Commit 9d54c8a3 authored by Ezequiel Garcia's avatar Ezequiel Garcia Committed by Artem Bityutskiy
Browse files

UBI: R/O block driver on top of UBI volumes 



This commit introduces read-only block device emulation on top of UBI volumes.

Given UBI takes care of wear leveling and bad block management it's possible
to add a thin layer to enable block device access to UBI volumes.
This allows to use a block-oriented filesystem on a flash device.

The UBI block devices are meant to be used in conjunction with any
regular, block-oriented file system (e.g. ext4), although it's primarily
targeted at read-only file systems, such as squashfs.

Block devices are created upon user request through new ioctls:
UBI_IOCVOLATTBLK to attach and UBI_IOCVOLDETBLK to detach.
Also, a new UBI module parameter is added 'ubi.block'. This parameter is
needed in order to attach a block device on boot-up time, allowing to
mount the rootfs on a ubiblock device.
For instance, you could have these kernel parameters:

  ubi.mtd=5 ubi.block=0,0 root=/dev/ubiblock0_0

Or, if you compile ubi as a module:

  $ modprobe ubi mtd=/dev/mtd5 block=/dev/ubi0_0

Artem: amend commentaries and massage the patch a little bit.

Signed-off-by: default avatarEzequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: default avatarArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
parent 5547fec7

drivers/mtd/ubi/Kconfig

+15 −0
Original line number Diff line number Diff line
@@ -87,4 +87,19 @@ config MTD_UBI_GLUEBI 
	   work on top of UBI. Do not enable this unless you use legacy

	   software.



config MTD_UBI_BLOCK

	bool "Read-only block devices on top of UBI volumes"

	default n

	help

	   This option enables read-only UBI block devices support. UBI block

	   devices will be layered on top of UBI volumes, which means that the

	   UBI driver will transparently handle things like bad eraseblocks and

	   bit-flips. You can put any block-oriented file system on top of UBI

	   volumes in read-only mode (e.g., ext4), but it is probably most

	   practical for read-only file systems, like squashfs.



	   When selected, this feature will be built in the UBI driver.



	   If in doubt, say "N".



endif # MTD_UBI

drivers/mtd/ubi/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -3,5 +3,6 @@ obj-$(CONFIG_MTD_UBI) += ubi.o 
ubi-y += vtbl.o vmt.o upd.o build.o cdev.o kapi.o eba.o io.o wl.o attach.o

ubi-y += misc.o debug.o

ubi-$(CONFIG_MTD_UBI_FASTMAP) += fastmap.o

ubi-$(CONFIG_MTD_UBI_BLOCK) += block.o



obj-$(CONFIG_MTD_UBI_GLUEBI) += gluebi.o

drivers/mtd/ubi/block.c

0 → 100644
+646 −0
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2014 Ezequiel Garcia

 * Copyright (c) 2011 Free Electrons

 *

 * Driver parameter handling strongly based on drivers/mtd/ubi/build.c

 *   Copyright (c) International Business Machines Corp., 2006

 *   Copyright (c) Nokia Corporation, 2007

 *   Authors: Artem Bityutskiy, Frank Haverkamp

 *

 * 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, version 2.

 *

 * 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.

 */



/*

 * Read-only block devices on top of UBI volumes

 *

 * A simple implementation to allow a block device to be layered on top of a

 * UBI volume. The implementation is provided by creating a static 1-to-1

 * mapping between the block device and the UBI volume.

 *

 * The addressed byte is obtained from the addressed block sector, which is

 * mapped linearly into the corresponding LEB:

 *

 *   LEB number = addressed byte / LEB size

 *

 * This feature is compiled in the UBI core, and adds a new 'block' parameter

 * to allow early block device attaching. Runtime  block attach/detach for UBI

 * volumes is provided through two new UBI ioctls: UBI_IOCVOLATTBLK and

 * UBI_IOCVOLDETBLK.

 */



#include <linux/module.h>

#include <linux/init.h>

#include <linux/err.h>

#include <linux/kernel.h>

#include <linux/list.h>

#include <linux/mutex.h>

#include <linux/slab.h>

#include <linux/vmalloc.h>

#include <linux/mtd/ubi.h>

#include <linux/workqueue.h>

#include <linux/blkdev.h>

#include <linux/hdreg.h>

#include <asm/div64.h>



#include "ubi-media.h"

#include "ubi.h"



/* Maximum number of supported devices */

#define UBIBLOCK_MAX_DEVICES 32



/* Maximum length of the 'block=' parameter */

#define UBIBLOCK_PARAM_LEN 63



/* Maximum number of comma-separated items in the 'block=' parameter */

#define UBIBLOCK_PARAM_COUNT 2



struct ubiblock_param {

	int ubi_num;

	int vol_id;

	char name[UBIBLOCK_PARAM_LEN+1];

};



/* Numbers of elements set in the @ubiblock_param array */

static int ubiblock_devs __initdata;



/* MTD devices specification parameters */

static struct ubiblock_param ubiblock_param[UBIBLOCK_MAX_DEVICES] __initdata;



struct ubiblock {

	struct ubi_volume_desc *desc;

	int ubi_num;

	int vol_id;

	int refcnt;

	int leb_size;



	struct gendisk *gd;

	struct request_queue *rq;



	struct workqueue_struct *wq;

	struct work_struct work;



	struct mutex dev_mutex;

	spinlock_t queue_lock;

	struct list_head list;

};



/* Linked list of all ubiblock instances */

static LIST_HEAD(ubiblock_devices);

static DEFINE_MUTEX(devices_mutex);

static int ubiblock_major;



static int __init ubiblock_set_param(const char *val,

				     const struct kernel_param *kp)

{

	int i, ret;

	size_t len;

	struct ubiblock_param *param;

	char buf[UBIBLOCK_PARAM_LEN];

	char *pbuf = &buf[0];

	char *tokens[UBIBLOCK_PARAM_COUNT];



	if (!val)

		return -EINVAL;



	len = strnlen(val, UBIBLOCK_PARAM_LEN);

	if (len == 0) {

		ubi_warn("block: empty 'block=' parameter - ignored\n");

		return 0;

	}



	if (len == UBIBLOCK_PARAM_LEN) {

		ubi_err("block: parameter \"%s\" is too long, max. is %d\n",

			val, UBIBLOCK_PARAM_LEN);

		return -EINVAL;

	}



	strcpy(buf, val);



	/* Get rid of the final newline */

	if (buf[len - 1] == '\n')

		buf[len - 1] = '\0';



	for (i = 0; i < UBIBLOCK_PARAM_COUNT; i++)

		tokens[i] = strsep(&pbuf, ",");



	param = &ubiblock_param[ubiblock_devs];

	if (tokens[1]) {

		/* Two parameters: can be 'ubi, vol_id' or 'ubi, vol_name' */

		ret = kstrtoint(tokens[0], 10, &param->ubi_num);

		if (ret < 0)

			return -EINVAL;



		/* Second param can be a number or a name */

		ret = kstrtoint(tokens[1], 10, &param->vol_id);

		if (ret < 0) {

			param->vol_id = -1;

			strcpy(param->name, tokens[1]);

		}



	} else {

		/* One parameter: must be device path */

		strcpy(param->name, tokens[0]);

		param->ubi_num = -1;

		param->vol_id = -1;

	}



	ubiblock_devs++;



	return 0;

}



static const struct kernel_param_ops ubiblock_param_ops = {

	.set    = ubiblock_set_param,

};

module_param_cb(block, &ubiblock_param_ops, NULL, 0);

MODULE_PARM_DESC(block, "Attach block devices to UBI volumes. Parameter format: block=<path|dev,num|dev,name>.\n"

			"Multiple \"block\" parameters may be specified.\n"

			"UBI volumes may be specified by their number, name, or path to the device node.\n"

			"Examples\n"

			"Using the UBI volume path:\n"

			"ubi.block=/dev/ubi0_0\n"

			"Using the UBI device, and the volume name:\n"

			"ubi.block=0,rootfs\n"

			"Using both UBI device number and UBI volume number:\n"

			"ubi.block=0,0\n");



static struct ubiblock *find_dev_nolock(int ubi_num, int vol_id)

{

	struct ubiblock *dev;



	list_for_each_entry(dev, &ubiblock_devices, list)

		if (dev->ubi_num == ubi_num && dev->vol_id == vol_id)

			return dev;

	return NULL;

}



static int ubiblock_read_to_buf(struct ubiblock *dev, char *buffer,

				int leb, int offset, int len)

{

	int ret;



	ret = ubi_read(dev->desc, leb, buffer, offset, len);

	if (ret) {

		ubi_err("%s ubi_read error %d",

			dev->gd->disk_name, ret);

		return ret;

	}

	return 0;

}



static int ubiblock_read(struct ubiblock *dev, char *buffer,

			 sector_t sec, int len)

{

	int ret, leb, offset;

	int bytes_left = len;

	int to_read = len;

	loff_t pos = sec << 9;



	/* Get LEB:offset address to read from */

	offset = do_div(pos, dev->leb_size);

	leb = pos;



	while (bytes_left) {

		/*

		 * We can only read one LEB at a time. Therefore if the read

		 * length is larger than one LEB size, we split the operation.

		 */

		if (offset + to_read > dev->leb_size)

			to_read = dev->leb_size - offset;



		ret = ubiblock_read_to_buf(dev, buffer, leb, offset, to_read);

		if (ret)

			return ret;



		buffer += to_read;

		bytes_left -= to_read;

		to_read = bytes_left;

		leb += 1;

		offset = 0;

	}

	return 0;

}



static int do_ubiblock_request(struct ubiblock *dev, struct request *req)

{

	int len, ret;

	sector_t sec;



	if (req->cmd_type != REQ_TYPE_FS)

		return -EIO;



	if (blk_rq_pos(req) + blk_rq_cur_sectors(req) >

	    get_capacity(req->rq_disk))

		return -EIO;



	if (rq_data_dir(req) != READ)

		return -ENOSYS; /* Write not implemented */



	sec = blk_rq_pos(req);

	len = blk_rq_cur_bytes(req);



	/*

	 * Let's prevent the device from being removed while we're doing I/O

	 * work. Notice that this means we serialize all the I/O operations,

	 * but it's probably of no impact given the NAND core serializes

	 * flash access anyway.

	 */

	mutex_lock(&dev->dev_mutex);

	ret = ubiblock_read(dev, req->buffer, sec, len);

	mutex_unlock(&dev->dev_mutex);



	return ret;

}



static void ubiblock_do_work(struct work_struct *work)

{

	struct ubiblock *dev =

		container_of(work, struct ubiblock, work);

	struct request_queue *rq = dev->rq;

	struct request *req;

	int res;



	spin_lock_irq(rq->queue_lock);



	req = blk_fetch_request(rq);

	while (req) {



		spin_unlock_irq(rq->queue_lock);

		res = do_ubiblock_request(dev, req);

		spin_lock_irq(rq->queue_lock);



		/*

		 * If we're done with this request,

		 * we need to fetch a new one

		 */

		if (!__blk_end_request_cur(req, res))

			req = blk_fetch_request(rq);

	}



	spin_unlock_irq(rq->queue_lock);

}



static void ubiblock_request(struct request_queue *rq)

{

	struct ubiblock *dev;

	struct request *req;



	dev = rq->queuedata;



	if (!dev)

		while ((req = blk_fetch_request(rq)) != NULL)

			__blk_end_request_all(req, -ENODEV);

	else

		queue_work(dev->wq, &dev->work);

}



static int ubiblock_open(struct block_device *bdev, fmode_t mode)

{

	struct ubiblock *dev = bdev->bd_disk->private_data;

	int ret;



	mutex_lock(&dev->dev_mutex);

	if (dev->refcnt > 0) {

		/*

		 * The volume is already open, just increase the reference

		 * counter.

		 */

		goto out_done;

	}



	/*

	 * We want users to be aware they should only mount us as read-only.

	 * It's just a paranoid check, as write requests will get rejected

	 * in any case.

	 */

	if (mode & FMODE_WRITE) {

		ret = -EPERM;

		goto out_unlock;

	}



	dev->desc = ubi_open_volume(dev->ubi_num, dev->vol_id, UBI_READONLY);

	if (IS_ERR(dev->desc)) {

		ubi_err("%s failed to open ubi volume %d_%d",

			dev->gd->disk_name, dev->ubi_num, dev->vol_id);

		ret = PTR_ERR(dev->desc);

		dev->desc = NULL;

		goto out_unlock;

	}



out_done:

	dev->refcnt++;

	mutex_unlock(&dev->dev_mutex);

	return 0;



out_unlock:

	mutex_unlock(&dev->dev_mutex);

	return ret;

}



static void ubiblock_release(struct gendisk *gd, fmode_t mode)

{

	struct ubiblock *dev = gd->private_data;



	mutex_lock(&dev->dev_mutex);

	dev->refcnt--;

	if (dev->refcnt == 0) {

		ubi_close_volume(dev->desc);

		dev->desc = NULL;

	}

	mutex_unlock(&dev->dev_mutex);

}



static int ubiblock_getgeo(struct block_device *bdev, struct hd_geometry *geo)

{

	/* Some tools might require this information */

	geo->heads = 1;

	geo->cylinders = 1;

	geo->sectors = get_capacity(bdev->bd_disk);

	geo->start = 0;

	return 0;

}



static const struct block_device_operations ubiblock_ops = {

	.owner = THIS_MODULE,

	.open = ubiblock_open,

	.release = ubiblock_release,

	.getgeo	= ubiblock_getgeo,

};



int ubiblock_add(struct ubi_volume_info *vi)

{

	struct ubiblock *dev;

	struct gendisk *gd;

	int disk_capacity;

	int ret;



	/* Check that the volume isn't already handled */

	mutex_lock(&devices_mutex);

	if (find_dev_nolock(vi->ubi_num, vi->vol_id)) {

		mutex_unlock(&devices_mutex);

		return -EEXIST;

	}

	mutex_unlock(&devices_mutex);



	dev = kzalloc(sizeof(struct ubiblock), GFP_KERNEL);

	if (!dev)

		return -ENOMEM;



	mutex_init(&dev->dev_mutex);



	dev->ubi_num = vi->ubi_num;

	dev->vol_id = vi->vol_id;

	dev->leb_size = vi->usable_leb_size;



	/* Initialize the gendisk of this ubiblock device */

	gd = alloc_disk(1);

	if (!gd) {

		ubi_err("block: alloc_disk failed");

		ret = -ENODEV;

		goto out_free_dev;

	}



	gd->fops = &ubiblock_ops;

	gd->major = ubiblock_major;

	gd->first_minor = dev->ubi_num * UBI_MAX_VOLUMES + dev->vol_id;

	gd->private_data = dev;

	sprintf(gd->disk_name, "ubiblock%d_%d", dev->ubi_num, dev->vol_id);

	disk_capacity = (vi->size * vi->usable_leb_size) >> 9;

	set_capacity(gd, disk_capacity);

	dev->gd = gd;



	spin_lock_init(&dev->queue_lock);

	dev->rq = blk_init_queue(ubiblock_request, &dev->queue_lock);

	if (!dev->rq) {

		ubi_err("block: blk_init_queue failed");

		ret = -ENODEV;

		goto out_put_disk;

	}



	dev->rq->queuedata = dev;

	dev->gd->queue = dev->rq;



	/*

	 * Create one workqueue per volume (per registered block device).

	 * Rembember workqueues are cheap, they're not threads.

	 */

	dev->wq = alloc_workqueue(gd->disk_name, 0, 0);

	if (!dev->wq)

		goto out_free_queue;

	INIT_WORK(&dev->work, ubiblock_do_work);



	mutex_lock(&devices_mutex);

	list_add_tail(&dev->list, &ubiblock_devices);

	mutex_unlock(&devices_mutex);



	/* Must be the last step: anyone can call file ops from now on */

	add_disk(dev->gd);

	ubi_msg("%s created from ubi%d:%d(%s)",

		dev->gd->disk_name, dev->ubi_num, dev->vol_id, vi->name);

	return 0;



out_free_queue:

	blk_cleanup_queue(dev->rq);

out_put_disk:

	put_disk(dev->gd);

out_free_dev:

	kfree(dev);



	return ret;

}



static void ubiblock_cleanup(struct ubiblock *dev)

{

	del_gendisk(dev->gd);

	blk_cleanup_queue(dev->rq);

	ubi_msg("%s released", dev->gd->disk_name);

	put_disk(dev->gd);

}



int ubiblock_del(struct ubi_volume_info *vi)

{

	struct ubiblock *dev;



	mutex_lock(&devices_mutex);

	dev = find_dev_nolock(vi->ubi_num, vi->vol_id);

	if (!dev) {

		mutex_unlock(&devices_mutex);

		return -ENODEV;

	}



	/* Found a device, let's lock it so we can check if it's busy */

	mutex_lock(&dev->dev_mutex);

	if (dev->refcnt > 0) {

		mutex_unlock(&dev->dev_mutex);

		mutex_unlock(&devices_mutex);

		return -EBUSY;

	}



	/* Remove from device list */

	list_del(&dev->list);

	mutex_unlock(&devices_mutex);



	/* Flush pending work and stop this workqueue */

	destroy_workqueue(dev->wq);



	ubiblock_cleanup(dev);

	mutex_unlock(&dev->dev_mutex);

	kfree(dev);

	return 0;

}



static void ubiblock_resize(struct ubi_volume_info *vi)

{

	struct ubiblock *dev;

	int disk_capacity;



	/*

	 * Need to lock the device list until we stop using the device,

	 * otherwise the device struct might get released in 'ubiblock_del()'.

	 */

	mutex_lock(&devices_mutex);

	dev = find_dev_nolock(vi->ubi_num, vi->vol_id);

	if (!dev) {

		mutex_unlock(&devices_mutex);

		return;

	}



	mutex_lock(&dev->dev_mutex);

	disk_capacity = (vi->size * vi->usable_leb_size) >> 9;

	set_capacity(dev->gd, disk_capacity);

	ubi_msg("%s resized to %d LEBs", dev->gd->disk_name, vi->size);

	mutex_unlock(&dev->dev_mutex);

	mutex_unlock(&devices_mutex);

}



static int ubiblock_notify(struct notifier_block *nb,

			 unsigned long notification_type, void *ns_ptr)

{

	struct ubi_notification *nt = ns_ptr;



	switch (notification_type) {

	case UBI_VOLUME_ADDED:

		/*

		 * We want to enforce explicit block device attaching for

		 * volumes, so when a volume is added we do nothing.

		 */

		break;

	case UBI_VOLUME_REMOVED:

		ubiblock_del(&nt->vi);

		break;

	case UBI_VOLUME_RESIZED:

		ubiblock_resize(&nt->vi);

		break;

	default:

		break;

	}

	return NOTIFY_OK;

}



static struct notifier_block ubiblock_notifier = {

	.notifier_call = ubiblock_notify,

};



static struct ubi_volume_desc * __init

open_volume_desc(const char *name, int ubi_num, int vol_id)

{

	if (ubi_num == -1)

		/* No ubi num, name must be a vol device path */

		return ubi_open_volume_path(name, UBI_READONLY);

	else if (vol_id == -1)

		/* No vol_id, must be vol_name */

		return ubi_open_volume_nm(ubi_num, name, UBI_READONLY);

	else

		return ubi_open_volume(ubi_num, vol_id, UBI_READONLY);

}



static int __init ubiblock_attach_from_param(void)

{

	int i, ret;

	struct ubiblock_param *p;

	struct ubi_volume_desc *desc;

	struct ubi_volume_info vi;



	for (i = 0; i < ubiblock_devs; i++) {

		p = &ubiblock_param[i];



		desc = open_volume_desc(p->name, p->ubi_num, p->vol_id);

		if (IS_ERR(desc)) {

			ubi_err("block: can't open volume, err=%ld\n",

				PTR_ERR(desc));

			ret = PTR_ERR(desc);

			break;

		}



		ubi_get_volume_info(desc, &vi);

		ubi_close_volume(desc);



		ret = ubiblock_add(&vi);

		if (ret) {

			ubi_err("block: can't add '%s' volume, err=%d\n",

				vi.name, ret);

			break;

		}

	}

	return ret;

}



static void ubiblock_detach_all(void)

{

	struct ubiblock *next;

	struct ubiblock *dev;



	list_for_each_entry_safe(dev, next, &ubiblock_devices, list) {

		/* Flush pending work and stop workqueue */

		destroy_workqueue(dev->wq);

		/* The module is being forcefully removed */

		WARN_ON(dev->desc);

		/* Remove from device list */

		list_del(&dev->list);

		ubiblock_cleanup(dev);

		kfree(dev);

	}

}



int __init ubiblock_init(void)

{

	int ret;



	ubiblock_major = register_blkdev(0, "ubiblock");

	if (ubiblock_major < 0)

		return ubiblock_major;



	/* Attach block devices from 'block=' module param */

	ret = ubiblock_attach_from_param();

	if (ret)

		goto err_detach;



	/*

	 * Block devices needs to be attached to volumes explicitly

	 * upon user request. So we ignore existing volumes.

	 */

	ret = ubi_register_volume_notifier(&ubiblock_notifier, 1);

	if (ret)

		goto err_unreg;

	return 0;



err_unreg:

	unregister_blkdev(ubiblock_major, "ubiblock");

err_detach:

	ubiblock_detach_all();

	return ret;

}



void __exit ubiblock_exit(void)

{

	ubi_unregister_volume_notifier(&ubiblock_notifier);

	ubiblock_detach_all();

	unregister_blkdev(ubiblock_major, "ubiblock");

}

drivers/mtd/ubi/build.c

+11 −0
Original line number Diff line number Diff line
@@ -1298,6 +1298,15 @@ static int __init ubi_init(void) 
		}

	}



	err = ubiblock_init();

	if (err) {

		ubi_err("block: cannot initialize, error %d", err);



		/* See comment above re-ubi_is_module(). */

		if (ubi_is_module())

			goto out_detach;

	}



	return 0;



out_detach:
@@ -1326,6 +1335,8 @@ static void __exit ubi_exit(void) 
{

	int i;



	ubiblock_exit();



	for (i = 0; i < UBI_MAX_DEVICES; i++)

		if (ubi_devices[i]) {

			mutex_lock(&ubi_devices_mutex);

drivers/mtd/ubi/cdev.c

+20 −0
Original line number Diff line number Diff line
@@ -561,6 +561,26 @@ static long vol_cdev_ioctl(struct file *file, unsigned int cmd, 
		break;

	}



	/* Attach a block device to an UBI volume */

	case UBI_IOCVOLATTBLK:

	{

		struct ubi_volume_info vi;



		ubi_get_volume_info(desc, &vi);

		err = ubiblock_add(&vi);

		break;

	}



	/* Dettach a block device from an UBI volume */

	case UBI_IOCVOLDETBLK:

	{

		struct ubi_volume_info vi;



		ubi_get_volume_info(desc, &vi);

		err = ubiblock_del(&vi);

		break;

	}



	default:

		err = -ENOTTY;

		break;

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