NetBSD/share/man/man9/vnsubr.9

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.Dd January 2, 2017
.Dt VNSUBR 9
.Os
.Sh NAME
.Nm vnsubr ,
.Nm vn_bwrite ,
.Nm vn_close ,
.Nm vn_default_error ,
.Nm vn_isunder ,
.Nm vn_lock ,
.Nm vn_markexec ,
.Nm vn_marktext ,
.Nm vn_rdwr ,
.Nm vn_open ,
.Nm vn_stat ,
.Nm vn_writechk
.Nd high-level convenience functions for vnode operations
.Sh SYNOPSIS
.In sys/param.h
.In sys/lock.h
.In sys/vnode.h
.Ft int
.Fn vn_bwrite "void *ap"
.Ft int
.Fn vn_close "struct vnode *vp" "int flags" "kauth_cred_t cred"
.Ft int
.Fn vn_default_error "void *v"
.Ft int
.Fn vn_isunder "struct vnode *dvp" "struct vnode *rvp" "struct lwp *l"
.Ft int
.Fn vn_lock "struct vnode *vp" "int flags"
.Ft void
.Fn vn_markexec "struct vnode *vp"
.Ft void
.Fn vn_marktext "struct vnode *vp"
.Ft int
.Fn vn_open "struct nameidata *ndp" "int fmode" "int cmode"
.Ft int
.Fo vn_rdwr
.Fa "enum uio_rw rw" "struct vnode *vp" "void *base"
.Fa "int len" "off_t offset" "enum uio_seg segflg" "int ioflg"
.Fa "kauth_cred_t cred" "size_t *aresid" "struct lwp *l"
.Fc
.Ft int
.Fn vn_readdir "file_t *fp" "char *buf" "int segflg" "u_int count" "int *done" "struct lwp *l" "off_t **cookies" "int *ncookies"
.Ft int
.Fn vn_stat "struct vnode *vp" "struct stat *sb"
.Ft int
.Fn vn_writechk "struct vnode *vp"
.Sh DESCRIPTION
The high-level functions described in this page are convenience
functions for simplified access to the vnode operations described in
.Xr vnodeops 9 .
.Sh FUNCTIONS
.Bl -tag -width compact
.It Fn vn_bwrite "ap"
Common code for block write operations.
.It Fn vn_close "vp" "flags" "cred"
Common code for a vnode close.
The argument
.Fa vp
is the unlocked vnode of the vnode to close.
.Fn vn_close
simply locks the vnode, invokes the vnode operation
.Xr VOP_CLOSE 9
and calls
.Fn vput
to return the vnode to the freelist or holdlist.
Note that
.Fn vn_close
expects an unlocked, referenced vnode and will dereference the vnode
prior to returning.
If the operation is successful zero is returned,
otherwise an appropriate error is returned.
.It Fn vn_default_error "v"
A generic "default" routine that just returns error.
It is used by a file system to specify unsupported operations in
the vnode operations vector.
.It Fn vn_isunder "dvp" "rvp" "l"
Common code to check if one directory specified by the vnode
.Fa rvp
can be found inside the directory specified by the vnode
.Fa dvp .
The argument
.Fa l
is the calling process.
.Fn vn_isunder
is intended to be used in
.Xr chroot 2 ,
.Xr chdir 2 ,
.Xr fchdir 2 ,
etc., to ensure that
.Xr chroot 2
actually means something.
If the operation is successful zero is returned, otherwise 1 is returned.
.It Fn vn_lock "vp" "flags"
Common code to acquire the lock for vnode
.Fa vp .
The argument
.Fa flags
specifies the flags used to lock the vnode.
There are the following flags:
.Pp
.Bl -tag -offset indent -width LK_EXCLUSIVE -compact
.It LK_SHARED
shared lock
.It LK_EXCLUSIVE
exclusive lock
.It LK_NOWAIT
do not sleep to await lock
.It LK_RETRY
allow lock operation on dead vnode
.El
.Pp
If the operation is successful zero is returned, otherwise an
appropriate error code is returned.
.Pp
.Fn vn_lock
must not be called when the vnode's reference count is zero.
.It Fn vn_markexec "vp"
Common code to mark the vnode
.Fa vp
as containing executable code of a running process.
.It Fn vn_marktext "vp"
Common code to mark the vnode
.Fa vp
as being the text of a running process.
.It Fn vn_open "ndp" "fmode" "cmode"
Common code for vnode open operations.
The pathname is described in the nameidata pointer (see
.Xr namei 9 ) .
The arguments
.Fa fmode
and
.Fa cmode
specify the
.Xr open 2
file mode and the access permissions for creation.
.Fn vn_open
checks  permissions and invokes the
.Xr VOP_OPEN 9
or
.Xr VOP_CREATE 9
vnode operations.
If the operation is successful zero is returned and the vnode is locked,
otherwise an appropriate error code is returned.
.It Fn vn_rdwr "rw" "vp" "base" "len" "offset" "segflg" "ioflg" "cred" "aresid" "l"
Common code to package up an I/O request on a vnode into a uio and
then perform the I/O.
The argument
.Fa rw
specifies whether the I/O is a read
.Dv ( UIO_READ )
or write
.Dv ( UIO_WRITE )
operation.
The vnode is specified by
.Fa vp .
The arguments
.Fa l
and
.Fa cred
are the calling lwp and its credentials.
If
.Fa ioflg
contains
.Dv IO_NODELOCKED ,
it is expected that the vnode is locked.
.Fa ioflg
will be passed to
.Fn VOP_READ Ns No / Ns Fn VOP_WRITE .
The remaining arguments specify the uio parameters.
For further information on these parameters see
.Xr uiomove 9 .
.It Fn vn_readdir "fp" "buf" "segflg" "count" "done" "l" "cookies" "ncookies"
Common code for reading the contents of a directory.
The argument
.Fa fp
is the file structure,
.Fa buf
is the buffer for placing the struct dirent structures.
The arguments
.Fa cookies
and
.Fa ncookies
specify the addresses for the list and number of directory seek
cookies generated for NFS.
Both
.Fa cookies
and
.Fa ncookies
should be
.Dv NULL
if they aren't required to be returned by
.Fn vn_readdir .
If the operation is successful zero is returned, otherwise an
appropriate error code is returned.
.It Fn vn_stat "vp" "sb"
Common code for a vnode stat operation.
The vnode is specified by the argument
.Fa vp ,
and
.Fa sb
is the buffer to return the stat information.
.Fn vn_stat
basically calls the vnode operation
.Xr VOP_GETATTR 9
and transfers the contents of a vattr structure into a struct stat.
If the operation is successful zero is returned, otherwise an
appropriate error code is returned.
.It Fn vn_writechk "vp"
Common code to check for write permission on the vnode
.Fa vp .
A vnode is read-only if it is in use as a process's text image.
If the vnode is read-only ETEXTBSY is returned, otherwise zero is
returned to indicate that the vnode can be written to.
.El
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EBUSY
The LK_NOWAIT flag was set and
.Fn vn_lock
would have slept.
.It Bq Er ENOENT
The vnode has been reclaimed and is dead.
This error is only returned if the LK_RETRY flag is not passed to
.Fn vn_lock .
.It Bq Er ETXTBSY
Cannot write to a vnode since is a process's text image.
.El
.Sh CODE REFERENCES
The high-level convenience functions are implemented within the files
.Pa sys/kern/vfs_vnops.c
and
.Pa sys/sys/vnode.h .
.Sh SEE ALSO
.Xr file 9 ,
.Xr intro 9 ,
.Xr lock 9 ,
.Xr namei 9 ,
.Xr vattr 9 ,
.Xr vfs 9 ,
.Xr vnode 9 ,
.Xr vnodeops 9