diff --git a/fs/dax.c b/fs/dax.c
index 1c6867810cbd..5ea7c0926b7f 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -398,7 +398,7 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping,
 		WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
 		if (dax_mapping_is_cow(page->mapping)) {
 			/* keep the CoW flag if this page is still shared */
-			if (page->index-- > 0)
+			if (page->index-- > 1)
 				continue;
 		} else
 			WARN_ON_ONCE(page->mapping && page->mapping != mapping);
@@ -840,12 +840,6 @@ static bool dax_fault_is_synchronous(const struct iomap_iter *iter,
 		(iter->iomap.flags & IOMAP_F_DIRTY);
 }
 
-static bool dax_fault_is_cow(const struct iomap_iter *iter)
-{
-	return (iter->flags & IOMAP_WRITE) &&
-		(iter->iomap.flags & IOMAP_F_SHARED);
-}
-
 /*
  * By this point grab_mapping_entry() has ensured that we have a locked entry
  * of the appropriate size so we don't have to worry about downgrading PMDs to
@@ -859,13 +853,14 @@ static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
 {
 	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
 	void *new_entry = dax_make_entry(pfn, flags);
-	bool dirty = !dax_fault_is_synchronous(iter, vmf->vma);
-	bool cow = dax_fault_is_cow(iter);
+	bool write = iter->flags & IOMAP_WRITE;
+	bool dirty = write && !dax_fault_is_synchronous(iter, vmf->vma);
+	bool shared = iter->iomap.flags & IOMAP_F_SHARED;
 
 	if (dirty)
 		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 
-	if (cow || (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE))) {
+	if (shared || (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE))) {
 		unsigned long index = xas->xa_index;
 		/* we are replacing a zero page with block mapping */
 		if (dax_is_pmd_entry(entry))
@@ -877,12 +872,12 @@ static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
 
 	xas_reset(xas);
 	xas_lock_irq(xas);
-	if (cow || dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+	if (shared || dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
 		void *old;
 
 		dax_disassociate_entry(entry, mapping, false);
 		dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address,
-				cow);
+				shared);
 		/*
 		 * Only swap our new entry into the page cache if the current
 		 * entry is a zero page or an empty entry.  If a normal PTE or
@@ -902,7 +897,7 @@ static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
 	if (dirty)
 		xas_set_mark(xas, PAGECACHE_TAG_DIRTY);
 
-	if (cow)
+	if (write && shared)
 		xas_set_mark(xas, PAGECACHE_TAG_TOWRITE);
 
 	xas_unlock_irq(xas);
@@ -1107,23 +1102,35 @@ static int dax_iomap_cow_copy(loff_t pos, uint64_t length, size_t align_size,
 	loff_t end = pos + length;
 	loff_t pg_end = round_up(end, align_size);
 	bool copy_all = head_off == 0 && end == pg_end;
+	/* write zero at edge if srcmap is a HOLE or IOMAP_UNWRITTEN */
+	bool zero_edge = srcmap->flags & IOMAP_F_SHARED ||
+			 srcmap->type == IOMAP_UNWRITTEN;
 	void *saddr = 0;
 	int ret = 0;
 
-	ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL);
-	if (ret)
-		return ret;
+	if (!zero_edge) {
+		ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL);
+		if (ret)
+			return ret;
+	}
 
 	if (copy_all) {
-		ret = copy_mc_to_kernel(daddr, saddr, length);
-		return ret ? -EIO : 0;
+		if (zero_edge)
+			memset(daddr, 0, size);
+		else
+			ret = copy_mc_to_kernel(daddr, saddr, length);
+		goto out;
 	}
 
 	/* Copy the head part of the range */
 	if (head_off) {
-		ret = copy_mc_to_kernel(daddr, saddr, head_off);
-		if (ret)
-			return -EIO;
+		if (zero_edge)
+			memset(daddr, 0, head_off);
+		else {
+			ret = copy_mc_to_kernel(daddr, saddr, head_off);
+			if (ret)
+				return -EIO;
+		}
 	}
 
 	/* Copy the tail part of the range */
@@ -1131,12 +1138,19 @@ static int dax_iomap_cow_copy(loff_t pos, uint64_t length, size_t align_size,
 		loff_t tail_off = head_off + length;
 		loff_t tail_len = pg_end - end;
 
-		ret = copy_mc_to_kernel(daddr + tail_off, saddr + tail_off,
-					tail_len);
-		if (ret)
-			return -EIO;
+		if (zero_edge)
+			memset(daddr + tail_off, 0, tail_len);
+		else {
+			ret = copy_mc_to_kernel(daddr + tail_off,
+						saddr + tail_off, tail_len);
+			if (ret)
+				return -EIO;
+		}
 	}
-	return 0;
+out:
+	if (zero_edge)
+		dax_flush(srcmap->dax_dev, daddr, size);
+	return ret ? -EIO : 0;
 }
 
 /*
@@ -1235,13 +1249,9 @@ static int dax_memzero(struct iomap_iter *iter, loff_t pos, size_t size)
 	if (ret < 0)
 		return ret;
 	memset(kaddr + offset, 0, size);
-	if (srcmap->addr != iomap->addr) {
-		ret = dax_iomap_cow_copy(pos, size, PAGE_SIZE, srcmap,
-					 kaddr);
-		if (ret < 0)
-			return ret;
-		dax_flush(iomap->dax_dev, kaddr, PAGE_SIZE);
-	} else
+	if (iomap->flags & IOMAP_F_SHARED)
+		ret = dax_iomap_cow_copy(pos, size, PAGE_SIZE, srcmap, kaddr);
+	else
 		dax_flush(iomap->dax_dev, kaddr + offset, size);
 	return ret;
 }
@@ -1258,6 +1268,15 @@ static s64 dax_zero_iter(struct iomap_iter *iter, bool *did_zero)
 	if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
 		return length;
 
+	/*
+	 * invalidate the pages whose sharing state is to be changed
+	 * because of CoW.
+	 */
+	if (iomap->flags & IOMAP_F_SHARED)
+		invalidate_inode_pages2_range(iter->inode->i_mapping,
+					      pos >> PAGE_SHIFT,
+					      (pos + length - 1) >> PAGE_SHIFT);
+
 	do {
 		unsigned offset = offset_in_page(pos);
 		unsigned size = min_t(u64, PAGE_SIZE - offset, length);
@@ -1318,12 +1337,13 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
 		struct iov_iter *iter)
 {
 	const struct iomap *iomap = &iomi->iomap;
-	const struct iomap *srcmap = &iomi->srcmap;
+	const struct iomap *srcmap = iomap_iter_srcmap(iomi);
 	loff_t length = iomap_length(iomi);
 	loff_t pos = iomi->pos;
 	struct dax_device *dax_dev = iomap->dax_dev;
 	loff_t end = pos + length, done = 0;
 	bool write = iov_iter_rw(iter) == WRITE;
+	bool cow = write && iomap->flags & IOMAP_F_SHARED;
 	ssize_t ret = 0;
 	size_t xfer;
 	int id;
@@ -1350,7 +1370,7 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
 	 * into page tables. We have to tear down these mappings so that data
 	 * written by write(2) is visible in mmap.
 	 */
-	if (iomap->flags & IOMAP_F_NEW) {
+	if (iomap->flags & IOMAP_F_NEW || cow) {
 		invalidate_inode_pages2_range(iomi->inode->i_mapping,
 					      pos >> PAGE_SHIFT,
 					      (end - 1) >> PAGE_SHIFT);
@@ -1384,8 +1404,7 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
 			break;
 		}
 
-		if (write &&
-		    srcmap->type != IOMAP_HOLE && srcmap->addr != iomap->addr) {
+		if (cow) {
 			ret = dax_iomap_cow_copy(pos, length, PAGE_SIZE, srcmap,
 						 kaddr);
 			if (ret)
@@ -1532,7 +1551,7 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
 		struct xa_state *xas, void **entry, bool pmd)
 {
 	const struct iomap *iomap = &iter->iomap;
-	const struct iomap *srcmap = &iter->srcmap;
+	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	size_t size = pmd ? PMD_SIZE : PAGE_SIZE;
 	loff_t pos = (loff_t)xas->xa_index << PAGE_SHIFT;
 	bool write = iter->flags & IOMAP_WRITE;
@@ -1563,8 +1582,7 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
 
 	*entry = dax_insert_entry(xas, vmf, iter, *entry, pfn, entry_flags);
 
-	if (write &&
-	    srcmap->type != IOMAP_HOLE && srcmap->addr != iomap->addr) {
+	if (write && iomap->flags & IOMAP_F_SHARED) {
 		err = dax_iomap_cow_copy(pos, size, size, srcmap, kaddr);
 		if (err)
 			return dax_fault_return(err);
@@ -1936,15 +1954,15 @@ int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
 		.len		= len,
 		.flags		= IOMAP_DAX,
 	};
-	int ret;
+	int ret, compared = 0;
 
-	while ((ret = iomap_iter(&src_iter, ops)) > 0) {
-		while ((ret = iomap_iter(&dst_iter, ops)) > 0) {
-			dst_iter.processed = dax_range_compare_iter(&src_iter,
-						&dst_iter, len, same);
-		}
-		if (ret <= 0)
-			src_iter.processed = ret;
+	while ((ret = iomap_iter(&src_iter, ops)) > 0 &&
+	       (ret = iomap_iter(&dst_iter, ops)) > 0) {
+		compared = dax_range_compare_iter(&src_iter, &dst_iter, len,
+						  same);
+		if (compared < 0)
+			return ret;
+		src_iter.processed = dst_iter.processed = compared;
 	}
 	return ret;
 }
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 07da03976ec1..d9401d0300ad 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1215,7 +1215,7 @@ xfs_read_iomap_begin(
 		return error;
 	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
 			       &nimaps, 0);
-	if (!error && (flags & IOMAP_REPORT))
+	if (!error && ((flags & IOMAP_REPORT) || IS_DAX(inode)))
 		error = xfs_reflink_trim_around_shared(ip, &imap, &shared);
 	xfs_iunlock(ip, lockmode);
 
@@ -1370,7 +1370,7 @@ xfs_zero_range(
 
 	if (IS_DAX(inode))
 		return dax_zero_range(inode, pos, len, did_zero,
-				      &xfs_direct_write_iomap_ops);
+				      &xfs_dax_write_iomap_ops);
 	return iomap_zero_range(inode, pos, len, did_zero,
 				&xfs_buffered_write_iomap_ops);
 }
@@ -1385,7 +1385,7 @@ xfs_truncate_page(
 
 	if (IS_DAX(inode))
 		return dax_truncate_page(inode, pos, did_zero,
-					&xfs_direct_write_iomap_ops);
+					&xfs_dax_write_iomap_ops);
 	return iomap_truncate_page(inode, pos, did_zero,
 				   &xfs_buffered_write_iomap_ops);
 }
