin <pasha.tatashin@soleen.com>,
        Brice Goglin <Brice.Goglin@inria.fr>,
        Dave Jiang <dave.jiang@intel.com>,
        Ira Weiny <ira.weiny@intel.com>, Jia He <justin.he@arm.com>,
        Joao Martins <joao.m.martins@oracle.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        akpm@linux-foundation.org, linux-nvdimm@lists.01.org,
        linux-mm@kvack.org
Date:   Wed, 14 Oct 2020 17:42:09 -0700
Message-ID: <160272252925.3136502.17220638073995895400.stgit@dwillia2-desk3.amr.corp.intel.com>
In-Reply-To: <160272252400.3136502.13635752844548960833.stgit@dwillia2-desk3.amr.corp.intel.com>
References: <160272252400.3136502.13635752844548960833.stgit@dwillia2-desk3.amr.corp.intel.com>
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Precedence: bulk

The conversion to request_mem_region() is broken because it assumes that
the range is marked busy prior to release. However, due to the way that
the kmem driver manipulates the IORESOURCE_BUSY flag (clears it to
let {add,remove}_memory() handle busy) it requires a manual
release_resource() to perform cleanup.

Given that the actual 'struct resource *' needs to be recalled, not just
the range, add that tracking to the kmem driver-data.

Reported-by: David Hildenbrand <david@redhat.com>
Fixes: 0513bd5bb114 ("device-dax/kmem: replace release_resource() with release_mem_region()")
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Brice Goglin <Brice.Goglin@inria.fr>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jia He <justin.he@arm.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/dax/kmem.c |   48 ++++++++++++++++++++++++++++++++++--------------
 1 file changed, 34 insertions(+), 14 deletions(-)

diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 6c933f2b604e..af04b6d1d263 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -35,11 +35,17 @@ static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r)
 	return 0;
 }
 
+struct dax_kmem_data {
+	const char *res_name;
+	struct resource *res[];
+};
+
 static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 {
 	struct device *dev = &dev_dax->dev;
+	struct dax_kmem_data *data;
+	int rc = -ENOMEM;
 	int i, mapped = 0;
-	char *res_name;
 	int numa_node;
 
 	/*
@@ -55,14 +61,17 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 		return -EINVAL;
 	}
 
-	res_name = kstrdup(dev_name(dev), GFP_KERNEL);
-	if (!res_name)
+	data = kzalloc(sizeof(*data) + sizeof(struct resource *) * dev_dax->nr_range, GFP_KERNEL);
+	if (!data)
 		return -ENOMEM;
 
+	data->res_name = kstrdup(dev_name(dev), GFP_KERNEL);
+	if (!data->res_name)
+		goto err_res_name;
+
 	for (i = 0; i < dev_dax->nr_range; i++) {
 		struct resource *res;
 		struct range range;
-		int rc;
 
 		rc = dax_kmem_range(dev_dax, i, &range);
 		if (rc) {
@@ -72,7 +81,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 		}
 
 		/* Region is permanently reserved if hotremove fails. */
-		res = request_mem_region(range.start, range_len(&range), res_name);
+		res = request_mem_region(range.start, range_len(&range), data->res_name);
 		if (!res) {
 			dev_warn(dev, "mapping%d: %#llx-%#llx could not reserve region\n",
 					i, range.start, range.end);
@@ -82,9 +91,10 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 			 */
 			if (mapped)
 				continue;
-			kfree(res_name);
-			return -EBUSY;
+			rc = -EBUSY;
+			goto err_request_mem;
 		}
+		data->res[i] = res;
 
 		/*
 		 * Set flags appropriate for System RAM.  Leave ..._BUSY clear
@@ -104,18 +114,25 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 		if (rc) {
 			dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
 					i, range.start, range.end);
-			release_mem_region(range.start, range_len(&range));
+			release_resource(res);
+			kfree(res);
+			data->res[i] = NULL;
 			if (mapped)
 				continue;
-			kfree(res_name);
-			return rc;
+			goto err_request_mem;
 		}
 		mapped++;
 	}
 
-	dev_set_drvdata(dev, res_name);
+	dev_set_drvdata(dev, data);
 
 	return 0;
+
+err_request_mem:
+	kfree(data->res_name);
+err_res_name:
+	kfree(data);
+	return rc;
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
@@ -123,7 +140,7 @@ static int dev_dax_kmem_remove(struct dev_dax *dev_dax)
 {
 	int i, success = 0;
 	struct device *dev = &dev_dax->dev;
-	const char *res_name = dev_get_drvdata(dev);
+	struct dax_kmem_data *data = dev_get_drvdata(dev);
 
 	/*
 	 * We have one shot for removing memory, if some memory blocks were not
@@ -142,7 +159,9 @@ static int dev_dax_kmem_remove(struct dev_dax *dev_dax)
 		rc = remove_memory(dev_dax->target_node, range.start,
 				range_len(&range));
 		if (rc == 0) {
-			release_mem_region(range.start, range_len(&range));
+			release_resource(data->res[i]);
+			kfree(data->res[i]);
+			data->res[i] = NULL;
 			success++;
 			continue;
 		}
@@ -153,7 +172,8 @@ static int dev_dax_kmem_remove(struct dev_dax *dev_dax)
 	}
 
 	if (success >= dev_dax->nr_range) {
-		kfree(res_name);
+		kfree(data->res_name);
+		kfree(data);
 		dev_set_drvdata(dev, NULL);
 	}