Messages in this thread | | | From | Dan Williams <> | Date | Thu, 13 Oct 2016 12:24:29 -0700 | Subject | Re: [PATCH] pmem: report error on clear poison failure |
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On Thu, Oct 13, 2016 at 11:16 AM, Kani, Toshimitsu <toshi.kani@hpe.com> wrote: > On Thu, 2016-10-13 at 10:22 -0700, Dan Williams wrote: >> On Thu, Oct 13, 2016 at 9:08 AM, Kani, Toshimitsu <toshi.kani@hpe.com >> > wrote: >> > >> > On Thu, 2016-10-13 at 09:01 -0700, Dan Williams wrote: >> > > >> > > On Thu, Oct 13, 2016 at 8:54 AM, Toshi Kani <toshi.kani@hpe.com> >> > > wrote: >> > > > >> > > > >> > > > ACPI Clear Uncorrectable Error DSM function may fail or may be >> > > > unsupported on a platform. pmem_clear_poison() returns without >> > > > clearing badblocks in such cases, which leads to a silent data >> > > > corruption. >> > > > >> > > > Change pmem_do_bvec() and pmem_clear_poison() to return -EIO >> > > > so that filesystem can log an error message. >> > > >> > > What's the silent data corruption scenario? If the clear poison >> > > fails I'm assuming that the poison will still be notified on the >> > > next >> > > read. >> > >> > I agree that the data is eventually read, but there is no guranteed >> > that when it is read soon enough, i.e. user might not access to the >> > data for a long time. >> >> ...but that's the same behavior for errors that we don't yet know >> about. That said, we indeed know that the write failed. I'd feel >> better about this patch if the justification / impact was clearer in >> the changelog, because "silent data corruption" is not the impact. > > Agreed. How about the following descritpion? > > === > ACPI Clear Uncorrectable Error DSM function may fail or may be > unsupported on a platform. pmem_clear_poison() returns without > clearing badblocks in such cases. This failure is detected at > the next read (-EIO). > > This behavior can lead to an issue when user keeps writing but > does not read immedicately. For instance, flight recorder file > may be only read when it is necessary for troubleshooting. > > Change pmem_do_bvec() and pmem_clear_poison() to return -EIO > so that filesystem can log an error message on a write error. > ===
Looks good, thanks Toshi. I'll update the nvdimm.git branches after -rc1 is out.
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