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VOP_LOOKUP(9)            BSD Kernel Developer's Manual           VOP_LOOKUP(9)

NAME
     VOP_LOOKUP -- vnode operations

SYNOPSIS
     #include <&lt;sys/vnode.h>&gt;

     int
     VOP_ABORTOP(struct vnode *dvp, struct componentname *cnp);

     int
     VOP_ACCESS(struct vnode *vp, int mode, struct ucred *cred,
         struct proc *p);

     int
     VOP_ADVLOCK(struct vnode *vp, void *id, int op, struct flock *fl,
         int flags);

     int
     VOP_BMAP(struct vnode *vp, daddr_t bn, struct vnode **vpp, daddr_t *bnp,
         int *runp);

     int
     VOP_BWRITE(struct buf *bp);

     int
     VOP_CLOSE(struct vnode *vp, int fflag, struct ucred *cred,
         struct proc *p);

     int
     VOP_CREATE(struct vnode *dvp, struct vnode **vpp,
         struct componentname *cnp, struct vattr *vap);

     int
     VOP_FSYNC(struct vnode *vp, struct ucred *cred, int waitfor,
         struct proc *p);

     int
     VOP_GETATTR(struct vnode *vp, struct vattr *vap, struct ucred *cred,
         struct proc *p);

     int
     VOP_INACTIVE(struct vnode *vp, struct proc *p);

     int
     VOP_IOCTL(struct vnode *vp, u_long command, void *data, int fflag,
         struct ucred *cred, struct proc *p);

     int
     VOP_ISLOCKED(struct vnode *vp);

     int
     VOP_KQFILTER(struct vnode *vp, struct knote *kn);

     int
     VOP_LINK(struct vnode *dvp, struct vnode *vp, struct componentname *cnp);

     int
     VOP_LOCK(struct vnode *vp, int flags, struct proc *p);

     int
     VOP_LOOKUP(struct vnode *dvp, struct vnode **vpp,
         struct componentname *cnp);

     int
     VOP_MKDIR(struct vnode *dvp, struct vnode **vpp,
         struct componentname *cnp, struct vattr *vap);

     int
     VOP_MKNOD(struct vnode *dvp, struct vnode **vpp,
         struct componentname *cnp, struct vattr *vap);

     int
     VOP_OPEN(struct vnode *vp, int mode, struct ucred *cred, struct proc *p);

     int
     VOP_PATHCONF(struct vnode *vp, int name, register_t *retval);

     int
     VOP_POLL(struct vnode *vp, int events, struct proc *p);

     int
     VOP_PRINT(struct vnode *vp);

     int
     VOP_READ(struct vnode *vp, struct uio *uio, int ioflag,
         struct ucred *cred);

     int
     VOP_READDIR(struct vnode *vp, struct uio *uio, struct ucred *cred,
         int *eofflag);

     int
     VOP_READLINK(struct vnode *vp, struct uio *uio, struct ucred *cred);

     int
     VOP_REALLOCBLKS(struct vnode *vp, struct cluster_save *buflist);

     int
     VOP_RECLAIM(struct vnode *vp, struct proc *p);

     int
     VOP_REMOVE(struct vnode *dvp, struct vnode *vp,
         struct componentname *cnp);

     int
     VOP_RENAME(struct vnode *fdvp, struct vnode *fvp,
         struct componentname *fcnp, struct vnode *tdvp, struct vnode *tvp,
         struct componentname *tcnp);

     int
     VOP_REVOKE(struct vnode *vp, int flags);

     int
     VOP_RMDIR(struct vnode *dvp, struct vnode *vp,
         struct componentname *cnp);

     int
     VOP_SETATTR(struct vnode *vp, struct vattr *vap, struct ucred *cred,
         struct proc *p);

     int
     VOP_STRATEGY(struct buf *bp);

     int
     VOP_SYMLINK(struct vnode *dvp, struct vnode **vpp,
         struct componentname *cnp, struct vattr *vap, char *target);

     int
     VOP_UNLOCK(struct vnode *vp, int flags, struct proc *p);

     int
     VOP_WRITE(struct vnode *vp, struct uio *uio, int ioflag,
         struct ucred *cred);

DESCRIPTION
     The VOP functions implement a generic way to perform operations on
     vnodes.  The VOP function called passes the arguments to the correct file
     system specific function.  Not all file systems implement all operations,
     in which case a generic method will be used.  These functions exist to
     provide an abstract method to invoke vnode operations without needing to
     know anything about the underlying file system.  Many system calls map
     directly to a specific VOP function.

     The arguments for each VOP function consist of one or more vnode pointers
     along with other data needed to perform the operation.  Care must be
     taken to obey the vnode locking discipline when using VOP functions.
     Many VOP calls take a struct proc *p argument.  This should be the cur-
     rent process.  VOP calls are not safe to call in an interrupt context.

     The following sections comment on the VOP functions from the consumer's
     perspective.

     VOP_ABORTOP(dvp, cnp)
             Abort any asynchronous operations pending on the vnode dvp asso-
             ciated with the path name cnp.  This is mostly used by internal
             VFS code and should not be needed by file system implementors.

     VOP_ACCESS(vp, mode, cred, p)
             Determine if the locked vnode vp can be accessed by the calling
             process p with credentials cred for the given access mode.

             mode may contain any of the following values:

                   VWRITE  check writeability
                   VREAD   check readability
                   VEXEC   check executability

             If the access check succeeds, zero is returned; otherwise, an
             appropriate error code is returned.

     VOP_ADVLOCK(vp, id, op, fl, flags)
             Perform advisory locking on the vnode vp according to the opera-
             tion op and lock specification fl.  id identifies the resource
             holding the lock (typically a pointer to the holding process).

             op may be one of the following operations:

                   F_GETLK  Get the first lock that would block a lock
                            request.
                   F_SETLK  Set a lock.
                   F_UNLCK  Release a lock.

             flags may contain the following flags:

                   F_WAIT   If required, block waiting to obtain an exclusive
                            lock.
                   F_POSIX  Follow POSIX locking semantics; see fcntl(2).
                   F_FLOCK  Follow flock(2) locking semantics.

             Upon success, zero is returned; otherwise, an appropriate error
             code is returned.

     VOP_BMAP(vp, bn, vpp, bnp, runp)
             Convert the logical block number bn of the file the locked vnode
             vp is associated with to its physical number on-disk.  The physi-
             cal block number is stored in *bnp on return.  vpp, if non-NULL,
             will be updated to point to the vnode of the block device of
             which vp is associated.  runp, if non-NULL, will be updated to
             the number of contiguous disk blocks following *bnp.  Upon suc-
             cess, zero is returned; otherwise, an appropriate error code is
             returned.

     VOP_BWRITE(bp)
             Write a file system buffer to disk.  Upon success, zero is
             returned; otherwise, an appropriate error code is returned.

     VOP_CLOSE(vp, fflag, cred, p)
             Close the file associated with the locked vnode vp with file
             flags fflag by the calling process p with credentials cred.  This
             operation should be performed only when the file is no longer
             being used.  Upon success, zero is returned; otherwise, an appro-
             priate error code is returned.

     VOP_CREATE(dvp, vpp, cnp, vap)
             Create a new directory entry for a regular file in the directory
             dvp and return a locked, referenced vnode in vpp.  The file name
             is in cnp and its permissions will be vap.

     VOP_FSYNC(vp, cred, waitfor, p)
             Flush any dirty buffers associated with vp to disk.  The vnode is
             locked on entry and exit.  waitfor can be set to MNT_WAIT to
             indicate that VOP_FSYNC() should not return until all data is
             written.

     VOP_GETATTR(vp, vap, cred, p)
     VOP_SETATTR(vp, vap, cred, p)
             Access the vnode attributes vap of the vnode vp by the calling
             process p with credentials cred.  VOP_SETATTR() requires that vp
             be locked.  A field value for any member of vap of VNOVAL repre-
             sents that the information could not be obtained by VOP_GETATTR()
             or should not be changed by VOP_SETATTR().  Upon success of
             obtaining or changing the attributes, zero is returned; other-
             wise, an appropriate error code is returned.

     VOP_INACTIVE(vp, p)
             Notify the underlying file system that the locked vnode vp is no
             longer in use.  The vnode will be unlocked upon return.  p speci-
             fies the calling process.  This may happen when the vnode refer-
             ence count reaches zero or when the underlying file system has
             disappeared or has been forcibly unmounted.

             Typically, the underlying file system will write any buffers
             associated with vp to disk or delete the file entry, if need be.
             The underlying file system may not necessarily release any buf-
             fers associated with vp so that it can be immediately reactivated
             in case the file is used again.  Upon success, zero is returned;
             otherwise, an appropriate error code is returned.

     VOP_IOCTL(vp, command, data, fflag, cred, p)
             Perform the control operation command with additional information
             data on the vnode vp, normally associated with a device, with
             file flags fflag by the calling process p with credentials cred.
             Upon success, zero is returned; otherwise, an appropriate error
             code is returned.

     VOP_ISLOCKED(vp)
     VOP_LOCK(vp, flags, p)
     VOP_UNLOCK(vp, flags, p)
             VOP_LOCK() is used internally by vn_lock(9) to lock a vnode.  It
             should not be used by other file system code.  VOP_UNLOCK()
             unlocks a vnode.  flags should be zero in most cases.
             VOP_ISLOCKED() returns 1 if vp is locked and 0 if not.  It should
             be used cautiously, as not all file systems implement locks
             effectively.  Note the asymmetry between vn_lock(9) and
             VOP_UNLOCK().

     VOP_KQFILTER(vp, kn)
             Register the knote(9) filtering information kn for the vnode vp.
             Only filters for EVFILT_READ, EVFILT_WRITE, and EVFILT_VNODE will
             invoke this operation.  Upon success, zero is returned; other-
             wise, a non-zero value is returned.

     VOP_LINK(dvp, vp, cnp)
             Increase the link count for the vnode vp.  A new entry with name
             cnp should be added to the directory dvp.  dvp is locked on entry
             and unlocked on exit.

     VOP_LOOKUP(dvp, vpp, cnp)
             Find the file corresponding to the name cnp in the directory dvp
             and return a vnode in vpp.  dvp is locked on entry and exit, and
             vpp is locked upon a successful return.  vpp will be NULL on
             error, and cnp-&gt;cn_flags will be set to PDIRUNLOCK if dvp has
             been unlocked for an unsuccessful return.

     VOP_MKDIR(dvp, vpp, cnp, vap)
             Create a new directory named by cnp with permissions vattr in the
             directory dvp.  On success, the new vnode is returned locked in
             vpp.  dvp must be locked on entry and is unlocked on exit.

     VOP_MKNOD(dvp, vpp, cnp, vap)
             Create a device special file with name cnp and attributes vap in
             the directory associated with the locked vnode dvp.  dvp will be
             unlocked on return (see vput(9)).  A pointer to the new, locked
             vnode will be returned in *vpp if vpp is not NULL.  Upon success,
             zero is returned; otherwise, an appropriate error code is
             returned.

     VOP_OPEN(vp, mode, cred, p)
             Open the file associated with the vnode vp with the access modes
             mode by the calling process p with credentials cred.  mode takes
             the flags described in open(2).

             For some underlying file systems, access permissions for the file
             by the process are checked; for others, this is a no-op.  In any
             case, this must be called before a process can access the file.
             Upon success, zero is returned; otherwise, an appropriate error
             code is returned.

     VOP_PATHCONF(vp, name, retval)
             Obtain the value of the applicable POSIX configurable pathname
             variable (see pathconf(2)) specified by name from the locked
             vnode vp.  The result is placed in *retval.  Upon success, zero
             is returned; otherwise, an appropriate error code is returned.

     VOP_POLL(vp, events, p)
             Determine whether the vnode vp is ready to perform the operations
             specified by events (see poll(2)) for the calling process p.  The
             selrecord() routine may be used to detect selection collisions
             for multiple processes sleeping on the same file, waiting for I/O
             to become possible, although all file systems currently assume
             that I/O is always possible.  The return value specifies which
             operations from events were found to be ready, which may be per-
             formed without the need for blocking.

     VOP_PRINT(vp)
             Print information about the vnode to the kernel message buffer.
             It is not used normally, but exists only for debugging purposes.

     VOP_READ(vp, uio, ioflag, cred)
             Copy data from the locked vnode vp to the buffers specified by
             uio with calling process credentials cred.

             ioflag may contain the following flags:

                   IO_NDELAY  Non-blocking I/O.
                   IO_UNIT    Do I/O as an atomic unit.

             Upon success, zero is returned; otherwise, an appropriate error
             code is returned.

     VOP_READDIR(vp, uio, cred, eofflag)
             Read the contents of the directory associated with the locked
             vnode vp, usually via VOP_READ(), and convert its file-system-
             specific format to that expected by the getdents(2) system call,
             storing the result into the buffers specified by uio.  cred spec-
             ifies the credentials of the calling process.  *eofflag is set to
             a non-zero value on return once successful end-of-file for the
             directory contents has been reached.

             Upon success, zero is returned; otherwise, an appropriate error
             code is returned.

     VOP_READLINK(vp, uio, cred)
             Read a symbolic link and return the target's name in uio.  vp is
             locked on entry and exit and must be a symlink.

     VOP_REALLOCBLKS(vp, buflist)
             Called by the VFS write clustering code.  It gives the file sys-
             tem an opportunity to rearrange the on-disk blocks for a file to
             reduce fragmentation.  vp is the locked vnode for the file, and
             buflist is a cluster of the outstanding buffers about to be writ-
             ten.  Currently, only FFS implements this call.

     VOP_RECLAIM(vp, p)
             Used by vclean(9) so that the file system has an opportunity to
             free memory and perform any other cleanup activity related to vp.
             vp is unlocked on entry and exit.  VOP_RECLAIM() should not be
             used by generic code.

     VOP_REMOVE(dvp, vp, cnp)
             Remove the link named cnp from the directory dvp.  This file cor-
             responds to the vnode vp.  Both dvp and vp are locked on entry
             and unlocked on exit, and each has its reference count decre-
             mented by one.  VOP_REMOVE() does not delete the file from disk
             unless its link count becomes zero (for file systems which sup-
             port multiple links).

     VOP_RENAME(fdvp, fvp, fcnp, tdvp, tvp, tcnp)
             Remove the link to the file with associated vnode fvp and name
             fcnp in the directory with associated vnode fdvp, and create a
             new link to the file with name tcnp (and associated locked vnode
             tvp, if the file already exists) residing in the directory with
             the associated locked vnode tdvp.  fdvp, fvp, and tvp (if not
             NULL) will be released (see vrele(9)) and tdvp will have its ref-
             erence count decremented (see vput(9)) on return.  If not NULL,
             tvp will be locked on return as well.  Upon success, zero is
             returned; otherwise, an appropriate error code is returned.

     VOP_REVOKE(vp, flags)
             Used by the revoke(2) system call to prevent any further access
             to a vnode.  The vnode ops will be changed to those of deadfs,
             which returns only errors.  vp must be unlocked.

     VOP_RMDIR(dvp, vp, cnp)
             Remove the directory vp from the directory dvp.  Both are locked
             on entry and unlocked on exit.  The name of the directory for
             removal is additionally contained in cnp.

     VOP_STRATEGY(bp)
             Call the appropriate strategy function for the device backing the
             buffer's vnode.

     VOP_SYMLINK(dvp, vpp, cnp, vap, target)
             Create a symbolic link with name cnp in the directory dvp with
             mode vap.  The link will point to target and a vnode for it is
             returned in vpp.  The directory vnode is locked on entry and
             unlocked on exit.  Note that unlike most VOP calls returning a
             vnode, VOP_SYMLINK() does not lock or reference vpp.

     VOP_WRITE(vp, uio, ioflag, cred)
             Copy data from the buffers specified by uio to the locked vnode
             vp with calling process credentials cred.

             ioflag may contain the following flags:

                   IO_APPEND  Perform write at the end of file.
                   IO_NDELAY  Non-blocking I/O.
                   IO_SYNC    Wait for I/O to complete.
                   IO_UNIT    Do I/O as an atomic unit.

             Upon success, zero is returned; otherwise, an appropriate error
             code is returned.

RETURN VALUES
     The VOP functions return 0 to indicate success and a non-zero error code
     to indicate failure.

SEE ALSO
     errno(2), uio(9), vfs(9), vn_lock(9), vnode(9)

AUTHORS
     This man page was written by Ted Unangst for OpenBSD.

BUGS
     The locking discipline is too complex.  Refer to vn_lock(9).

BSD                            September 8, 2014                           BSD