VNSUBR(9)              NetBSD Kernel Developer's Manual              VNSUBR(9)

     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

     #include <sys/param.h>
     #include <sys/lock.h>
     #include <sys/vnode.h>

     vn_bwrite(void *ap);

     vn_close(struct vnode *vp, int flags, kauth_cred_t cred);

     vn_default_error(void *v);

     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 nameidata *ndp, int fmode, int cmode);

     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
              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

              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(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.

              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 8.1                      January 2, 2017                     NetBSD 8.1

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