VNODEOPS(9) BSD 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_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_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 *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 *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 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 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_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 vode 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 func‐
tion 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.
*/
char *cn_pnbuf; /* pathname buffer */
const char *cn_nameptr; /* pointer to looked up name */
size_t cn_namelen; /* length of looked up component */
u_long cn_hash; /* hash value of looked up name */
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 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
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 indicates VOP_LOOKUP() the reason for requesting
the lookup and uses it to cache file system type specific infor‐
mation in the vnode for subsequent operations.
There are three types of lookups: ".", ".." (ISDOTDOT), and reg‐
ular. 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. This process preserves 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. dvp is always
returned locked.
On failure *vpp is NULL, and *dvp is left locked. If the opera‐
tion is successful *vpp is locked and zero is returned. Typi‐
cally, 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.
Regardless of the return value, the directory vnode dvp will be
unlocked on return.
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)
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_NON‐
BLOCK, 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 con‐
tains 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).
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 argu‐
ment cred specifies the calling credentials. VOP_SETATTR() uses
the file system type specific data object vp->v_data to refer‐
ence 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_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 argu‐
ment fflags is a set of flags. The argument cred is the call‐
er'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 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. 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 spec‐
ified by events that may have occurred for the file. The argu‐
ment 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 suc‐
cessful 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 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.
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 map‐
ping, 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, oth‐
erwise 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 path‐
name 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 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 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 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 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 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 and
uio->uio_offset is set to the offset of the next unread direc‐
tory 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 appropri‐
ate 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 allo‐
cated 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 argu‐
ment 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 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 hap‐
pening 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, respec‐
tively.
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, 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 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 mecha‐
nism.
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 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.
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 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.
VOP_DELETEEXTATTR(vp, attrnamespace, name, cred)
Remove attribute name from file associated with vp. The argu‐
ment 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 direc‐
tory; 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 ALSOextattr(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.
BSD February 13, 2012 BSD
