Re: [PATCH] docs: add virtiofsd(1) man page

[Marc-André Lureau]

Hi

On Wed, Jan 29, 2020 at 4:40 PM Christophe de Dinechin
<address@hidden> wrote:
>
>
> Stefan Hajnoczi writes:
>
> > Document the virtiofsd(1) program and its command-line options.  This
> > man page is a rST conversion of the original texi documentation that I
> > wrote.
> >
> > Signed-off-by: Stefan Hajnoczi <address@hidden>
> > ---
> > Based-on: address@hidden
> >           ("[PATCH v2 0/8] qemu-img, qemu-trace-stap, virtfs-proxy-helper: 
> > convert to rST")
> > ---
> >  MAINTAINERS                |   1 +
> >  Makefile                   |   8 ++-
> >  docs/interop/conf.py       |   5 +-
> >  docs/interop/index.rst     |   1 +
> >  docs/interop/virtiofsd.rst | 123 +++++++++++++++++++++++++++++++++++++
> >  5 files changed, 136 insertions(+), 2 deletions(-)
> >  create mode 100644 docs/interop/virtiofsd.rst
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 83fb32b860..1da0709129 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -1603,6 +1603,7 @@ S: Supported
> >  F: tools/virtiofsd/*
> >  F: hw/virtio/vhost-user-fs*
> >  F: include/hw/virtio/vhost-user-fs.h
> > +F: docs/interop/virtiofsd.rst
> >
> >  virtio-input
> >  M: Gerd Hoffmann <address@hidden>
> > diff --git a/Makefile b/Makefile
> > index 539f9ef079..ecd26044bc 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -348,6 +348,9 @@ DOCS=qemu-doc.html qemu-doc.txt qemu.1
> >  DOCS+=$(MANUAL_BUILDDIR)/interop/qemu-img.1
> >  DOCS+=$(MANUAL_BUILDDIR)/interop/qemu-nbd.8
> >  DOCS+=$(MANUAL_BUILDDIR)/interop/qemu-ga.8
> > +ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP)$(CONFIG_LIBCAP_NG),yyy)
> > +DOCS+=$(MANUAL_BUILDDIR)/interop/virtiofsd.1
> > +endif
> >  DOCS+=$(MANUAL_BUILDDIR)/system/qemu-block-drivers.7
> >  DOCS+=docs/interop/qemu-qmp-ref.html docs/interop/qemu-qmp-ref.txt 
> > docs/interop/qemu-qmp-ref.7
> >  DOCS+=docs/interop/qemu-ga-ref.html docs/interop/qemu-ga-ref.txt 
> > docs/interop/qemu-ga-ref.7
> > @@ -861,6 +864,9 @@ ifdef CONFIG_VIRTFS
> >       $(INSTALL_DIR) "$(DESTDIR)$(mandir)/man1"
> >       $(INSTALL_DATA) $(MANUAL_BUILDDIR)/interop/virtfs-proxy-helper.1 
> > "$(DESTDIR)$(mandir)/man1"
> >  endif
> > +ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP)$(CONFIG_LIBCAP_NG),yyy)
> > +     $(INSTALL_DATA) docs/interop/virtiofsd.1 "$(DESTDIR)$(mandir)/man1"
> > +endif
> >
> >  install-datadir:
> >       $(INSTALL_DIR) "$(DESTDIR)$(qemu_datadir)"
> > @@ -1052,7 +1058,7 @@ $(MANUAL_BUILDDIR)/system/index.html: $(call 
> > manual-deps,system)
> >
> >  $(call define-manpage-rule,interop,\
> >         qemu-ga.8 qemu-img.1 qemu-nbd.8 qemu-trace-stap.1\
> > -       virtfs-proxy-helper.1,\
> > +       virtiofsd.1 virtfs-proxy-helper.1,\
> >         $(SRC_PATH/qemu-img-cmds.hx))
> >
> >  $(call define-manpage-rule,system,qemu-block-drivers.7)
> > diff --git a/docs/interop/conf.py b/docs/interop/conf.py
> > index b0f322207c..b3cda17042 100644
> > --- a/docs/interop/conf.py
> > +++ b/docs/interop/conf.py
> > @@ -27,5 +27,8 @@ man_pages = [
> >       [], 1),
> >      ('virtfs-proxy-helper', 'virtfs-proxy-helper',
> >       u'QEMU 9p virtfs proxy filesystem helper',
> > -     ['M. Mohan Kumar'], 1)
> > +     ['M. Mohan Kumar'], 1),
> > +    ('virtiofsd', 'virtiofsd', u'QEMU virtio-fs shared file system daemon',
> > +     ['Stefan Hajnoczi <address@hidden>',
> > +      'Masayoshi Mizuma <address@hidden>'], 1),
> >  ]
> > diff --git a/docs/interop/index.rst b/docs/interop/index.rst
> > index 3b763b1eeb..e8455b4270 100644
> > --- a/docs/interop/index.rst
> > +++ b/docs/interop/index.rst
> > @@ -24,3 +24,4 @@ Contents:
> >     vhost-user
> >     vhost-user-gpu
> >     virtfs-proxy-helper
> > +   virtiofsd
> > diff --git a/docs/interop/virtiofsd.rst b/docs/interop/virtiofsd.rst
> > new file mode 100644
> > index 0000000000..51a657ac0c
> > --- /dev/null
> > +++ b/docs/interop/virtiofsd.rst
> > @@ -0,0 +1,123 @@
> > +QEMU virtio-fs shared file system daemon
> > +========================================
> > +
> > +Synopsis
> > +--------
> > +
> > +**virtiofsd** [*OPTIONS*]
> > +
> > +Description
> > +-----------
> > +
> > +Share a host directory tree with a guest through a virtio-fs device.  This
> > +program is a vhost-user backend that implements the virtio-fs device.  Each
> > +virtio-fs device instance requires its own virtiofsd process.
> > +
> > +This program is designed to work with QEMU's ``--device vhost-user-fs-pci``
> > +but should work with any virtual machine monitor (VMM) that supports
> > +vhost-user.  See the Examples section below.
> > +
> > +This program must be run as the root user.  Upon startup the program will
> > +switch into a new file system namespace with the shared directory tree as 
> > its
> > +root.  This prevents "file system escapes" due to symlinks and other file
> > +system objects that might lead to files outside the shared directory.  The
> > +program also sandboxes itself using seccomp(2) to prevent ptrace(2) and 
> > other
> > +vectors that could allow an attacker to compromise the system after gaining
> > +control of the virtiofsd process.
> > +
> > +Options
> > +-------
> > +
> > +.. program:: virtiofsd
> > +
> > +.. option:: -h, --help
> > +
> > +  Print help.
> > +
> > +.. option:: -V, --version
> > +
> > +  Print version.
> > +
> > +.. option:: -d
> > +
> > +  Enable debug output.
> > +
> > +.. option:: --syslog
> > +
> > +  Print log messages to syslog instead of stderr.
> > +
> > +.. option:: -o OPTION
> > +
> > +  * debug -
> > +    Enable debug output.
> > +
> > +  * flock|no_flock -
> > +    Enable/disable flock.  The default is ``no_flock``.
> > +
> > +  * log_level=LEVEL -
> > +    Print only log messages matching LEVEL or more severe.  LEVEL is one of
> > +    ``err``, ``warn``, ``info``, or ``debug``.  The default is ``info``.
> > +
> > +  * norace -
> > +    Disable racy fallback.  The default is false.
>
> It's not a problem with the doc, but seeing it exposes that options are
> not overly consistent in their spelling. "norace" has no _ but no_flock
> does (as does no_writeback).
>
> > +
> > +  * posix_lock|no_posix_lock -
> > +    Enable/disable remote POSIX locks.  The default is ``posix_lock``.
> > +
> > +  * readdirplus|no_readdirplus -
> > +    Enable/disable readdirplus.  The default is ``readdirplus``.
> > +
> > +  * source=PATH -
> > +    Share host directory tree located at PATH.  This option is required.
> > +
> > +  * timeout=TIMEOUT -
> > +    I/O timeout in seconds.  The default depends on cache= option.
> > +
> > +  * vhost_user_socket=PATH -
> > +    Listen on vhost-user UNIX domain socket at PATH.
>
> I believe that this option has been removed.
>
> > +
> > +  * writeback|no_writeback -
> > +    Enable/disable writeback cache. The cache alows the FUSE client to 
> > buffer
> > +    and merge write requests.  The default is ``no_writeback``.
> > +
> > +  * xattr|no_xattr -
> > +    Enable/disable extended attributes (xattr) on files and directories.  
> > The
> > +    default is ``no_xattr``.
> > +
> > +.. option:: --socket-path=PATH
> > +
> > +  Listen on vhost-user UNIX domain socket at PATH.
>
> Not related to the doc, but this looks like an option that might deserve
> a short form.
>
> > +
> > +.. option:: --fd=FDNUM
> > +
> > +  Accept connections from vhost-user UNIX domain socket file descriptor 
> > FDNUM.
> > +  The file descriptor must already be listening for connections.
>
> Not directly related to the manual itself, but any reason why it's
> "socket-path" and "fd" (as opposed e.g. to "socket-path" and
> "socket-fd"?


This dates back from commit 482580a658df58f5d9f91a87d957660637d59432
("vhost-user: define conventions for vhost-user backends"). I agree it
lacks some consistency. It's a bit late to change it though

>
>
> > +
> > +.. option:: --thread-pool-size=NUM
> > +
> > +  Restrict the number of worker threads per request queue to NUM.  The 
> > default
> > +  is 64.
> > +
> > +.. option:: --cache=none|auto|always
> > +
> > +  Select the desired trade-off between coherency and performance.  ``none``
> > +  forbids the FUSE client from caching to achieve best coherency at the 
> > cost of
> > +  performance.  ``auto`` acts similar to NFS with a 1 second metadata cache
> > +  timeout.  ``always`` sets a long cache lifetime at the expense of 
> > coherency.
> > +
> > +Examples
> > +--------
> > +
> > +Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> > +``/var/run/vm001-vhost-fs.sock``:
> > +
> > +::
> > +
> > +  host# virtiofsd --socket-path=/var/run/vm001-vhost-fs.sock -o 
> > source=/var/lib/fs/vm001
> > +  host# qemu-system-x86_64 \
> > +      -chardev socket,id=char0,path=/var/run/vm001-vhost-fs.sock \
> > +      -device vhost-user-fs-pci,chardev=char0,tag=myfs \
> > +      -object 
> > memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on \
> > +      -numa node,memdev=mem \
> > +      ...
> > +  guest# mount -t virtio_fs myfs /mnt
>
>
> --
> Cheers,
> Christophe de Dinechin (IRC c3d)
>
>


-- 
Marc-André Lureau