Commit 0798cea8 authored by Artem Bityutskiy's avatar Artem Bityutskiy
Browse files

UBI: improve corrupted flash handling 



This patch improves the way UBI handles corrupted flash, or flash
containing garbage or non-UBI data, which is the same from UBI POW.
Namely, we do the following:

* if 5% or more PEBs are corrupted, refuse the flash
* if less than 5% PEBs are corrupted, do not refuse the flash
  and format these PEBs
* if less than 8 PEBs are corrupted, format them silently, otherwise
  print a warning message.

Reported-by: default avatarSebastian Andrzej Siewior <sebastian@breakpoint.cc>
Signed-off-by: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: default avatarSebastian Andrzej Siewior <sebastian@breakpoint.cc>
Tested-by: default avatarSebastian Andrzej Siewior <sebastian@breakpoint.cc>
parent 33789fb9

drivers/mtd/ubi/scan.c

+82 −19
Original line number Diff line number Diff line
@@ -760,8 +760,6 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si, 
		bitflips = 1;

	}



	si->is_empty = 0;



	if (!ec_corr) {

		int image_seq;
@@ -891,6 +889,85 @@ adjust_mean_ec: 
	return 0;

}



/**

 * check_what_we_have - check what PEB were found by scanning.

 * @ubi: UBI device description object

 * @si: scanning information

 *

 * This is a helper function which takes a look what PEBs were found by

 * scanning, and decides whether the flash is empty and should be formatted and

 * whether there are too many corrupted PEBs and we should not attach this

 * MTD device. Returns zero if we should proceed with attaching the MTD device,

 * and %-EINVAL if we should not.

 */

static int check_what_we_have(const struct ubi_device *ubi,

			      struct ubi_scan_info *si)

{

	struct ubi_scan_leb *seb;

	int max_corr;



	max_corr = ubi->peb_count - si->bad_peb_count - si->alien_peb_count;

	max_corr = max_corr / 20 ?: 8;



	/*

	 * Few corrupted PEBs are not a problem and may be just a result of

	 * unclean reboots. However, many of them may indicate some problems

	 * with the flash HW or driver.

	 */

	if (si->corr_peb_count >= 8) {

		ubi_warn("%d PEBs are corrupted", si->corr_peb_count);

		printk(KERN_WARNING "corrupted PEBs are:");

		list_for_each_entry(seb, &si->corr, u.list)

			printk(KERN_CONT " %d", seb->pnum);

		printk(KERN_CONT "\n");



		/*

		 * If too many PEBs are corrupted, we refuse attaching,

		 * otherwise, only print a warning.

		 */

		if (si->corr_peb_count >= max_corr) {

			ubi_err("too many corrupted PEBs, refusing this device");

			return -EINVAL;

		}

	}



	if (si->free_peb_count + si->used_peb_count +

	    si->alien_peb_count == 0) {

		/* No UBI-formatted eraseblocks were found */

		if (si->corr_peb_count == si->read_err_count &&

		    si->corr_peb_count < 8) {

			/* No or just few corrupted PEBs, and all of them had a

			 * read error. We assume that those are bad PEBs, which

			 * were just not marked as bad so far.

			 *

			 * This piece of code basically tries to distinguish

			 * between the following 2 situations:

			 *

			 * 1. Flash is empty, but there are few bad PEBs, which

			 *    are not marked as bad so far, and which were read

			 *    with error. We want to go ahead and format this

			 *    flash. While formating, the faulty PEBs will

			 *    probably be marked as bad.

			 *

			 * 2. Flash probably contains non-UBI data and we do

			 * not want to format it and destroy possibly needed

			 * data (e.g., consider the case when the bootloader

			 * MTD partition was accidentally fed to UBI).

			 */

			si->is_empty = 1;

			ubi_msg("empty MTD device detected");

		} else {

			ubi_err("MTD device possibly contains non-UBI data, "

				"refusing it");

			return -EINVAL;

		}

	}



	if (si->corr_peb_count >= 0)

		ubi_msg("corrupted PEBs will be formatted");

	return 0;

}



/**

 * ubi_scan - scan an MTD device.

 * @ubi: UBI device description object
@@ -915,7 +992,6 @@ struct ubi_scan_info *ubi_scan(struct ubi_device *ubi) 
	INIT_LIST_HEAD(&si->erase);

	INIT_LIST_HEAD(&si->alien);

	si->volumes = RB_ROOT;

	si->is_empty = 1;



	err = -ENOMEM;

	ech = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);
@@ -941,22 +1017,9 @@ struct ubi_scan_info *ubi_scan(struct ubi_device *ubi) 
	if (si->ec_count)

		si->mean_ec = div_u64(si->ec_sum, si->ec_count);



	if (si->is_empty)

		ubi_msg("empty MTD device detected");



	/*

	 * Few corrupted PEBs are not a problem and may be just a result of

	 * unclean reboots. However, many of them may indicate some problems

	 * with the flash HW or driver. Print a warning in this case.

	 */

	if (si->corr_peb_count >= 8 ||

	    si->corr_peb_count >= ubi->peb_count / 4) {

		ubi_warn("%d PEBs are corrupted", si->corr_peb_count);

		printk(KERN_WARNING "corrupted PEBs are:");

		list_for_each_entry(seb, &si->corr, u.list)

			printk(KERN_CONT " %d", seb->pnum);

		printk(KERN_CONT "\n");

	}

	err = check_what_we_have(ubi, si);

	if (err)

		goto out_vidh;



	/*

	 * In case of unknown erase counter we use the mean erase counter

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