[GIT PULL] xen: xenfs fixes for 4.9-rc2

[GIT PULL] xen: xenfs fixes for 4.9-rc2

[David Vrabel]

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Linus,

Please git pull the following tag:

 git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git for-linus-4.9-fs-rc2-tag

I have separated these fixes out from the previous set because they
contain changes to generic filesystem code.  Despite reposts and pings,
these changes got no response from the relevant maintainer.

I think the changes are trivial and uncontroversial.  Please consider
merging.

xen: xenfs fixes for 4.9-rc2

- - Fix issues with simultaneous writes and reads to /proc/xen/xenbus.
- - Fix /proc/xen inside filesystem namespaces.

Thanks.

David

 drivers/xen/privcmd.c                    |  5 +----
 drivers/xen/privcmd.h                    |  3 ---
 drivers/xen/xenbus/xenbus_comms.h        |  2 --
 drivers/xen/xenbus/xenbus_dev_frontend.c |  3 +--
 drivers/xen/xenbus/xenbus_probe.c        |  2 +-
 drivers/xen/xenfs/super.c                | 10 ++++------
 fs/libfs.c                               | 15 +++++++++++++--
 fs/proc/generic.c                        |  1 +
 fs/proc/internal.h                       |  1 -
 include/linux/fs.h                       |  2 +-
 include/linux/proc_fs.h                  |  2 ++
 11 files changed, 24 insertions(+), 22 deletions(-)

David Vrabel (2):
      libfs: allow simple_fill_super() to add symlinks
      xenfs: replace xenbus and privcmd with symlinks

Seth Forshee (1):
      xenbus: Use proc_create_mount_point() to create /proc/xen
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Re: [GIT PULL] xen: xenfs fixes for 4.9-rc2

[Linus Torvalds]

On Mon, Oct 24, 2016 at 9:37 AM, David Vrabel <dvrabel@cantab.net> wrote:
>
> I think the changes are trivial and uncontroversial.

Hmm. Sadly, they are also buggy.

This:

                if (files->mode & S_IFLNK) {

is simply wrong. The correct test for S_IFLNK is to do

                if ((files->mode & S_IFMT) == S_IFLNK) {

and quite frankly, the right model is almost certainly to just do a
switch-statement that does something like

                switch (files->mode & S_IFMT) {
                case S_IFLNK:
                        ...
                case S_IFREG:
                case 0:
                        ....
                default:
                        ..error..

because maybe somebody wants to add other cases later (and even if
not, it's just wrong to randomly change any other mode into S_IFREG).

And while I could easily do an evil merge and fix that part up, I
really don't want to do things like that. So I'm not going to pull
this.

               Linus