NAME

vnodeops, VOP_LOOKUP, VOP_CREATE, VOP_MKNOD, VOP_OPEN, VOP_CLOSE, VOP_ACCESS, VOP_GETATTR, VOP_SETATTR, VOP_READ, VOP_WRITE, VOP_FALLOCATE, VOP_FDISCARD, VOP_IOCTL, VOP_FCNTL, VOP_POLL, VOP_KQFILTER, VOP_REVOKE, VOP_MMAP, VOP_FSYNC, VOP_SEEK, VOP_REMOVE, VOP_LINK, VOP_RENAME, VOP_MKDIR, VOP_RMDIR, VOP_SYMLINK, VOP_READDIR, VOP_READLINK, VOP_ABORTOP, VOP_INACTIVE, VOP_RECLAIM, VOP_LOCK, VOP_UNLOCK, VOP_ISLOCKED, VOP_BMAP, VOP_PRINT, VOP_PATHCONF, VOP_ADVLOCK, VOP_WHITEOUT, VOP_GETPAGES, VOP_PUTPAGES, VOP_STRATEGY, VOP_BWRITE, VOP_GETEXTATTR, VOP_SETEXTATTR, VOP_LISTEXTATTR, VOP_DELETEEXTATTR — vnode operations

SYNOPSIS

#include <sys/param.h>
#include <sys/buf.h>
#include <sys/dirent.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/unistd.h>
#include <sys/fcntl.h>
#include <sys/lockf.h>
#include <sys/extattr.h>

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

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_OPEN(struct vnode *vp, int mode, kauth_cred_t cred);

int
VOP_CLOSE(struct vnode *vp, int fflag, kauth_cred_t cred);

int
VOP_ACCESS(struct vnode *vp, int mode, kauth_cred_t cred);

int
VOP_GETATTR(struct vnode *vp, struct vattr *vap, kauth_cred_t cred);

int
VOP_SETATTR(struct vnode *vp, struct vattr *vap, kauth_cred_t cred);

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

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

int
VOP_FALLOCATE(struct vnode *vp, off_t pos, off_t len);

int
VOP_FDISCARD(struct vnode *vp, off_t pos, off_t len);

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

int
VOP_FCNTL(struct vnode *vp, u_int command, void *data, int fflag, kauth_cred_t cred);

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

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

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

int
VOP_MMAP(struct vnode *vp, vm_prot_t prot, kauth_cred_t cred);

int
VOP_FSYNC(struct vnode *vp, kauth_cred_t cred, int flags, off_t offlo, off_t offhi);

int
VOP_SEEK(struct vnode *vp, off_t oldoff, off_t newoff, kauth_cred_t cred);

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

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

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

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

int
VOP_READDIR(struct vnode *vp, struct uio *uio, kauth_cred_t cred, int *eofflag, off_t **cookies, int *ncookies);

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

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

int
VOP_INACTIVE(struct vnode *vp);

int
VOP_RECLAIM(struct vnode *vp);

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

int
VOP_UNLOCK(struct vnode *vp);

int
VOP_ISLOCKED(struct vnode *vp);

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

int
VOP_PRINT(struct vnode *vp);

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

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

int
VOP_WHITEOUT(struct vnode *dvp, struct componentname *cnp, int flags);

int
VOP_GETPAGES(struct vnode *vp, voff_t offset, struct vm_page **m, int *count, int centeridx, vm_prot_t access_type, int advice, int flags);

int
VOP_PUTPAGES(struct vnode *vp, voff_t offlo, voff_t offhi, int flags);

int
VOP_STRATEGY(struct vnode *vp, struct buf *bp);

int
VOP_BWRITE(struct vnode *vp, struct buf *bp);

int
VOP_GETEXTATTR(struct vnode *vp, int attrnamespace, const char *name, struct uio *uio, size_t *size, kauth_cred_t cred);

int
VOP_SETEXTATTR(struct vnode *vp, int attrnamespace, const char *name, struct uio *uio, kauth_cred_t cred);

int
VOP_LISTEXTATTR(struct vnode *vp, int attrnamespace, struct uio *uio, size_t *size, kauth_cred_t cred);

int
VOP_DELETEEXTATTR(struct vnode *vp, int attrnamespace, const char *name, kauth_cred_t cred);

Not all header files are required for each function.

DESCRIPTION

The vnode operations vector describes what operations can be done to the file associated with the vnode. The system maintains one vnode operations vector for each file system type configured into the kernel. The vnode operations vector contains a pointer to a function for each operation supported by the file system. Many of the functions described in the vnode operations vector are closely related to their corresponding system calls. In most cases, they are called as a result of the system call associated with the operation being invoked.

Functions in the vnode operations vector are invoked using specialized macros. The following table gives a summary of the operations.

Macro	Description
VOP_LOOKUP	Lookup file name in name cache
VOP_CREATE	Create a new file
VOP_MKNOD	Make a new device
VOP_OPEN	Open a file
VOP_CLOSE	Close a file
VOP_ACCESS	Determine file accessibility
VOP_GETATTR	Get file attributes
VOP_SETATTR	Set file attributes
VOP_READ	Read from a file
VOP_WRITE	Write to a file
VOP_FALLOCATE	Allocate backing for a file
VOP_FDISCARD	Discard backing for a file
VOP_IOCTL	Perform device-specific I/O
VOP_FCNTL	Perform file control
VOP_POLL	Test if poll event has occurred
VOP_KQFILTER	Register a knote
VOP_REVOKE	Eliminate vnode activity
VOP_MMAP	Map file into user address space
VOP_FSYNC	Flush pending data to disk
VOP_SEEK	Test if file is seekable
VOP_REMOVE	Remove a file
VOP_LINK	Link a file
VOP_RENAME	Rename a file
VOP_MKDIR	Make a new directory
VOP_RMDIR	Remove a directory
VOP_SYMLINK	Create a symbolic link
VOP_READDIR	Read directory entry
VOP_READLINK	Read contents of a symlink
VOP_ABORTOP	Abort pending operation
VOP_INACTIVE	Release the inactive vnode
VOP_RECLAIM	Reclaim vnode for another file
VOP_LOCK	Sleep until vnode lock is free
VOP_UNLOCK	Wake up process sleeping on lock
VOP_ISLOCKED	Test if vnode is locked
VOP_BMAP	Logical block number conversion
VOP_PRINT	Print debugging information
VOP_PATHCONF	Return POSIX pathconf data
VOP_ADVLOCK	Advisory record locking
VOP_WHITEOUT	Whiteout vnode
VOP_GETPAGES	Read VM pages from file
VOP_PUTPAGES	Write VM pages to file
VOP_STRATEGY	Read/write a file system buffer
VOP_BWRITE	Write a file system buffer
VOP_GETEXTATTR	Get extended attribute
VOP_SETEXTATTR	Set extended attribute
VOP_LISTEXTATTR	List extended attributes
VOP_DELETEEXTATTR	Remove extended attribute

The implementation details of the vnode operations vector are not quite what is described here.

If the file system type does not support a specific operation, it must nevertheless assign an appropriate stub in the vnode operations vector to do the minimum required of it. In most cases, such functions either do nothing or return an error value to the effect that it is not supported.

Many of the functions in the vnode operations vector take a componentname structure. It is used to encapsulate many parameters into a single function argument. It has the following structure:

struct componentname { 
        /* 
         * Arguments to lookup. 
         */ 
        uint32_t cn_nameiop;    /* namei operation */ 
        uint32_t cn_flags;      /* flags to namei */ 
        kauth_cred_t cn_cred;   /* credentials */ 
        /* 
         * Shared between lookup and commit routines. 
         */ 
        const char *cn_nameptr; /* pointer to looked up name */ 
        size_t  cn_namelen;     /* length of looked up component */ 
        size_t  cn_consume;     /* chars to consume in lookup() */ 
};

The top half of the structure is used exclusively for the pathname lookups using VOP_LOOKUP() and is initialized by the caller. The semantics of the lookup are affected by the lookup operation specified in cn_nameiop and the flags specified in cn_flags. Valid operations are:

LOOKUP

perform name lookup only

CREATE

set up for file creation

DELETE

set up for file deletion

RENAME

set up for file renaming

OPMASK

mask for operation

Valid values for cn->cn_flags are:

LOCKLEAF

lock inode on return

LOCKPARENT

want parent vnode returned locked

NOCACHE

name must not be left in name cache (see namecache(9))

FOLLOW

follow symbolic links

NOFOLLOW

do not follow symbolic links (pseudo)

MODMASK

mask of operational modifiers

No vnode operations may be called from interrupt context. Most operations also require the vnode to be locked on entry. To prevent deadlocks, when acquiring locks on multiple vnodes, the lock of parent directory must be acquired before the lock on the child directory.

Vnode operations for a file system type generally should not be called directly from the kernel, but accessed indirectly through the high-level convenience functions discussed in vnsubr(9).

FUNCTIONS

VOP_LOOKUP(dvp, vpp, cnp)

Lookup a single pathname component in a given directory. The argument dvp is the locked vnode of the directory to search and cnp is the pathname component to be searched for. If the pathname component is found, the address of the resulting unlocked vnode is returned in vpp. The operation specified in cnp->cn_nameiop indicates VOP_LOOKUP() the reason for requesting the lookup and uses it to cache file system type specific information in the vnode for subsequent operations.

There are three types of lookups: ".", ".." (ISDOTDOT), and regular. If the pathname component being searched for is ".", then dvp has an extra reference added to it and it is returned in *vpp. For other pathname components, VOP_LOOKUP() checks the accessibility of the directory and searches the name cache for the pathname component. See namecache(9). If the pathname is not found in the name cache, the directory is searched for the pathname. The resulting unlocked vnode is returned in vpp. dvp is always returned locked.

On failure *vpp is NULL, and *dvp is left locked. If the operation is successful *vpp is unlocked and zero is returned. Typically, if *vpp and dvp are the same vnode the caller will need to release twice (decrement the reference count) and unlock once.

VOP_CREATE(dvp, vpp, cnp, vap)

Create a new file in a given directory. The argument dvp is the locked vnode of the directory to create the new file in and cnp is the pathname component of the new file. The argument vap specifies the attributes that the new file should be created with. If the file is successfully created, the address of the resulting unlocked vnode is returned in vpp and zero is returned.

This function is called after VOP_LOOKUP() when a file is being created. Normally, VOP_LOOKUP() 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, this memory is released. If the file is created successfully it will be released unless the SAVESTART flags in specified in cnp->cn_flags.

VOP_MKNOD(dvp, vpp, cnp, vap)

Make a new device-special file in a given directory. The argument dvp is the locked vnode of the directory to create the new device-special file in and cnp is the pathname component of the new device-special file. The argument vap specifies the attributes that the new device-special file should be created with. If the file is successfully created, the address of the resulting unlocked vnode is returned in vpp and zero is returned.

This function is called after VOP_LOOKUP() when a device-special file is being created. Normally, VOP_LOOKUP() 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 device-special file, this memory is released. If the device-special file is created successfully it will be released unless the SAVESTART flags in specified in cnp->cn_flags.

VOP_OPEN(vp, mode, cred)

Open a file. The argument vp is the vnode of the file to open and mode specifies the access mode required by the calling process. The calling credentials are specified by cred. The access mode is a set of flags, including FREAD, FWRITE, O_NONBLOCK, O_APPEND, etc. VOP_OPEN() must be called before a file can be accessed by a thread. The vnode reference count is incremented.

VOP_OPEN() expects the vnode vp to be locked on entry and will leave it locked on return. If the operation is successful zero is returned, otherwise an appropriate error code is returned.

VOP_CLOSE(vp, fflag, cred)

Close a file. The argument vp is the vnode of the file to close and fflag specifies the access mode by the calling process. The possible flags are FREAD, FWRITE and FNONBLOCK. The calling credentials are specified by cred. VOP_CLOSE() frees resources allocated by VOP_OPEN().

The vnode vp will be locked on entry and should remain locked on return.

VOP_ACCESS(vp, mode, cred)

Determine the accessibility (permissions) of the file against the specified credentials. The argument vp is the vnode of the file to check, mode is the type of access required and cred contains the user credentials to check. The argument mode is a mask which can contain VREAD, VWRITE or VEXEC. If the file is accessible in the specified way, zero is returned, otherwise an appropriate error code is returned.

The vnode vp will be locked on entry and should remain locked on return.

VOP_GETATTR(vp, vap, cred)

Get specific vnode attributes on a file. The argument vp is the vnode of the file to get the attributes for. The argument cred specifies the calling credentials. VOP_GETATTR() uses the file system type specific data object vp->v_data to reference the underlying file attributes. Attributes associated with the file are collected by setting the required attribute bits in vap->va_mask. The attributes are returned in vap. Attributes which are not available are set to the value VNOVAL.

For more information on vnode attributes see vattr(9). Historically it was considered acceptable to call VOP_GETATTR() without first locking the vnode. This usage is deprecated.

The vnode vp will be locked on entry and should remain locked on return.

VOP_SETATTR(vp, vap, cred)

Set specific vnode attributes on a file. The argument vp is the locked vnode of the file to set the attributes for. The argument cred specifies the calling credentials. VOP_SETATTR() uses the file system type specific data object vp->v_data to reference the underlying file attributes. The new attributes are defined in vap. Attributes associated with the file are set by setting the required attribute bits in vap->va_mask. Attributes which are not being modified by VOP_SETATTR() should be set to the value VNOVAL. If the operation is successful zero is returned, otherwise an appropriate error is returned.

For more information on vnode attributes see vattr(9).

VOP_READ(vp, uio, ioflag, cred)

Read the contents of a file. The argument vp is the vnode of the file to read from, uio is the location to read the data into, ioflag is a set of flags and cred are the credentials of the calling process.

The ioflag argument is used to give directives and hints to the file system. When attempting a read, the high 16 bits are used to provide a read-ahead hint (in unit of file system blocks) that the file system should attempt. The low 16 bits are a bit mask which can contain the following flags:

IO_UNIT

do I/O as atomic unit

IO_APPEND

append write to end

IO_SYNC

sync I/O file integrity completion

IO_NODELOCKED

underlying node already locked

IO_NDELAY

FNDELAY flag set in file table

IO_DSYNC

sync I/O data integrity completion

IO_ALTSEMANTICS

use alternate I/O semantics

IO_NORMAL

operate on regular data

IO_EXT

operate on extended attributes

IO_DIRECT

do not buffer data in the kernel

Zero is returned on success, otherwise an error is returned. The vnode should be locked on entry and remains locked on exit.

VOP_WRITE(vp, uio, ioflag, cred)

Write to a file. The argument vp is the vnode of the file to write to, uio is the location of the data to write, ioflag is a set of flags and cred are the credentials of the calling process.

The ioflag argument is used to give directives and hints to the file system. The low 16 bits are a bit mask which can contain the same flags as VOP_READ().

Zero is returned on success, otherwise an error is returned. The vnode should be locked on entry and remains locked on exit.

VOP_FALLOCATE(vp, pos, len)

Allocate backing store. The argument vp is the vnode for the file. The pos and len arguments (specified in bytes) name an extent within the file. The blocks underlying this range, rounding up at the top and down at the bottom if needed, are checked; if no physical storage is allocated, a physical block is allocated and zeroed. This operation removes “holes” from files.

VOP_FDISCARD(vp, pos, len)

Discard backing store. The argument vp is the vnode for the file. The pos and len arguments (specified in bytes) name an extent within the file. The blocks underlying this range, rounding down at the top and up at the bottom if needed, are checked. If any physical storage is used, it is deallocated. This operation creates “holes” in files. Discarded blocks of regular files read back afterwards as zeroes. On devices, the underlying discard-block operation if any (e.g. ATA TRIM) is issued. The device handles this as it sees fit. In particular it is not guaranteed that discarded blocks on devices will be zeroed; reading a discarded block might produce zeros, or ones, or the previously existing data, or some other data, or trash.

VOP_IOCTL(vp, command, data, fflag, cred)

Perform device-specific I/O. The argument vp is the locked vnode of the file, normally representing a device. The argument command specifies the device-specific operation to perform and cnp provides extra data for the specified operation. The argument fflags is a set of flags. The argument cred is the caller's credentials. If the operation is successful, zero is returned, otherwise an appropriate error code is returned.

Most file systems do not supply a function for VOP_IOCTL(). This function implements the ioctl(2) system call.

VOP_FCNTL(vp, command, data, fflag, cred)

Perform file control. The argument vp is the locked vnode of the file. The argument command specifies the operation to perform and cnp provides extra data for the specified operation. The argument fflags is a set of flags. The argument cred is the caller's credentials. If the operation is successful, zero is returned, otherwise an appropriate error code is returned.

VOP_POLL(vp, events)

Test if a poll event has occurred. The argument vp is the vnode of the file to poll. It returns any events of interest as specified by events that may have occurred for the file. The argument events is a set of flags as specified by poll(2).

The vnode vp remains unlocked throughout the whole operation.

VOP_KQFILTER(vp, kn)

Register a knote kn with the vnode vn. If the operation is successful zero is returned, otherwise an appropriate error code is returned.

The vnode vp remains unlocked throughout the whole operation.

VOP_REVOKE(vp, flags)

Eliminate all activity associated with the vnode vp. The argument flags is a set of flags. If REVOKEALL is set in flags all vnodes aliased to the vnode vp are also eliminated. If the operation is successful zero is returned, otherwise an appropriate error is returned.

The vnode vp remains unlocked throughout the whole operation.

VOP_MMAP(vp, prot, cred)

Inform file system that vp is in the process of being memory mapped. The argument prot specifies the vm access protection the vnode is going to be mapped with. The argument cred is the caller's credentials. If the file system allows the memory mapping, zero is returned, otherwise an appropriate error code is returned.

Most file systems do not supply a function for VOP_MMAP() and use genfs_mmap() to default for success. Only file systems which do not integrate with the page cache at all typically want to disallow memory mapping.

VOP_FSYNC(vp, cred, flags, offlo, offhi)

Flush pending data buffers for a file to disk. The argument vp is the locked vnode of the file for flush. The argument cred is the caller's credentials. The argument flags is a set of flags. If FSYNC_WAIT is specified in flags, the function should wait for I/O to complete before returning. The argument offlo and offhi specify the range of file to flush. If the operation is successful zero is returned, otherwise an appropriate error code is returned.

This function implements the sync(2) and fsync(2) system calls.

VOP_SEEK(vp, oldoff, newoff, cred)

Test if the file is seekable for the specified offset newoff. The argument vp is the locked vnode of the file to test. For most file systems this function simply tests if newoff is valid. If the specified newoff is less than zero, the function returns error code EINVAL.

VOP_REMOVE(dvp, vp, cnp)

Remove a file. The argument dvp is the locked vnode of the directory to remove the file from and vp is the locked vnode of the file to remove. The argument cnp is the pathname component about the file to remove. If the operation is successful zero is returned, otherwise an appropriate error code is returned. Both dvp and vp are locked on entry and are to be unlocked before returning.

VOP_LINK(dvp, vp, cnp)

Link to a file. The argument dvp is the locked node of the directory to create the new link and vp is the vnode of the file to be linked. The argument cnp is the pathname component of the new link. If the operation is successful zero is returned, otherwise an error code is returned. The directory vnode dvp should be locked on entry and will be released and unlocked on return. The vnode vp should not be locked on entry and will remain unlocked on return.

VOP_RENAME(fdvp, fvp, fcnp, tdvp, tvp, tcnp)

Rename a file. The argument fdvp is the vnode of the old parent directory containing in the file to be renamed and fvp is the vnode of the file to be renamed. The argument fcnp is the pathname component about the file to be renamed. The argument tdvp is the vnode of the new directory of the target file and tvp is the vnode of the target file (if it exists). The argument tcnp is the pathname component about the file's new name. If the operation is successful zero is returned, otherwise an error code is returned.

The caller must hold the target file system's rename lock. The source directory and file vnodes should be unlocked and their reference counts should be incremented before entry. The target directory and file vnodes should both be locked on entry. VOP_RENAME() updates the reference counts prior to returning.

Because of the complexity and nastiness of the interface, please do not write new code that calls VOP_RENAME() directly until such time as ongoing cleanup work reaches a point where the interface has been rendered halfway sane.

VOP_MKDIR(dvp, vpp, cnp, vap)

Make a new directory in a given directory. The argument dvp is the locked vnode of the directory to create the new directory in and cnp is the pathname component of the new directory. The argument vap specifies the attributes that the new directory should be created with. If the file is successfully created, the address of the resulting unlocked vnode is returned in vpp and zero is returned.

This function is called after VOP_LOOKUP() when a directory is being created. Normally, VOP_LOOKUP() 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 directory, this memory is released. If the directory is created successfully it will be released unless the SAVESTART flags in specified in cnp->cn_flags.

VOP_RMDIR(dvp, vp, cnp)

Remove a directory in a given directory. The argument dvp is the locked vnode of the directory to remove the directory from and vp is the locked vnode of the directory to remove. The argument cnp is the pathname component of the directory. Zero is returned on success, otherwise an error code is returned. Both dvp and vp should be locked on entry and will be released and unlocked on return.

VOP_SYMLINK(dvp, vpp, cnp, vap, target)

Create a symbolic link in a given directory. The argument dvp is the locked vnode of the directory to create the symbolic link in and cnp is the pathname component of the symbolic link. The argument vap specifies the attributes that the symbolic link should be created with and target specifies the pathname of the target of the symbolic link. If the symbolic link is successfully created, the address of the resulting unlocked vnode is returned in vpp and zero is returned.

This function is called after VOP_LOOKUP() when a symbolic link is being created. Normally, VOP_LOOKUP() 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 symbolic link, this memory is released. If the symbolic link is created successfully it will be released unless the SAVESTART flags in specified in cnp->cn_flags.

VOP_READDIR(vp, uio, cred, eofflag, cookies, ncookies)

Read directory entry. The argument vp is the vnode of the directory to read the contents of and uio is the destination location to read the contents into. The argument cred is the caller's credentials. The argument eofflag is the pointer to a flag which is set by VOP_READDIR() to indicate an end-of-file condition. If eofflag is NULL, the end-of-file condition is not returned. 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 VOP_READDIR(). The directory contents are read into struct dirent structures and uio->uio_offset is set to the offset of the next unread directory entry. This offset may be used in a following invocation to continue a sequential read of the directory contents. If the operation is successful zero is returned, otherwise an appropriate error code is returned.

The directory should be locked on entry and will remain locked on return.

In case ncookies and cookies are supplied, one cookie should be returned per directory entry. The value of the cookie for each directory entry should be the offset within the directory where the on-disk version of the following directory entry starts. That is, for each directory entry i, the corresponding cookie should refer to the offset of directory entry i + 1.

Note that the cookies array must be allocated by the callee using the M_TEMP malloc type as callers of VOP_READDIR() must be able to free the allocation.

VOP_READLINK(vp, uio, cred)

Read the contents of a symbolic link. The argument vp is the locked vnode of the symlink and uio is the destination location to read the contents into. The argument cred is the credentials of the caller. If the operation is successful zero is returned, otherwise an error code is returned.

The vnode should be locked on entry and will remain locked on return.

VOP_ABORTOP(dvp, cnp)

Abort pending operation on vnode dvp and free resources allocated in cnp.

This operation is rarely implemented in file systems and genfs_abortop() is typically used instead.

VOP_INACTIVE(vp)

Release the inactive vnode. VOP_INACTIVE() is called when the kernel is no longer using the vnode. This may be because the reference count reaches zero or it may be that the file system is being forcibly unmounted while there are open files. It can be used to reclaim space for open but deleted files. The argument vp is the locked vnode to be released. If the operation is successful zero is returned, otherwise an appropriate error code is returned. The vnode vp must be locked on entry, and will be unlocked on return.

VOP_RECLAIM(vp)

Reclaim the vnode for another file system. VOP_RECLAIM() is called when a vnode is being reused for a different file system. Any file system specific resources associated with the vnode should be freed. The argument vp is the vnode to be reclaimed. If the operation is successful zero is returned, otherwise an appropriate error code is returned. The vnode vp should not be locked on entry, and will remain unlocked on return.

VOP_LOCK(vp, flags)

Sleep until vnode lock is free. The argument vp is the vnode of the file to be locked. The argument flags is LK_EXCLUSIVE to take the lock exclusively or LK_SHARED to take a shared lock. If flags contains LK_NOWAIT and the lock is busy, the operation will return immediately with an error code. If flags contains LK_RETRY this is a hint the caller wants the lock on dead vnodes too. If the operation is successful zero is returned, otherwise an appropriate error code is returned. VOP_LOCK() is used to serialize access to the file system such as to prevent two writes to the same file from happening at the same time. Kernel code should use vn_lock(9) to lock a vnode rather than calling VOP_LOCK() directly.

VOP_UNLOCK(vp)

Wake up process sleeping on lock. The argument vp is the vnode of the file to be unlocked. If the operation is successful zero is returned, otherwise an appropriate error code is returned. VOP_UNLOCK() is used to serialize access to the file system such as to prevent two writes to the same file from happening at the same time.

VOP_ISLOCKED(vp)

Test if the vnode vp is locked. Possible return values are LK_EXCLUSIVE, LK_SHARED or 0 for lock held exclusively by the calling thread, shared lock held by anyone or unlocked, respectively.

This function must never be used to make locking decisions at run time: it is provided only for diagnostic purposes.

VOP_BMAP(vp, bn, vpp, bnp, runp)

Convert the logical block number bn of a file specified by vnode vp to its physical block number on the disk. The physical block is returned in bnp. In case the logical block is not allocated, -1 is used.

If vpp is not NULL, the vnode of the device vnode for the file system is returned in the address specified by vpp. If runp is not NULL, the number of contiguous blocks starting from the next block after the queried block will be returned in runp.

VOP_PRINT(vp)

Print debugging information. The argument vp is the vnode to print. If the operation is successful zero is returned, otherwise an appropriate error code is returned.

VOP_PATHCONF(vp, name, retval)

Implement POSIX pathconf(2) and fpathconf(2) support. The argument vp is the locked vnode to get information about. The argument name specified the type of information to return. The information is returned in the address specified by retval. Valid values for name are:

_PC_LINK_MAX

return the maximum number of links to a file

_PC_NAME_MAX

return the maximum number of bytes in a file name

_PC_PATH_MAX

return the maximum number of bytes in a pathname

_PC_PIPE_BUF

return the maximum number of bytes which will be written atomically to a pipe

_PC_CHOWN_RESTRICTED

return 1 if appropriate privileges are required for the chown(2) system call, otherwise zero

_PC_NO_TRUNC

return 0 if file names longer than {NAME_MAX} are silently truncated

If name is recognized, *retval is set to the specified value and zero is returned, otherwise an appropriate error is returned.

VOP_ADVLOCK(vp, id, op, fl, flags)

Manipulate Advisory record locks on a vnode. The argument vp is the vnode on which locks are manipulated. The argument id is the id token which is changing the lock and op is the fcntl(2) operation to perform. Valid values are:

F_SETLK

set lock

F_GETLK

get the first conflicted lock

F_UNLCK

clear lock

The argument fl is a description of the lock. In the case of SEEK_CUR, The caller should add the current file offset to fl->l_start beforehand. VOP_ADVLOCK() treats SEEK_CUR as SEEK_SET.

The argument flags is the set of flags. Valid values are:

F_WAIT

wait until lock is granted

F_FLOCK

use flock(2) semantics for lock

F_POSIX

use POSIX semantics for lock

If the operation is successful zero is returned, otherwise an appropriate error is returned.

VOP_WHITEOUT(dvp, cnp, flags)

Whiteout pathname component in directory with vnode dvp. The argument cnp specifies the pathname component to whiteout.

The vnode dvp should be locked on entry and will remain locked on return.

VOP_GETPAGES(vp, offset, m, count, centeridx, access_type, advice, flags)

Read VM pages from file. The argument vp is the locked vnode to read the VM pages from. The argument offset is offset in the file to start accessing and m is an array of VM pages. The argument count points a variable that specifies the number of pages to read. If the operation is successful zero is returned, otherwise an appropriate error code is returned. If PGO_LOCKED is specified in flags, VOP_GETPAGES() might return less pages than requested. In that case, the variable pointed to by count will be updated.

This function is primarily used by the page-fault handing mechanism.

VOP_PUTPAGES(vp, offlo, offhi, flags)

Write modified (dirty) VM pages to file. The argument vp is the vnode to write the VM pages to. The vnode's vm object lock (v_uobj.vmobjlock) must be held by the caller and will be released upon return. The arguments offlo and offhi specify the range of VM pages to write. In case offhi is given as 0, all pages at and after the start offset offlo belonging the vnode vp will be written. The argument flags controls the behavior of the routine and takes the vm pager's flags (PGO_ -prefixed). If the operation is successful zero is returned, otherwise an appropriate error code is returned.

The function is primarily used by the pageout handling mechanism and is commonly implemented indirectly by genfs_putpages() with the help of VOP_STRATEGY() and VOP_BMAP().

VOP_STRATEGY(vp, bp)

Read/write a file system buffer. The argument vp is the vnode to read/write to. The argument bp is the buffer to be read or written. VOP_STRATEGY() will either read or write data to the file depending on the value of bp->b_flags. If the operation is successful zero is returned, otherwise an appropriate error code is returned.

VOP_BWRITE(vp, bp)

Write a file system buffer. The argument vp is the vnode to write to. The argument bp specifies the buffer to be written. If the operation is successful zero is returned, otherwise an appropriate error code is returned.

VOP_GETEXTATTR(vp, attrnamespace, name, uio, size, cred)

Get an extended attribute. The argument vp is the locked vnode of the file or directory from which to retrieve the attribute. The argument attrnamespace specifies the extended attribute namespace. The argument name is a nul-terminated character string naming the attribute to retrieve. The argument uio, if not NULL, specifies where the extended attribute value is to be written. The argument size, if not NULL, will contain the number of bytes required to read all of the attribute data upon return. In most cases, uio will be NULL when size is not, and vice versa. The argument cred specifies the user credentials to use when authorizing the request.

VOP_SETEXTATTR(vp, attrnamespace, name, uio, cred)

Set an extended attribute. The argument vp is the locked vnode of the file or directory to which to store the attribute. The argument namespace specifies the extended attribute namespace. The argument name is a nul-terminated character string naming the attribute to store. The argument uio specifies the source of the extended attribute data. The argument cred specifies the user credentials to use when authorizing the request.

VOP_LISTEXTATTR(vp, attrnamespace, uio, size, cred)

Retrieve the list of extended attributes. The argument vp is the locked vnode of the file or directory whose attributes are to be listed. The argument attrnamespace specifies the extended attribute namespace. The argument uio, if not NULL, specifies where the extended attribute list is to be written. The argument size, if not NULL, will contain the number of bytes required to read all of the attribute names upon return. In most cases, uio will be NULL when size is not, and vice versa. The argument cred specifies the user credentials to use when authorizing the request.

VOP_DELETEEXTATTR(vp, attrnamespace, name, cred)

Remove attribute name from file associated with vp. The argument attrnamespace specifies the extended attribute namespace. If full removal is not supported, the file system should return EOPNOTSUPP to allow the caller to zero out the value with VOP_SETEXTATTR().

The vnode vp should be locked on entry and will remain locked on return.

FILES

src/sys/kern/vnode_if.src contains the list of vnode functions, their definitions and an exact locking protocol.

ERRORS

[EACCES]

Access for the specified operation is denied.

[EDQUOT]

Quota exceeded.

[EINVAL]

attempt to read from an illegal offset in the directory; unrecognized input

[EIO]

a read error occurred while reading the directory or reading the contents of a symbolic link

[EJUSTRETURN]

A CREATE or RENAME operation would be successful.

[ENOATTR]

The requested attribute is not defined for this vnode.

[ENOENT]

The component was not found in the directory.

[ENOSPC]

The file system is full.

[ENOTDIR]

The vnode does not represent a directory.

[ENOTEMPTY]

attempt to remove a directory which is not empty

[EPERM]

an attempt was made to change an immutable file

[EROFS]

the file system is read-only

SEE ALSO

extattr(9), intro(9), namei(9), vattr(9), vfs(9), vfsops(9), vnode(9)

HISTORY

The vnode operations vector, its functions and the corresponding macros appeared in 4.3BSD.