Hi,

Local: Windows 7
GNU Emacs 27.0.50 (build 1, x86_64-w64-mingw32) of 2017-11-24
(backup-by-copying t)

File is on a server which is mapped as network driver in Windows 7. It
seems a samba according to the SID below.
The SDDL from file-acl is
"O:S-1-22-1-79077G:S-1-22-2-108D:P(A;;0x1e01ff;;;S-1-22-1-79077)(A;;FR;;;S-1-22-2-108)(A;;FR;;;WD)"

After I edited the file and write it, the backup meets error:

Debugger entered--Lisp error: (file-error "Setting ACL" "Operation not
permitted"
"c:/Users/username/HOME/.emacs.d/autosave/Rfiles/!drive_i!test_fixed_IA_time.r.~2~")

set-file-acl("c:/Users/username/HOME/.emacs.d/autosave/Rfiles/!drive_i!test_fixed_IA_time.r.~2~"
"O:S-1-22-1-79077G:S-1-22-2-108D:P(A;;0x1e01ff;;;S-1-22-1-79077)(A;;FR;;;S-1-22-2-108)(A;;FR;;;WD)")

set-file-extended-attributes("c:/Users/username/HOME/.emacs.d/autosave/Rfiles/!drive_i!test_fixed_IA_time.r.~2~"
((acl .
"O:S-1-22-1-79077G:S-1-22-2-108D:P(A;;0x1e01ff;;;S-1-22-1-79077)(A;;FR;;;S-1-22-2-108)(A;;FR;;;WD)")
(selinux-context nil nil nil nil)))
  backup-buffer-copy("i:/power/permutation_test_fixed_IA_time.r"
"c:/Users/username/HOME/.emacs.d/autosave/Rfiles/!drive_i!test_fixed_IA_time.r.~2~"
438 ((acl .
"O:S-1-22-1-79077G:S-1-22-2-108D:P(A;;0x1e01ff;;;S-1-22-1-79077)(A;;FR;;;S-1-22-2-108)(A;;FR;;;WD)")
(selinux-context nil nil nil nil)))
  backup-buffer()
  basic-save-buffer-2()
  basic-save-buffer-1()
  basic-save-buffer(t)
  save-buffer(1)
  funcall-interactively(save-buffer 1)
  call-interactively(save-buffer nil nil)
  command-execute(save-buffer)

The ACL of a local file looks like:
"O:S-1-5-21-1213861250-xxx-207145G:DUD:AI(A;ID;FA;;;SY)(A;ID;FA;;;BA)(A;ID;FA;;;S-1-5-21-1213861250-xx-207145)(A;ID;FA;;;LA)"

I think it is a bug because:
1. I have the write access to the mapped network driver
2. If I copy a local file to the mapped network driver, the ACL would be
set up well.
So I don't think there should be a write permission in this backup case.


Best Regards
Shuguang Sun