@@ -87,4 +87,23 @@ config MTD_UBI_GLUEBI
work on top of UBI. Do not enable this unless you use legacy
software.
+config MTD_UBI_BLOCK
+ bool "Block device access to UBI volumes"
+ default n
+ help
+ Since UBI already takes care of eraseblock wear leveling
+ and bad block handling, it's possible to implement a block
+ device on top of it and therefore mount regular filesystems
+ (i.e. not flash-oriented, as ext4).
+ In other words, this is a software flash translation layer.
+
+ This can be particularly interesting to allow mounting a read-only
+ filesystem, such as squashfs, on a NAND device.
+
+ When selected, this feature will be built-in the ubi module
+ and block devices will be able to be created and removed using
+ the userspace 'ubiblkvol' tool (provided mtd-utils).
+
+ If in doubt, say "N".
+
endif # MTD_UBI
@@ -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
new file mode 100644
@@ -0,0 +1,660 @@
+/*
+ * Copyright (c) 2014 Ezequiel Garcia
+ * Copyright (c) 2011 Free Electrons
+ *
+ * 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.
+ */
+
+/*
+ * Block interface for UBI volumes
+ *
+ * A simple implementation to allow a block device interface 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
+ *
+ * The current implementation support only read operation. Write-support
+ * addition shouldn't be too hard and could be implemented in the future.
+ * It was suggested to implement this using the already existent BLKROSET
+ * block ioctl to turn it on and off, thus avoiding undesirable writes.
+ *
+ * Contrary to the MTD block interface implementation, there's no cache
+ * involved. The reasons behind this choice is that the filesystems
+ * that would be mounted on top of UBI blocks already provide caching and
+ * are able to do it more efficiently.
+ *
+ * We may add a cache here, but it would be desirable to register a memory
+ * shrinker to match the requirements of memory-constrained platforms.
+ *
+ * This feature is compiled in the UBI core, and adds a new 'block'
+ * parameter to allow early block interface creation. Runtime
+ * block attach/detach for UBI volumes is provided through two
+ * 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 "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;
+ struct ubi_volume_info *vi;
+ 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 vol_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, ¶m->ubi_num);
+ if (ret < 0)
+ return -EINVAL;
+
+ /* Second param can be a number or a name */
+ ret = kstrtoint(tokens[1], 10, ¶m->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, int pos, int len)
+{
+ int leb, offset, ret;
+ int bytes_left = len;
+ int to_read = len;
+
+ /* Get leb:offset address to read from */
+ leb = pos / dev->leb_size;
+ offset = pos % dev->leb_size;
+
+ 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++;
+ offset = 0;
+ }
+ return 0;
+}
+
+static int do_ubiblock_request(struct ubiblock *dev, struct request *req)
+{
+ int pos, len, ret;
+
+ 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 */
+
+ pos = blk_rq_pos(req) << 9;
+ 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 acceses anywafy.
+ */
+ mutex_lock(&dev->vol_mutex);
+ ret = ubiblock_read(dev, req->buffer, pos, len);
+ mutex_unlock(&dev->vol_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->vol_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;
+ }
+
+ dev->vi = kzalloc(sizeof(struct ubi_volume_info), GFP_KERNEL);
+ if (!dev->vi) {
+ ret = -ENOMEM;
+ goto out_close;
+ }
+ ubi_get_volume_info(dev->desc, dev->vi);
+ dev->leb_size = dev->vi->usable_leb_size;
+
+out_done:
+ dev->refcnt++;
+ mutex_unlock(&dev->vol_mutex);
+ return 0;
+
+out_close:
+ ubi_close_volume(dev->desc);
+ dev->desc = NULL;
+out_unlock:
+ mutex_unlock(&dev->vol_mutex);
+ return ret;
+}
+
+static void ubiblock_release(struct gendisk *gd, fmode_t mode)
+{
+ struct ubiblock *dev = gd->private_data;
+
+ mutex_lock(&dev->vol_mutex);
+
+ dev->refcnt--;
+ if (dev->refcnt == 0) {
+ kfree(dev->vi);
+ ubi_close_volume(dev->desc);
+
+ dev->vi = NULL;
+ dev->desc = NULL;
+ }
+
+ mutex_unlock(&dev->vol_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->vol_mutex);
+
+ dev->ubi_num = vi->ubi_num;
+ dev->vol_id = vi->vol_id;
+
+ /* 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->vol_mutex);
+
+ if (dev->refcnt > 0) {
+ mutex_unlock(&dev->vol_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->vol_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->vol_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->vol_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 void __init ubiblock_add_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_warn("block: can't open volume, err=%ld\n",
+ PTR_ERR(desc));
+ continue;
+ }
+
+ ubi_get_volume_info(desc, &vi);
+ ret = ubiblock_add(&vi);
+ if (ret)
+ ubi_warn("block: can't add '%s' volume, err=%d\n",
+ vi.name, ret);
+ ubi_close_volume(desc);
+ }
+}
+
+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 */
+ ubiblock_add_from_param();
+
+ /*
+ * 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 < 0)
+ unregister_blkdev(ubiblock_major, "ubiblock");
+ return ret;
+}
+
+void __exit ubiblock_exit(void)
+{
+ struct ubiblock *next;
+ struct ubiblock *dev;
+
+ ubi_unregister_volume_notifier(&ubiblock_notifier);
+
+ 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);
+ }
+
+ unregister_blkdev(ubiblock_major, "ubiblock");
+}
@@ -1298,6 +1298,9 @@ static int __init ubi_init(void)
}
}
+ if (ubiblock_init() < 0)
+ ubi_warn("cannot init block device access");
+
return 0;
out_detach:
@@ -1326,6 +1329,8 @@ 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);
@@ -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;
@@ -864,6 +864,20 @@ int ubi_update_fastmap(struct ubi_device *ubi);
int ubi_scan_fastmap(struct ubi_device *ubi, struct ubi_attach_info *ai,
int fm_anchor);
+/* block.c */
+#ifdef CONFIG_MTD_UBI_BLOCK
+int ubiblock_init(void);
+void ubiblock_exit(void);
+int ubiblock_add(struct ubi_volume_info *vi);
+int ubiblock_del(struct ubi_volume_info *vi);
+#else
+static inline int ubiblock_init(void) { return 0; }
+static inline void ubiblock_exit(void) {}
+static inline int ubiblock_add(struct ubi_volume_info *vi) { return -ENOTTY; }
+static inline int ubiblock_del(struct ubi_volume_info *vi) { return -ENOTTY; }
+#endif
+
+
/*
* ubi_rb_for_each_entry - walk an RB-tree.
* @rb: a pointer to type 'struct rb_node' to use as a loop counter
@@ -134,6 +134,13 @@
* used. A pointer to a &struct ubi_set_vol_prop_req object is expected to be
* passed. The object describes which property should be set, and to which value
* it should be set.
+ *
+ * Block device access to UBI volumes
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * To attach or detach a block device from an UBI volume the %UBI_IOCVOLATTBLK
+ * and %UBI_IOCVOLDETBLK ioctl commands should be used, respectively.
+ * These commands take no arguments.
*/
/*
@@ -191,6 +198,10 @@
/* Set an UBI volume property */
#define UBI_IOCSETVOLPROP _IOW(UBI_VOL_IOC_MAGIC, 6, \
struct ubi_set_vol_prop_req)
+/* Attach a block device to an UBI volume */
+#define UBI_IOCVOLATTBLK _IO(UBI_VOL_IOC_MAGIC, 7)
+/* Detach a block device from an UBI volume */
+#define UBI_IOCVOLDETBLK _IO(UBI_VOL_IOC_MAGIC, 8)
/* Maximum MTD device name length supported by UBI */
#define MAX_UBI_MTD_NAME_LEN 127
This commit introduces block device emulation on top of ubi volumes, in the most featureless and skinniest way: read-only, uncached access. 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. As opposed to mtdblock, which uses a 1-LEB cache, we've chosen not to implement any caching policy. The UBI block interface is meant to be used in conjunction with regular block-oriented filesystems (primarily, squashfs). These filesystems are better prepared to do their own caching, rendering a block-level cache useless. Write support has not been implemented. This might be added in the future, using BLKROSET block ioctl to enable/disable it dynamically, thus providing the means to protect the device from unwanted writes. 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 Cc: Artem Bityutskiy <dedekind1@gmail.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Brian Norris <computersforpeace@gmail.com> Cc: Michael Opdenacker <michael.opdenacker@free-electrons.com> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Cc: Mike Frysinger <vapier@gentoo.org> Cc: Piergiorgio Beruto <piergiorgio.beruto@gmail.com> Cc: Willy Tarreau <w@1wt.eu> Cc: Richard Weinberger <richard.weinberger@gmail.com> Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com> --- drivers/mtd/ubi/Kconfig | 19 ++ drivers/mtd/ubi/Makefile | 1 + drivers/mtd/ubi/block.c | 660 ++++++++++++++++++++++++++++++++++++++++++++ drivers/mtd/ubi/build.c | 5 + drivers/mtd/ubi/cdev.c | 20 ++ drivers/mtd/ubi/ubi.h | 14 + include/uapi/mtd/ubi-user.h | 11 + 7 files changed, 730 insertions(+) create mode 100644 drivers/mtd/ubi/block.c