[PATCH v2 09/18] fsdax: Rework dax_insert_entry() calling convention

Dan Williams
2022-09-16T03:36:38Z

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@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
fs/dax.c | 44 +++++++++++++++++++++++++++++++++++---------
1 file changed, 35 insertions(+), 9 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index bd5c6b6e371e..5d9f30105db4 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -75,12 +75,20 @@ fs_initcall(init_dax_wait_table);
* block allocation.
*/
#define DAX_SHIFT (5)
+#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)
#define DAX_ZAP (1UL << 4)

+/*
+ * 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;
@@ -88,7 +96,8 @@ 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)
@@ -880,6 +889,20 @@ 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
@@ -888,13 +911,13 @@ 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)
@@ -1189,7 +1212,8 @@ 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;

@@ -1220,8 +1244,9 @@ 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;

@@ -1600,7 +1625,8 @@ 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;