NetBSD/share/man/man9/vnsubr.9

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.Dd May 25, 2004
.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_restorerecurse ,
.Nm vn_setrecurse ,
.Nm vn_open ,
.Nm vn_stat ,
.Nm vn_writechk ,
.Nm vn_start_write ,
.Nm vn_finished_write ,
.Nm vn_cow_establish ,
.Nm vn_cow_disestablish
.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" "struct ucred *cred" "struct proc *p"
.Ft int
.Fn vn_default_error "void *v"
.Ft int
.Fn vn_isunder "struct vnode *dvp" "struct vnode *rvp" "struct proc *p"
.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 u_int
.Fn vn_setrecurse "struct vnode *vp"
.Ft void
.Fn vn_restorerecurse "struct vnode *vp" "u_int flags"
.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" "caddr_t base"
.Fa "int len" "off_t offset" "enum uio_seg segflg" "int ioflg"
.Fa "struct ucred *cred" "size_t *aresid" "struct proc *p"
.Fc
.Ft int
.Fn vn_readdir "struct file *fp" "char *buf" "int segflg" "u_int count" "int *done" "struct proc *p" "off_t **cookies" "int *ncookies"
.Ft int
.Fn vn_stat "struct vnode *vp" "struct stat *sb" "struct proc *p"
.Ft int
.Fn vn_writechk "struct vnode *vp"
.Ft int
.Fn vn_start_write "struct vnode *vp" "struct mount **mpp" "int flags"
.Ft void
.Fn vn_finished_write "struct mount *mp" "int flags"
.Ft int
.Fn vn_cow_establish "struct vnode *vp" "int (*func)(void *, struct buf *)" "void *cookie"
.Ft int
.Fn vn_cow_disestablish "struct vnode *vp" "int (*func)(void *, struct buf *)" "void *cookie"
.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" "p"
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" "p"
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 p
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
.Xr lockmgr 9
flags used to lock the vnode.
If the operation is successful zero is returned, otherwise an
appropriate error code is returned.
The vnode interlock
.Em v_interlock
is releases on return.
.Pp
.Fn vn_lock
must not be called when the vnode's reference count is zero.
Instead,
.Xr vget 9
should be used.
.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_setrecurse "vp"
Common code to enable LK_CANRECURSE on the vnode lock for vnode
.Fa vp .
.Fn vn_setrecurse
returns the new
.Xr lockmgr 9
flags after the update.
.It Fn vn_restorerecurse "vp" "flags"
Common code to restore the vnode lock flags for the vnode
.Fa vp .
It is called when done with
.Fn vn_setrecurse .
.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,
otherwise an appropriate error code is returned.
.It Fn vn_rdwr "rw" "vp" "base" "len" "offset" "segflg" "ioflg" "cred" "aresid" "p"
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 (UIO_READ) or write (UIO_WRITE)
operation.
The unlocked vnode is specified by
.Fa vp .
The arguments
.Fa p
and
.Fa cred
are the calling process and its credentials.
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" "p" "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 NULL is 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" "p"
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.
The argument
.Fa p
is the calling process.
.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.
.It Fn vn_start_write "vp" "mpp" "flags"
Prepare to start a file system write operation.
If the operation is permitted, bump the count of operations in progress and
proceed.
If a suspend request is in progress (see
.Xr vfs_write_suspend 9 ) ,
wait until the suspension is over
and proceed.
If
.Fa vp
is not
.Dv NULL ,
its mount point is assigned to
.Fa mpp .
If the
.Dv V_WAIT
flag is set,
.Fn vn_start_write
waits until the suspension is over.
Otherwise it returns
.Er EWOULDBLOCK .
If the
.Dv V_PCATCH
flag is set,
.Dv PCATCH
gets added to the
.Fn tsleep
flags.
If the
.Dv V_SLEEPONLY
flag is set, the operations count is not bumped.
If the
.Dv V_LOWER
flag is set, no further vnodes must be locked.
If it is not set, no vnodes must be already locked.
If the operation is permitted zero is returned, otherwise
.Er EWOULDBLOCK
is returned.
.It Fn vn_finished_write "mp" "flags"
A file system write operation has finished.
Adjust the count of operations in progress and return.
Only the
.Dv V_LOWER
flag is valid.
.It Fn vn_cow_establish "vp" "func" "cookie"
Establish a copy-on-write callback on spec vnode
.Fa vp .
.Fa func
will be called for every buffer written through the strategy routine of
.Fa vp .
.It Fn vn_cow_disestablish "vp" "func" "cookie"
Disestablish a copy-on-write callback registered with
.Fn vn_cow_establish .
.El
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ETXTBSY
Cannot write to a vnode since is a process's text image.
.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 EBUSY
The LK_NOWAIT flag was set and
.Fn vn_lock
would have slept.
.El
.Sh CODE REFERENCES
This section describes places within the
.Nx
source tree where actual code implementing or using the vnode
framework can be found.
All pathnames are relative to
.Pa /usr/src .
.Pp
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