Messages in this thread | | | Subject | Re: [PATCH v1 11/11] mtd: new support oops logger based on pstore/blk | From | liaoweixiong <> | Date | Fri, 7 Feb 2020 18:30:37 +0800 |
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hi Miquel Raynal,
On 2020/2/7 下午4:41, Miquel Raynal wrote: > Hi Liao, > > liaoweixiong <liaoweixiong@allwinnertech.com> wrote on Fri, 7 Feb 2020 > 12:13:08 +0800: > >> hi Miquel Raynal, >> >> On 2020/2/6 PM 11:45, Miquel Raynal wrote: >>> Hi liao, >>> >>> liaoweixiong <liaoweixiong@allwinnertech.com> wrote on Thu, 6 Feb 2020 >>> 21:10:47 +0800: >>> >>>> hi Miquel Raynal, >>>> >>>> On 2020/1/23 AM 1:41, Miquel Raynal wrote: >>>>> Hello, >>>>> >>>>> >>>>>>>> +/* >>>>>>>>>> + * All zones will be read as pstore/blk will read zone one by one when do >>>>>>>>>> + * recover. >>>>>>>>>> + */ >>>>>>>>>> +static ssize_t mtdpstore_read(char *buf, size_t size, loff_t off) >>>>>>>>>> +{ >>>>>>>>>> + struct mtdpstore_context *cxt = &oops_cxt; >>>>>>>>>> + size_t retlen; >>>>>>>>>> + int ret; >>>>>>>>>> + >>>>>>>>>> + if (mtdpstore_block_isbad(cxt, off)) >>>>>>>>>> + return -ENEXT; >>>>>>>>>> + >>>>>>>>>> + pr_debug("try to read off 0x%llx size %zu\n", off, size); >>>>>>>>>> + ret = mtd_read(cxt->mtd, off, size, &retlen, (u_char *)buf); >>>>>>>>>> + if ((ret < 0 && !mtd_is_bitflip(ret)) || size != retlen) { >>>>>>>>> >>>>>>>>> IIRC size != retlen does not mean it failed, but that you should >>>>>>>>> continue reading after retlen bytes, no? >>>>>>>>> >> >>>>>>>> Yes, you are right. I will fix it. Thanks. >>>>>>>> >>>>> Also, mtd_is_bitflip() does not mean that you are reading a false >>>>>>>>> buffer, but that the data has been corrected as it contained bitflips. >>>>>>>>> mtd_is_eccerr() however, would be meaningful. >>>>>>>>> >> >>>>>>>> Sure I know mtd_is_bitflip() does not mean failure, but I do not think >>>>>>>> mtd_is_eccerr() should be here since the codes are ret < 0 and NOT >>>>>>>> mtd_is_bitflip(). >>>>>>> >>>>>>> Yes, just drop this check, only keep ret < 0. >>>>>>> >> >>>>>> If I don't get it wrong, it should not be dropped here. Like your words, >>>>>> "mtd_is_bitflip() does not mean that you are reading a false buffer, >>>>>> but that the data has been corrected as it contained bitflips.", the >>>>>> data I get are valid even if mtd_is_bitflip() return true. It's correct >>>>>> data and it's no need to go to handle error. To me, the codes >>>>>> should be: >>>>>> if (ret < 0 && !mit_is_bitflip()) >>>>>> [error handling] >>>>> >>>>> Please check the implementation of mtd_is_bitflip(). You'll probably >>>>> figure out what I am saying. >>>>> >>>>> https://elixir.bootlin.com/linux/latest/source/include/linux/mtd/mtd.h#L585 >>>>> >> >>>> How about the codes as follows: >>>> >>>> for (done = 0, retlen = 0; done < size; done += retlen) { >>>> ret = mtd_read(..., &retlen, ...); >>>> if (!ret) >>>> continue; >>>> /* >>>> * do nothing if bitflip and ecc error occurs because whether >>>> * it's bitflip or ECC error, just a small number of bits flip >>>> * and the impact on log data is so small. The mtdpstore just >>>> * hands over what it gets and user can judge whether the data >>>> * is valid or not. >>>> */ >>>> if (mtd_is_bitflip(ret)) { >>>> dev_warn("bitflip at...."); >>>> continue; >> >>> I don't understand why do you check for bitflips. Bitflips have been >>> corrected at this stage, you just get the information that there >>> has been bitflips, but the data integrity is fine. >>> >> >> Both of bitflip and eccerror are not real wrong in this >> case. So we must check them. >> >>> I am not against ignoring ECC errors in this case though. I would >>> propose: >>> >>> for (...) { >>> if (ret < 0) { >>> complain; >>> return; >>> } >>> >> >> -117 (-EUCLEAN) means bitflip but be corrected. >> -74 (-EBADMSG) means ecc error that uncorrectable >> All of them are negative number that smaller than 0. If it just keeps >> "ret < 0", it can never make a difference between bitflip/eccerror >> and others. > > I forgot about these, your're right, so what about: > > static bool mtdpstore_is_io_error(int ret) > { > return ret < 0 && !mtd_is_eccerr(ret)> && !mtd_is_bitflip(ret); > } > > for (...) { > if (mtdpstore_is_io_error(ret)) > return ret; > > /* > * Comment explaining why we still return valid data > * despite ECC errors. > */ > if (mtd_is_eccerr(ret)) > just-complain(); > } > > This snippet makes a difference between any "controller/bus > timeout/error : data could not be retrieved" and "ECC error, maybe we > can still read it and try to understand (risky, must be warned)". >
That seems good to me. I will fix it later. Thanks for your review.
>> >>> if (mtd_is_eccerr()) >>> complain; >>> } >>> >>>> } else if (mtd_is_eccerr(ret)) { >>>> dev_warn("eccerr at...."); >>>> retlen = retlen == 0 ? size : retlen; >>>> continue; >>>> } else { >>>> dev_err("read failure at..."); >>>> /* this zone is broken, try next one */ >>>> return -ENEXT; >>>> } >>>> } >>>> >>> >>> >>> Thanks, >>> Miquèl >>> > > Thanks, > Miquèl >
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