Re: [PATCH v7 4/6] dax: add DAX_RECOVERY flag and .recovery_write dev_pgmap_ops

[Jane Chu <jane.chu@oracle.com>]

On 4/11/2022 5:08 PM, Dan Williams wrote:
> On Tue, Apr 5, 2022 at 12:48 PM Jane Chu <jane.chu@oracle.com> wrote:
>>
>> Introduce DAX_RECOVERY flag to dax_direct_access(). The flag is
>> not set by default in dax_direct_access() such that the helper
>> does not translate a pmem range to kernel virtual address if the
>> range contains uncorrectable errors.  When the flag is set,
>> the helper ignores the UEs and return kernel virtual adderss so
>> that the caller may get on with data recovery via write.
>>
>> 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.
>>
>> Signed-off-by: Jane Chu <jane.chu@oracle.com>
>> ---
>>   drivers/dax/super.c             | 17 ++++++++--
>>   drivers/md/dm-linear.c          |  4 +--
>>   drivers/md/dm-log-writes.c      |  5 +--
>>   drivers/md/dm-stripe.c          |  4 +--
>>   drivers/md/dm-target.c          |  2 +-
>>   drivers/md/dm-writecache.c      |  5 +--
>>   drivers/md/dm.c                 |  5 +--
>>   drivers/nvdimm/pmem.c           | 57 +++++++++++++++++++++++++++------
>>   drivers/nvdimm/pmem.h           |  2 +-
>>   drivers/s390/block/dcssblk.c    |  4 +--
>>   fs/dax.c                        | 24 ++++++++++----
>>   fs/fuse/dax.c                   |  4 +--
>>   include/linux/dax.h             | 11 +++++--
>>   include/linux/device-mapper.h   |  2 +-
>>   include/linux/memremap.h        |  7 ++++
>>   tools/testing/nvdimm/pmem-dax.c |  2 +-
>>   16 files changed, 116 insertions(+), 39 deletions(-)
>>
>> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
>> index 0211e6f7b47a..8252858cd25a 100644
>> --- a/drivers/dax/super.c
>> +++ b/drivers/dax/super.c
>> @@ -13,6 +13,7 @@
>>   #include <linux/uio.h>
>>   #include <linux/dax.h>
>>   #include <linux/fs.h>
>> +#include <linux/memremap.h>
>>   #include "dax-private.h"
>>
>>   /**
>> @@ -117,6 +118,7 @@ enum dax_device_flags {
>>    * @dax_dev: a dax_device instance representing the logical memory range
>>    * @pgoff: offset in pages from the start of the device to translate
>>    * @nr_pages: number of consecutive pages caller can handle relative to @pfn
>> + * @flags: by default 0, set to DAX_RECOVERY to kick start dax recovery
>>    * @kaddr: output parameter that returns a virtual address mapping of pfn
>>    * @pfn: output parameter that returns an absolute pfn translation of @pgoff
>>    *
>> @@ -124,7 +126,7 @@ enum dax_device_flags {
>>    * pages accessible at the device relative @pgoff.
>>    */
>>   long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
>> -               void **kaddr, pfn_t *pfn)
>> +               int flags, void **kaddr, pfn_t *pfn)
>>   {
>>          long avail;
>>
>> @@ -137,7 +139,7 @@ long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
>>          if (nr_pages < 0)
>>                  return -EINVAL;
>>
>> -       avail = dax_dev->ops->direct_access(dax_dev, pgoff, nr_pages,
>> +       avail = dax_dev->ops->direct_access(dax_dev, pgoff, nr_pages, flags,
>>                          kaddr, pfn);
>>          if (!avail)
>>                  return -ERANGE;
>> @@ -194,6 +196,17 @@ 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,
>> +               pfn_t pfn, void *addr, size_t bytes, struct iov_iter *iter)
>> +{
>> +       struct dev_pagemap *pgmap = get_dev_pagemap(pfn_t_to_pfn(pfn), NULL);
>> +
>> +       if (!pgmap || !pgmap->ops || !pgmap->ops->recovery_write)
>> +               return 0;
>> +       return pgmap->ops->recovery_write(pgmap, pgoff, addr, bytes, iter);
>> +}
>> +EXPORT_SYMBOL_GPL(dax_recovery_write);
>> +
>>   #ifdef CONFIG_ARCH_HAS_PMEM_API
>>   void arch_wb_cache_pmem(void *addr, size_t size);
>>   void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
>> diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
>> index 76b486e4d2be..9e6d8bdf3b2a 100644
>> --- a/drivers/md/dm-linear.c
>> +++ b/drivers/md/dm-linear.c
>> @@ -172,11 +172,11 @@ static struct dax_device *linear_dax_pgoff(struct dm_target *ti, pgoff_t *pgoff)
>>   }
>>
>>   static long linear_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
>> -               long nr_pages, void **kaddr, pfn_t *pfn)
>> +               long nr_pages, int flags, void **kaddr, pfn_t *pfn)
>>   {
>>          struct dax_device *dax_dev = linear_dax_pgoff(ti, &pgoff);
>>
>> -       return dax_direct_access(dax_dev, pgoff, nr_pages, kaddr, pfn);
>> +       return dax_direct_access(dax_dev, pgoff, nr_pages, flags, kaddr, pfn);
>>   }
>>
>>   static int linear_dax_zero_page_range(struct dm_target *ti, pgoff_t pgoff,
>> diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
>> index c9d036d6bb2e..e23f062ade5f 100644
>> --- a/drivers/md/dm-log-writes.c
>> +++ b/drivers/md/dm-log-writes.c
>> @@ -889,11 +889,12 @@ static struct dax_device *log_writes_dax_pgoff(struct dm_target *ti,
>>   }
>>
>>   static long log_writes_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
>> -                                        long nr_pages, void **kaddr, pfn_t *pfn)
>> +                                        long nr_pages, int flags,
>> +                                        void **kaddr, pfn_t *pfn)
>>   {
>>          struct dax_device *dax_dev = log_writes_dax_pgoff(ti, &pgoff);
>>
>> -       return dax_direct_access(dax_dev, pgoff, nr_pages, kaddr, pfn);
>> +       return dax_direct_access(dax_dev, pgoff, nr_pages, flags, kaddr, pfn);
>>   }
>>
>>   static int log_writes_dax_zero_page_range(struct dm_target *ti, pgoff_t pgoff,
>> diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
>> index c81d331d1afe..b89339c78702 100644
>> --- a/drivers/md/dm-stripe.c
>> +++ b/drivers/md/dm-stripe.c
>> @@ -315,11 +315,11 @@ static struct dax_device *stripe_dax_pgoff(struct dm_target *ti, pgoff_t *pgoff)
>>   }
>>
>>   static long stripe_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
>> -               long nr_pages, void **kaddr, pfn_t *pfn)
>> +               long nr_pages, int flags, void **kaddr, pfn_t *pfn)
>>   {
>>          struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);
>>
>> -       return dax_direct_access(dax_dev, pgoff, nr_pages, kaddr, pfn);
>> +       return dax_direct_access(dax_dev, pgoff, nr_pages, flags, kaddr, pfn);
>>   }
>>
>>   static int stripe_dax_zero_page_range(struct dm_target *ti, pgoff_t pgoff,
>> diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
>> index 64dd0b34fcf4..24b1e5628f3a 100644
>> --- a/drivers/md/dm-target.c
>> +++ b/drivers/md/dm-target.c
>> @@ -142,7 +142,7 @@ static void io_err_release_clone_rq(struct request *clone,
>>   }
>>
>>   static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
>> -               long nr_pages, void **kaddr, pfn_t *pfn)
>> +               long nr_pages, int flags, void **kaddr, pfn_t *pfn)
>>   {
>>          return -EIO;
>>   }
>> diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
>> index 5630b470ba42..180ca8fa383e 100644
>> --- a/drivers/md/dm-writecache.c
>> +++ b/drivers/md/dm-writecache.c
>> @@ -286,7 +286,8 @@ static int persistent_memory_claim(struct dm_writecache *wc)
>>
>>          id = dax_read_lock();
>>
>> -       da = dax_direct_access(wc->ssd_dev->dax_dev, offset, p, &wc->memory_map, &pfn);
>> +       da = dax_direct_access(wc->ssd_dev->dax_dev, offset, p, 0,
>> +                       &wc->memory_map, &pfn);
>>          if (da < 0) {
>>                  wc->memory_map = NULL;
>>                  r = da;
>> @@ -309,7 +310,7 @@ static int persistent_memory_claim(struct dm_writecache *wc)
>>                  do {
>>                          long daa;
>>                          daa = dax_direct_access(wc->ssd_dev->dax_dev, offset + i, p - i,
>> -                                               NULL, &pfn);
>> +                                               0, NULL, &pfn);
>>                          if (daa <= 0) {
>>                                  r = daa ? daa : -EINVAL;
>>                                  goto err3;
>> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
>> index ad2e0bbeb559..a8c697bb6603 100644
>> --- a/drivers/md/dm.c
>> +++ b/drivers/md/dm.c
>> @@ -1087,7 +1087,8 @@ static struct dm_target *dm_dax_get_live_target(struct mapped_device *md,
>>   }
>>
>>   static long dm_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
>> -                                long nr_pages, void **kaddr, pfn_t *pfn)
>> +                                long nr_pages, int flags, void **kaddr,
>> +                                pfn_t *pfn)
>>   {
>>          struct mapped_device *md = dax_get_private(dax_dev);
>>          sector_t sector = pgoff * PAGE_SECTORS;
>> @@ -1105,7 +1106,7 @@ static long dm_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
>>          if (len < 1)
>>                  goto out;
>>          nr_pages = min(len, nr_pages);
>> -       ret = ti->type->direct_access(ti, pgoff, nr_pages, kaddr, pfn);
>> +       ret = ti->type->direct_access(ti, pgoff, nr_pages, flags, kaddr, pfn);
>>
>>    out:
>>          dm_put_live_table(md, srcu_idx);
>> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
>> index 30c71a68175b..0400c5a7ba39 100644
>> --- a/drivers/nvdimm/pmem.c
>> +++ b/drivers/nvdimm/pmem.c
>> @@ -238,12 +238,23 @@ static int pmem_rw_page(struct block_device *bdev, sector_t sector,
>>
>>   /* see "strong" declaration in tools/testing/nvdimm/pmem-dax.c */
>>   __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;
>> +       sector_t sector = PFN_PHYS(pgoff) >> SECTOR_SHIFT;
>> +       unsigned int num = PFN_PHYS(nr_pages) >> SECTOR_SHIFT;
>> +       struct badblocks *bb = &pmem->bb;
>> +       sector_t first_bad;
>> +       int num_bad;
>> +       bool bad_in_range;
>> +       long actual_nr;
>> +
>> +       if (!bb->count)
>> +               bad_in_range = false;
>> +       else
>> +               bad_in_range = !!badblocks_check(bb, sector, num, &first_bad, &num_bad);
> 
> Why all this change. >
>>
>> -       if (unlikely(is_bad_pmem(&pmem->bb, PFN_PHYS(pgoff) / 512,
>> -                                       PFN_PHYS(nr_pages))))
> 
> ...instead of adding "&& !(flags & DAX_RECOVERY)" to this statement?
> 
>> +       if (bad_in_range && !(flags & DAX_RECOVERY))
>>                  return -EIO;
>>
>>          if (kaddr)
>> @@ -251,13 +262,26 @@ __weak long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,
>>          if (pfn)
>>                  *pfn = phys_to_pfn_t(pmem->phys_addr + offset, pmem->pfn_flags);
>>
>> +       if (!bad_in_range) {
>> +               /*
>> +                * If badblock is present but not in the range, limit known good range
>> +                * to the requested range.
>> +                */
>> +               if (bb->count)
>> +                       return nr_pages;
>> +               return PHYS_PFN(pmem->size - pmem->pfn_pad - offset);
>> +       }
>> +
>>          /*
>> -        * If badblocks are present, limit known good range to the
>> -        * requested range.
>> +        * In case poison is found in the given range and DAX_RECOVERY flag is set,
>> +        * recovery stride is set to kernel page size because the underlying driver and
>> +        * firmware clear poison functions don't appear to handle large chunk (such as
>> +        * 2MiB) reliably.
>>           */
>> -       if (unlikely(pmem->bb.count))
>> -               return nr_pages;
>> -       return PHYS_PFN(pmem->size - pmem->pfn_pad - offset);
>> +       actual_nr = PHYS_PFN(PAGE_ALIGN((first_bad - sector) << SECTOR_SHIFT));
>> +       dev_dbg(pmem->bb.dev, "start sector(%llu), nr_pages(%ld), first_bad(%llu), actual_nr(%ld)\n",
>> +                       sector, nr_pages, first_bad, actual_nr);
>> +       return (actual_nr == 0) ? 1 : actual_nr;
> 
> Similar feedback as above that this is more change than I would expect.
> 
> I think just adding...
> 
> if (flags & DAX_RECOVERY)
>     return 1;
> 
> ...before the typical return path is enough.

I plan to use the re-organized code by Christoph - looks cleaner to me.

thanks!
-jane