xfs: disable map_sync for async flush

Dont support 'MAP_SYNC' with non-DAX files and DAX files
with asynchronous dax_device. Virtio pmem provides
asynchronous host page cache flush mechanism. We don't
support 'MAP_SYNC' with virtio pmem and xfs.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 76748255f843..a06af58af475 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1203,11 +1203,14 @@ xfs_file_mmap(
         struct file     *filp,
         struct vm_area_struct *vma)
 {
+        struct dax_device       *dax_dev;
+
+        dax_dev = xfs_find_daxdev_for_inode(file_inode(filp));
         /*
-         * We don't support synchronous mappings for non-DAX files. At least
-         * until someone comes with a sensible use case.
+         * We don't support synchronous mappings for non-DAX files and
+         * for DAX files if underneath dax_device is not synchronous.
          */
-        if (!IS_DAX(file_inode(filp)) && (vma->vm_flags & VM_SYNC))
+        if (!daxdev_mapping_supported(vma, dax_dev))
                 return -EOPNOTSUPP;
 
         file_accessed(filp);