UBI: handle bit-flips when no header found

Currently UBI has one small flaw - when we read EC or VID header, but find only
0xFF bytes, we return UBI_IO_FF and do not report whether we had bit-flips or
not. In case of the VID header, the scanning code adds this PEB to the free list,
even though there were bit-flips.

Imagine the following situation: we start writing VID header to a PEB and have a
power cut, so the PEB becomes unstable. When we scan and read the PEB, we get
a bit-flip. Currently, UBI would just ignore this and treat the PEB as free. This
patch changes UBI behavior and now UBI will schedule this PEB for erasure.

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

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index a9e7c9eed703..605ecb1e22bb 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -759,6 +759,16 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
                         dbg_wl("PEB %d has no VID header", e1->pnum);
                         protect = 1;
                         goto out_not_moved;
+                } else if (err == UBI_IO_FF_BITFLIPS) {
+                        /*
+                         * The same situation as %UBI_IO_FF, but bit-flips were
+                         * detected. It is better to schedule this PEB for
+                         * scrubbing.
+                         */
+                        dbg_wl("PEB %d has no VID header but has bit-flips",
+                               e1->pnum);
+                        scrubbing = 1;
+                        goto out_not_moved;
                 }
 
                 ubi_err("error %d while reading VID header from PEB %d",