diff options
| -rw-r--r-- | drivers/mtd/ubi/scan.c | 45 |
1 files changed, 34 insertions, 11 deletions
diff --git a/drivers/mtd/ubi/scan.c b/drivers/mtd/ubi/scan.c index e7b800b1d072..3c631863bf40 100644 --- a/drivers/mtd/ubi/scan.c +++ b/drivers/mtd/ubi/scan.c @@ -45,14 +45,26 @@ * many warnings and error messages. The idea is that we do not lose * important data in these case - we may lose only the data which was being * written to the media just before the power cut happened, and the upper - * layers are supposed to handle these situations. UBI puts these PEBs to - * the head of the @erase list and they are scheduled for erasure. + * layers (e.g., UBIFS) are supposed to handle these situations. UBI puts + * these PEBs to the head of the @erase list and they are scheduled for + * erasure. * * 2. Unexpected corruptions which are not caused by power cuts. During * scanning, such PEBs are put to the @corr list and UBI preserves them. * Obviously, this lessens the amount of available PEBs, and if at some * point UBI runs out of free PEBs, it switches to R/O mode. UBI also loudly * informs about such PEBs every time the MTD device is attached. + * + * However, it is difficult to reliably distinguish between these types of + * corruptions and UBI's strategy is as follows. UBI assumes (2.) if the VID + * header is corrupted and the data area does not contain all 0xFFs, and there + * were not bit-flips or integrity errors while reading the data area. Otherwise + * UBI assumes (1.). The assumptions are: + * o if the data area contains only 0xFFs, there is no data, and it is safe + * to just erase this PEB. + * o if the data area has bit-flips and data integrity errors (ECC errors on + * NAND), it is probably a PEB which was being erased when power cut + * happened. */ #include <linux/err.h> @@ -741,24 +753,24 @@ struct ubi_scan_leb *ubi_scan_get_free_peb(struct ubi_device *ubi, } /** - * check_data_ff - make sure PEB contains only 0xFF data. + * check_corruption - check the data area of PEB. * @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 + * 0xFF bytes in 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. + * probably 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) +static int check_corruption(struct ubi_device *ubi, struct ubi_vid_hdr *vid_hdr, + int pnum) { int err; @@ -767,7 +779,18 @@ static int check_data_ff(struct ubi_device *ubi, struct ubi_vid_hdr *vid_hdr, err = ubi_io_read(ubi, ubi->peb_buf1, pnum, ubi->leb_start, ubi->leb_size); - if (err && err != UBI_IO_BITFLIPS && err != -EBADMSG) + if (err == UBI_IO_BITFLIPS || err == -EBADMSG) { + /* + * Bit-flips or integrity errors while reading the data area. + * It is difficult to say for sure what type of corruption is + * this, but presumably a power cut happened while this PEB was + * erased, so it became unstable and corrupted, and should be + * erased. + */ + return 0; + } + + if (err) return err; if (ubi_check_pattern(ubi->peb_buf1, 0xFF, ubi->leb_size)) { @@ -926,7 +949,7 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si, * 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 + * contains garbage because of a power cut during erase * operation. So we just schedule this PEB for erasure. */ err = 0; @@ -935,7 +958,7 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si, * 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); + err = check_corruption(ubi, vidh, pnum); if (err < 0) return err; |