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

NetBSD 6.1.5                   January 30, 2010                   NetBSD 6.1.5

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