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>

1 files changed, 6 insertions, 4 deletions

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 2c5baa5e8291..4feeecae8db6 100644
--- 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);