On Thu, Mar 10, 2016 at 4:39 PM, Verma, Vishal L
<vishal.l.verma@xxxxxxxxx> wrote:
> On Tue, 2016-03-08 at 14:47 -0800, Dan Williams wrote:
>> If a write is directed at a known bad block perform the following:
>>
>> 1/ write the data
>>
>> 2/ send a clear poison command
>>
>> 3/ invalidate the poison out of the cache hierarchy
>>
>> Cc: <x86@xxxxxxxxxx>
>> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
>> Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
>> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
>> ---
>> arch/x86/include/asm/pmem.h | 5 +++++
>> drivers/nvdimm/bus.c | 46
>> +++++++++++++++++++++++++++++++++++++++++++
>> drivers/nvdimm/nd.h | 2 ++
>> drivers/nvdimm/pmem.c | 29 ++++++++++++++++++++++++++-
>> include/linux/pmem.h | 19 ++++++++++++++++++
>> 5 files changed, 100 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/pmem.h b/arch/x86/include/asm/pmem.h
>> index c57fd1ea9689..bf8b35d2035a 100644
>> --- a/arch/x86/include/asm/pmem.h
>> +++ b/arch/x86/include/asm/pmem.h
>
> <>
>
>> static int pmem_do_bvec(struct pmem_device *pmem, struct page *page,
>> unsigned int len, unsigned int off, int rw,
>> sector_t sector)
>> {
>> int rc = 0;
>> + bool bad_pmem = false;
>> void *mem = kmap_atomic(page);
>> phys_addr_t pmem_off = sector * 512 + pmem->data_offset;
>> void __pmem *pmem_addr = pmem->virt_addr + pmem_off;
>>
>> + if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
>> + bad_pmem = true;
>> +
>> if (rw == READ) {
>> - if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
>> + if (unlikely(bad_pmem))
>> rc = -EIO;
>> else {
>> memcpy_from_pmem(mem + off, pmem_addr, len);
>> @@ -81,6 +104,10 @@ static int pmem_do_bvec(struct pmem_device *pmem,
>> struct page *page,
>> } else {
>> flush_dcache_page(page);
>> memcpy_to_pmem(pmem_addr, mem + off, len);
>> + if (unlikely(bad_pmem)) {
>> + pmem_clear_poison(pmem, pmem_off, len);
>> + memcpy_to_pmem(pmem_addr, mem + off, len);
>> + }
>> }
>
> Just noticed this -- why do we memcpy_to_pmem twice in the error case?
> Sh
> ouldn't it be:
>
> if (unlikely(bad_pmem))
> pmem_clear_poison(pmem, pmem_off, len);
> memcpy_to_pmem(pmem_addr, mem + off, len);
>
There is an open question of whether clear_poison implementations
guarantee determinant data after clear, or otherwise guarantee that
the data written before the clear_poison stays in place. So I write
twice to cover all those bases. Probably deserves a comment.
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