1 files changed, 74 insertions, 2 deletions

diff --git a/drivers/mtd/ubi/scan.c b/drivers/mtd/ubi/scan.c
index 19dc5e04fd61..def0bf03d7fe 100644
--- a/drivers/mtd/ubi/scan.c
+++ b/drivers/mtd/ubi/scan.c
@@ -123,8 +123,8 @@ static int add_to_list(struct ubi_scan_info *si, int pnum, int ec, int to_head,
  * @ec: erase counter of the physical eraseblock
  *
  * This function adds corrupted physical eraseblock @pnum to the 'corr' list.
- * Returns zero in case of success and a negative error code in case of
- * failure.
+ * The corruption was presumably not caused by a power cut. Returns zero in
+ * case of success and a negative error code in case of failure.
  */
 static int add_corrupted(struct ubi_scan_info *si, int pnum, int ec)
 {
@@ -751,6 +751,53 @@ struct ubi_scan_leb *ubi_scan_get_free_peb(struct ubi_device *ubi,
 }
 
 /**
+ * check_data_ff - make sure PEB contains only 0xFF data.
+ * @ubi: UBI device description object
+ * @vid_hrd: the (corrupted) VID header of this PEB
+ * @pnum: the physical eraseblock number to check
+ *
+ * This is a helper function which is used to distinguish between VID header
+ * corruptions caused by power cuts and other reasons. If the PEB contains only
+ * 0xFF bytes at the data area, the VID header is most probably corrupted
+ * because of a power cut (%0 is returned in this case). Otherwise, it was
+ * corrupted for some other reasons (%1 is returned in this case). A negative
+ * error code is returned if a read error occurred.
+ *
+ * If the corruption reason was a power cut, UBI can safely erase this PEB.
+ * Otherwise, it should preserve it to avoid possibly destroying important
+ * information.
+ */
+static int check_data_ff(struct ubi_device *ubi, struct ubi_vid_hdr *vid_hdr,
+                         int pnum)
+{
+        int err;
+
+        mutex_lock(&ubi->buf_mutex);
+        memset(ubi->peb_buf1, 0x00, ubi->leb_size);
+
+        err = ubi_io_read(ubi, ubi->peb_buf1, pnum, ubi->leb_start,
+                          ubi->leb_size);
+        if (err && err != UBI_IO_BITFLIPS && err != -EBADMSG)
+                return err;
+
+        if (ubi_check_pattern(ubi->peb_buf1, 0xFF, ubi->leb_size)) {
+                mutex_unlock(&ubi->buf_mutex);
+                return 0;
+        }
+
+        ubi_err("PEB %d contains corrupted VID header, and the data does not "
+                "contain all 0xFF, this may be a non-UBI PEB or a severe VID "
+                "header corruption which requires manual inspection", pnum);
+        ubi_dbg_dump_vid_hdr(vid_hdr);
+        dbg_msg("hexdump of PEB %d offset %d, length %d",
+                pnum, ubi->leb_start, ubi->leb_size);
+        ubi_dbg_print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1,
+                               ubi->peb_buf1, ubi->leb_size, 1);
+        mutex_unlock(&ubi->buf_mutex);
+        return -EINVAL;
+}
+
+/**
  * process_eb - read, check UBI headers, and add them to scanning information.
  * @ubi: UBI device description object
  * @si: scanning information
@@ -883,6 +930,31 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
                          */
                         si->maybe_bad_peb_count += 1;
         case UBI_IO_BAD_HDR:
+                if (ec_err)
+                        /*
+                         * Both headers are corrupted. There is a possibility
+                         * that this a valid UBI PEB which has corresponding
+                         * LEB, but the headers are corrupted. However, it is
+                         * impossible to distinguish it from a PEB which just
+                         * contains garbage because a power cut during erase
+                         * operation. So we just schedule this PEB for erasure.
+                         */
+                        err = 0;
+                else
+                        /*
+                         * The EC was OK, but the VID header is corrupted. We
+                         * have to check what is in the data area.
+                         */
+                        err = check_data_ff(ubi, vidh, pnum);
+                if (!err)
+                        /* This corruption is caused by a power cut */
+                        err = add_to_list(si, pnum, ec, 1, &si->erase);
+                else
+                        /* This is an unexpected corruption */
+                        err = add_corrupted(si, pnum, ec);
+                if (err)
+                        return err;
+                goto adjust_mean_ec;
         case UBI_IO_FF_BITFLIPS:
                 err = add_to_list(si, pnum, ec, 1, &si->erase);
                 if (err)