VNSUBR(9)

VNSUBR(9) | 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).

# FUNCTIONS

`vn_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 dereference the vnode prior to returning. If the operation is successful 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
    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 zero.

`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 arguments 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 arguments 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 argument 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 ALSO

file(9), intro(9), lock(9), namei(9), vattr(9), vfs(9), vnode(9), vnodeops(9)

January 2, 2017 | NetBSD 9.4