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.
> 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.
