Merge tag 'libnvdimm-for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

Pull libnvdimm and dax updates from Dan Williams:
 "Save for a few late fixes, all of these commits have shipped in -next
  releases since before the merge window opened, and 0day has given a
  build success notification.

  The ext4 touches came from Jan, and the xfs touches have Darrick's
  reviewed-by. An xfstest for the MAP_SYNC feature has been through
  a few round of reviews and is on track to be merged.

   - Introduce MAP_SYNC and MAP_SHARED_VALIDATE, a mechanism to enable
     'userspace flush' of persistent memory updates via filesystem-dax
     mappings. It arranges for any filesystem metadata updates that may
     be required to satisfy a write fault to also be flushed ("on disk")
     before the kernel returns to userspace from the fault handler.
     Effectively every write-fault that dirties metadata completes an
     fsync() before returning from the fault handler. The new
     MAP_SHARED_VALIDATE mapping type guarantees that the MAP_SYNC flag
     is validated as supported by the filesystem's ->mmap() file
     operation.

   - Add support for the standard ACPI 6.2 label access methods that
     replace the NVDIMM_FAMILY_INTEL (vendor specific) label methods.
     This enables interoperability with environments that only implement
     the standardized methods.

   - Add support for the ACPI 6.2 NVDIMM media error injection methods.

   - Add support for the NVDIMM_FAMILY_INTEL v1.6 DIMM commands for
     latch last shutdown status, firmware update, SMART error injection,
     and SMART alarm threshold control.

   - Cleanup physical address information disclosures to be root-only.

   - Fix revalidation of the DIMM "locked label area" status to support
     dynamic unlock of the label area.

   - Expand unit test infrastructure to mock the ACPI 6.2 Translate SPA
     (system-physical-address) command and error injection commands.

  Acknowledgements that came after the commits were pushed to -next:

   - 957ac8c421ad ("dax: fix PMD faults on zero-length files"):
       Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>

   - a39e596baa07 ("xfs: support for synchronous DAX faults") and
     7b565c9f965b ("xfs: Implement xfs_filemap_pfn_mkwrite() using __xfs_filemap_fault()")
        Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>"

* tag 'libnvdimm-for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm: (49 commits)
  acpi, nfit: add 'Enable Latch System Shutdown Status' command support
  dax: fix general protection fault in dax_alloc_inode
  dax: fix PMD faults on zero-length files
  dax: stop requiring a live device for dax_flush()
  brd: remove dax support
  dax: quiet bdev_dax_supported()
  fs, dax: unify IOMAP_F_DIRTY read vs write handling policy in the dax core
  tools/testing/nvdimm: unit test clear-error commands
  acpi, nfit: validate commands against the device type
  tools/testing/nvdimm: stricter bounds checking for error injection commands
  xfs: support for synchronous DAX faults
  xfs: Implement xfs_filemap_pfn_mkwrite() using __xfs_filemap_fault()
  ext4: Support for synchronous DAX faults
  ext4: Simplify error handling in ext4_dax_huge_fault()
  dax: Implement dax_finish_sync_fault()
  dax, iomap: Add support for synchronous faults
  mm: Define MAP_SYNC and VM_SYNC flags
  dax: Allow tuning whether dax_insert_mapping_entry() dirties entry
  dax: Allow dax_iomap_fault() to return pfn
  dax: Fix comment describing dax_iomap_fault()
  ...

1 files changed, 219 insertions, 100 deletions

diff --git a/fs/dax.c b/fs/dax.c
index 3652b26a0048..95981591977a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -526,13 +526,13 @@ static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev,
 static void *dax_insert_mapping_entry(struct address_space *mapping,
                                       struct vm_fault *vmf,
                                       void *entry, sector_t sector,
-                                      unsigned long flags)
+                                      unsigned long flags, bool dirty)
 {
         struct radix_tree_root *page_tree = &mapping->page_tree;
         void *new_entry;
         pgoff_t index = vmf->pgoff;
 
-        if (vmf->flags & FAULT_FLAG_WRITE)
+        if (dirty)
                 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 
         if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_ZERO_PAGE)) {
@@ -569,7 +569,7 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
                 entry = new_entry;
         }
 
-        if (vmf->flags & FAULT_FLAG_WRITE)
+        if (dirty)
                 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
 
         spin_unlock_irq(&mapping->tree_lock);
@@ -825,38 +825,42 @@ out:
 }
 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
 
-static int dax_insert_mapping(struct address_space *mapping,
-                struct block_device *bdev, struct dax_device *dax_dev,
-                sector_t sector, size_t size, void *entry,
-                struct vm_area_struct *vma, struct vm_fault *vmf)
+static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
 {
-        unsigned long vaddr = vmf->address;
-        void *ret, *kaddr;
+        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)
+{
+        const sector_t sector = dax_iomap_sector(iomap, pos);
         pgoff_t pgoff;
+        void *kaddr;
         int id, rc;
-        pfn_t pfn;
+        long length;
 
-        rc = bdev_dax_pgoff(bdev, sector, size, &pgoff);
+        rc = bdev_dax_pgoff(iomap->bdev, sector, size, &pgoff);
         if (rc)
                 return rc;
-
         id = dax_read_lock();
-        rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
-        if (rc < 0) {
-                dax_read_unlock(id);
-                return rc;
+        length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
+                                   &kaddr, pfnp);
+        if (length < 0) {
+                rc = length;
+                goto out;
         }
+        rc = -EINVAL;
+        if (PFN_PHYS(length) < size)
+                goto out;
+        if (pfn_t_to_pfn(*pfnp) & (PHYS_PFN(size)-1))
+                goto out;
+        /* For larger pages we need devmap */
+        if (length > 1 && !pfn_t_devmap(*pfnp))
+                goto out;
+        rc = 0;
+out:
         dax_read_unlock(id);
-
-        ret = dax_insert_mapping_entry(mapping, vmf, entry, sector, 0);
-        if (IS_ERR(ret))
-                return PTR_ERR(ret);
-
-        trace_dax_insert_mapping(mapping->host, vmf, ret);
-        if (vmf->flags & FAULT_FLAG_WRITE)
-                return vm_insert_mixed_mkwrite(vma, vaddr, pfn);
-        else
-                return vm_insert_mixed(vma, vaddr, pfn);
+        return rc;
 }
 
 /*
@@ -882,7 +886,7 @@ static int dax_load_hole(struct address_space *mapping, void *entry,
         }
 
         entry2 = dax_insert_mapping_entry(mapping, vmf, entry, 0,
-                        RADIX_DAX_ZERO_PAGE);
+                        RADIX_DAX_ZERO_PAGE, false);
         if (IS_ERR(entry2)) {
                 ret = VM_FAULT_SIGBUS;
                 goto out;
@@ -941,11 +945,6 @@ int __dax_zero_page_range(struct block_device *bdev,
 }
 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
 
-static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
-{
-        return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
-}
-
 static loff_t
 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
                 struct iomap *iomap)
@@ -1085,19 +1084,33 @@ static int dax_fault_return(int error)
         return VM_FAULT_SIGBUS;
 }
 
-static int dax_iomap_pte_fault(struct vm_fault *vmf,
+/*
+ * MAP_SYNC on a dax mapping guarantees dirty metadata is
+ * flushed on write-faults (non-cow), but not read-faults.
+ */
+static bool dax_fault_is_synchronous(unsigned long flags,
+                struct vm_area_struct *vma, struct iomap *iomap)
+{
+        return (flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC)
+                && (iomap->flags & IOMAP_F_DIRTY);
+}
+
+static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
                                const struct iomap_ops *ops)
 {
-        struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+        struct vm_area_struct *vma = vmf->vma;
+        struct address_space *mapping = vma->vm_file->f_mapping;
         struct inode *inode = mapping->host;
         unsigned long vaddr = vmf->address;
         loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
-        sector_t sector;
         struct iomap iomap = { 0 };
         unsigned flags = IOMAP_FAULT;
         int error, major = 0;
+        bool write = vmf->flags & FAULT_FLAG_WRITE;
+        bool sync;
         int vmf_ret = 0;
         void *entry;
+        pfn_t pfn;
 
         trace_dax_pte_fault(inode, vmf, vmf_ret);
         /*
@@ -1110,7 +1123,7 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf,
                 goto out;
         }
 
-        if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
+        if (write && !vmf->cow_page)
                 flags |= IOMAP_WRITE;
 
         entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
@@ -1145,9 +1158,9 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf,
                 goto error_finish_iomap;
         }
 
-        sector = dax_iomap_sector(&iomap, pos);
-
         if (vmf->cow_page) {
+                sector_t sector = dax_iomap_sector(&iomap, pos);
+
                 switch (iomap.type) {
                 case IOMAP_HOLE:
                 case IOMAP_UNWRITTEN:
@@ -1173,22 +1186,55 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf,
                 goto finish_iomap;
         }
 
+        sync = dax_fault_is_synchronous(flags, vma, &iomap);
+
         switch (iomap.type) {
         case IOMAP_MAPPED:
                 if (iomap.flags & IOMAP_F_NEW) {
                         count_vm_event(PGMAJFAULT);
-                        count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
+                        count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
                         major = VM_FAULT_MAJOR;
                 }
-                error = dax_insert_mapping(mapping, iomap.bdev, iomap.dax_dev,
-                                sector, PAGE_SIZE, entry, vmf->vma, vmf);
+                error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
+                if (error < 0)
+                        goto error_finish_iomap;
+
+                entry = dax_insert_mapping_entry(mapping, vmf, entry,
+                                                 dax_iomap_sector(&iomap, pos),
+                                                 0, write && !sync);
+                if (IS_ERR(entry)) {
+                        error = PTR_ERR(entry);
+                        goto error_finish_iomap;
+                }
+
+                /*
+                 * If we are doing synchronous page fault and inode needs fsync,
+                 * we can insert PTE into page tables only after that happens.
+                 * Skip insertion for now and return the pfn so that caller can
+                 * insert it after fsync is done.
+                 */
+                if (sync) {
+                        if (WARN_ON_ONCE(!pfnp)) {
+                                error = -EIO;
+                                goto error_finish_iomap;
+                        }
+                        *pfnp = pfn;
+                        vmf_ret = VM_FAULT_NEEDDSYNC | major;
+                        goto finish_iomap;
+                }
+                trace_dax_insert_mapping(inode, vmf, entry);
+                if (write)
+                        error = vm_insert_mixed_mkwrite(vma, vaddr, pfn);
+                else
+                        error = vm_insert_mixed(vma, vaddr, pfn);
+
                 /* -EBUSY is fine, somebody else faulted on the same PTE */
                 if (error == -EBUSY)
                         error = 0;
                 break;
         case IOMAP_UNWRITTEN:
         case IOMAP_HOLE:
-                if (!(vmf->flags & FAULT_FLAG_WRITE)) {
+                if (!write) {
                         vmf_ret = dax_load_hole(mapping, entry, vmf);
                         goto finish_iomap;
                 }
@@ -1223,53 +1269,11 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf,
 }
 
 #ifdef CONFIG_FS_DAX_PMD
-static int dax_pmd_insert_mapping(struct vm_fault *vmf, struct iomap *iomap,
-                loff_t pos, void *entry)
-{
-        struct address_space *mapping = vmf->vma->vm_file->f_mapping;
-        const sector_t sector = dax_iomap_sector(iomap, pos);
-        struct dax_device *dax_dev = iomap->dax_dev;
-        struct block_device *bdev = iomap->bdev;
-        struct inode *inode = mapping->host;
-        const size_t size = PMD_SIZE;
-        void *ret = NULL, *kaddr;
-        long length = 0;
-        pgoff_t pgoff;
-        pfn_t pfn = {};
-        int id;
-
-        if (bdev_dax_pgoff(bdev, sector, size, &pgoff) != 0)
-                goto fallback;
-
-        id = dax_read_lock();
-        length = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
-        if (length < 0)
-                goto unlock_fallback;
-        length = PFN_PHYS(length);
-
-        if (length < size)
-                goto unlock_fallback;
-        if (pfn_t_to_pfn(pfn) & PG_PMD_COLOUR)
-                goto unlock_fallback;
-        if (!pfn_t_devmap(pfn))
-                goto unlock_fallback;
-        dax_read_unlock(id);
-
-        ret = dax_insert_mapping_entry(mapping, vmf, entry, sector,
-                        RADIX_DAX_PMD);
-        if (IS_ERR(ret))
-                goto fallback;
-
-        trace_dax_pmd_insert_mapping(inode, vmf, length, pfn, ret);
-        return vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd,
-                        pfn, vmf->flags & FAULT_FLAG_WRITE);
-
-unlock_fallback:
-        dax_read_unlock(id);
-fallback:
-        trace_dax_pmd_insert_mapping_fallback(inode, vmf, length, pfn, ret);
-        return VM_FAULT_FALLBACK;
-}
+/*
+ * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
+ * more often than one might expect in the below functions.
+ */
+#define PG_PMD_COLOUR   ((PMD_SIZE >> PAGE_SHIFT) - 1)
 
 static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
                 void *entry)
@@ -1288,7 +1292,7 @@ static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
                 goto fallback;
 
         ret = dax_insert_mapping_entry(mapping, vmf, entry, 0,
-                        RADIX_DAX_PMD | RADIX_DAX_ZERO_PAGE);
+                        RADIX_DAX_PMD | RADIX_DAX_ZERO_PAGE, false);
         if (IS_ERR(ret))
                 goto fallback;
 
@@ -1310,13 +1314,14 @@ fallback:
         return VM_FAULT_FALLBACK;
 }
 
-static int dax_iomap_pmd_fault(struct vm_fault *vmf,
+static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
                                const struct iomap_ops *ops)
 {
         struct vm_area_struct *vma = vmf->vma;
         struct address_space *mapping = vma->vm_file->f_mapping;
         unsigned long pmd_addr = vmf->address & PMD_MASK;
         bool write = vmf->flags & FAULT_FLAG_WRITE;
+        bool sync;
         unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
         struct inode *inode = mapping->host;
         int result = VM_FAULT_FALLBACK;
@@ -1325,6 +1330,7 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf,
         void *entry;
         loff_t pos;
         int error;
+        pfn_t pfn;
 
         /*
          * Check whether offset isn't beyond end of file now. Caller is
@@ -1332,7 +1338,7 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf,
          * this is a reliable test.
          */
         pgoff = linear_page_index(vma, pmd_addr);
-        max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+        max_pgoff = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
 
         trace_dax_pmd_fault(inode, vmf, max_pgoff, 0);
 
@@ -1356,13 +1362,13 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf,
         if ((pmd_addr + PMD_SIZE) > vma->vm_end)
                 goto fallback;
 
-        if (pgoff > max_pgoff) {
+        if (pgoff >= max_pgoff) {
                 result = VM_FAULT_SIGBUS;
                 goto out;
         }
 
         /* If the PMD would extend beyond the file size */
-        if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
+        if ((pgoff | PG_PMD_COLOUR) >= max_pgoff)
                 goto fallback;
 
         /*
@@ -1400,9 +1406,37 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf,
         if (iomap.offset + iomap.length < pos + PMD_SIZE)
                 goto finish_iomap;
 
+        sync = dax_fault_is_synchronous(iomap_flags, vma, &iomap);
+
         switch (iomap.type) {
         case IOMAP_MAPPED:
-                result = dax_pmd_insert_mapping(vmf, &iomap, pos, entry);
+                error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
+                if (error < 0)
+                        goto finish_iomap;
+
+                entry = dax_insert_mapping_entry(mapping, vmf, entry,
+                                                dax_iomap_sector(&iomap, pos),
+                                                RADIX_DAX_PMD, write && !sync);
+                if (IS_ERR(entry))
+                        goto finish_iomap;
+
+                /*
+                 * If we are doing synchronous page fault and inode needs fsync,
+                 * we can insert PMD into page tables only after that happens.
+                 * Skip insertion for now and return the pfn so that caller can
+                 * insert it after fsync is done.
+                 */
+                if (sync) {
+                        if (WARN_ON_ONCE(!pfnp))
+                                goto finish_iomap;
+                        *pfnp = pfn;
+                        result = VM_FAULT_NEEDDSYNC;
+                        goto finish_iomap;
+                }
+
+                trace_dax_pmd_insert_mapping(inode, vmf, PMD_SIZE, pfn, entry);
+                result = vmf_insert_pfn_pmd(vma, vmf->address, vmf->pmd, pfn,
+                                            write);
                 break;
         case IOMAP_UNWRITTEN:
         case IOMAP_HOLE:
@@ -1442,7 +1476,7 @@ out:
         return result;
 }
 #else
-static int dax_iomap_pmd_fault(struct vm_fault *vmf,
+static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
                                const struct iomap_ops *ops)
 {
         return VM_FAULT_FALLBACK;
@@ -1452,7 +1486,9 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf,
 /**
  * dax_iomap_fault - handle a page fault on a DAX file
  * @vmf: The description of the fault
- * @ops: iomap ops passed from the file system
+ * @pe_size: Size of the page to fault in
+ * @pfnp: PFN to insert for synchronous faults if fsync is required
+ * @ops: Iomap ops passed from the file system
  *
  * When a page fault occurs, filesystems may call this helper in
  * their fault handler for DAX files. dax_iomap_fault() assumes the caller
@@ -1460,15 +1496,98 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf,
  * successfully.
  */
 int dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
-                    const struct iomap_ops *ops)
+                    pfn_t *pfnp, const struct iomap_ops *ops)
 {
         switch (pe_size) {
         case PE_SIZE_PTE:
-                return dax_iomap_pte_fault(vmf, ops);
+                return dax_iomap_pte_fault(vmf, pfnp, ops);
         case PE_SIZE_PMD:
-                return dax_iomap_pmd_fault(vmf, ops);
+                return dax_iomap_pmd_fault(vmf, pfnp, ops);
         default:
                 return VM_FAULT_FALLBACK;
         }
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+/**
+ * dax_insert_pfn_mkwrite - insert PTE or PMD entry into page tables
+ * @vmf: The description of the fault
+ * @pe_size: Size of entry to be inserted
+ * @pfn: PFN to insert
+ *
+ * This function inserts writeable PTE or PMD entry into page tables for mmaped
+ * DAX file.  It takes care of marking corresponding radix tree entry as dirty
+ * as well.
+ */
+static int dax_insert_pfn_mkwrite(struct vm_fault *vmf,
+                                  enum page_entry_size pe_size,
+                                  pfn_t pfn)
+{
+        struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+        void *entry, **slot;
+        pgoff_t index = vmf->pgoff;
+        int vmf_ret, error;
+
+        spin_lock_irq(&mapping->tree_lock);
+        entry = get_unlocked_mapping_entry(mapping, index, &slot);
+        /* Did we race with someone splitting entry or so? */
+        if (!entry ||
+            (pe_size == PE_SIZE_PTE && !dax_is_pte_entry(entry)) ||
+            (pe_size == PE_SIZE_PMD && !dax_is_pmd_entry(entry))) {
+                put_unlocked_mapping_entry(mapping, index, entry);
+                spin_unlock_irq(&mapping->tree_lock);
+                trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
+                                                      VM_FAULT_NOPAGE);
+                return VM_FAULT_NOPAGE;
+        }
+        radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);
+        entry = lock_slot(mapping, slot);
+        spin_unlock_irq(&mapping->tree_lock);
+        switch (pe_size) {
+        case PE_SIZE_PTE:
+                error = vm_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
+                vmf_ret = dax_fault_return(error);
+                break;
+#ifdef CONFIG_FS_DAX_PMD
+        case PE_SIZE_PMD:
+                vmf_ret = vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd,
+                        pfn, true);
+                break;
+#endif
+        default:
+                vmf_ret = VM_FAULT_FALLBACK;
+        }
+        put_locked_mapping_entry(mapping, index);
+        trace_dax_insert_pfn_mkwrite(mapping->host, vmf, vmf_ret);
+        return vmf_ret;
+}
+
+/**
+ * dax_finish_sync_fault - finish synchronous page fault
+ * @vmf: The description of the fault
+ * @pe_size: Size of entry to be inserted
+ * @pfn: PFN to insert
+ *
+ * This function ensures that the file range touched by the page fault is
+ * stored persistently on the media and handles inserting of appropriate page
+ * table entry.
+ */
+int dax_finish_sync_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
+                          pfn_t pfn)
+{
+        int err;
+        loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT;
+        size_t len = 0;
+
+        if (pe_size == PE_SIZE_PTE)
+                len = PAGE_SIZE;
+        else if (pe_size == PE_SIZE_PMD)
+                len = PMD_SIZE;
+        else
+                WARN_ON_ONCE(1);
+        err = vfs_fsync_range(vmf->vma->vm_file, start, start + len - 1, 1);
+        if (err)
+                return VM_FAULT_SIGBUS;
+        return dax_insert_pfn_mkwrite(vmf, pe_size, pfn);
+}
+EXPORT_SYMBOL_GPL(dax_finish_sync_fault);