Add information about the new "virtiofs" file system.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

SETUPMAPPING is a command for use with 'virtiofsd', a fuse-over-virtio
implementation; it may find use in other fuse impelementations as well in
which the kernel does not have access to the address space of the daemon
directly.

A SETUPMAPPING operation causes a section of a file to be mapped into a
memory window visible to the kernel.  The offsets in the file and the
window are defined by the kernel performing the operation.

The daemon may reject the request, for reasons including permissions and
limited resources.

When a request perfectly overlaps a previous mapping, the previous mapping
is replaced.  When a mapping partially overlaps a previous mapping, the
previous mapping is split into one or two smaller mappings.

REMOVEMAPPING is the complement to SETUPMAPPING; it unmaps a range of
mapped files from the window visible to the kernel.

The map_alignment field communicates the alignment constraint for
FUSE_SETUPMAPPING/FUSE_REMOVEMAPPING and allows the daemon to constrain the
addresses and file offsets chosen by the kernel.
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

virtio fs tunnels fuse over a virtio channel.  One issue is two sides might
be speaking different endian-ness. To detects this, host side looks at the
opcode value in the FUSE_INIT command.  Works fine at the moment but might
fail if a future version of fuse will use such an opcode for
initialization.  Let's reserve this opcode so we remember and don't do
this.

Same for CUSE_INIT.
Signed-off-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>

Allow virtio-fs to also send DESTROY request.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Don't hold onto dentry in lru list if need to re-lookup it anyway at next
access.  Only do this if explicitly enabled, otherwise it could result in
performance regression.

More advanced version of this patch would periodically flush out dentries
from the lru which have gone stale.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

As of now fuse_dev_alloc() both allocates a fuse device and installs it in
fuse_conn list.  fuse_dev_alloc() can fail if fuse_device allocation fails.

virtio-fs needs to initialize multiple fuse devices (one per virtio queue).
It initializes one fuse device as part of call to fuse_fill_super_common()
and rest of the devices are allocated and installed after that.

But, we can't afford to fail after calling fuse_fill_super_common() as we
don't have a way to undo all the actions done by fuse_fill_super_common().
So to avoid failures after the call to fuse_fill_super_common(),
pre-allocate all fuse devices early and install them into fuse connection
later.

This patch provides two separate helpers for fuse device allocation and
fuse device installation in fuse_conn.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The /dev/fuse device uses fiq->waitq and fasync to signal that requests are
available.  These mechanisms do not apply to virtio-fs.  This patch
introduces callbacks so alternative behavior can be used.

Note that queue_interrupt() changes along these lines:

  spin_lock(&fiq->waitq.lock);
  wake_up_locked(&fiq->waitq);
+ kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
  spin_unlock(&fiq->waitq.lock);
- kill_fasync(&fiq->fasync, SIGIO, POLL_IN);

Since queue_request() and queue_forget() also call kill_fasync() inside
the spinlock this should be safe.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fuse_fill_super() includes code to process the fd= option and link the
struct fuse_dev to the fd's struct file.  In virtio-fs there is no file
descriptor because /dev/fuse is not used.

This patch extracts fuse_fill_super_common() so that both classic fuse and
virtio-fs can share the code to initialize a mount.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

File systems like virtio-fs need to do not have to play directly with
forget list data structures. There is a helper function use that instead.

Rename dequeue_forget() to fuse_dequeue_forget() and export it so that
stacked filesystems can use it.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

virtio-fs will need unique IDs for FORGET requests from outside
fs/fuse/dev.c.  Make the symbol visible.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This will be used by virtio-fs to send init request to fuse server after
initialization of virt queues.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

virtio-fs will need to query the length of fuse_arg lists.  Make the symbol
visible.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

virtio-fs will need to complete requests from outside fs/fuse/dev.c.  Make
the symbol visible.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The size of struct fuse_req was reduced from 392B to 144B on a non-debug
config, thus the sanitize_global_limit() helper was setting a larger
default limit.  This doesn't really reflect reduction in the memory used by
requests, since the fields removed from fuse_req were added to fuse_args
derived structs; e.g. sizeof(struct fuse_writepages_args) is 248B, thus
resulting in slightly more memory being used for writepage requests
overalll (due to using 256B slabs).

Make the calculatation ignore the size of fuse_req and use the old 392B
value.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The page array pointers are also duplicated across fuse_args_pages and
fuse_req.  Get rid of the fuse_req ones.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

No need to duplicate the argument arrays in fuse_req, so just dereference
req->args instead of copying to the fuse_req internal ones.

This allows further cleanup of the fuse_req structure.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Get rid of request specific fields in fuse_req that are not used anymore.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Page arrays are not allocated together with the request anymore.  Get rid
of the dead code
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

All requests are now sent with one of the fuse_simple_... helpers.  Get rid
of the old api from the fuse internal header.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Rename fuse_request_send_notify_reply() to fuse_simple_notify_reply() and
convert to passing fuse_args instead of fuse_req.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Since we cannot reserve the request structure up-front, make sure that the
request allocation doesn't fail using __GFP_NOFAIL.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This is a straightforward conversion.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Bypass the fc->initialized check by setting the force flag.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Derive fuse_writepage_args from fuse_io_args.

Sending the request is tricky since it was done with fi->lock held, hence
we must either use atomic allocation or release the lock.  Both are
possible so try atomic first and if it fails, release the lock and do the
regular allocation with GFP_NOFS and __GFP_NOFAIL.  Both flags are
necessary for correct operation.

Move the page realloc function from dev.c to file.c and convert to using
fuse_writepage_args.

The last caller of fuse_write_fill() is gone, so get rid of it.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The old fuse_read_fill() helper can be deleted, now that the last user is
gone.

The fuse_io_args struct is moved to fuse_i.h so it can be shared between
readdir/read code.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Need to extend fuse_io_args with 'attr_ver' and 'ff' members, that take the
functionality of the same named members in fuse_req.

fuse_short_read() can now take struct fuse_args_pages.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Change of semantics in fuse_async_req_send/fuse_send_(read|write): these
can now return error, in which case the 'end' callback isn't called, so the
fuse_io_args object needs to be freed.

Added verification that the return value is sane (less than or equal to the
requested read/write size).
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Create a helper named fuse_simple_background() that is similar to
fuse_simple_request().  Unlike the latter, it returns immediately and calls
the supplied 'end' callback when the reply is received.

The supplied 'args' pointer is stored in 'fuse_req' which allows the
callback to interpret the output arguments decoded from the reply.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Extract a fuse_write_flags() helper that converts ki_flags relevant write
to open flags.

The other parts of fuse_send_write() aren't used in the
fuse_perform_write() case.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Derive fuse_io_args from struct fuse_args_pages.  This will be used for
both synchronous and asynchronous read/write requests.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This will allow the use of this function when converting to the simple api
(which doesn't use fuse_req).
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fuse_simple_request() is converted to return length of last (instead of
single) out arg, since FUSE_IOCTL_OUT has two out args, the second of which
is variable length.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fuse_req_pages_alloc() is moved to file.c, since its internal use by the
device code will eventually be removed.

Rename to fuse_pages_alloc() to signify that it's not only usable for
fuse_req page array.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Also turn BUG_ON into gracefully recovered WARN_ON.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Derive fuse_args_pages from fuse_args. This is used to handle requests
which use pages for input or output.  The related flags are added to
fuse_args.

New FR_ALLOC_PAGES flags is added to indicate whether the page arrays in
fuse_req need to be freed by fuse_put_request() or not.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

We can use the "force" flag to make sure the DESTROY request is always sent
to userspace.  So no need to keep it allocated during the lifetime of the
filesystem.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

In some cases it makes no sense to set pid/uid/gid fields in the request
header.  Allow fuse_simple_background() to omit these.  This is only
required in the "force" case, so for now just WARN if set otherwise.

Fold fuse_get_req_nofail_nopages() into its only caller.  Comment is
obsolete anyway.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Move this function to the readdir.c where its only caller resides.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This will be used by fuse_force_forget().

We can expand fuse_request_send() into fuse_simple_request().  The
FR_WAITING bit has already been set, no need to check.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>