VNODEOPS(9) NetBSD Kernel Developer's Manual VNODEOPS(9)
NAME
vnodeops, VOP_LOOKUP, VOP_CREATE, VOP_MKNOD, VOP_OPEN, VOP_CLOSE, VOP_ACCESS, VOP_GETATTR, VOP_SETATTR, VOP_READ, VOP_WRITE, VOP_IOCTL, VOP_FCNTL, VOP_POLL, 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_BLKATOFF, VOP_VALLOC, VOP_BALLOC, VOP_REALLOCBLKS, VOP_VFREE, VOP_TRUNCATE, VOP_UPDATE, VOP_LEASE, VOP_WHITEOUT, VOP_GETPAGES, VOP_PUTPAGES, VOP_STRATEGY, VOP_BWRITE, VOP_GETEXTATTR, VOP_SETEXTATTR, VOP_LISTEXTATTR, -- vnode operations
SYNOPSIS
#include <sys/param.h> #include <sys/buf.h> #include <sys/dirent.h> #include <sys/lock.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, struct ucred *cred, struct proc *p); int VOP_CLOSE(struct vnode *vp, int fflag, struct ucred *cred, struct proc *p); int VOP_ACCESS(struct vnode *vp, int mode, struct ucred *cred, struct proc *p); int VOP_GETATTR(struct vnode *vp, struct vattr *vap, struct ucred *cred, struct proc *p); int VOP_SETATTR(struct vnode *vp, struct vattr *vap, struct ucred *cred, struct proc *p); int VOP_READ(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred); int VOP_WRITE(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred); int VOP_IOCTL(struct vnode *vp, u_long command, void *data, int fflag, struct ucred *cred, struct proc *p); int VOP_FCNTL(struct vnode *vp, u_int command, void *data, int fflag, struct ucred *cred, struct proc *p); int VOP_POLL(struct vnode *vp, int events, struct proc *p); int VOP_REVOKE(struct vnode *vp, int flags); int VOP_MMAP(struct vnode *vp, int fflags, struct ucred *cred, struct proc *p); int VOP_FSYNC(struct vnode *vp, struct ucred *cred, int flags, off_t offlo, off_t offhi, struct proc *p); int VOP_SEEK(struct vnode *vp, off_t oldoff, off_t newoff, struct ucred *cred); int VOP_REMOVE(struct vnode *vp, 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 *vp, struct componentname *fcnp, struct componentname *tdvp, struct vnode *tvp, struct componentname *tcnp); int VOP_MKDIR(struct vnode *vp, struct vnode **vpp, struct componentname *cnp, struct vattr *vap); int VOP_RMDIR(struct vnode *vp, 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, struct ucred *cred, int *eofflag, cookies, ncookies); int VOP_READLINK(struct vnode *vp, struct uio *uio, struct ucred *cred); int VOP_ABORTOP(struct vnode *dvp, struct componentname *cnp); int VOP_INACTIVE(struct vnode *vp, struct proc *p); int VOP_RECLAIM(struct vnode *vp, struct proc *p); int VOP_LOCK(struct vnode *vp, int flags); int VOP_UNLOCK(struct vnode *vp, int flags); 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_BLKATOFF(struct vnode *vp, off_t offset, char **res, struct buf **bpp); int VOP_VALLOC(struct vnode *pvp, int mode, struct ucred *cred, struct vnode **vpp); int VOP_BALLOC(struct vnode *vp, off_t startoffset, int size, struct ucred *cred, int flags, struct buf **bpp); int VOP_REALLOCBLKS(struct vnode *vp, struct cluster_save *buflist); int VOP_VFREE(struct vnode *pvp, ino_t ino, int mode); int VOP_TRUNCATE(struct vnode *vp, off_t length, int flags, struct ucred *cred, struct proc *p); int VOP_UPDATE(struct vnode *vp, struct timespec *access, struct timespec *modify, int flags); int VOP_LEASE(struct vnode *vp, struct proc *p, struct ucred *cred, int flag); 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 offlo, int flags); int VOP_STRATEGY(struct vnode *vp, struct buf *bp); int VOP_BWRITE(struct buf *bp); int VOP_GETEXTATTR(struct vnode *vp, int attrnamespace, const char *name, struct uio *uio, size_t *size, struct ucred *cred, struct proc *p); int VOP_SETEXTATTR(struct vnode *vp, int attrnamespace, const char *name, struct uio *uio, struct ucred *cred, struct proc *p); int VOP_LISTEXTATTR(struct vnode *vp, int attrnamespace, struct uio *uio, size_t *size, struct ucred *cred, struct proc *p); 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 opera- tions vector for each file system type configured into the kernel. The vnode operations vector contains a pointer to a function for each opera- tion 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 specialised macros. The following table lists the elements of the vnode operations vector, the corresponding invocation macro, and a description of the ele- ment. Vector element Macro Description int (*vop_lookup)() VOP_LOOKUP Lookup file name in name cache int (*vop_create)() VOP_CREATE Create a new file int (*vop_mknod)() VOP_MKNOD Make a new device int (*vop_open)() VOP_OPEN Open a file int (*vop_close)() VOP_CLOSE Close a file int (*vop_access)() VOP_ACCESS Determine file accessibility int (*vop_getattr)() VOP_GETATTR Get file attributes int (*vop_setattr)() VOP_SETATTR Set file attributes int (*vop_read)() VOP_READ Read from a file int (*vop_write)() VOP_WRITE Write to a file int (*vop_ioctl)() VOP_IOCTL Perform device-specific I/O int (*vop_fcntl)() VOP_FCNTL Perform file control int (*vop_poll)() VOP_POLL Test if poll event has occurred int (*vop_revoke)() VOP_REVOKE Eliminate vode activity int (*vop_mmap)() VOP_MMAP Map file into user address space int (*vop_fsync)() VOP_FSYNC Flush pending data to disk int (*vop_seek)() VOP_SEEK Test if file is seekable int (*vop_remove)() VOP_REMOVE Remove a file int (*vop_link)() VOP_LINK Link a file int (*vop_rename)() VOP_RENAME Rename a file int (*vop_mkdir)() VOP_MKDIR Make a new directory int (*vop_rmdir)() VOP_RMDIR Remove a directory int (*vop_symlink)() VOP_SYMLINK Create a symbolic link int (*vop_readdir)() VOP_READDIR Read directory entry int (*vop_readlink)() VOP_READLINK Read contents of a symlink int (*vop_abortop)() VOP_ABORTOP Abort pending operation int (*vop_inactive)() VOP_INACTIVE Release the inactive vnode int (*vop_reclaim)() VOP_RECLAIM Reclaim vnode for another file int (*vop_lock)() VOP_LOCK Sleep until vnode lock is free int (*vop_unlock)() VOP_UNLOCK Wake up process sleeping on lock int (*vop_islocked)() VOP_ISLOCKED Test if vnode is locked int (*vop_bmap)() VOP_BMAP Logical block number conversion int (*vop_print)() VOP_PRINT Print debugging information int (*vop_pathconf)() VOP_PATHCONF Return POSIX pathconf data int (*vop_advlock)() VOP_ADVLOCK Advisory record locking int (*vop_blkatoff)() VOP_BLKATOFF Retrieve buffer from offset int (*vop_valloc)() VOP_VALLOC Allocate fs-specific data int (*vop_balloc)() VOP_BALLOC Allocate physical blocks int (*vop_reallocblks)() VOP_REALLOCBLKS Rearrange blocks contiguously int (*vop_vfree)() VOP_VFREE Release file resources int (*vop_truncate)() VOP_TRUNCATE Truncate file and free blocks int (*vop_update)() VOP_UPDATE Update time on a file int (*vop_lease)() VOP_LEASE Validate vnode credentials int (*vop_whiteout)() VOP_WHITEOUT Whiteout vnode int (*vop_getpages)() VOP_GETPAGES Read VM pages from file int (*vop_putpages)() VOP_PUTPAGES Write VM pages to file int (*vop_strategy)() VOP_STRATEGY Read/write a file system buffer int (*vop_bwrite)() VOP_BWRITE Write a file system buffer int (*vop_getextattr)() VOP_GETEXTATTR Get extended attribute int (*vop_setextattr)() VOP_SETEXTATTR Set extended attribute int (*vop_listextattr)() VOP_LISTEXTATTR List extended attributes 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 function in the vnode operations vec- tor 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. Is is used to encapsulate many parameters into a single func- tion argument. It has the following structure: struct componentname { /* * Arguments to lookup. */ u_long cn_nameiop; /* namei operation */ u_long cn_flags; /* flags to namei */ struct proc *cn_proc; /* process requesting lookup */ struct ucred *cn_cred; /* credentials */ /* * Shared between lookup and commit routines. */ char *cn_pnbuf; /* pathname buffer */ const char *cn_nameptr; /* pointer to looked up name */ long cn_namelen; /* length of looked up component */ u_long cn_hash; /* hash value of looked up name */ long 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 initialised by the caller. The seman- tics 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 WANTPARENT want parent vnode returned unlocked 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 opera- tions also require the vnode to be locked on entry. To prevent dead- locks, when acquiring locks on multiple vnodes, the lock of parent direc- tory 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 path- name component is found, the address of the resulting locked vnode is returned in vpp. The operation specified in cnp->cn_nameiop gives VOP_LOOKUP() hints about the reason for requesting the lookup and uses it to cache file system type spe- cific information in the vnode for subsequent operations. There are three types of lookups: ".", ".." (ISDOTDOT), and other. If the pathname component being searched for is ".", then dvp has an extra reference added to it and it is returned in *vpp. If the pathname component being search for is ".." (ISDOTDOT), dvp is unlocked, the ".." node is locked and then dvp is relocked if and only if LOCKPARENT and ISLASTCN is set in cnp->cn_flags. If LOCKPARENT or ISLASTCN is not set, dvp is returned unlocked on a successful lookup. This process pre- serves the protocol of always locking nodes from root downward and prevents deadlock. 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 locked vnode is returned in vpp. If LOCKPARENT or ISLASTCN is not set, dvp is returned unlocked on a successful lookup. On failure *vpp is NULL, and *dvp is left locked. If there was an error relocking dvp (for instance in the ISDOTDOT case) the error is returned with PDIRUNLOCK set in cnp->cn_flags. This flag signals to the caller that dvp ' s lock state has changed. If the operation is successful *vpp is locked 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 locked 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 argu- ment 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 locked 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, p) 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 process and its credentials are specified by p and cred respectively. 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, p) Close a file. The argument vp is the vnode of the file to close and fflags specifies the access mode by the calling process. The calling process and its credentials are specified by p and cred respectively. VOP_CLOSE() must be called after a file is finished with. VOP_CLOSE() expects at least a reference to be associated with the vnode and does not care whether the vnode is locked. The lock and reference state is left unchanged on return. VOP_ACCESS(vp, mode, cred, p) 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, cred con- tains the user credentials to check and p is the process which is checking the credentials. 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, p) Get specific vnode attributes on a file. The argument vp is the locked vnode of the file to get the attributes for. The argu- ments p and cred specifies the calling process and its creden- tials respectively. 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 avail- able are set to the value VNOVAL. For more information on vnode attributes see vattr(9). VOP_SETATTR(vp, vap, cred, p) Set specific vnode attributes on a file. The argument vp is the locked vnode of the file to set the attributes for. The argu- ments p and cred specifies the calling process and its creden- tials respectively. 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 do I/O synchronously IO_NODELOCKED underlying node already locked IO_NDELAY FNDELAY flag set in file table IO_VMIO data already in VMIO space 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_IOCTL(vp, command, data, fflag, cred, p) 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 argu- ment fflags is a set of flags. The argument cred is the caller's credentials and p the calling process. If the opera- tion 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, p) Perform file control. The argument vp is the locked vnode of the file. The argument command specifies the operation to per- form 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 and p the calling process. If the opera- tion is successful, zero is returned, otherwise an appropriate error code is returned. VOP_POLL(vp, events, p) Test if a poll event has occurred. The argument vp is the locked vnode of the file to poll and p is the calling process. 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). If the operation is successful zero is returned, otherwise an appropriate error code is returned. VOP_REVOKE(vp, flags) Eliminate all activity associated with the vnode vp. The argu- ment 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 appropri- ate error is returned. VOP_MMAP(vp, fflags, cred, p) Map file into user address space. The argument vp is the locked vnode of the file to map into an address space. The argument fflags is a set of flags. The argument cred is the caller's credentials and p the calling process requesting the map. 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_MMAP(). This function implements the mmap(2) system call. VOP_FSYNC(vp, cred, flags, offlo, offhi, p) 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 and p the calling process. The argu- ment 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 filesystems 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 should be locked on entry and remain locked on return. 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, oth- erwise an error code is returned. The directory vnode dvp should be locked on entry and will remain locked 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 path- name component about the file to be remained. 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 and error code is returned. 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. 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 locked 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 SAVE- NAME 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 remain locked 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 success- fully created, the address of the resulting locked 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 and 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 gen- erated 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. 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. If VOP_READDIR() is called from the NFS server, the extra argu- ments eofflag, ncookies and cookies are used. The value of *eofflag will be set to TRUE if the end of the directory is reached while reading. The directory seek cookies are returned to the NFS client and may be used later to restart a directory read part way through the directory. There should be one cookie returned per directory entry. The value of the cookie should be the offset within the directory where the on-disk version of the appropriate directory entry starts. 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. This operation is rarely implemented in file systems. VOP_INACTIVE(vp, p) 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 argu- ment vp is the locked vnode to be released. The argument p is the calling process. 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, p) 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 locked vnode to be reclaimed. The argument p is the calling process. If the oper- ation 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 a set of lockmgr(9) flags. If the operation is successful zero is returned, otherwise an appropriate error code is returned. VOP_LOCK() is used to serialise access to the file system such as to present 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, flags) Wake up process sleeping on lock. The argument vp is the vnode of the file to be unlocked. The argument flags is a set of lockmgr(9) flags. If the operation is successful zero is returned, otherwise an appropriate error code is returned. VOP_UNLOCK() is used to serialise access to the file system such as to present two writes to the same file from happening at the same time. VOP_ISLOCKED(vp) Test if the vnode vp is locked. A non-zero values is returned if the vnode is not locked, otherwise zero is returned. 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. 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 maximum blocksize is returned in the address specified by runp. VOP_PRINT(vp) Print debugging information. The argument vp is the vnode to print. If the operation is successful zero is returned, other- wise an appropriate error code is returned. VOP_PATHCONF(vp, name, retval) Implement POSIX pathconf(2) and fpathconf(2) support. The argu- ment vp is the locked vnode to get information about. The argu- ment 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 if file names longer than KERN_NAME_MAX are truncated If name is recognised, *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 file. The argument vp is the vnode is the file for the advisory record lock. The argu- ment 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. 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_BLKATOFF(vp, offset, res, bpp) Return buffer bpp with the contents of block offset from the beginning of directory specified by vnode vp. If res is non- zero, fill it in with a pointer to the remaining space in the directory. VOP_VALLOC(pvp, mode, cred, vpp) Allocate file system type specific data a new file in the file system. The argument pvp specifies the vnode of the directory to create the new file. The argument mode specifies file system type specific flags and cred are the credentials of the calling process. The vnode of the new file is returned in the address specified by vpp. VOP_BALLOC(vp, startoffset, size, cred, flags, bpp) Allocate the physical blocks on a device given the vnode vp and the offset logical block number startoffset in a file. The argument size specifies the size to be allocated. The creden- tials of the calling processing are specified by cred. If the argument bpp is not NULL, the buffer is written to the allocated blocks. The argument flags is a set of flags controlling the low-level allocation when the buffer is written. Valid values defined in <sys/buf.h> are: B_CLRBUF request allocated buffer be cleared B_SYNC do all allocations synchronously If the operation is successful zero is returned, otherwise an appropriate error is returned. VOP_REALLOCBLKS(vp, buflist) Rearrange block in a file to be contiguous. The argument vp is the vnode of the file to manipulate. The argument buflist is a list of buffers to rearrange. If the operation is successful zero is returned, otherwise an appropriate error is returned. VOP_VFREE(pvp, ino, mode) Release file resources. This function is used by the file sys- tem to release cached file system specific data associated with the file when the vnode is recycled. VOP_TRUNCATE(vp, length, flags, cred, p) Truncate the file specified by the vnode vp to at most length size and free the unused disk blocks. The arguments p and cred is the calling process and its credentials respectively. The argument flags is a set of I/O flags. Valid values are: 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 If the operation is successful zero is returned, otherwise an appropriate error is returned. VOP_UPDATE(vp, access, modify, flags) Update times on file with vnode vp. The access and modification times are specified by the arguments access and modify respec- tively. The change time is always taken from the current time. The argument flags is a set of file system type dependent flags indicating how times should be updated: UPDATE_WAIT wait for completion UPDATE_DIROP hint to file system to wait or not VOP_LEASE(vp, p, cred, flags) Validate vnode credentials and operation type. The argument vp is the locked vnode of the file to validate credentials cred. The argument p specifies the calling process and flags specifies the operation flags. If the operation is successful zero is returned, otherwise an appropriate error code is returned. The vnode must be locked on entry and remains locked on return. VOP_WHITEOUT(dvp, cnp, flags) Whiteout pathname component in directory with vnode dvp. The argument cnp specifies the pathname component to whiteout. 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 mecha- nism. VOP_PUTPAGES(vp, offset, len, flags) Write modified (dirty) VM pages to file. The argument vp is the locked vnode to write the VM pages to and offset and len speci- fies the range of VM pages to write. There seems to be some confusion in the code whether offset and len specify the start and length of the VM pages for the start and end of the VM pages. The argument flags specifies whether the pages should be written asynchronously and also whether they should be marked invalid one the write back operation has completed. If the operation is successful zero is returned, otherwise an appropri- ate error code is returned. The function is primarily used by the pageout handling mecha- nism. 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(bp) Write a file system buffer. 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, p) 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 num- ber 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. The argument p specifies the process requesting the extended attribute. VOP_SETEXTATTR(vp, attrnamespace, name, uio, cred, p) 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. The argu- ment p specifies the process setting the extended attribute. VOP_LISTEXTATTR(vp, attrnamespace, uio, size, cred, p) 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 argu- ment 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. The argument p specifies the process requesting the extended attribute list.
ERRORS
[ENOATTR] The requested attribute is not defined for this vnode. [ENOTDIR] The vnode does not represent a directory. [ENOENT] The component was not found in the directory. [ENOSPC] The file system is full. [EDQUOT] Quota exceeded. [EACCES] Access for the specified operation is denied. [EJUSTRETURN] A CREATE or RENAME operation would be successful. [EPERM] an attempt was made to change an immutable file [ENOTEMPTY] attempt to remove a directory which is not empty [EINVAL] attempt to read from an illegal offset in the direc- tory; unrecognised input [EIO] a read error occurred while reading the directory or reading the contents of a symbolic link [EROFS] the filesystem is read-only
SEE ALSO
extattr(9), intro(9), lock(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. NetBSD 3.0.1 January 2, 2005 NetBSD 3.0.1
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