[PATCH v9 5/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero

[Shiyang Ruan]

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
CoW operation for not aligned case in dax_iomap_zero().

Signed-off-by: Shiyang Ruan <ruansy.f...@fujitsu.com>
Reviewed-by: Ritesh Harjani <rite...@linux.ibm.com>
Reviewed-by: Darrick J. Wong <djw...@kernel.org>
---
 fs/dax.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 4f346e25e488..ca4308c85988 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1212,6 +1212,7 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, 
struct vm_fault *vmf,
 s64 dax_iomap_zero(struct iomap_iter *iter, loff_t pos, u64 length)
 {
        const struct iomap *iomap = &iter->iomap;
+       const struct iomap *srcmap = &iter->srcmap;
        sector_t sector = iomap_sector(iomap, pos & PAGE_MASK);
        pgoff_t pgoff;
        long rc, id;
@@ -1230,21 +1231,27 @@ s64 dax_iomap_zero(struct iomap_iter *iter, loff_t pos, 
u64 length)
 
        id = dax_read_lock();
 
-       if (page_aligned)
+       if (page_aligned) {
                rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
-       else
-               rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &kaddr, NULL);
-       if (rc < 0) {
-               dax_read_unlock(id);
-               return rc;
+               goto out;
        }
 
-       if (!page_aligned) {
-               memset(kaddr + offset, 0, size);
+       rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &kaddr, NULL);
+       if (rc < 0)
+               goto out;
+       memset(kaddr + offset, 0, size);
+       if (srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) {
+               rc = dax_iomap_cow_copy(pos, size, PAGE_SIZE, srcmap,
+                                       kaddr);
+               if (rc < 0)
+                       goto out;
+               dax_flush(iomap->dax_dev, kaddr, PAGE_SIZE);
+       } else
                dax_flush(iomap->dax_dev, kaddr + offset, size);
-       }
+
+out:
        dax_read_unlock(id);
-       return size;
+       return rc < 0 ? rc : size;
 }
 
 static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
-- 
2.33.0