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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

drivers/mtd/ubi/cdev.c

+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;

drivers/mtd/ubi/ubi.h

+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,

drivers/mtd/ubi/wl.c

+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

include/uapi/mtd/ubi-user.h

+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'