libnvdimm: infrastructure for btt devices

NVDIMM namespaces, in addition to accepting "struct bio" based requests,
also have the capability to perform byte-aligned accesses.  By default
only the bio/block interface is used.  However, if another driver can
make effective use of the byte-aligned capability it can claim namespace
interface and use the byte-aligned ->rw_bytes() interface.

The BTT driver is the initial first consumer of this mechanism to allow
adding atomic sector update semantics to a pmem or blk namespace.  This
patch is the sysfs infrastructure to allow configuring a BTT instance
for a namespace.  Enabling that BTT and performing i/o is in a
subsequent patch.

Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 422 insertions, 0 deletions

diff --git a/drivers/nvdimm/btt_devs.c b/drivers/nvdimm/btt_devs.c
new file mode 100644
index 000000000000..effb70a88347
--- /dev/null
+++ b/drivers/nvdimm/btt_devs.c
@@ -0,0 +1,422 @@
+/*
+ * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#include <linux/blkdev.h>
+#include <linux/device.h>
+#include <linux/genhd.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include "nd-core.h"
+#include "btt.h"
+#include "nd.h"
+
+static void __nd_btt_detach_ndns(struct nd_btt *nd_btt)
+{
+	struct nd_namespace_common *ndns = nd_btt->ndns;
+
+	dev_WARN_ONCE(&nd_btt->dev, !mutex_is_locked(&ndns->dev.mutex)
+			|| ndns->claim != &nd_btt->dev,
+			"%s: invalid claim\n", __func__);
+	ndns->claim = NULL;
+	nd_btt->ndns = NULL;
+	put_device(&ndns->dev);
+}
+
+static void nd_btt_detach_ndns(struct nd_btt *nd_btt)
+{
+	struct nd_namespace_common *ndns = nd_btt->ndns;
+
+	if (!ndns)
+		return;
+	get_device(&ndns->dev);
+	device_lock(&ndns->dev);
+	__nd_btt_detach_ndns(nd_btt);
+	device_unlock(&ndns->dev);
+	put_device(&ndns->dev);
+}
+
+static bool __nd_btt_attach_ndns(struct nd_btt *nd_btt,
+		struct nd_namespace_common *ndns)
+{
+	if (ndns->claim)
+		return false;
+	dev_WARN_ONCE(&nd_btt->dev, !mutex_is_locked(&ndns->dev.mutex)
+			|| nd_btt->ndns,
+			"%s: invalid claim\n", __func__);
+	ndns->claim = &nd_btt->dev;
+	nd_btt->ndns = ndns;
+	get_device(&ndns->dev);
+	return true;
+}
+
+static bool nd_btt_attach_ndns(struct nd_btt *nd_btt,
+		struct nd_namespace_common *ndns)
+{
+	bool claimed;
+
+	device_lock(&ndns->dev);
+	claimed = __nd_btt_attach_ndns(nd_btt, ndns);
+	device_unlock(&ndns->dev);
+	return claimed;
+}
+
+static void nd_btt_release(struct device *dev)
+{
+	struct nd_region *nd_region = to_nd_region(dev->parent);
+	struct nd_btt *nd_btt = to_nd_btt(dev);
+
+	dev_dbg(dev, "%s\n", __func__);
+	nd_btt_detach_ndns(nd_btt);
+	ida_simple_remove(&nd_region->btt_ida, nd_btt->id);
+	kfree(nd_btt->uuid);
+	kfree(nd_btt);
+}
+
+static struct device_type nd_btt_device_type = {
+	.name = "nd_btt",
+	.release = nd_btt_release,
+};
+
+bool is_nd_btt(struct device *dev)
+{
+	return dev->type == &nd_btt_device_type;
+}
+EXPORT_SYMBOL(is_nd_btt);
+
+struct nd_btt *to_nd_btt(struct device *dev)
+{
+	struct nd_btt *nd_btt = container_of(dev, struct nd_btt, dev);
+
+	WARN_ON(!is_nd_btt(dev));
+	return nd_btt;
+}
+EXPORT_SYMBOL(to_nd_btt);
+
+static const unsigned long btt_lbasize_supported[] = { 512, 4096, 0 };
+
+static ssize_t sector_size_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct nd_btt *nd_btt = to_nd_btt(dev);
+
+	return nd_sector_size_show(nd_btt->lbasize, btt_lbasize_supported, buf);
+}
+
+static ssize_t sector_size_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct nd_btt *nd_btt = to_nd_btt(dev);
+	ssize_t rc;
+
+	device_lock(dev);
+	nvdimm_bus_lock(dev);
+	rc = nd_sector_size_store(dev, buf, &nd_btt->lbasize,
+			btt_lbasize_supported);
+	dev_dbg(dev, "%s: result: %zd wrote: %s%s", __func__,
+			rc, buf, buf[len - 1] == '\n' ? "" : "\n");
+	nvdimm_bus_unlock(dev);
+	device_unlock(dev);
+
+	return rc ? rc : len;
+}
+static DEVICE_ATTR_RW(sector_size);
+
+static ssize_t uuid_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct nd_btt *nd_btt = to_nd_btt(dev);
+
+	if (nd_btt->uuid)
+		return sprintf(buf, "%pUb\n", nd_btt->uuid);
+	return sprintf(buf, "\n");
+}
+
+static ssize_t uuid_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct nd_btt *nd_btt = to_nd_btt(dev);
+	ssize_t rc;
+
+	device_lock(dev);
+	rc = nd_uuid_store(dev, &nd_btt->uuid, buf, len);
+	dev_dbg(dev, "%s: result: %zd wrote: %s%s", __func__,
+			rc, buf, buf[len - 1] == '\n' ? "" : "\n");
+	device_unlock(dev);
+
+	return rc ? rc : len;
+}
+static DEVICE_ATTR_RW(uuid);
+
+static ssize_t namespace_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct nd_btt *nd_btt = to_nd_btt(dev);
+	ssize_t rc;
+
+	nvdimm_bus_lock(dev);
+	rc = sprintf(buf, "%s\n", nd_btt->ndns
+			? dev_name(&nd_btt->ndns->dev) : "");
+	nvdimm_bus_unlock(dev);
+	return rc;
+}
+
+static int namespace_match(struct device *dev, void *data)
+{
+	char *name = data;
+
+	return strcmp(name, dev_name(dev)) == 0;
+}
+
+static bool is_nd_btt_idle(struct device *dev)
+{
+	struct nd_region *nd_region = to_nd_region(dev->parent);
+	struct nd_btt *nd_btt = to_nd_btt(dev);
+
+	if (nd_region->btt_seed == dev || nd_btt->ndns || dev->driver)
+		return false;
+	return true;
+}
+
+static ssize_t __namespace_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct nd_btt *nd_btt = to_nd_btt(dev);
+	struct nd_namespace_common *ndns;
+	struct device *found;
+	char *name;
+
+	if (dev->driver) {
+		dev_dbg(dev, "%s: -EBUSY\n", __func__);
+		return -EBUSY;
+	}
+
+	name = kstrndup(buf, len, GFP_KERNEL);
+	if (!name)
+		return -ENOMEM;
+	strim(name);
+
+	if (strncmp(name, "namespace", 9) == 0 || strcmp(name, "") == 0)
+		/* pass */;
+	else {
+		len = -EINVAL;
+		goto out;
+	}
+
+	ndns = nd_btt->ndns;
+	if (strcmp(name, "") == 0) {
+		/* detach the namespace and destroy / reset the btt device */
+		nd_btt_detach_ndns(nd_btt);
+		if (is_nd_btt_idle(dev))
+			nd_device_unregister(dev, ND_ASYNC);
+		else {
+			nd_btt->lbasize = 0;
+			kfree(nd_btt->uuid);
+			nd_btt->uuid = NULL;
+		}
+		goto out;
+	} else if (ndns) {
+		dev_dbg(dev, "namespace already set to: %s\n",
+				dev_name(&ndns->dev));
+		len = -EBUSY;
+		goto out;
+	}
+
+	found = device_find_child(dev->parent, name, namespace_match);
+	if (!found) {
+		dev_dbg(dev, "'%s' not found under %s\n", name,
+				dev_name(dev->parent));
+		len = -ENODEV;
+		goto out;
+	}
+
+	ndns = to_ndns(found);
+	if (__nvdimm_namespace_capacity(ndns) < SZ_16M) {
+		dev_dbg(dev, "%s too small to host btt\n", name);
+		len = -ENXIO;
+		goto out_attach;
+	}
+
+	WARN_ON_ONCE(!is_nvdimm_bus_locked(&nd_btt->dev));
+	if (!nd_btt_attach_ndns(nd_btt, ndns)) {
+		dev_dbg(dev, "%s already claimed\n",
+				dev_name(&ndns->dev));
+		len = -EBUSY;
+	}
+
+ out_attach:
+	put_device(&ndns->dev); /* from device_find_child */
+ out:
+	kfree(name);
+	return len;
+}
+
+static ssize_t namespace_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	ssize_t rc;
+
+	nvdimm_bus_lock(dev);
+	device_lock(dev);
+	rc = __namespace_store(dev, attr, buf, len);
+	dev_dbg(dev, "%s: result: %zd wrote: %s%s", __func__,
+			rc, buf, buf[len - 1] == '\n' ? "" : "\n");
+	device_unlock(dev);
+	nvdimm_bus_unlock(dev);
+
+	return rc;
+}
+static DEVICE_ATTR_RW(namespace);
+
+static struct attribute *nd_btt_attributes[] = {
+	&dev_attr_sector_size.attr,
+	&dev_attr_namespace.attr,
+	&dev_attr_uuid.attr,
+	NULL,
+};
+
+static struct attribute_group nd_btt_attribute_group = {
+	.attrs = nd_btt_attributes,
+};
+
+static const struct attribute_group *nd_btt_attribute_groups[] = {
+	&nd_btt_attribute_group,
+	&nd_device_attribute_group,
+	NULL,
+};
+
+static struct device *__nd_btt_create(struct nd_region *nd_region,
+		unsigned long lbasize, u8 *uuid,
+		struct nd_namespace_common *ndns)
+{
+	struct nd_btt *nd_btt;
+	struct device *dev;
+
+	nd_btt = kzalloc(sizeof(*nd_btt), GFP_KERNEL);
+	if (!nd_btt)
+		return NULL;
+
+	nd_btt->id = ida_simple_get(&nd_region->btt_ida, 0, 0, GFP_KERNEL);
+	if (nd_btt->id < 0) {
+		kfree(nd_btt);
+		return NULL;
+	}
+
+	nd_btt->lbasize = lbasize;
+	if (uuid)
+		uuid = kmemdup(uuid, 16, GFP_KERNEL);
+	nd_btt->uuid = uuid;
+	dev = &nd_btt->dev;
+	dev_set_name(dev, "btt%d.%d", nd_region->id, nd_btt->id);
+	dev->parent = &nd_region->dev;
+	dev->type = &nd_btt_device_type;
+	dev->groups = nd_btt_attribute_groups;
+	device_initialize(&nd_btt->dev);
+	if (ndns && !__nd_btt_attach_ndns(nd_btt, ndns)) {
+		dev_dbg(&ndns->dev, "%s failed, already claimed by %s\n",
+				__func__, dev_name(ndns->claim));
+		put_device(dev);
+		return NULL;
+	}
+	return dev;
+}
+
+struct device *nd_btt_create(struct nd_region *nd_region)
+{
+	struct device *dev = __nd_btt_create(nd_region, 0, NULL, NULL);
+
+	if (dev)
+		__nd_device_register(dev);
+	return dev;
+}
+
+/*
+ * nd_btt_sb_checksum: compute checksum for btt info block
+ *
+ * Returns a fletcher64 checksum of everything in the given info block
+ * except the last field (since that's where the checksum lives).
+ */
+u64 nd_btt_sb_checksum(struct btt_sb *btt_sb)
+{
+	u64 sum, sum_save;
+
+	sum_save = btt_sb->checksum;
+	btt_sb->checksum = 0;
+	sum = nd_fletcher64(btt_sb, sizeof(*btt_sb), 1);
+	btt_sb->checksum = sum_save;
+	return sum;
+}
+EXPORT_SYMBOL(nd_btt_sb_checksum);
+
+static int __nd_btt_probe(struct nd_btt *nd_btt,
+		struct nd_namespace_common *ndns, struct btt_sb *btt_sb)
+{
+	u64 checksum;
+
+	if (!btt_sb || !ndns || !nd_btt)
+		return -ENODEV;
+
+	if (nvdimm_read_bytes(ndns, SZ_4K, btt_sb, sizeof(*btt_sb)))
+		return -ENXIO;
+
+	if (nvdimm_namespace_capacity(ndns) < SZ_16M)
+		return -ENXIO;
+
+	if (memcmp(btt_sb->signature, BTT_SIG, BTT_SIG_LEN) != 0)
+		return -ENODEV;
+
+	checksum = le64_to_cpu(btt_sb->checksum);
+	btt_sb->checksum = 0;
+	if (checksum != nd_btt_sb_checksum(btt_sb))
+		return -ENODEV;
+	btt_sb->checksum = cpu_to_le64(checksum);
+
+	nd_btt->lbasize = le32_to_cpu(btt_sb->external_lbasize);
+	nd_btt->uuid = kmemdup(btt_sb->uuid, 16, GFP_KERNEL);
+	if (!nd_btt->uuid)
+		return -ENOMEM;
+
+	__nd_device_register(&nd_btt->dev);
+
+	return 0;
+}
+
+int nd_btt_probe(struct nd_namespace_common *ndns, void *drvdata)
+{
+	int rc;
+	struct device *dev;
+	struct btt_sb *btt_sb;
+	struct nd_region *nd_region = to_nd_region(ndns->dev.parent);
+
+	if (ndns->force_raw)
+		return -ENODEV;
+
+	nvdimm_bus_lock(&ndns->dev);
+	dev = __nd_btt_create(nd_region, 0, NULL, ndns);
+	nvdimm_bus_unlock(&ndns->dev);
+	if (!dev)
+		return -ENOMEM;
+	dev_set_drvdata(dev, drvdata);
+	btt_sb = kzalloc(sizeof(*btt_sb), GFP_KERNEL);
+	rc = __nd_btt_probe(to_nd_btt(dev), ndns, btt_sb);
+	kfree(btt_sb);
+	dev_dbg(&ndns->dev, "%s: btt: %s\n", __func__,
+			rc == 0 ? dev_name(dev) : "<none>");
+	if (rc < 0) {
+		__nd_btt_detach_ndns(to_nd_btt(dev));
+		put_device(dev);
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL(nd_btt_probe);