Pull vfs file system parameter updates from Al Viro:
 "Saner fs_parser.c guts and data structures. The system-wide registry
  of syntax types (string/enum/int32/oct32/.../etc.) is gone and so is
  the horror switch() in fs_parse() that would have to grow another case
  every time something got added to that system-wide registry.

  New syntax types can be added by filesystems easily now, and their
  namespace is that of functions - not of system-wide enum members. IOW,
  they can be shared or kept private and if some turn out to be widely
  useful, we can make them common library helpers, etc., without having
  to do anything whatsoever to fs_parse() itself.

  And we already get that kind of requests - the thing that finally
  pushed me into doing that was "oh, and let's add one for timeouts -
  things like 15s or 2h". If some filesystem really wants that, let them
  do it. Without somebody having to play gatekeeper for the variants
  blessed by direct support in fs_parse(), TYVM.

  Quite a bit of boilerplate is gone. And IMO the data structures make a
  lot more sense now. -200LoC, while we are at it"

* 'merge.nfs-fs_parse.1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (25 commits)
  tmpfs: switch to use of invalfc()
  cgroup1: switch to use of errorfc() et.al.
  procfs: switch to use of invalfc()
  hugetlbfs: switch to use of invalfc()
  cramfs: switch to use of errofc() et.al.
  gfs2: switch to use of errorfc() et.al.
  fuse: switch to use errorfc() et.al.
  ceph: use errorfc() and friends instead of spelling the prefix out
  prefix-handling analogues of errorf() and friends
  turn fs_param_is_... into functions
  fs_parse: handle optional arguments sanely
  fs_parse: fold fs_parameter_desc/fs_parameter_spec
  fs_parser: remove fs_parameter_description name field
  add prefix to fs_context->log
  ceph_parse_param(), ceph_parse_mon_ips(): switch to passing fc_log
  new primitive: __fs_parse()
  switch rbd and libceph to p_log-based primitives
  struct p_log, variants of warnf() et.al. taking that one instead
  teach logfc() to handle prefices, give it saner calling conventions
  get rid of cg_invalf()
  ...

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

The former contains nothing but a pointer to an array of the latter...

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

Unused now.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Fixes coccicheck warning:

fs/fuse/readdir.c:335:1-19: WARNING: Assignment of 0/1 to bool variable
fs/fuse/file.c:1398:2-19: WARNING: Assignment of 0/1 to bool variable
fs/fuse/file.c:1400:2-20: WARNING: Assignment of 0/1 to bool variable
fs/fuse/cuse.c:454:1-20: WARNING: Assignment of 0/1 to bool variable
fs/fuse/cuse.c:455:1-19: WARNING: Assignment of 0/1 to bool variable
fs/fuse/inode.c:497:2-17: WARNING: Assignment of 0/1 to bool variable
fs/fuse/inode.c:504:2-23: WARNING: Assignment of 0/1 to bool variable
fs/fuse/inode.c:511:2-22: WARNING: Assignment of 0/1 to bool variable
fs/fuse/inode.c:518:2-23: WARNING: Assignment of 0/1 to bool variable
fs/fuse/inode.c:522:2-26: WARNING: Assignment of 0/1 to bool variable
fs/fuse/inode.c:526:2-18: WARNING: Assignment of 0/1 to bool variable
fs/fuse/inode.c:1000:1-20: WARNING: Assignment of 0/1 to bool variable

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Virtio-fs does not accept any mount options, so it's confusing and wrong to
show any in /proc/mounts.

Reported-by: Stefan Hajnoczi <stefanha@redhat.com> 
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Pull fuse virtio-fs support from Miklos Szeredi:
 "Virtio-fs allows exporting directory trees on the host and mounting
  them in guest(s).

  This isn't actually a new filesystem, but a glue layer between the
  fuse filesystem and a virtio based back-end.

  It's similar in functionality to the existing virtio-9p solution, but
  significantly faster in benchmarks and has better POSIX compliance.
  Further permformance improvements can be achieved by sharing the page
  cache between host and guest, allowing for faster I/O and reduced
  memory use.

  Kata Containers have been including the out-of-tree virtio-fs (with
  the shared page cache patches as well) since version 1.7 as an
  experimental feature. They have been active in development and plan to
  switch from virtio-9p to virtio-fs as their default solution. There
  has been interest from other sources as well.

  The userspace infrastructure is slated to be merged into qemu once the
  kernel part hits mainline.

  This was developed by Vivek Goyal, Dave Gilbert and Stefan Hajnoczi"

* tag 'virtio-fs-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  virtio-fs: add virtiofs filesystem
  virtio-fs: add Documentation/filesystems/virtiofs.rst
  fuse: reserve values for mapping protocol

account per-file, dentry, and inode data

blockdev/superblock and temporary per-request data was left alone, as
this usually isn't accounted

Reviewed-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Add a basic file system module for virtio-fs.  This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.

Design Overview
===============

With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.

 - Use fuse protocol (instead of 9p) for communication between guest and
   host.  Guest kernel will be fuse client and a fuse server will run on
   host to serve the requests.

 - For data access inside guest, mmap portion of file in QEMU address space
   and guest accesses this memory using dax.  That way guest page cache is
   bypassed and there is only one copy of data (on host).  This will also
   enable mmap(MAP_SHARED) between guests.

 - For metadata coherency, there is a shared memory region which contains
   version number associated with metadata and any guest changing metadata
   updates version number and other guests refresh metadata on next access.
   This is yet to be implemented.

How virtio-fs differs from existing approaches
==============================================

The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).

DAX allows file contents to be accessed without communication with the
hypervisor.  The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.

By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols.  In addition, this also makes it easier to achieve
local file system semantics (coherency).

These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine.  This is why we decided to build virtio-fs rather than
focus on 9P or NFS.

Caching Modes
=============

Like virtio-9p, different caching modes are supported which determine the
coherency level as well.  The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.

 - cache=none
   metadata, data and pathname lookup are not cached in guest.  They are
   always fetched from host and any changes are immediately pushed to host.

 - cache=always
   metadata, data and pathname lookup are cached in guest and never expire.

 - cache=auto
   metadata and pathname lookup cache expires after a configured amount of
   time (default is 1 second).  Data is cached while the file is open
   (close to open consistency).

 - writeback/no_writeback
   These options control the writeback strategy.  If writeback is disabled,
   then normal writes will immediately be synchronized with the host fs.
   If writeback is enabled, then writes may be cached in the guest until
   the file is closed or an fsync(2) performed.  This option has no effect
   on mmap-ed writes or writes going through the DAX mechanism.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

virtio-fs does not support aborting requests which are being
processed. That is requests which have been sent to fuse daemon on host.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>