ext4: 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 ext4.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 2c5baa5..4feeeca 100644 (file)
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -367,15 +367,17 @@ static const struct vm_operations_struct ext4_file_vm_ops = {
 static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
        struct inode *inode = file->f_mapping->host;
+       struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+       struct dax_device *dax_dev = sbi->s_daxdev;
 
-       if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
+       if (unlikely(ext4_forced_shutdown(sbi)))
                return -EIO;
 
        /*
-        * 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(file)) && (vma->vm_flags & VM_SYNC))
+       if (!daxdev_mapping_supported(vma, dax_dev))
                return -EOPNOTSUPP;
 
        file_accessed(file);