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.\" $OpenBSD: fusebuf.9,v 1.3 2013/06/03 16:35:55 tedu Exp $
.\"
.\" Copyright (c) 2013 Sylvestre Gallon <ccna.syl@gmail.com>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: June 3 2013 $
.Dt FUSE 9
.Os
.Sh NAME
.Nm fusebuf
.Nd kernel messaging mechanism for file system in userland
.Sh SYNOPSIS
.Fd #include <sys/fusebuf.h>
.Ft struct fusebuf *
.Fn fb_setup "size_t size" "ino_t inode" "int type" "struct proc *p"
.Ft int
.Fn fb_queue "dev_t dev" "struct fusebuf *fbuf"
.Bd -literal
#define FUSEFDSIZE sizeof(((struct fusebuf *)0)->F_dat.FD)
#define FUSELEN (PAGE_SIZE - sizeof(struct fb_hdr) - \\
sizeof(union uFD))
struct fb_hdr {
SIMPLEQ_ENTRY(fusebuf) fh_next;
size_t fh_len;
size_t fh_resid;
uint32_t fh_err;
int fh_type;
ino_t fh_ino;
uint64_t fh_uuid;
};
struct fb_io {
uint64_t fi_fd;
ino_t fi_ino;
off_t fi_off;
size_t fi_len;
mode_t fi_mode;
uint32_t fi_flags;
};
struct fusebuf {
struct fb_hdr fb_hdr;
struct {
union uFD {
struct statvfs FD_stat;
struct vattr FD_vattr;
struct fb_io FD_io;
} FD;
char F_databuf[FUSELEN];
} F_dat;
};
#define fb_next fb_hdr.fh_next
#define fb_len fb_hdr.fh_len
#define fb_resid fb_hdr.fh_resid
#define fb_err fb_hdr.fh_err
#define fb_type fb_hdr.fh_type
#define fb_ino fb_hdr.fh_ino
#define fb_uuid fb_hdr.fh_uuid
#define fb_stat F_dat.FD.FD_stat
#define fb_vattr F_dat.FD.FD_vattr
#define fb_io_fd F_dat.FD.FD_io.fi_fd
#define fb_io_ino F_dat.FD.FD_io.fi_ino
#define fb_io_off F_dat.FD.FD_io.fi_off
#define fb_io_len F_dat.FD.FD_io.fi_len
#define fb_io_mode F_dat.FD.FD_io.fi_mode
#define fb_io_flags F_dat.FD.FD_io.fi_flags
#define fb_dat F_dat.F_databuf
.Ed
.Sh DESCRIPTION
Fusebufs functions provide a way to manage the kernel messaging mechanism
for filesystem in userland. It is based on
.Xr mbuf 9 .
There is some changes with the original
.Xr mbuf 9 ,
the
.Fa mbuf_ext
and
.Fa pkthdr
are not needed so not existant.
.Pp
Each fuse operation fit in a
.Nm
except for read write and readdirs. These operations are splitted in severals
fusebufs with a changing value in
.Fa fb_io_off
each time. Several functions and macros are used to handle fusebufs. The size
of an fusebuf is
.Fa PAGE_SIZE
.Pp
An fusebuf structure is defined as an
.Fa fb_hdr
followed by a structure containing an union and a buffer
.Fa F_Dat .
The header contains the following elements:
.Bl -tag -width foobarmoocow
.It Fa fh_next
This is a
.Xr SIMPLEQ_ENTRY 9
needed to store the different fusebufs stored with
.Fa fb_queue
.It Fa fh_len
Indicates the amount of data in
.Fa F_dat
.It Fa fh_resid
Is used to for partial
.Xr fuse 4
read. if a the read is inferior of the fusebuf, we store
the number of bytes of
.Fa F_dat
written in this field.
.It Fa fh_err
Indicates the
.Xr errno 2
failure of a fusebuf
.It Fa fh_type
Indicates the type of fusebuf transaction (see below).
.It Fa fh_ino
Indicates the ino on which the
.Xr fuse 4
operation is done.
.It Fa fh_uuid
Uuid to track the answer. This number is generated with
.Xr arc4random 9 .
.El
.Pp
The
.Fa fh_type
variable can take the following values:
.Pp
.Bl -tag -compact -offset indent -width XXXXXXXXXXXXXXXXXX
.It Dv FBT_LOOKUP
the fusebuf is a lookup operation.
.It Dv FBT_GETATTR
the fusebuf is a gettattr operation.
.It Dv FBT_SETATTR
the fusebuf is a setattr operation.
.It Dv FBT_READLINK
the fusebuf is a readlink operation.
.It Dv FBT_SYMLINK
the fusebuf is a symlink operation.
.It Dv FBT_MKNOD
the fusebuf is a mknod operation.
.It Dv FBT_MKDIR
the fusebuf is a mkdir operation.
.It Dv FBT_UNLINK
the fusebuf is a unlink operation.
.It Dv FBT_RMDIR
the fusebuf is a rmdir operation.
.It Dv FBT_RENAME
the fusebuf is a rename operation.
.It Dv FBT_LINK
the fusebuf is a link operation.
.It Dv FBT_OPEN
the fusebuf is a open operation.
.It Dv FBT_READ
the fusebuf is a read operation.
.It Dv FBT_WRITE
the fusebuf is a write operation.
.It Dv FBT_STATFS
the fusebuf is a statfs operation.
.It Dv FBT_RELEASE
the fusebuf is a file close operation.
.It Dv FBT_FSYNC
the fusebuf is a file sync operation.
.It Dv FBT_FLUSH
the fusebuf is a flush operation.
.It Dv FBT_INIT
the fusebuf initialise the fuse connection.
.It Dv FBT_OPENDIR
the fusebuf is an opendir operation.
.It Dv FBT_READDIR
the fusebuf is a readdir operation.
.It Dv FBT_RELEASEDIR
the fusebuf is a close dir operation.
.It Dv FBT_FSYNCDIR
the fusebuf is a dir sync operation.
.It Dv FBT_ACCESS
the fusebuf is a access operation.
.It Dv FBT_CREATE
the fusebuf is a create file operation.
.It Dv FBT_DESTROY
the fusebuf close the fuse connection.
.El
.Pp
All the data needed by the fuse clients are contained in the
.Fa F_dat
structure. This structure contained an union
.Fa FD
of frequently used type
and a buffer
.Fa F_databuf
to send datas to libfuse.
The union contains the following elements:
.Bl -tag -width foobarmoocow
.It Fa FD_stat
Is a struct
.Xr statvfs 3
fill by the fuse client statfs for the fuse VFS statfs code.
.It Fa FD_vattr
Is used by the getattr and setattr calls.
.It Fa FD_io
Contains all fields commonly used by fuse clients callback to
give information to fuse vnops. It is used by access, readdir,
release, releasedir, read, write, create, mkdir and setattr.
.El
.Pp
Setattr use a struct fb_io and a struct vattr. To do that settattr used
.Fa FD_stat
and encapsulate a struct fb_io in
.Fa F_databuf
with
.Fa fbtod
.Sh SEE ALSO
.Xr errno 2 ,
.Xr fuse 3 ,
.Xr queue 3 ,
.Xr statvfs 3,
.Xr fuse 4 ,
.Xr arc4random 9 ,
.Xr mbuf 9
.Sh HISTORY
The
.Nm
API first appeared in
.Ox 5.4 .
|
