On Wed, Aug 04, 2021 at 12:44:38AM +0100, Matthew Wilcox wrote:

I don't understand how so many ntfs-classic xfstests pass:

config NTFS_RW
        bool "NTFS write support"
        depends on NTFS_FS
        help
          This enables the partial, but safe, write support in the NTFS driver.

          The only supported operation is overwriting existing files, without
          changing the file length.  No file or directory creation, deletion or
          renaming is possible.  Note only non-resident files can be written to
          so you may find that some very small files (<500 bytes or so) cannot
          be written to.

Are the tests really passing, or just claiming to pass?

This was the ntfs provided by the Debian package ntfs-3g (which is the
only source of a mkfs.ntfs that I could find, BTW).  This is a
fuse-based ntfs, not the in-kernel ntfs file system.  Apologies for
not making that clear.

<tytso.root@cwcc> {/usr/projects/linux/ext4}, level 2   (ntfs3)
1003# mkfs.ntfs /dev/cwcc-vg/scratch
Cluster size has been automatically set to 4096 bytes.
Initializing device with zeroes: 100% - Done.
Creating NTFS volume structures.
mkntfs completed successfully. Have a nice day.
<tytso.root@cwcc> {/usr/projects/linux/ext4}, level 2   (ntfs3)
1004# mount -t ntfs /dev/cwcc-vg/scratch /mnt
<tytso.root@cwcc> {/usr/projects/linux/ext4}, level 2   (ntfs3)
1005# grep /mnt /proc/mounts
/dev/mapper/cwcc--vg-scratch /mnt fuseblk rw,relatime,user_id=0,group_id=0,allow_other,blksize=4096 0 0

TBH, I had forgotten that we had an in-kernel ntfs implementation.
Whenver I've ever needed to access ntfs files, I've always used the
ntfs-3g FUSE package.

			     	  	  - Ted