VNSUBR(9) BSD Kernel Developer's Manual VNSUBR(9)NAME
vnsubr, vn_bwrite, vn_close, vn_default_error, vn_isunder, vn_lock,
vn_markexec, vn_marktext, vn_rdwr, vn_open, vn_stat, vn_writechk — high-
level convenience functions for vnode operations
SYNOPSIS
#include <sys/param.h>
#include <sys/lock.h>
#include <sys/vnode.h>
int
vn_bwrite(void *ap);
int
vn_close(struct vnode *vp, int flags, kauth_cred_t cred);
int
vn_default_error(void *v);
int
vn_isunder(struct vnode *dvp, struct vnode *rvp, struct lwp *l);
int
vn_lock(struct vnode *vp, int flags);
void
vn_markexec(struct vnode *vp);
void
vn_marktext(struct vnode *vp);
int
vn_open(struct nameidata *ndp, int fmode, int cmode);
int
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);
int
vn_readdir(file_t *fp, char *buf, int segflg, u_int count, int *done,
struct lwp *l, off_t **cookies, int *ncookies);
int
vn_stat(struct vnode *vp, struct stat *sb);
int
vn_writechk(struct vnode *vp);
DESCRIPTION
The high-level functions described in this page are convenience functions
for simplified access to the vnode operations described in vnodeops(9).
FUNCTIONSvn_bwrite(ap)
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
returned.
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.
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.
vn_lock(vp, flags)
Common code to acquire the lock for vnode vp. The argument
flags specifies the flags used to lock the vnode. There are the
following flags:
LK_SHARED shared lock
LK_EXCLUSIVE exclusive lock
LK_NOWAIT do not sleep to await lock
LK_RETRY retry lock operation until locked
If the operation is successful zero is returned, otherwise an
appropriate error code is returned. The vnode interlock
v_interlock is released on return.
vn_lock() must not be called when the vnode's reference count is
zero. Instead, vget(9) should be used.
vn_markexec(vp)
Common code to mark the vnode vp as containing executable code
of a running process.
vn_marktext(vp)
Common code to mark the vnode vp as being the text of a running
process.
vn_open(ndp, fmode, cmode)
Common code for vnode open operations. The pathname is
described in the nameidata pointer (see namei(9)). The argu‐
ments fmode and cmode specify the open(2) file mode and the
access permissions for creation. vn_open() checks permissions
and invokes the VOP_OPEN(9) or 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.
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.
vn_stat(vp, sb)
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.
vn_writechk(vp)
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.
ERRORS
[EBUSY] The LK_NOWAIT flag was set and vn_lock() would have
slept.
[ENOENT] The vnode has been reclaimed and is dead. This error
is only returned if the LK_RETRY flag is not passed to
vn_lock().
[ETXTBSY] Cannot write to a vnode since is a process's text
image.
CODE REFERENCES
The high-level convenience functions are implemented within the files
sys/kern/vfs_vnops.c and sys/sys/vnode.h.
SEE ALSOfile(9), intro(9), lock(9), namei(9), vattr(9), vfs(9), vnode(9),
vnodeops(9)BSD January 30, 2010 BSD
