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UBI: handle bit-flips when no header found

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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>
This commit is contained in:
Artem Bityutskiy 2010-09-03 14:22:17 +03:00
parent 74d82d2660
commit 92e1a7d9e7
4 changed files with 51 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
drivers/mtd/ubi/io.c
View File

@ -720,16 +720,16 @@ bad:
int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
struct ubi_ec_hdr *ec_hdr, int verbose)
{
int err, read_err = 0;
int err, read_err;
uint32_t crc, magic, hdr_crc;
dbg_io("read EC header from PEB %d", pnum);
ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
err = ubi_io_read(ubi, ec_hdr, pnum, 0, UBI_EC_HDR_SIZE);
if (err) {
if (err != UBI_IO_BITFLIPS && err != -EBADMSG)
return err;
read_err = ubi_io_read(ubi, ec_hdr, pnum, 0, UBI_EC_HDR_SIZE);
if (read_err) {
if (read_err != UBI_IO_BITFLIPS && read_err != -EBADMSG)
return read_err;
/*
* We read all the data, but either a correctable bit-flip
@ -740,14 +740,12 @@ int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
* this. If the EC header is still OK, we just report this as
* there was a bit-flip, to force scrubbing.
*/
if (err == -EBADMSG)
read_err = UBI_IO_BAD_HDR_EBADMSG;
}
magic = be32_to_cpu(ec_hdr->magic);
if (magic != UBI_EC_HDR_MAGIC) {
if (read_err)
return read_err;
if (read_err == -EBADMSG)
return UBI_IO_BAD_HDR_EBADMSG;
/*
* The magic field is wrong. Let's check if we have read all
@ -762,7 +760,10 @@ int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
else if (UBI_IO_DEBUG)
dbg_msg("no EC header found at PEB %d, "
"only 0xFF bytes", pnum);
return UBI_IO_FF;
if (!read_err)
return UBI_IO_FF;
else
return UBI_IO_FF_BITFLIPS;
}
/*
@ -790,7 +791,11 @@ int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
} else if (UBI_IO_DEBUG)
dbg_msg("bad EC header CRC at PEB %d, calculated "
"%#08x, read %#08x", pnum, crc, hdr_crc);
return read_err ?: UBI_IO_BAD_HDR;
if (!read_err)
return UBI_IO_BAD_HDR;
else
return UBI_IO_BAD_HDR_EBADMSG;
}
/* And of course validate what has just been read from the media */
@ -986,7 +991,7 @@ bad:
int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
struct ubi_vid_hdr *vid_hdr, int verbose)
{
int err, read_err = 0;
int err, read_err;
uint32_t crc, magic, hdr_crc;
void *p;
@ -994,20 +999,15 @@ int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
p = (char *)vid_hdr - ubi->vid_hdr_shift;
err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
read_err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
ubi->vid_hdr_alsize);
if (err) {
if (err != UBI_IO_BITFLIPS && err != -EBADMSG)
return err;
if (err == -EBADMSG)
read_err = UBI_IO_BAD_HDR_EBADMSG;
}
if (read_err && read_err != UBI_IO_BITFLIPS && read_err != -EBADMSG)
return read_err;
magic = be32_to_cpu(vid_hdr->magic);
if (magic != UBI_VID_HDR_MAGIC) {
if (read_err)
return read_err;
if (read_err == -EBADMSG)
return UBI_IO_BAD_HDR_EBADMSG;
if (check_pattern(vid_hdr, 0xFF, UBI_VID_HDR_SIZE)) {
if (verbose)
@ -1016,7 +1016,10 @@ int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
else if (UBI_IO_DEBUG)
dbg_msg("no VID header found at PEB %d, "
"only 0xFF bytes", pnum);
return UBI_IO_FF;
if (!read_err)
return UBI_IO_FF;
else
return UBI_IO_FF_BITFLIPS;
}
if (verbose) {
@ -1040,7 +1043,10 @@ int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
} else if (UBI_IO_DEBUG)
dbg_msg("bad CRC at PEB %d, calculated %#08x, "
"read %#08x", pnum, crc, hdr_crc);
return read_err ?: UBI_IO_BAD_HDR;
if (!read_err)
return UBI_IO_BAD_HDR;
else
return UBI_IO_BAD_HDR_EBADMSG;
}
err = validate_vid_hdr(ubi, vid_hdr);

4
drivers/mtd/ubi/scan.c
View File

@ -748,7 +748,7 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
return err;
else if (err == UBI_IO_BITFLIPS)
bitflips = 1;
else if (err == UBI_IO_FF)
else if (err == UBI_IO_FF || err == UBI_IO_FF_BITFLIPS)
return add_to_list(si, pnum, UBI_SCAN_UNKNOWN_EC, &si->erase);
else if (err == UBI_IO_BAD_HDR_EBADMSG || err == UBI_IO_BAD_HDR) {
/*
@ -817,7 +817,7 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
else if (err == UBI_IO_BITFLIPS)
bitflips = 1;
else if (err == UBI_IO_BAD_HDR_EBADMSG || err == UBI_IO_BAD_HDR ||
(err == UBI_IO_FF && ec_corr)) {
(err == UBI_IO_FF && ec_corr) || err == UBI_IO_FF_BITFLIPS) {
/* VID header is corrupted */
if (err == UBI_IO_BAD_HDR_EBADMSG ||
ec_corr == UBI_IO_BAD_HDR_EBADMSG)

10
drivers/mtd/ubi/ubi.h
View File

@ -86,17 +86,25 @@
* Error codes returned by the I/O sub-system.
*
* UBI_IO_FF: the read region of flash contains only 0xFFs
* UBI_IO_FF_BITFLIPS: the same as %UBI_IO_FF, but also also there was a data
* integrity error reported by the MTD driver
* (uncorrectable ECC error in case of NAND)
* UBI_IO_BAD_HDR: the EC or VID header is corrupted (bad magic or CRC)
* UBI_IO_BAD_HDR_EBADMSG: the same as %UBI_IO_BAD_HDR, but also there was a
* data integrity error reported by the MTD driver
* (uncorrectable ECC error in case of NAND)
* UBI_IO_BITFLIPS: bit-flips were detected and corrected
*
* Note, it is probably better to have bit-flip and ebadmsg as flags which can
* be or'ed with other error code. But this is a big change because there are
* may callers, so it does not worth the risk of introducing a bug
*/
enum {
UBI_IO_FF = 1,
UBI_IO_FF_BITFLIPS,
UBI_IO_BAD_HDR,
UBI_IO_BAD_HDR_EBADMSG,
UBI_IO_BITFLIPS
UBI_IO_BITFLIPS,
};
/*

10
drivers/mtd/ubi/wl.c
View File

@ -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",