VOP_CREATE(9)

NAME
VOP_CREATE, VOP_MKNOD, VOP_MKDIR, VOP_SYMLINK - create a file, socket, fifo, device, directory or symlink

SYNOPSIS
#include <sys/vnode.h>
#include <sys/namei.h>
int
VOP_CREATE(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_MKDIR(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp, struct vattr *vap);
VOP_SYMLINK(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp, struct vattr *vap, char *target);

DESCRIPTION
These entry points create a new file, socket, fifo, device, directory or symlink in a given directory.

The arguments are:

dvp the locked vnode of the directory

vpp the address of a variable where the resulting locked vnode should be stored

cnp the pathname component created

vap the attributes that the new object should be created with

target
    the pathname of the target of the symlink

These entry points are called after VOP_LOOKUP(9) when an object is being created. Normally, VOP_LOOKUP(9) will have set the SAVENAME flag in cnp->cn_flags to keep the memory pointed to by cnp->cn_pnbuf valid. If an error is detected when creating the file, then this memory will be freed. If the file is created successfully, then it will be freed unless the SAVESTART flag is specified in cnp.

LOCKS
The directory, dvp should be locked on entry and will be unlocked and released on exit. If the call is successful, the new object will be returned locked, unless the call is VOP_MKNOD(9) or VOP_SYMLINK(9) in which case the new object is not returned at all. It is not clear why VOP_MKNOD(9) and VOP_SYMLINK(9) need a *vpp argument at all.

RETURN VALUES
If successful, the vnode for the new object is placed in *vpp and zero is returned. Otherwise, an appropriate error is returned.

PSEUDOCODE

    int
    vop_create(struct vnode *dvp,
    	   struct vnode **vpp,
    	   struct componentname *cnp
    	   struct vattr *vap)
    {
        int mode = MAKEIMODE(vap->va_type, vap->va_mode);
        struct vnode *vp;
        int error;
        *vpp = NULL;
        if ((mode & IFMT) == 0)
    	mode |= IFREG;
        error = VOP_VALLOC(dvp, mode, cnp->cn_cred, &vp);
        if (error) {
    	free(cnp->cn_pnbuf, M_NAMEI);
    	vput(dvp);
    	return error;
        }
        /*
         * Update the permissions for the new vnode, including
         * copying the group from the directory.
         */
        ...;
    #ifdef QUOTA
        /*
         * Possibly check quota information.
         */
        ...;
    #endif
        /*
         * Enter new vnode in directory, taking care that the vnode
         * hits the disk before the directory contents are changed.
         */
        error = ...;
        if (error)
    	goto bad;
        if ((cnp->cn_flags & SAVESTART) == 0)
    	free(cnp->cn_pnbuf, M_NAMEI);
        vput(dvp);
        *vpp = vp;
        return 0;
    bad:
        /*
         * Write error occurred trying to update the inode
         * or the directory so must deallocate the inode.
         */
        free(cnp->cn_pnbuf, M_NAMEI);
        vput(vp);
        /*
         * Deallocate filesystem resources for vp.
         */
        ...;
        vput(dvp);
        return error;
    }

ERRORS

[ENOSPC]
    The filesystem is full.

[EDQUOT]
    Quota exceeded.

SEE ALSO
VOP_LOOKUP(9), VOP_VALLOC(9)

HISTORY
The function VOP_CREATE appeared in 4.3BSD.

SEE ALSO
vnode(9)

AUTHORS
This man page was written by Doug Rabson.