UBI: compatible fallback in absense of sequence numbers
authorAdrian Hunter <Adrian.Hunter@nokia.com>
Fri, 24 Jul 2009 16:16:04 +0000 (19:16 +0300)
committerArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Fri, 24 Jul 2009 17:08:52 +0000 (20:08 +0300)
Fall back onto thinking everything's OK if either of the sequence
numbers we are asked to compare is zero, which is what was used
before sequence numbers were introduced.

[ Artem: modified the patch to be applicable to upstream UBI, added
        big comment ]

Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
drivers/mtd/ubi/scan.c

index a423131b617141faaaf7b998e49ceb8b23146fce..b847745394b42d46869cdc892043abe46288809d 100644 (file)
@@ -781,11 +781,22 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
                        return -EINVAL;
                }
 
+               /*
+                * Make sure that all PEBs have the same image sequence number.
+                * This allows us to detect situations when users flash UBI
+                * images incorrectly, so that the flash has the new UBI image
+                * and leftovers from the old one. This feature was added
+                * relatively recently, and the sequence number was always
+                * zero, because old UBI implementations always set it to zero.
+                * For this reasons, we do not panic if some PEBs have zero
+                * sequence number, while other PEBs have non-zero sequence
+                * number.
+                */
                image_seq = be32_to_cpu(ech->image_seq);
                if (!si->image_seq_set) {
                        ubi->image_seq = image_seq;
                        si->image_seq_set = 1;
-               } else if (ubi->image_seq != image_seq) {
+               } else if (ubi->image_seq && ubi->image_seq != image_seq) {
                        ubi_err("bad image sequence number %d in PEB %d, "
                                "expected %d", image_seq, pnum, ubi->image_seq);
                        ubi_dbg_dump_ec_hdr(ech);