[PATCH 1/7] fsdax: Output address in dax_iomap_pfn() and rename it

[Shiyang Ruan <ruansy.fnst@xxxxxxxxxxxxxx>]

Add address output in dax_iomap_pfn() in order to perform a memcpy() in
CoW case.  Since this function both output address and pfn, rename it to
dax_iomap_direct_access().

Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxxxxx>
---
 fs/dax.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 5b47834f2e1b..b012b2db7ba2 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -998,8 +998,8 @@ static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
 	return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
 }
 
-static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
-			 pfn_t *pfnp)
+static int dax_iomap_direct_access(struct iomap *iomap, loff_t pos, size_t size,
+		void **kaddr, pfn_t *pfnp)
 {
 	const sector_t sector = dax_iomap_sector(iomap, pos);
 	pgoff_t pgoff;
@@ -1011,11 +1011,13 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
 		return rc;
 	id = dax_read_lock();
 	length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
-				   NULL, pfnp);
+				   kaddr, pfnp);
 	if (length < 0) {
 		rc = length;
 		goto out;
 	}
+	if (!pfnp)
+		goto out_check_addr;
 	rc = -EINVAL;
 	if (PFN_PHYS(length) < size)
 		goto out;
@@ -1025,6 +1027,12 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
 	if (length > 1 && !pfn_t_devmap(*pfnp))
 		goto out;
 	rc = 0;
+
+out_check_addr:
+	if (!kaddr)
+		goto out;
+	if (!*kaddr)
+		rc = -EFAULT;
 out:
 	dax_read_unlock(id);
 	return rc;
@@ -1348,7 +1356,8 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 			count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
 			major = VM_FAULT_MAJOR;
 		}
-		error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
+		error = dax_iomap_direct_access(&iomap, pos, PAGE_SIZE,
+						NULL, &pfn);
 		if (error < 0)
 			goto error_finish_iomap;
 
@@ -1566,7 +1575,8 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
 
 	switch (iomap.type) {
 	case IOMAP_MAPPED:
-		error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
+		error = dax_iomap_direct_access(&iomap, pos, PMD_SIZE,
+						NULL, &pfn);
 		if (error < 0)
 			goto finish_iomap;
 
-- 
2.30.0