[PATCH 06/13] fsdax: Rework dax_insert_entry() calling convention

[Dan Williams <dan.j.williams@xxxxxxxxx>]

Move the determination of @dirty and @cow in dax_insert_entry() to flags
(DAX_DIRTY and DAX_COW) that are passed in. This allows the iomap
related code to remain fs/dax.c in preparation for the Xarray
infrastructure to move to drivers/dax/mapping.c.

Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: "Darrick J. Wong" <djwong@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 fs/dax.c |   44 +++++++++++++++++++++++++++++++++++---------
 1 file changed, 35 insertions(+), 9 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index fad1c8a1d913..65d55c5ecdef 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -75,11 +75,19 @@ fs_initcall(init_dax_wait_table);
  * block allocation.
  */
 #define DAX_SHIFT	(4)
+#define DAX_MASK	((1UL << DAX_SHIFT) - 1)
 #define DAX_LOCKED	(1UL << 0)
 #define DAX_PMD		(1UL << 1)
 #define DAX_ZERO_PAGE	(1UL << 2)
 #define DAX_EMPTY	(1UL << 3)
 
+/*
+ * These flags are not conveyed in Xarray value entries, they are just
+ * modifiers to dax_insert_entry().
+ */
+#define DAX_DIRTY (1UL << (DAX_SHIFT + 0))
+#define DAX_COW   (1UL << (DAX_SHIFT + 1))
+
 static unsigned long dax_to_pfn(void *entry)
 {
 	return xa_to_value(entry) >> DAX_SHIFT;
@@ -87,7 +95,8 @@ static unsigned long dax_to_pfn(void *entry)
 
 static void *dax_make_entry(pfn_t pfn, unsigned long flags)
 {
-	return xa_mk_value(flags | (pfn_t_to_pfn(pfn) << DAX_SHIFT));
+	return xa_mk_value((flags & DAX_MASK) |
+			   (pfn_t_to_pfn(pfn) << DAX_SHIFT));
 }
 
 static bool dax_is_locked(void *entry)
@@ -846,6 +855,20 @@ static bool dax_fault_is_cow(const struct iomap_iter *iter)
 		(iter->iomap.flags & IOMAP_F_SHARED);
 }
 
+static unsigned long dax_iter_flags(const struct iomap_iter *iter,
+				    struct vm_fault *vmf)
+{
+	unsigned long flags = 0;
+
+	if (!dax_fault_is_synchronous(iter, vmf->vma))
+		flags |= DAX_DIRTY;
+
+	if (dax_fault_is_cow(iter))
+		flags |= DAX_COW;
+
+	return flags;
+}
+
 /*
  * 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
@@ -854,13 +877,13 @@ static bool dax_fault_is_cow(const struct iomap_iter *iter)
  * appropriate.
  */
 static vm_fault_t dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
-				   const struct iomap_iter *iter, void **pentry,
-				   pfn_t pfn, unsigned long flags)
+				   void **pentry, pfn_t pfn,
+				   unsigned long flags)
 {
 	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 dirty = flags & DAX_DIRTY;
+	bool cow = flags & DAX_COW;
 	void *entry = *pentry;
 
 	if (dirty)
@@ -1155,7 +1178,8 @@ static vm_fault_t dax_load_hole(struct xa_state *xas, struct vm_fault *vmf,
 	pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr));
 	vm_fault_t ret;
 
-	ret = dax_insert_entry(xas, vmf, iter, entry, pfn, DAX_ZERO_PAGE);
+	ret = dax_insert_entry(xas, vmf, entry, pfn,
+			       DAX_ZERO_PAGE | dax_iter_flags(iter, vmf));
 	if (ret)
 		goto out;
 
@@ -1186,8 +1210,9 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
 		goto fallback;
 
 	pfn = page_to_pfn_t(zero_page);
-	ret = dax_insert_entry(xas, vmf, iter, entry, pfn,
-			       DAX_PMD | DAX_ZERO_PAGE);
+	ret = dax_insert_entry(xas, vmf, entry, pfn,
+			       DAX_PMD | DAX_ZERO_PAGE |
+				       dax_iter_flags(iter, vmf));
 	if (ret)
 		return ret;
 
@@ -1566,7 +1591,8 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
 	if (err)
 		return pmd ? VM_FAULT_FALLBACK : dax_fault_return(err);
 
-	ret = dax_insert_entry(xas, vmf, iter, entry, pfn, entry_flags);
+	ret = dax_insert_entry(xas, vmf, entry, pfn,
+			       entry_flags | dax_iter_flags(iter, vmf));
 	if (ret)
 		return ret;