Re: [PATCH v7 4/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero

[Shiyang Ruan <ruansy.fnst@fujitsu.com>]

On 2021/8/20 10:39, Dan Williams wrote:
> On Sun, Aug 15, 2021 at 11:04 PM Shiyang Ruan <ruansy.fnst@fujitsu.com> wrote:
>>
>> Punch hole on a reflinked file needs dax_iomap_cow_copy() too.
>> Otherwise, data in not aligned area will be not correct.  So, add the
>> srcmap to dax_iomap_zero() and replace memset() as dax_iomap_cow_copy().
>>
>> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
>> Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
>> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
>> ---
>>   fs/dax.c               | 25 +++++++++++++++----------
>>   fs/iomap/buffered-io.c |  4 ++--
>>   include/linux/dax.h    |  3 ++-
>>   3 files changed, 19 insertions(+), 13 deletions(-)
>>
>> diff --git a/fs/dax.c b/fs/dax.c
>> index e49ba68cc7e4..91ceb518f66a 100644
>> --- a/fs/dax.c
>> +++ b/fs/dax.c
>> @@ -1198,7 +1198,8 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
>>   }
>>   #endif /* CONFIG_FS_DAX_PMD */
>>
>> -s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap)
>> +s64 dax_iomap_zero(loff_t pos, u64 length, const struct iomap *iomap,
>> +               const struct iomap *srcmap)
>>   {
>>          sector_t sector = iomap_sector(iomap, pos & PAGE_MASK);
>>          pgoff_t pgoff;
>> @@ -1220,19 +1221,23 @@ s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap)
>>
>>          if (page_aligned)
>>                  rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
>> -       else
>> +       else {
>>                  rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &kaddr, NULL);
>> -       if (rc < 0) {
>> -               dax_read_unlock(id);
>> -               return rc;
>> -       }
>> -
>> -       if (!page_aligned) {
>> -               memset(kaddr + offset, 0, size);
>> +               if (rc < 0)
>> +                       goto out;
>> +               if (iomap->addr != srcmap->addr) {
>> +                       rc = dax_iomap_cow_copy(pos, size, PAGE_SIZE, srcmap,
>> +                                               kaddr);
> 
> Apologies, I'm confused, why is it ok to skip zeroing here?
> 

That was a mistake.  Will be fixed in next version.


--
Thanks,
Ruan.