[linux-cifs-client] [PATCH 0/5] [CIFS] add new mount option to control "dynamic" mode setting

[Jeff Layton]

Hi Steve,

Here's a respin of the unapplied patches to fix the "ephemeral modes"
problem. This set adds a new "dynperm" mount option. When unix
extensions aren't negotiated and cifsacl isn't turned on, this makes the
modes "float". Mode changes will have no effect on the server and will
exist in memory only.

This is a little different from the current behavior, which would try to
make the write bits on the file track ATTR_READONLY in some cases. We
could make it so that this still happens when we use dynperm, but I'm
not sure what to do in the following case:

Suppose we have a CIFS mount with file_mode=02767, and we change the
mode to something like this (which turns off ATTR_READONLY on the
server):

    # chmod 0400 testfile.txt

...now, suppose someone turns on the ATTR_READONLY bit on the server.
What write bits should be reenabled? Turning them all on (per the
default file_mode) would seem to be contrary to the wishes of the user.

Signed-off-by: Jeff Layton <jlayton at redhat.com>