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Commit 663586c0 authored by Richard Weinberger's avatar Richard Weinberger
Browse files

ubi: Expose the bitrot interface



Using UBI_IOCRPEB and UBI_IOCSPEB userspace can force
reading and scrubbing of PEBs.

In case of bitflips UBI will automatically take action
and move data to a different PEB.
This interface allows a daemon to foster your NAND.

Signed-off-by: default avatarRichard Weinberger <richard@nod.at>
parent b32b78f8
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+30 −0
Original line number Diff line number Diff line
@@ -974,6 +974,36 @@ static long ubi_cdev_ioctl(struct file *file, unsigned int cmd,
		break;
	}

	/* Check a specific PEB for bitflips and scrub it if needed */
	case UBI_IOCRPEB:
	{
		int pnum;

		err = get_user(pnum, (__user int32_t *)argp);
		if (err) {
			err = -EFAULT;
			break;
		}

		err = ubi_bitflip_check(ubi, pnum, 0);
		break;
	}

	/* Force scrubbing for a specific PEB */
	case UBI_IOCSPEB:
	{
		int pnum;

		err = get_user(pnum, (__user int32_t *)argp);
		if (err) {
			err = -EFAULT;
			break;
		}

		err = ubi_bitflip_check(ubi, pnum, 1);
		break;
	}

	default:
		err = -ENOTTY;
		break;
+1 −0
Original line number Diff line number Diff line
@@ -929,6 +929,7 @@ int ubi_wl_put_fm_peb(struct ubi_device *ubi, struct ubi_wl_entry *used_e,
int ubi_is_erase_work(struct ubi_work *wrk);
void ubi_refill_pools(struct ubi_device *ubi);
int ubi_ensure_anchor_pebs(struct ubi_device *ubi);
int ubi_bitflip_check(struct ubi_device *ubi, int pnum, int force_scrub);

/* io.c */
int ubi_io_read(const struct ubi_device *ubi, void *buf, int pnum, int offset,
+144 −0
Original line number Diff line number Diff line
@@ -1440,6 +1440,150 @@ int ubi_wl_flush(struct ubi_device *ubi, int vol_id, int lnum)
	return err;
}

static bool scrub_possible(struct ubi_device *ubi, struct ubi_wl_entry *e)
{
	if (in_wl_tree(e, &ubi->scrub))
		return false;
	else if (in_wl_tree(e, &ubi->erroneous))
		return false;
	else if (ubi->move_from == e)
		return false;
	else if (ubi->move_to == e)
		return false;

	return true;
}

/**
 * ubi_bitflip_check - Check an eraseblock for bitflips and scrub it if needed.
 * @ubi: UBI device description object
 * @pnum: the physical eraseblock to schedule
 * @force: dont't read the block, assume bitflips happened and take action.
 *
 * This function reads the given eraseblock and checks if bitflips occured.
 * In case of bitflips, the eraseblock is scheduled for scrubbing.
 * If scrubbing is forced with @force, the eraseblock is not read,
 * but scheduled for scrubbing right away.
 *
 * Returns:
 * %EINVAL, PEB is out of range
 * %ENOENT, PEB is no longer used by UBI
 * %EBUSY, PEB cannot be checked now or a check is currently running on it
 * %EAGAIN, bit flips happened but scrubbing is currently not possible
 * %EUCLEAN, bit flips happened and PEB is scheduled for scrubbing
 * %0, no bit flips detected
 */
int ubi_bitflip_check(struct ubi_device *ubi, int pnum, int force)
{
	int err;
	struct ubi_wl_entry *e;

	if (pnum < 0 || pnum >= ubi->peb_count) {
		err = -EINVAL;
		goto out;
	}

	/*
	 * Pause all parallel work, otherwise it can happen that the
	 * erase worker frees a wl entry under us.
	 */
	down_write(&ubi->work_sem);

	/*
	 * Make sure that the wl entry does not change state while
	 * inspecting it.
	 */
	spin_lock(&ubi->wl_lock);
	e = ubi->lookuptbl[pnum];
	if (!e) {
		spin_unlock(&ubi->wl_lock);
		err = -ENOENT;
		goto out_resume;
	}

	/*
	 * Does it make sense to check this PEB?
	 */
	if (!scrub_possible(ubi, e)) {
		spin_unlock(&ubi->wl_lock);
		err = -EBUSY;
		goto out_resume;
	}
	spin_unlock(&ubi->wl_lock);

	if (!force) {
		mutex_lock(&ubi->buf_mutex);
		err = ubi_io_read(ubi, ubi->peb_buf, pnum, 0, ubi->peb_size);
		mutex_unlock(&ubi->buf_mutex);
	}

	if (err == UBI_IO_BITFLIPS || force) {
		/*
		 * Okay, bit flip happened, let's figure out what we can do.
		 */
		spin_lock(&ubi->wl_lock);

		/*
		 * Recheck. We released wl_lock, UBI might have killed the
		 * wl entry under us.
		 */
		e = ubi->lookuptbl[pnum];
		if (!e) {
			spin_unlock(&ubi->wl_lock);
			err = -ENOENT;
			goto out_resume;
		}

		/*
		 * Need to re-check state
		 */
		if (!scrub_possible(ubi, e)) {
			spin_unlock(&ubi->wl_lock);
			err = -EBUSY;
			goto out_resume;
		}

		if (in_pq(ubi, e)) {
			prot_queue_del(ubi, e->pnum);
			wl_tree_add(e, &ubi->scrub);
			spin_unlock(&ubi->wl_lock);

			err = ensure_wear_leveling(ubi, 1);
		} else if (in_wl_tree(e, &ubi->used)) {
			rb_erase(&e->u.rb, &ubi->used);
			wl_tree_add(e, &ubi->scrub);
			spin_unlock(&ubi->wl_lock);

			err = ensure_wear_leveling(ubi, 1);
		} else if (in_wl_tree(e, &ubi->free)) {
			rb_erase(&e->u.rb, &ubi->free);
			ubi->free_count--;
			spin_unlock(&ubi->wl_lock);

			/*
			 * This PEB is empty we can schedule it for
			 * erasure right away. No wear leveling needed.
			 */
			err = schedule_erase(ubi, e, UBI_UNKNOWN, UBI_UNKNOWN,
					     force ? 0 : 1, true);
		} else {
			spin_unlock(&ubi->wl_lock);
			err = -EAGAIN;
		}

		if (!err && !force)
			err = -EUCLEAN;
	} else {
		err = 0;
	}

out_resume:
	up_write(&ubi->work_sem);
out:

	return err;
}

/**
 * tree_destroy - destroy an RB-tree.
 * @ubi: UBI device description object
+5 −0
Original line number Diff line number Diff line
@@ -171,6 +171,11 @@
/* Re-name volumes */
#define UBI_IOCRNVOL _IOW(UBI_IOC_MAGIC, 3, struct ubi_rnvol_req)

/* Read the specified PEB and scrub it if there are bitflips */
#define UBI_IOCRPEB _IOW(UBI_IOC_MAGIC, 4, __s32)
/* Force scrubbing on the specified PEB */
#define UBI_IOCSPEB _IOW(UBI_IOC_MAGIC, 5, __s32)

/* ioctl commands of the UBI control character device */

#define UBI_CTRL_IOC_MAGIC 'o'