| Message ID | 26017351.61791396316965998.JavaMail.weblogic@epv6ml06 |
|---|---|
| State | Changes Requested |
| Headers | show |
On Tue, 2014-04-01 at 01:49 +0000, Eunbong Song wrote: > Even if the meaning of EUCLEAN was changed by commit edbc4540. > There is still possibility of read-only mount in UBIFS with ubifs_scan() "corrupt empty space at LEB". > So i made this patch for fix that problem. Please elaborate on the nature of the problem. > This patch do as follow. > - If there are ecc errors which is equal to or less than chip->ecc.strength in page. > - Check that page has how many zero bits, and if zero bits are equal to or less than > chip->ecc.strength then overwrite 1 to zero bits in buf. This is difficult to parse, with no mention in this sentence that you're talking about corrupted empty pages. > ubifs_scan() cannot detect corrupted empty space because buf is recovered by this patch. > And this is safe because ecc controller can correct up to chip->ecc.strength bits. So the concern is that is_blank is failing to report a page that has not been written to but has errors that would have been correctable if the page had been written? Do most drivers handle this? > Signed-off-by: Eunbong Song <eunb.song@samsung.com> > --- > drivers/mtd/nand/fsl_ifc_nand.c | 41 +++++++++++++++++++++++++++++++++++++++ > 1 files changed, 41 insertions(+), 0 deletions(-) > > diff --git a/drivers/mtd/nand/fsl_ifc_nand.c b/drivers/mtd/nand/fsl_ifc_nand.c > index 90ca7e7..2129c39 100644 > --- a/drivers/mtd/nand/fsl_ifc_nand.c > +++ b/drivers/mtd/nand/fsl_ifc_nand.c > @@ -277,6 +277,42 @@ static int is_blank(struct mtd_info *mtd, unsigned int bufnum) > return 1; > } > > +static int num_zero_bits(uint8_t val) > +{ > + int i, ret=0; > + > + for(i=7; i>=0 ; i--) > + if(!(0x1 & (val >> i))) > + ret++; Whitespace (here and elsewhere) Also, use hweight8(~val) instead of reimplementing it. Or better, use hweight64() and process the data in larger chunks. > + return ret; > +} > + > +static int is_corrupted_blank(struct mtd_info *mtd, uint8_t * buf) > +{ > + struct nand_chip *chip = mtd->priv; > + int i; > + int zero_bits = 0; > + > + for (i = 0; i < mtd->writesize ; i++) { > + if(buf[i] != 0xff) { > + zero_bits += num_zero_bits(buf[i]); > + } > + } > + > + if(zero_bits && (zero_bits <= chip->ecc.strength)){ > + return 1; > + } > + > + return 0; > +} What if it's a page that legitimately has only a handful of zero bits? You need to count zero bits in the ECC as well. Also, this could be combined with is_blank(). > +static void recover_corrupted_blank(struct mtd_info *mtd, uint8_t * buf) > +{ > + memset(buf, 0xff, mtd->writesize); > + return; > +} > + > /* returns nonzero if entire page is blank */ > static int check_read_ecc(struct mtd_info *mtd, struct fsl_ifc_ctrl *ctrl, > u32 *eccstat, unsigned int bufnum) > @@ -760,6 +796,11 @@ static int fsl_ifc_read_page(struct mtd_info *mtd, struct nand_chip *chip, > if (ctrl->nand_stat != IFC_NAND_EVTER_STAT_OPC) > mtd->ecc_stats.failed++; > > + if(nctrl->max_bitflips && (nctrl->max_bitflips <= chip->ecc.strength)){ > + if(is_corrupted_blank(mtd, buf)) > + recover_corrupted_blank(mtd, buf); > + } If the page is blank except for errors, most likely max_bitflips will be zero because fsl_ifc_run_command() already considered it an uncorrectable error and set ECCER instead. Moving corrupted blank page detection into is_blank() wouldn't have this problem. How did you test this patch? -Scott
diff --git a/drivers/mtd/nand/fsl_ifc_nand.c b/drivers/mtd/nand/fsl_ifc_nand.c index 90ca7e7..2129c39 100644 --- a/drivers/mtd/nand/fsl_ifc_nand.c +++ b/drivers/mtd/nand/fsl_ifc_nand.c @@ -277,6 +277,42 @@ static int is_blank(struct mtd_info *mtd, unsigned int bufnum) return 1; } +static int num_zero_bits(uint8_t val) +{ + int i, ret=0; + + for(i=7; i>=0 ; i--) + if(!(0x1 & (val >> i))) + ret++; + + return ret; +} + +static int is_corrupted_blank(struct mtd_info *mtd, uint8_t * buf) +{ + struct nand_chip *chip = mtd->priv; + int i; + int zero_bits = 0; + + for (i = 0; i < mtd->writesize ; i++) { + if(buf[i] != 0xff) { + zero_bits += num_zero_bits(buf[i]); + } + } + + if(zero_bits && (zero_bits <= chip->ecc.strength)){ + return 1; + } + + return 0; +} + +static void recover_corrupted_blank(struct mtd_info *mtd, uint8_t * buf) +{ + memset(buf, 0xff, mtd->writesize); + return; +} + /* returns nonzero if entire page is blank */ static int check_read_ecc(struct mtd_info *mtd, struct fsl_ifc_ctrl *ctrl, u32 *eccstat, unsigned int bufnum) @@ -760,6 +796,11 @@ static int fsl_ifc_read_page(struct mtd_info *mtd, struct nand_chip *chip, if (ctrl->nand_stat != IFC_NAND_EVTER_STAT_OPC) mtd->ecc_stats.failed++; + if(nctrl->max_bitflips && (nctrl->max_bitflips <= chip->ecc.strength)){ + if(is_corrupted_blank(mtd, buf)) + recover_corrupted_blank(mtd, buf); + } + return nctrl->max_bitflips; }
Even if the meaning of EUCLEAN was changed by commit edbc4540. There is still possibility of read-only mount in UBIFS with ubifs_scan() "corrupt empty space at LEB". So i made this patch for fix that problem. This patch do as follow. - If there are ecc errors which is equal to or less than chip->ecc.strength in page. - Check that page has how many zero bits, and if zero bits are equal to or less than chip->ecc.strength then overwrite 1 to zero bits in buf. ubifs_scan() cannot detect corrupted empty space because buf is recovered by this patch. And this is safe because ecc controller can correct up to chip->ecc.strength bits. Signed-off-by: Eunbong Song <eunb.song@samsung.com> --- drivers/mtd/nand/fsl_ifc_nand.c | 41 +++++++++++++++++++++++++++++++++++++++ 1 files changed, 41 insertions(+), 0 deletions(-)