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.
>
>>>> 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.
>
Getting dax_direct_access to return pfn seems straight forward,
what do you think of below change?
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -195,10 +195,10 @@ int dax_zero_page_range(struct dax_device
*dax_dev, pgoff_t pgoff,
}
EXPORT_SYMBOL_GPL(dax_zero_page_range);
-size_t dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
+size_t dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
pfn_t pfn,
void *addr, size_t bytes, struct iov_iter *iter)
{
- struct dev_pagemap *pgmap = dax_dev->pgmap;
+ struct dev_pagemap *pgmap = get_dev_pagemap(pfn_t_to_pfn(pfn),
NULL);
if (!pgmap || !pgmap->ops->recovery_write)
return -EIO;
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1243,6 +1243,7 @@ static loff_t dax_iomap_iter(const struct
iomap_iter *iomi,
int flags, recov;
void *kaddr;
long nrpg;
+ pfn_t pfn;
if (fatal_signal_pending(current)) {
ret = -EINTR;
@@ -1257,7 +1258,7 @@ static loff_t dax_iomap_iter(const struct
iomap_iter *iomi,
if ((map_len == -EIO) && (iov_iter_rw(iter) == WRITE)) {
flags |= DAX_RECOVERY;
map_len = dax_direct_access(dax_dev, pgoff, nrpg,
- flags, &kaddr, NULL);
+ flags, &kaddr, &pfn);
if (map_len > 0)
recov++;
}
@@ -1273,7 +1274,7 @@ static loff_t dax_iomap_iter(const struct
iomap_iter *iomi,
map_len = end - pos;
if (recov)
- xfer = dax_recovery_write(dax_dev, pgoff, kaddr,
+ xfer = dax_recovery_write(dax_dev, pgoff, pfn,
kaddr,
map_len, iter);
else if (iov_iter_rw(iter) == WRITE)
xfer = dax_copy_from_iter(dax_dev, pgoff, kaddr,
thanks!
-jane
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