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VNSUBR(9) NetBSD Kernel Developer's Manual VNSUBR(9)
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vnsubr, vn_bwrite, vn_close, vn_default_error, vn_isunder, vn_lock,
vn_markexec, vn_marktext, vn_rdwr, vn_open, vn_bdev_open,
vn_bdev_openpath, vn_stat, vn_writechk -- high-level convenience func-
tions for vnode operations
vn_close(struct vnode *vp, int flags, kauth_cred_t cred);
vn_isunder(struct vnode *dvp, struct vnode *rvp, struct lwp *l);
vn_lock(struct vnode *vp, int flags);
vn_markexec(struct vnode *vp);
vn_marktext(struct vnode *vp);
vn_open(struct vnode *at_dvp, struct pathbuf *pb, int nmode, int fmode,
int cmode, struct vnode **ret_vp, bool *ret_domove, int *ret_fd);
vn_bdev_open(dev_t dev, struct vnode **vpp, struct lwp *l);
vn_bdev_openpath(struct pathbuf *pb, struct vnode **vpp, struct lwp *l);
vn_rdwr(enum uio_rw rw, struct vnode *vp, void *base, int len,
off_t offset, enum uio_seg segflg, int ioflg, kauth_cred_t cred,
size_t *aresid, struct lwp *l);
vn_readdir(file_t *fp, char *buf, int segflg, u_int count, int *done,
struct lwp *l, off_t **cookies, int *ncookies);
vn_stat(struct vnode *vp, struct stat *sb);
vn_writechk(struct vnode *vp);
The high-level functions described in this page are convenience functions
for simplified access to the vnode operations described in vnodeops(9).
Common code for block write operations.
vn_close(vp, flags, cred)
Common code for a vnode close. The argument vp is the unlocked
vnode of the vnode to close. vn_close() simply locks the vnode,
invokes the vnode operation VOP_CLOSE(9) and calls vput() to
return the vnode to the freelist or holdlist. Note that
vn_close() expects an unlocked, referenced vnode and will deref-
erence the vnode prior to returning. If the operation is suc-
cessful zero is returned, otherwise an appropriate error is
A generic "default" routine that just returns error. It is used
by a file system to specify unsupported operations in the vnode
vn_isunder(dvp, rvp, l)
Common code to check if one directory specified by the vnode rvp
can be found inside the directory specified by the vnode dvp.
The argument l is the calling process. vn_isunder() is intended
to be used in chroot(2), chdir(2), fchdir(2), etc., to ensure
that chroot(2) actually means something. If the operation is
successful zero is returned, otherwise 1 is returned.
Common code to acquire the lock for vnode vp. The argument
flags specifies the flags used to lock the vnode. There are the
LK_SHARED shared lock
LK_EXCLUSIVE exclusive lock
LK_NOWAIT do not sleep to await lock
LK_RETRY allow lock operation on dead vnode
If the operation is successful zero is returned, otherwise an
appropriate error code is returned.
vn_lock() must not be called when the vnode's reference count is
Common code to mark the vnode vp as containing executable code
of a running process.
Common code to mark the vnode vp as being the text of a running
vn_open(at_dvp, pb, nmode, fmode, cmode, ret_vp, ret_domove, ret_fd)
Common code for vnode open operations. The at_dvp argument, if
not NULL, provides the directory relative paths start from, as
per openat(2). The pb argument gives the pathname. The argu-
ments nmode, fmode and cmode specify additional namei(9) flags,
the open(2) flags (converted to F* from O_* form) and the access
mode (permissions) for creation, respectively. The nmode argu-
ment is restricted to one or perhaps both of the flags
TRYEMULROOT and NOCHROOT. Other name(9) modes should be
selected via fmode(). The ret_vp, ret_domove, and ret_fd argu-
ments encode the possible return values. When called, vn_open()
checks permissions and invokes the VOP_OPEN(9) or VOP_CREATE(9)
vnode operations. If the operation is unsuccessful an appropri-
ate error code is returned. Otherwise, zero is returned. If a
vnode is produced, it is returned locked via ret_vp. If a file
descriptor number is produced instead, the pointer passed via
ret_vp is NULL, the file descriptor is returned via ret_fd, and
the ret_domove returns a value that is true if the file descrip-
tor should be moved rather than copied. These cases correspond
to the internal errors EMOVEFD and EDUPFD respectively. See
errno(9) for further information. Callers unprepared to handle
file descriptors can set ret_fd and ret_domove to NULL, in which
case an operation that would produce a file descriptor will
instead fail with EOPNOTSUPP.
vn_bdev_open(dev, vpp, l)
Opens a block device by its device number for reading and writ-
ing, and stores the vnode pointer into *vpp. The argument l is
the calling process. The vnode can be closed and freed with
vn_bdev_openpath(pb, vpp, l)
Works like vn_bdev_open() but looks up a file system path pb to
determine the device ID.
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 rw specifies whether the
I/O is a read (UIO_READ) or write (UIO_WRITE) operation. The
vnode is specified by vp. The arguments l and cred are the
calling lwp and its credentials. If ioflg contains
IO_NODELOCKED, it is expected that the vnode is locked. ioflg
will be passed to VOP_READ()/VOP_WRITE(). The remaining argu-
ments specify the uio parameters. For further information on
these parameters see uiomove(9).
vn_readdir(fp, buf, segflg, count, done, l, cookies, ncookies)
Common code for reading the contents of a directory. The argu-
ment fp is the file structure, buf is the buffer for placing the
struct dirent structures. The arguments cookies and ncookies
specify the addresses for the list and number of directory seek
cookies generated for NFS. Both cookies and ncookies should be
NULL if they aren't required to be returned by vn_readdir(). If
the operation is successful zero is returned, otherwise an
appropriate error code is returned.
Common code for a vnode stat operation. The vnode is specified
by the argument vp, and sb is the buffer to return the stat
information. vn_stat() basically calls the vnode operation
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.
Common code to check for write permission on the vnode 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.
[EBUSY] The LK_NOWAIT flag was set and vn_lock() would have
[ENOENT] The vnode has been reclaimed and is dead. This error
is only returned if the LK_RETRY flag is not passed to
[ETXTBSY] Cannot write to a vnode since is a process's text
The high-level convenience functions are implemented within the files
sys/kern/vfs_vnops.c and sys/sys/vnode.h.
file(9), intro(9), lock(9), namei(9), vattr(9), vfs(9), vnode(9),
NetBSD 10.99 June 28, 2021 NetBSD 10.99