[PATCH v2] osdblk: a Linux block device for OSD objects

[Jeff Garzik]

This is a client for libosd.  This block driver exports a single OSD
object as a Linux block device.

See the comment block at the top of the driver for usage instructions.

The major remaining pre-merge FIXME is its handling of bio's, as pointed
out by Jens.  This perhaps requires looking at libosd, and a bit of
discussion w/ Boaz and crew.

Not-yet-signed-off-by: me

---
Other changes since last posting:
- use strict_strtoul (akpm review)
- add barrier support, and issue OSD flush requests
- replace global array of devices with linked list (jejb review)
- fix OSD credentials (boaz rev)
- use block layer tagging (jejb rev)
- use GFP_ATOMIC rather than GFP_NOIO (axboe rev)
- improve comments
- module refcounting

 drivers/block/Kconfig  |   16 +
 drivers/block/Makefile |    1 
 drivers/block/osdblk.c |  630 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 647 insertions(+)

diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index ddea8e4..34722c8 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -298,6 +298,22 @@ config BLK_DEV_NBD
 
 	  If unsure, say N.
 
+config BLK_DEV_OSD
+	tristate "OSD object-as-blkdev support"
+	depends on SCSI_OSD_INITIATOR
+	---help---
+	  Saying Y or M here will allow the exporting of a single SCSI
+	  OSD (object-based storage) object as a Linux block device.
+
+	  For example, if you create a 2G object on an OSD device,
+	  you can then use this module to present that 2G object as
+	  a Linux block device.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called osdblk.
+
+	  If unsure, say N.
+
 config BLK_DEV_SX8
 	tristate "Promise SATA SX8 support"
 	depends on PCI
diff --git a/drivers/block/Makefile b/drivers/block/Makefile
index 7755a5e..cdaa3f8 100644
--- a/drivers/block/Makefile
+++ b/drivers/block/Makefile
@@ -23,6 +23,7 @@ obj-$(CONFIG_XILINX_SYSACE)	+= xsysace.o
 obj-$(CONFIG_CDROM_PKTCDVD)	+= pktcdvd.o
 obj-$(CONFIG_MG_DISK)		+= mg_disk.o
 obj-$(CONFIG_SUNVDC)		+= sunvdc.o
+obj-$(CONFIG_BLK_DEV_OSD)	+= osdblk.o
 
 obj-$(CONFIG_BLK_DEV_UMEM)	+= umem.o
 obj-$(CONFIG_BLK_DEV_NBD)	+= nbd.o
diff --git a/drivers/block/osdblk.c b/drivers/block/osdblk.c
new file mode 100644
index 0000000..645ccc6
--- /dev/null
+++ b/drivers/block/osdblk.c
@@ -0,0 +1,630 @@
+
+/*
+   osdblk.c -- Export a single SCSI OSD object as a Linux block device
+
+
+   Copyright 2009 Red Hat, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms 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.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+
+   Instructions for use
+   --------------------
+
+   1) Map a Linux block device to an existing OSD object.
+
+      In this example, we will use partition id 1234, object id 5678,
+      OSD device /dev/osd1.
+
+      $ echo "1234 5678 /dev/osd1" > /sys/class/osdblk/add
+
+
+   2) List all active blkdev<->object mappings.
+
+      In this example, we have performed step #1 twice, creating two blkdevs,
+      mapped to two separate OSD objects.
+
+      $ cat /sys/class/osdblk/list
+      0 174 1234 5678 /dev/osd1
+      1 179 1994 897123 /dev/osd0
+
+      The columns, in order, are:
+      - blkdev unique id
+      - blkdev assigned major
+      - OSD object partition id
+      - OSD object id
+      - OSD device
+
+
+   3) Remove an active blkdev<->object mapping.
+
+      In this example, we remove the mapping with blkdev unique id 1.
+
+      $ echo 1 > /sys/class/osdblk/remove
+
+
+   NOTE:  The actual creation and deletion of OSD objects is outside the scope
+   of this driver.
+
+ */
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <scsi/osd_initiator.h>
+#include <scsi/osd_attributes.h>
+#include <scsi/osd_sec.h>
+
+#define DRV_NAME "osdblk"
+#define PFX DRV_NAME ": "
+
+struct osdblk_device;
+
+enum {
+	OSDBLK_MINORS_PER_MAJOR	= 256,		/* max minors per blkdev */
+	OSDBLK_MAX_REQ		= 32,		/* max parallel requests */
+	OSDBLK_OP_TIMEOUT	= 4 * 60,	/* sync OSD req timeout */
+};
+
+struct osdblk_request {
+	struct request		*rq;		/* blk layer request */
+	struct bio		*bio;		/* cloned bio */
+	struct osdblk_device	*osdev;		/* associated blkdev */
+};
+
+struct osdblk_device {
+	int			id;		/* blkdev unique id */
+
+	int			major;		/* blkdev assigned major */
+	struct gendisk		*disk;		/* blkdev's gendisk and rq */
+	struct request_queue	*q;
+
+	struct osd_dev		*osd;		/* associated OSD */
+
+	char			name[32];	/* blkdev name, e.g. osdblk34 */
+
+	spinlock_t		lock;		/* queue lock */
+
+	struct osd_obj_id	obj;		/* OSD partition, obj id */
+	uint8_t			obj_cred[OSD_CAP_LEN]; /* OSD cred */
+
+	struct osdblk_request	req[OSDBLK_MAX_REQ]; /* request table */
+
+	struct list_head	node;
+
+	char			osd_path[0];	/* OSD device path */
+};
+
+static struct class *class_osdblk;		/* /sys/class/osdblk */
+static struct mutex ctl_mutex;	/* Serialize open/close/setup/teardown */
+static LIST_HEAD(osdblkdev_list);
+
+static struct block_device_operations osdblk_bd_ops = {
+	.owner		= THIS_MODULE,
+};
+
+static const struct osd_attr g_attr_logical_length = ATTR_DEF(
+	OSD_APAGE_OBJECT_INFORMATION, OSD_ATTR_OI_LOGICAL_LENGTH, 8);
+
+/* copied from exofs; move to libosd? */
+static void osd_make_credential(u8 cred_a[OSD_CAP_LEN],
+				const struct osd_obj_id *obj)
+{
+	osd_sec_init_nosec_doall_caps(cred_a, obj, false, true);
+}
+
+/*
+ * Perform a synchronous OSD operation.  copied from exofs; move to libosd?
+ */
+static int osd_sync_op(struct osd_request *or, int timeout, uint8_t *credential)
+{
+	int ret;
+
+	or->timeout = timeout;
+	ret = osd_finalize_request(or, 0, credential, NULL);
+	if (ret)
+		return ret;
+
+	ret = osd_execute_request(or);
+
+	/* osd_req_decode_sense(or, ret); */
+	return ret;
+}
+
+/*
+ * Perform an asynchronous OSD operation.  copied from exofs; move to libosd?
+ */
+static int osd_async_op(struct osd_request *or, osd_req_done_fn *async_done,
+		   void *caller_context, u8 *cred)
+{
+	int ret;
+
+	ret = osd_finalize_request(or, 0, cred, NULL);
+	if (ret)
+		return ret;
+
+	ret = osd_execute_request_async(or, async_done, caller_context);
+
+	return ret;
+}
+
+/* copied from exofs; move to libosd? */
+static int extract_attr_from_req(struct osd_request *or, struct osd_attr *attr)
+{
+	struct osd_attr cur_attr = {.attr_page = 0}; /* start with zeros */
+	void *iter = NULL;
+	int nelem;
+
+	do {
+		nelem = 1;
+		osd_req_decode_get_attr_list(or, &cur_attr, &nelem, &iter);
+		if ((cur_attr.attr_page == attr->attr_page) &&
+		    (cur_attr.attr_id == attr->attr_id)) {
+			attr->len = cur_attr.len;
+			attr->val_ptr = cur_attr.val_ptr;
+			return 0;
+		}
+	} while (iter);
+
+	return -EIO;
+}
+
+static int osdblk_get_obj_size(struct osdblk_device *osdev, u64 *size_out)
+{
+	struct osd_request *or;
+	struct osd_attr attr;
+	int ret;
+
+	/* start request */
+	or = osd_start_request(osdev->osd, GFP_KERNEL);
+	if (!or)
+		return -ENOMEM;
+
+	/* create a get-attributes(length) request */
+	osd_req_get_attributes(or, &osdev->obj);
+
+	osd_req_add_get_attr_list(or, &g_attr_logical_length, 1);
+
+	/* execute op synchronously */
+	ret = osd_sync_op(or, OSDBLK_OP_TIMEOUT, osdev->obj_cred);
+	if (ret)
+		goto out;
+
+	/* extract length from returned attribute info */
+	attr = g_attr_logical_length;
+	ret = extract_attr_from_req(or, &attr);
+	if (ret)
+		goto out;
+
+	*size_out = get_unaligned_be64(attr.val_ptr);
+
+out:
+	osd_end_request(or);
+	return ret;
+
+}
+
+static void osdblk_end_request(struct osdblk_device *osdev,
+			       struct osdblk_request *orq,
+			       int error)
+{
+	struct request *rq = orq->rq;
+	int rc;
+
+	/* complete request, at block layer */
+	rc = __blk_end_request(rq, error, blk_rq_bytes(rq));
+}
+
+static void osdblk_osd_complete(struct osd_request *or, void *private)
+{
+	struct osdblk_request *orq = private;
+	struct osd_sense_info osi;
+	int ret = osd_req_decode_sense(or, &osi);
+
+	if (ret)
+		ret = -EIO;
+
+	/* complete OSD request */
+	osd_end_request(or);
+
+	/* complete request passed to osdblk by block layer */
+	osdblk_end_request(orq->osdev, orq, ret);
+}
+
+static void osdblk_rq_fn(struct request_queue *q)
+{
+	struct osdblk_device *osdev = q->queuedata;
+	struct request *rq;
+	struct osdblk_request *orq;
+	struct osd_request *or;
+	struct bio *bio;
+	int do_write, do_flush;
+
+	while (1) {
+		/* peek at request from block layer */
+		rq = elv_next_request(q);
+		if (!rq)
+			break;
+
+		/* filter out block requests we don't understand */
+		if (!blk_fs_request(rq) && !blk_barrier_rq(rq)) {
+			end_request(rq, 0);
+			continue;
+		}
+
+		/* deduce our operation (read, write, flush) */
+		/* I wish the block layer simplified cmd_type/cmd_flags/cmd[]
+		 * into a clearly defined set of RPC commands:
+		 * read, write, flush, scsi command, power mgmt req,
+		 * driver-specific, etc.
+		 */
+
+		do_flush = (rq->special == (void *) 0xdeadbeefUL);
+		do_write = (rq_data_dir(rq) == WRITE);
+
+		/* a bio clone to be passed down to OSD request */
+		bio = bio_clone(rq->bio, GFP_ATOMIC);
+		if (!bio)
+			break;
+
+		/* alloc internal OSD request, for OSD command execution */
+		or = osd_start_request(osdev->osd, GFP_ATOMIC);
+		if (!or) {
+			bio_put(bio);
+			break;
+		}
+
+		orq = &osdev->req[rq->tag];
+		orq->rq = rq;
+		orq->bio = bio;
+		orq->osdev = osdev;
+
+		/* init OSD command: flush, write or read */
+		if (do_flush)
+			osd_req_flush_object(or, &osdev->obj,
+					     OSD_CDB_FLUSH_ALL, 0, 0);
+		else if (do_write)
+			osd_req_write(or, &osdev->obj, bio,
+				      rq->sector * 512ULL);
+		else
+			osd_req_read(or, &osdev->obj, bio,
+				     rq->sector * 512ULL);
+
+		/* begin OSD command execution */
+		if (osd_async_op(or, osdblk_osd_complete, orq,
+				 osdev->obj_cred)) {
+			osd_end_request(or);
+			blk_requeue_request(q, rq);
+			bio_put(bio);
+		}
+
+		/* remove the special 'flush' marker, now that the command
+		 * is executing
+		 */
+		rq->special = NULL;
+	}
+}
+
+static void osdblk_prepare_flush(struct request_queue *q, struct request *rq)
+{
+	/* add driver-specific marker, to indicate that this request
+	 * is a flush command
+	 */
+	rq->special = (void *) 0xdeadbeefUL;
+}
+
+static void osdblk_free_disk(struct osdblk_device *osdev)
+{
+	struct gendisk *disk = osdev->disk;
+
+	if (!disk)
+		return;
+
+	if (disk->flags & GENHD_FL_UP)
+		del_gendisk(disk);
+	if (disk->queue)
+		blk_cleanup_queue(disk->queue);
+	put_disk(disk);
+}
+
+static int osdblk_init_disk(struct osdblk_device *osdev)
+{
+	struct gendisk *disk;
+	struct request_queue *q;
+	int rc;
+	u64 obj_size = 0;
+
+	/* contact OSD, request size info about the object being mapped */
+	rc = osdblk_get_obj_size(osdev, &obj_size);
+	if (rc)
+		return rc;
+
+	/* create gendisk info */
+	disk = alloc_disk(OSDBLK_MINORS_PER_MAJOR);
+	if (!disk)
+		return -ENOMEM;
+
+	sprintf(disk->disk_name, DRV_NAME "/%d", osdev->id);
+	disk->major = osdev->major;
+	disk->first_minor = 0;
+	disk->fops = &osdblk_bd_ops;
+	disk->private_data = osdev;
+
+	/* init rq */
+	q = blk_init_queue(osdblk_rq_fn, &osdev->lock);
+	if (!q) {
+		put_disk(disk);
+		return -ENOMEM;
+	}
+
+	/* switch queue to TCQ mode; allocate tag map */
+	rc = blk_queue_init_tags(q, OSDBLK_MAX_REQ, NULL);
+	if (rc) {
+		blk_cleanup_queue(q);
+		put_disk(disk);
+		return rc;
+	}
+
+	blk_queue_prep_rq(q, blk_queue_start_tag);
+	blk_queue_ordered(q, QUEUE_ORDERED_DRAIN_FLUSH, osdblk_prepare_flush);
+
+	disk->queue = q;
+
+	q->queuedata = osdev;
+
+	osdev->disk = disk;
+	osdev->q = q;
+
+	/* finally, announce the disk to the world */
+	set_capacity(disk, obj_size);
+	add_disk(disk);
+
+	return 0;
+}
+
+/********************************************************************
+  /sys/class/osdblk/
+                     add	map OSD object to blkdev
+                     remove	unmap OSD object
+                     list	show mappings
+ *******************************************************************/
+
+static void class_osdblk_release(struct class *cls)
+{
+	kfree(cls);
+}
+
+static ssize_t class_osdblk_list(struct class *c, char *data)
+{
+	int n = 0;
+	struct list_head *tmp;
+
+	mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+
+	list_for_each(tmp, &osdblkdev_list) {
+		struct osdblk_device *osdev;
+
+		osdev = list_entry(tmp, struct osdblk_device, node);
+
+		n += sprintf(data+n, "%d %d %llu %llu %s\n",
+			osdev->id,
+			osdev->major,
+			osdev->obj.partition,
+			osdev->obj.id,
+			osdev->osd_path);
+	}
+
+	mutex_unlock(&ctl_mutex);
+	return n;
+}
+
+static ssize_t class_osdblk_add(struct class *c, const char *buf, size_t count)
+{
+	struct osdblk_device *osdev;
+	ssize_t rc;
+	int irc, new_id = 0;
+	struct list_head *tmp;
+
+	if (!try_module_get(THIS_MODULE))
+		return -ENODEV;
+
+	/* new osdblk_device object */
+	osdev = kzalloc(sizeof(*osdev) + strlen(buf) + 1, GFP_KERNEL);
+	if (!osdev) {
+		rc = -ENOMEM;
+		goto err_out_mod;
+	}
+
+	/* static osdblk_device initialization */
+	spin_lock_init(&osdev->lock);
+	INIT_LIST_HEAD(&osdev->node);
+
+	/* generate unique id: find highest unique id, add one */
+
+	mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+
+	list_for_each(tmp, &osdblkdev_list) {
+		struct osdblk_device *osdev;
+
+		osdev = list_entry(tmp, struct osdblk_device, node);
+		if (osdev->id > new_id)
+			new_id = osdev->id + 1;
+	}
+
+	osdev->id = new_id;
+
+	/* add to global list */
+	list_add_tail(&osdev->node, &osdblkdev_list);
+
+	mutex_unlock(&ctl_mutex);
+
+	/* parse add command */
+	if (sscanf(buf, "%llu %llu %s", &osdev->obj.partition, &osdev->obj.id,
+		   osdev->osd_path) != 3) {
+		rc = -EINVAL;
+		goto err_out_slot;
+	}
+
+	/* initialize rest of new object */
+	sprintf(osdev->name, DRV_NAME "%d", osdev->id);
+
+	/* contact requested OSD */
+	osdev->osd = osduld_path_lookup(osdev->osd_path);
+	if (IS_ERR(osdev->osd)) {
+		rc = PTR_ERR(osdev->osd);
+		goto err_out_slot;
+	}
+
+	/* build OSD credential */
+	osd_make_credential(osdev->obj_cred, &osdev->obj);
+
+	/* register our block device */
+	irc = register_blkdev(0, osdev->name);
+	if (irc < 0) {
+		rc = irc;
+		goto err_out_osd;
+	}
+
+	osdev->major = irc;
+
+	/* set up and announce blkdev mapping */
+	rc = osdblk_init_disk(osdev);
+	if (rc)
+		goto err_out_blkdev;
+
+	return 0;
+
+err_out_blkdev:
+	unregister_blkdev(osdev->major, osdev->name);
+err_out_osd:
+	osduld_put_device(osdev->osd);
+err_out_slot:
+	mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+	list_del_init(&osdev->node);
+	mutex_unlock(&ctl_mutex);
+
+	kfree(osdev);
+err_out_mod:
+	module_put(THIS_MODULE);
+	return rc;
+}
+
+static ssize_t class_osdblk_remove(struct class *c, const char *buf,
+					size_t count)
+{
+	struct osdblk_device *osdev = NULL;
+	int target_id, rc;
+	unsigned long ul;
+	struct list_head *tmp;
+
+	rc = strict_strtoul(buf, 10, &ul);
+	if (rc)
+		return rc;
+
+	/* convert to int; abort if we lost anything in the conversion */
+	target_id = (int) ul;
+	if (target_id != ul)
+		return -EINVAL;
+
+	/* remove object from list immediately */
+	mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+
+	list_for_each(tmp, &osdblkdev_list) {
+		osdev = list_entry(tmp, struct osdblk_device, node);
+		if (osdev->id == target_id) {
+			list_del_init(&osdev->node);
+			break;
+		}
+		osdev = NULL;
+	}
+
+	mutex_unlock(&ctl_mutex);
+
+	if (!osdev)
+		return -ENOENT;
+
+	/* clean up and free blkdev and associated OSD connection */
+	osdblk_free_disk(osdev);
+	unregister_blkdev(osdev->major, osdev->name);
+	osduld_put_device(osdev->osd);
+	kfree(osdev);
+
+	/* release module ref */
+	module_put(THIS_MODULE);
+
+	return 0;
+}
+
+static struct class_attribute class_osdblk_attrs[] = {
+	__ATTR(add,	0200, NULL, class_osdblk_add),
+	__ATTR(remove,	0200, NULL, class_osdblk_remove),
+	__ATTR(list,	0444, class_osdblk_list, NULL),
+	__ATTR_NULL
+};
+
+static int osdblk_sysfs_init(void)
+{
+	int ret = 0;
+
+	/*
+	 * create control files in sysfs
+	 * /sys/class/osdblk/...
+	 */
+	class_osdblk = kzalloc(sizeof(*class_osdblk), GFP_KERNEL);
+	if (!class_osdblk)
+		return -ENOMEM;
+
+	class_osdblk->name = DRV_NAME;
+	class_osdblk->owner = THIS_MODULE;
+	class_osdblk->class_release = class_osdblk_release;
+	class_osdblk->class_attrs = class_osdblk_attrs;
+
+	ret = class_register(class_osdblk);
+	if (ret) {
+		kfree(class_osdblk);
+		class_osdblk = NULL;
+		printk(PFX "failed to create class osdblk\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static void osdblk_sysfs_cleanup(void)
+{
+	if (class_osdblk)
+		class_destroy(class_osdblk);
+	class_osdblk = NULL;
+}
+
+static int __init osdblk_init(void)
+{
+	int rc;
+
+	rc = osdblk_sysfs_init();
+	if (rc)
+		return rc;
+
+	return 0;
+}
+
+static void __exit osdblk_exit(void)
+{
+	osdblk_sysfs_cleanup();
+}
+
+module_init(osdblk_init);
+module_exit(osdblk_exit);
+
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