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_bdev_open, vn_bdev_openpath, vn_stat, vn_writechk -- high-level convenience func- tions 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 vnode *at_dvp, struct pathbuf *pb, int nmode, int fmode, int cmode, struct vnode **ret_vp, bool *ret_domove, int *ret_fd); int vn_bdev_open(dev_t dev, struct vnode **vpp, struct lwp *l); int vn_bdev_openpath(struct pathbuf *pb, struct vnode **vpp, struct lwp *l); 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 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(at_dvp, pb, nmode, fmode, cmode, ret_vp, ret_domove, ret_fd) Common code for vnode open operations. The at_dvp argument, if not NULL, provides the directory relative paths start from, as per openat(2). The pb argument gives the pathname. The argu- ments nmode, fmode and cmode specify additional namei(9) flags, the open(2) flags (converted to F* from O_* form) and the access mode (permissions) for creation, respectively. The nmode argu- ment is restricted to one or perhaps both of the flags TRYEMULROOT and NOCHROOT. Other name(9) modes should be selected via fmode(). The ret_vp, ret_domove, and ret_fd argu- ments encode the possible return values. When called, vn_open() checks permissions and invokes the VOP_OPEN(9) or VOP_CREATE(9) vnode operations. If the operation is unsuccessful an appropri- ate error code is returned. Otherwise, zero is returned. If a vnode is produced, it is returned locked via ret_vp. If a file descriptor number is produced instead, the pointer passed via ret_vp is NULL, the file descriptor is returned via ret_fd, and the ret_domove returns a value that is true if the file descrip- tor should be moved rather than copied. These cases correspond to the internal errors EMOVEFD and EDUPFD respectively. See errno(9) for further information. Callers unprepared to handle file descriptors can set ret_fd and ret_domove to NULL, in which case an operation that would produce a file descriptor will instead fail with EOPNOTSUPP. vn_bdev_open(dev, vpp, l) Opens a block device by its device number for reading and writ- ing, and stores the vnode pointer into *vpp. The argument l is the calling process. The vnode can be closed and freed with vn_close. vn_bdev_openpath(pb, vpp, l) Works like vn_bdev_open() but looks up a file system path pb to determine the device ID. 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 10.0 June 28, 2021 NetBSD 10.0
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