[PATCH 04/10] fs/dax: make it possible to check dev dax support without a VMA

[Lorenzo Stoakes]

This is a prerequisite for adapting those filesystems to use the
.mmap_prepare() hook for mmap()'ing which invoke this check as this hook
does not have access to a VMA pointer.

To effect this, change the signature of daxdev_mapping_supported() and
update its callers (ext4 and xfs mmap()'ing hook code).

Signed-off-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>
---
 fs/ext4/file.c      |  2 +-
 fs/xfs/xfs_file.c   |  3 ++-
 include/linux/dax.h | 16 +++++++++-------
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 21df81347147..08a814fcd956 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -821,7 +821,7 @@ static int ext4_file_mmap(struct file *file, struct 
vm_area_struct *vma)
         * We don't support synchronous mappings for non-DAX files and
         * for DAX files if underneath dax_device is not synchronous.
         */
-       if (!daxdev_mapping_supported(vma, dax_dev))
+       if (!daxdev_mapping_supported(vma->vm_flags, vma->vm_file, dax_dev))
                return -EOPNOTSUPP;
 
        file_accessed(file);
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 48254a72071b..ab97ce1f9087 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1924,7 +1924,8 @@ xfs_file_mmap(
         * We don't support synchronous mappings for non-DAX files and
         * for DAX files if underneath dax_device is not synchronous.
         */
-       if (!daxdev_mapping_supported(vma, target->bt_daxdev))
+       if (!daxdev_mapping_supported(vma->vm_flags, vma->vm_file,
+                                     target->bt_daxdev))
                return -EOPNOTSUPP;
 
        file_accessed(file);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index dcc9fcdf14e4..d0092cefb963 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -65,12 +65,13 @@ size_t dax_recovery_write(struct dax_device *dax_dev, 
pgoff_t pgoff,
 /*
  * Check if given mapping is supported by the file / underlying device.
  */
-static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
-                                            struct dax_device *dax_dev)
+static inline bool daxdev_mapping_supported(vm_flags_t vm_flags,
+                                           struct file *file,
+                                           struct dax_device *dax_dev)
 {
-       if (!(vma->vm_flags & VM_SYNC))
+       if (!(vm_flags & VM_SYNC))
                return true;
-       if (!IS_DAX(file_inode(vma->vm_file)))
+       if (!IS_DAX(file_inode(file)))
                return false;
        return dax_synchronous(dax_dev);
 }
@@ -110,10 +111,11 @@ static inline void set_dax_nomc(struct dax_device 
*dax_dev)
 static inline void set_dax_synchronous(struct dax_device *dax_dev)
 {
 }
-static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
-                               struct dax_device *dax_dev)
+static inline bool daxdev_mapping_supported(vm_flags_t vm_flags,
+                                           struct file *file,
+                                           struct dax_device *dax_dev)
 {
-       return !(vma->vm_flags & VM_SYNC);
+       return !(vm_flags & VM_SYNC);
 }
 static inline size_t dax_recovery_write(struct dax_device *dax_dev,
                pgoff_t pgoff, void *addr, size_t bytes, struct iov_iter *i)
-- 
2.49.0