[PATCH v8 4/7] 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
srcmap to dax_iomap_zero() and replace memset() as dax_iomap_cow_copy().

Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
Reviewed-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
 fs/dax.c               | 26 ++++++++++++++++----------
 fs/iomap/buffered-io.c |  4 ++--
 include/linux/dax.h    |  3 ++-
 3 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index f4acb79cb811..b294900e574e 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1209,7 +1209,8 @@ 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;
@@ -1231,19 +1232,24 @@ 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) {
+		if (rc < 0)
+			goto out;
 		memset(kaddr + offset, 0, size);
-		dax_flush(iomap->dax_dev, kaddr + offset, size);
+		if (iomap->addr != srcmap->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,
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 71b4806266d7..6e8d40877d01 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -889,7 +889,7 @@ static s64 __iomap_zero_iter(struct iomap_iter *iter, loff_t pos, u64 length)
 
 static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 {
-	struct iomap *iomap = &iter->iomap;
+	const struct iomap *iomap = &iter->iomap;
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	loff_t pos = iter->pos;
 	loff_t length = iomap_length(iter);
@@ -903,7 +903,7 @@ static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		s64 bytes;
 
 		if (IS_DAX(iter->inode))
-			bytes = dax_iomap_zero(pos, length, iomap);
+			bytes = dax_iomap_zero(pos, length, iomap, srcmap);
 		else
 			bytes = __iomap_zero_iter(iter, pos, length);
 		if (bytes < 0)
diff --git a/include/linux/dax.h b/include/linux/dax.h
index b52f084aa643..c63559605369 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -237,7 +237,8 @@ vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf,
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
 int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
 				      pgoff_t index);
-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);
 static inline bool dax_mapping(struct address_space *mapping)
 {
 	return mapping->host && IS_DAX(mapping->host);
-- 
2.32.0