UBI: remove pre-sqnum images support

Before UBI got into mainline, there was a slight flash format
change - we did not have sequence number support, then added it.

We have carried full support of those ancient images till this
moment. Now the support is removed, well, not fully removed.

Now UBI will support only _clean_ old images, which were cleanly
detached last time (just before kernel upgrade). This is most
likely the case.

But we will not support unclean ancient images. Surprisingly,
this allows us to remove a big chunk of legacy code.

And the same should be true for downgrading: clean images should
downgrade fine, but unclean ones will not.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 24 insertions, 63 deletions

diff --git a/drivers/mtd/ubi/scan.c b/drivers/mtd/ubi/scan.c
index 4dfbf27b0656..967bb4406df9 100644
--- a/drivers/mtd/ubi/scan.c
+++ b/drivers/mtd/ubi/scan.c
@@ -246,46 +246,21 @@ static int compare_lebs(struct ubi_device *ubi, const struct ubi_scan_leb *seb,
 	struct ubi_vid_hdr *vh = NULL;
 	unsigned long long sqnum2 = be64_to_cpu(vid_hdr->sqnum);
 
-	if (seb->sqnum == 0 && sqnum2 == 0) {
-		long long abs;
-		long long v1 = seb->leb_ver, v2 = be32_to_cpu(vid_hdr->leb_ver);
-
+	if (sqnum2 == seb->sqnum) {
 		/*
-		 * UBI constantly increases the logical eraseblock version
-		 * number and it can overflow. Thus, we have to bear in mind
-		 * that versions that are close to %0xFFFFFFFF are less then
-		 * versions that are close to %0.
-		 *
-		 * The UBI WL sub-system guarantees that the number of pending
-		 * tasks is not greater then %0x7FFFFFFF. So, if the difference
-		 * between any two versions is greater or equivalent to
-		 * %0x7FFFFFFF, there was an overflow and the logical
-		 * eraseblock with lower version is actually newer then the one
-		 * with higher version.
-		 *
-		 * FIXME: but this is anyway obsolete and will be removed at
-		 * some point.
+		 * This must be a really ancient UBI image which has been
+		 * created before sequence numbers support has been added. At
+		 * that times we used 32-bit LEB versions stored in logical
+		 * eraseblocks. That was before UBI got into mainline. We do not
+		 * support these images anymore. Well, those images will work
+		 * still work, but only if no unclean reboots happened.
 		 */
-		dbg_bld("using old crappy leb_ver stuff");
-
-		if (v1 == v2) {
-			ubi_err("PEB %d and PEB %d have the same version %lld",
-				seb->pnum, pnum, v1);
-			return -EINVAL;
-		}
+		ubi_err("unsupported on-flash UBI format\n");
+		return -EINVAL;
+	}
 
-		abs = v1 - v2;
-		if (abs < 0)
-			abs = -abs;
-
-		if (abs < 0x7FFFFFFF)
-			/* Non-overflow situation */
-			second_is_newer = (v2 > v1);
-		else
-			second_is_newer = (v2 < v1);
-	} else
-		/* Obviously the LEB with lower sequence counter is older */
-		second_is_newer = sqnum2 > seb->sqnum;
+	/* Obviously the LEB with lower sequence counter is older */
+	second_is_newer = !!(sqnum2 > seb->sqnum);
 
 	/*
 	 * Now we know which copy is newer. If the copy flag of the PEB with
@@ -293,7 +268,7 @@ static int compare_lebs(struct ubi_device *ubi, const struct ubi_scan_leb *seb,
 	 * check data CRC. For the second PEB we already have the VID header,
 	 * for the first one - we'll need to re-read it from flash.
 	 *
-	 * FIXME: this may be optimized so that we wouldn't read twice.
+	 * Note: this may be optimized so that we wouldn't read twice.
 	 */
 
 	if (second_is_newer) {
@@ -399,7 +374,6 @@ int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
 		      int bitflips)
 {
 	int err, vol_id, lnum;
-	uint32_t leb_ver;
 	unsigned long long sqnum;
 	struct ubi_scan_volume *sv;
 	struct ubi_scan_leb *seb;
@@ -408,10 +382,9 @@ int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
 	vol_id = be32_to_cpu(vid_hdr->vol_id);
 	lnum = be32_to_cpu(vid_hdr->lnum);
 	sqnum = be64_to_cpu(vid_hdr->sqnum);
-	leb_ver = be32_to_cpu(vid_hdr->leb_ver);
 
-	dbg_bld("PEB %d, LEB %d:%d, EC %d, sqnum %llu, ver %u, bitflips %d",
-		pnum, vol_id, lnum, ec, sqnum, leb_ver, bitflips);
+	dbg_bld("PEB %d, LEB %d:%d, EC %d, sqnum %llu, bitflips %d",
+		pnum, vol_id, lnum, ec, sqnum, bitflips);
 
 	sv = add_volume(si, vol_id, pnum, vid_hdr);
 	if (IS_ERR(sv) < 0)
@@ -444,25 +417,20 @@ int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
 		 */
 
 		dbg_bld("this LEB already exists: PEB %d, sqnum %llu, "
-			"LEB ver %u, EC %d", seb->pnum, seb->sqnum,
-			seb->leb_ver, seb->ec);
-
-		/*
-		 * Make sure that the logical eraseblocks have different
-		 * versions. Otherwise the image is bad.
-		 */
-		if (seb->leb_ver == leb_ver && leb_ver != 0) {
-			ubi_err("two LEBs with same version %u", leb_ver);
-			ubi_dbg_dump_seb(seb, 0);
-			ubi_dbg_dump_vid_hdr(vid_hdr);
-			return -EINVAL;
-		}
+			"EC %d", seb->pnum, seb->sqnum, seb->ec);
 
 		/*
 		 * Make sure that the logical eraseblocks have different
 		 * sequence numbers. Otherwise the image is bad.
 		 *
-		 * FIXME: remove 'sqnum != 0' check when leb_ver is removed.
+		 * However, if the sequence number is zero, we assume it must
+		 * be an ancient UBI image from the era when UBI did not have
+		 * sequence numbers. We still can attach these images, unless
+		 * there is a need to distinguish between old and new
+		 * eraseblocks, in which case we'll refuse the image in
+		 * 'compare_lebs()'. In other words, we attach old clean
+		 * images, but refuse attaching old images with duplicated
+		 * logical eraseblocks because there was an unclean reboot.
 		 */
 		if (seb->sqnum == sqnum && sqnum != 0) {
 			ubi_err("two LEBs with same sequence number %llu",
@@ -502,7 +470,6 @@ int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
 			seb->pnum = pnum;
 			seb->scrub = ((cmp_res & 2) || bitflips);
 			seb->sqnum = sqnum;
-			seb->leb_ver = leb_ver;
 
 			if (sv->highest_lnum == lnum)
 				sv->last_data_size =
@@ -539,7 +506,6 @@ int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
 	seb->lnum = lnum;
 	seb->sqnum = sqnum;
 	seb->scrub = bitflips;
-	seb->leb_ver = leb_ver;
 
 	if (sv->highest_lnum <= lnum) {
 		sv->highest_lnum = lnum;
@@ -1263,11 +1229,6 @@ static int paranoid_check_si(struct ubi_device *ubi, struct ubi_scan_info *si)
 				ubi_err("bad data_pad %d", sv->data_pad);
 				goto bad_vid_hdr;
 			}
-
-			if (seb->leb_ver != be32_to_cpu(vidh->leb_ver)) {
-				ubi_err("bad leb_ver %u", seb->leb_ver);
-				goto bad_vid_hdr;
-			}
 		}
 
 		if (!last_seb)