The + at the end of the permissions string indicates that the directory has an Access Control List (ACL) applied to it.
It is likely that your ACL is somehow denying the user sftpuser write access to the directory.
To view the ACL for the html directory, use the command:
This should output something like the following:
# file: html
# owner: ...
You can not mount ntfs so that permissions are disabled, I suppose (I am even in doubt that this was possible in Win XP).
But you can bypass file permissions as Administrator, or any other account possessing backup privilege. You can even mount ntfs volume readonly (to be sure you did not accidentally change anything on the volume while you copied files) and ...
I had similar problems and never got it working with 9p, and as other commenters have said 9p is not mature.
I ended up using samba to mount a host filesystem and it's working fine. Any other network filesystem would do the job, too, probably (e.g. NFS, which is recommended by Red Hat; see link from @Diagon's comment https://access.redhat.com/discussions/...