Pull more iov_iter updates from Al Viro:

 - more new_sync_{read,write}() speedups - ITER_UBUF introduction

 - ITER_PIPE cleanups

 - unification of iov_iter_get_pages/iov_iter_get_pages_alloc and
   switching them to advancing semantics

 - making ITER_PIPE take high-order pages without splitting them

 - handling copy_page_from_iter() for high-order pages properly

* tag 'pull-work.iov_iter-rebased' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (32 commits)
  fix copy_page_from_iter() for compound destinations
  hugetlbfs: copy_page_to_iter() can deal with compound pages
  copy_page_to_iter(): don't split high-order page in case of ITER_PIPE
  expand those iov_iter_advance()...
  pipe_get_pages(): switch to append_pipe()
  get rid of non-advancing variants
  ceph: switch the last caller of iov_iter_get_pages_alloc()
  9p: convert to advancing variant of iov_iter_get_pages_alloc()
  af_alg_make_sg(): switch to advancing variant of iov_iter_get_pages()
  iter_to_pipe(): switch to advancing variant of iov_iter_get_pages()
  block: convert to advancing variants of iov_iter_get_pages{,_alloc}()
  iov_iter: advancing variants of iov_iter_get_pages{,_alloc}()
  iov_iter: saner helper for page array allocation
  fold __pipe_get_pages() into pipe_get_pages()
  ITER_XARRAY: don't open-code DIV_ROUND_UP()
  unify the rest of iov_iter_get_pages()/iov_iter_get_pages_alloc() guts
  unify xarray_get_pages() and xarray_get_pages_alloc()
  unify pipe_get_pages() and pipe_get_pages_alloc()
  iov_iter_get_pages(): sanity-check arguments
  iov_iter_get_pages_alloc(): lift freeing pages array on failure exits into wrapper
  ...

Most of the users immediately follow successful iov_iter_get_pages()
with advancing by the amount it had returned.

Provide inline wrappers doing that, convert trivial open-coded
uses of those.

BTW, iov_iter_get_pages() never returns more than it had been asked
to; such checks in cifs ought to be removed someday...

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Equivalent of single-segment iovec.  Initialized by iov_iter_ubuf(),
checked for by iter_is_ubuf(), otherwise behaves like ITER_IOVEC
ones.

We are going to expose the things like ->write_iter() et.al. to those
in subsequent commits.

New predicate (user_backed_iter()) that is true for ITER_IOVEC and
ITER_UBUF; places like direct-IO handling should use that for
checking that pages we modify after getting them from iov_iter_get_pages()
would need to be dirtied.

DO NOT assume that replacing iter_is_iovec() with user_backed_iter()
will solve all problems - there's code that uses iter_is_iovec() to
decide how to poke around in iov_iter guts and for that the predicate
replacement obviously won't suffice.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Pull fuse updates from Miklos Szeredi:

 - Fix an issue with reusing the bdi in case of block based filesystems

 - Allow root (in init namespace) to access fuse filesystems in user
   namespaces if expicitly enabled with a module param

 - Misc fixes

* tag 'fuse-update-6.0' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: retire block-device-based superblock on force unmount
  vfs: function to prevent re-use of block-device-based superblocks
  virtio_fs: Modify format for virtio_fs_direct_access
  virtiofs: delete unused parameter for virtio_fs_cleanup_vqs
  fuse: Add module param for CAP_SYS_ADMIN access bypassing allow_other
  fuse: Remove the control interface for virtio-fs
  fuse: ioctl: translate ENOSYS
  fuse: limit nsec
  fuse: avoid unnecessary spinlock bump
  fuse: fix deadlock between atomic O_TRUNC and page invalidation
  fuse: write inode in fuse_release()

Force unmount of FUSE severes the connection with the user space, even if
there are still open files.  Subsequent remount tries to re-use the
superblock held by the open files, which is meaningless in the FUSE case
after disconnect - reused super block doesn't have userspace counterpart
attached to it and is incapable of doing any IO.

This patch adds the functionality only for the block-device-based supers,
since the primary use case of the feature is to gracefully handle force
unmount of external devices, mounted with FUSE.  This can be further
extended to cover all superblocks, if the need arises.

Signed-off-by: Daniil Lunev <dlunev@chromium.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

We should isolate operators with spaces.

Signed-off-by: Deming Wang <wangdeming@inspur.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs parameter not used. So, it needs to be deleted.

Signed-off-by: Deming Wang <wangdeming@inspur.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Since commit 73f03c2b4b52 ("fuse: Restrict allow_other to the superblock's
namespace or a descendant"), access to allow_other FUSE filesystems has
been limited to users in the mounting user namespace or descendants. This
prevents a process that is privileged in its userns - but not its parent
namespaces - from mounting a FUSE fs w/ allow_other that is accessible to
processes in parent namespaces.

While this restriction makes sense overall it breaks a legitimate usecase:
I have a tracing daemon which needs to peek into process' open files in
order to symbolicate - similar to 'perf'. The daemon is a privileged
process in the root userns, but is unable to peek into FUSE filesystems
mounted by processes in child namespaces.

This patch adds a module param, allow_sys_admin_access, to act as an escape
hatch for this descendant userns logic and for the allow_other mount option
in general. Setting allow_sys_admin_access allows processes with
CAP_SYS_ADMIN in the initial userns to access FUSE filesystems irrespective
of the mounting userns or whether allow_other was set. A sysadmin setting
this param must trust FUSEs on the host to not DoS processes as described
in 73f03c2b4b52.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The commit 15c8e72e88e0 ("fuse: allow skipping control interface and forced
unmount") tries to remove the control interface for virtio-fs since it does
not support aborting requests which are being processed. But it doesn't
work now.

This patch fixes it by skipping creating the control interface if
fuse_conn->no_control is set.

Fixes: 15c8e72e88e0 ("fuse: allow skipping control interface and forced unmount")
Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Overlayfs may fail to complete updates when a filesystem lacks
fileattr/xattr syscall support and responds with an ENOSYS error code,
resulting in an unexpected "Function not implemented" error.

This bug may occur with FUSE filesystems, such as davfs2.

Steps to reproduce:

  # install davfs2, e.g., apk add davfs2
  mkdir /test mkdir /test/lower /test/upper /test/work /test/mnt
  yes '' | mount -t davfs -o ro http://some-web-dav-server/path \
    /test/lower
  mount -t overlay -o upperdir=/test/upper,lowerdir=/test/lower \
    -o workdir=/test/work overlay /test/mnt

  # when "some-file" exists in the lowerdir, this fails with "Function
  # not implemented", with dmesg showing "overlayfs: failed to retrieve
  # lower fileattr (/some-file, err=-38)"
  touch /test/mnt/some-file

The underlying cause of this regresion is actually in FUSE, which fails to
translate the ENOSYS error code returned by userspace filesystem (which
means that the ioctl operation is not supported) to ENOTTY.

Reported-by: Christian Kohlschütter <christian@kohlschutter.com>
Fixes: 72db82115d2b ("ovl: copy up sync/noatime fileattr flags")
Fixes: 59efec7b9039 ("fuse: implement ioctl support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>