On 3/22/2022 10:45 PM, Christoph Hellwig wrote:
> On Tue, Mar 22, 2022 at 11:05:09PM +0000, Jane Chu wrote:
>>> This DAX_RECOVERY doesn't actually seem to be used anywhere here or
>>> in the subsequent patches. Did I miss something?
>>
>> dax_iomap_iter() uses the flag in the same patch,
>> + if ((map_len == -EIO) && (iov_iter_rw(iter) == WRITE)) {
>> + flags |= DAX_RECOVERY;
>> + map_len = dax_direct_access(dax_dev, pgoff, nrpg,
>> + flags, &kaddr, NULL);
>
> Yes, it passes it on to dax_direct_access, and dax_direct_access passes
> it onto ->direct_access. But nothing in this series actually checks
> for it as far as I can tell.
The flag is checked here, again, I'll spell out the flag rather than
using it as a boolean.
__weak long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,
- long nr_pages, void **kaddr, pfn_t *pfn)
+ long nr_pages, int flags, void **kaddr, pfn_t *pfn)
{
resource_size_t offset = PFN_PHYS(pgoff) + pmem->data_offset;
- if (unlikely(is_bad_pmem(&pmem->bb, PFN_PHYS(pgoff) / 512,
+ if (!flags && unlikely(is_bad_pmem(&pmem->bb, PFN_PHYS(pgoff) / 512,
PFN_PHYS(nr_pages))))
return -EIO;
>
>>>> Also introduce a new dev_pagemap_ops .recovery_write function.
>>>> The function is applicable to FSDAX device only. The device
>>>> page backend driver provides .recovery_write function if the
>>>> device has underlying mechanism to clear the uncorrectable
>>>> errors on the fly.
>>>
>>> Why is this not in struct dax_operations?
>>
>> Per Dan's comments to the v5 series, adding .recovery_write to
>> dax_operations causes a number of trivial dm targets changes.
>> Dan suggested that adding .recovery_write to pagemap_ops could
>> cut short the logistics of figuring out whether the driver backing
>> up a page is indeed capable of clearing poison. Please see
>> https://lkml.org/lkml/2022/2/4/31
>
> But at least in this series there is 1:1 association between the
> pgmap and the dax_device so that scheme won't work. It would
> have to lookup the pgmap based on the return physical address from
> dax_direct_access. Which sounds more complicated than just adding
> the (annoying) boilerplate code to DM.
>
Yes, good point! Let me look into this.
>> include/linux/memremap.h doesn't know struct iov_iter which is defined
>> in include/linux/uio.h, would you prefer to adding include/linux/uio.h
>> to include/linux/memremap.h ?
>
> As it is not derefences just adding a
>
> struct iov_iter;
>
> line to memremap.h below the includes should be all that is needed.
Sure, will do.
Thanks!
-jane
