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+.\" $NetBSD: vnodeops.9,v 1.101 2023/06/15 09:13:36 hannken Exp $
+.\"
+.\" Copyright (c) 2001, 2005, 2006 The NetBSD Foundation, Inc.
+.\" All rights reserved.
+.\"
+.\" This code is derived from software contributed to The NetBSD Foundation
+.\" by Gregory McGarry.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+.\" POSSIBILITY OF SUCH DAMAGE.
+.\"
+.Dd June 15, 2023
+.Dt VNODEOPS 9
+.Os
+.Sh NAME
+.Nm vnodeops ,
+.Nm VOP_LOOKUP ,
+.Nm VOP_CREATE ,
+.Nm VOP_MKNOD ,
+.Nm VOP_OPEN ,
+.Nm VOP_CLOSE ,
+.Nm VOP_ACCESS ,
+.Nm VOP_GETATTR ,
+.Nm VOP_SETATTR ,
+.Nm VOP_READ ,
+.Nm VOP_WRITE ,
+.Nm VOP_FALLOCATE ,
+.Nm VOP_FDISCARD ,
+.Nm VOP_IOCTL ,
+.Nm VOP_FCNTL ,
+.Nm VOP_POLL ,
+.Nm VOP_KQFILTER ,
+.Nm VOP_REVOKE ,
+.Nm VOP_MMAP ,
+.Nm VOP_FSYNC ,
+.Nm VOP_SEEK ,
+.Nm VOP_REMOVE ,
+.Nm VOP_LINK ,
+.Nm VOP_RENAME ,
+.Nm VOP_MKDIR ,
+.Nm VOP_RMDIR ,
+.Nm VOP_SYMLINK ,
+.Nm VOP_READDIR ,
+.Nm VOP_READLINK ,
+.Nm VOP_ABORTOP ,
+.Nm VOP_INACTIVE ,
+.Nm VOP_RECLAIM ,
+.Nm VOP_LOCK ,
+.Nm VOP_UNLOCK ,
+.Nm VOP_ISLOCKED ,
+.Nm VOP_BMAP ,
+.Nm VOP_PRINT ,
+.Nm VOP_PATHCONF ,
+.Nm VOP_ADVLOCK ,
+.Nm VOP_WHITEOUT ,
+.Nm VOP_GETPAGES ,
+.Nm VOP_PUTPAGES ,
+.Nm VOP_STRATEGY ,
+.Nm VOP_BWRITE ,
+.Nm VOP_GETEXTATTR ,
+.Nm VOP_SETEXTATTR ,
+.Nm VOP_LISTEXTATTR ,
+.Nm VOP_DELETEEXTATTR
+.Nd vnode operations
+.Sh SYNOPSIS
+.In sys/param.h
+.In sys/buf.h
+.In sys/dirent.h
+.In sys/vnode.h
+.In sys/mount.h
+.In sys/namei.h
+.In sys/unistd.h
+.In sys/fcntl.h
+.In sys/lockf.h
+.In sys/extattr.h
+.Ft int
+.Fn VOP_LOOKUP "struct vnode *dvp" "struct vnode **vpp" \
+"struct componentname *cnp"
+.Ft int
+.Fn VOP_CREATE "struct vnode *dvp" "struct vnode **vpp" \
+"struct componentname *cnp" "struct vattr *vap"
+.Ft int
+.Fn VOP_MKNOD "struct vnode *dvp" "struct vnode **vpp" \
+"struct componentname *cnp" "struct vattr *vap"
+.Ft int
+.Fn VOP_OPEN "struct vnode *vp" "int mode" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_CLOSE "struct vnode *vp" "int fflag" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_ACCESS "struct vnode *vp" "int mode" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_GETATTR "struct vnode *vp" "struct vattr *vap" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_SETATTR "struct vnode *vp" "struct vattr *vap" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_READ "struct vnode *vp" "struct uio *uio" "int ioflag" \
+"kauth_cred_t cred"
+.Ft int
+.Fn VOP_WRITE "struct vnode *vp" "struct uio *uio" "int ioflag" \
+"kauth_cred_t cred"
+.Ft int
+.Fn VOP_FALLOCATE "struct vnode *vp" "off_t pos" "off_t len"
+.Ft int
+.Fn VOP_FDISCARD "struct vnode *vp" "off_t pos" "off_t len"
+.Ft int
+.Fn VOP_IOCTL "struct vnode *vp" "u_long command" "void *data" \
+"int fflag" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_FCNTL "struct vnode *vp" "u_int command" "void *data" \
+"int fflag" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_POLL "struct vnode *vp" "int events"
+.Ft int
+.Fn VOP_KQFILTER "struct vnode *vp" "struct knote *kn"
+.Ft int
+.Fn VOP_REVOKE "struct vnode *vp" "int flags"
+.Ft int
+.Fn VOP_MMAP "struct vnode *vp" "vm_prot_t prot" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_FSYNC "struct vnode *vp" "kauth_cred_t cred" "int flags" \
+"off_t offlo" "off_t offhi"
+.Ft int
+.Fn VOP_SEEK "struct vnode *vp" "off_t oldoff" "off_t newoff" \
+"kauth_cred_t cred"
+.Ft int
+.Fn VOP_REMOVE "struct vnode *dvp" "struct vnode *vp" \
+"struct componentname *cnp"
+.Ft int
+.Fn VOP_LINK "struct vnode *dvp" "struct vnode *vp" \
+"struct componentname *cnp"
+.Ft int
+.Fn VOP_RENAME "struct vnode *fdvp" "struct vnode *fvp" \
+"struct componentname *fcnp" "struct vnode *tdvp" \
+"struct vnode *tvp" "struct componentname *tcnp"
+.Ft int
+.Fn VOP_MKDIR "struct vnode *dvp" "struct vnode **vpp" \
+"struct componentname *cnp" "struct vattr *vap"
+.Ft int
+.Fn VOP_RMDIR "struct vnode *dvp" "struct vnode *vp" \
+"struct componentname *cnp"
+.Ft int
+.Fn VOP_SYMLINK "struct vnode *dvp" "struct vnode **vpp" \
+"struct componentname *cnp" "struct vattr *vap" "char *target"
+.Ft int
+.Fn VOP_READDIR "struct vnode *vp" "struct uio *uio" \
+"kauth_cred_t cred" "int *eofflag" "off_t **cookies" "int *ncookies"
+.Ft int
+.Fn VOP_READLINK "struct vnode *vp" "struct uio *uio" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_ABORTOP "struct vnode *dvp" "struct componentname *cnp"
+.Ft int
+.Fn VOP_INACTIVE "struct vnode *vp"
+.Ft int
+.Fn VOP_RECLAIM "struct vnode *vp"
+.Ft int
+.Fn VOP_LOCK "struct vnode *vp" "int flags"
+.Ft int
+.Fn VOP_UNLOCK "struct vnode *vp"
+.Ft int
+.Fn VOP_ISLOCKED "struct vnode *vp"
+.Ft int
+.Fn VOP_BMAP "struct vnode *vp" "daddr_t bn" "struct vnode **vpp" \
+"daddr_t *bnp" "int *runp"
+.Ft int
+.Fn VOP_PRINT "struct vnode *vp"
+.Ft int
+.Fn VOP_PATHCONF "struct vnode *vp" "int name" "register_t *retval"
+.Ft int
+.Fn VOP_ADVLOCK "struct vnode *vp" "void *id" "int op" \
+"struct flock *fl" "int flags"
+.Ft int
+.Fn VOP_WHITEOUT "struct vnode *dvp" "struct componentname *cnp" \
+"int flags"
+.Ft int
+.Fn 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"
+.Ft int
+.Fn VOP_PUTPAGES "struct vnode *vp" "voff_t offlo" "voff_t offhi" \
+"int flags"
+.Ft int
+.Fn VOP_STRATEGY "struct vnode *vp" "struct buf *bp"
+.Ft int
+.Fn VOP_BWRITE "struct vnode *vp" "struct buf *bp"
+.Ft int
+.Fn VOP_GETEXTATTR "struct vnode *vp" "int attrnamespace" "const char *name" \
+"struct uio *uio" "size_t *size" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_SETEXTATTR "struct vnode *vp" "int attrnamespace" "const char *name" \
+"struct uio *uio" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_LISTEXTATTR "struct vnode *vp" "int attrnamespace" "struct uio *uio" \
+"size_t *size" "kauth_cred_t cred"
+.Ft int
+.Fn VOP_DELETEEXTATTR "struct vnode *vp" "int attrnamespace" \
+"const char *name" "kauth_cred_t cred"
+.Pp
+Not all header files are required for each function.
+.Sh 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.
+.Pp
+Functions in the vnode operations vector are invoked using specialized
+macros.
+The following table gives a summary of the operations.
+.Pp
+.Bl -column "VOP_DELETEEXTATTR" "Wake up process sleeping on lock" -compact
+.It Sy Macro Ta Sy Description
+.It VOP_LOOKUP Lookup file name in name cache
+.It VOP_CREATE Create a new file
+.It VOP_MKNOD Make a new device
+.It VOP_OPEN Open a file
+.It VOP_CLOSE Close a file
+.It VOP_ACCESS Determine file accessibility
+.It VOP_GETATTR Get file attributes
+.It VOP_SETATTR Set file attributes
+.It VOP_READ Read from a file
+.It VOP_WRITE Write to a file
+.It VOP_FALLOCATE Allocate backing for a file
+.It VOP_FDISCARD Discard backing for a file
+.It VOP_IOCTL Perform device-specific I/O
+.It VOP_FCNTL Perform file control
+.It VOP_POLL Test if poll event has occurred
+.It VOP_KQFILTER Register a knote
+.It VOP_REVOKE Eliminate vnode activity
+.It VOP_MMAP Map file into user address space
+.It VOP_FSYNC Flush pending data to disk
+.It VOP_SEEK Test if file is seekable
+.It VOP_REMOVE Remove a file
+.It VOP_LINK Link a file
+.It VOP_RENAME Rename a file
+.It VOP_MKDIR Make a new directory
+.It VOP_RMDIR Remove a directory
+.It VOP_SYMLINK Create a symbolic link
+.It VOP_READDIR Read directory entry
+.It VOP_READLINK Read contents of a symlink
+.It VOP_ABORTOP Abort pending operation
+.It VOP_INACTIVE Release the inactive vnode
+.It VOP_RECLAIM Reclaim vnode for another file
+.It VOP_LOCK Sleep until vnode lock is free
+.It VOP_UNLOCK Wake up process sleeping on lock
+.It VOP_ISLOCKED Test if vnode is locked
+.It VOP_BMAP Logical block number conversion
+.It VOP_PRINT Print debugging information
+.It VOP_PATHCONF Return POSIX pathconf data
+.It VOP_ADVLOCK Advisory record locking
+.It VOP_WHITEOUT Whiteout vnode
+.It VOP_GETPAGES Read VM pages from file
+.It VOP_PUTPAGES Write VM pages to file
+.It VOP_STRATEGY Read/write a file system buffer
+.It VOP_BWRITE Write a file system buffer
+.It VOP_GETEXTATTR Get extended attribute
+.It VOP_SETEXTATTR Set extended attribute
+.It VOP_LISTEXTATTR List extended attributes
+.It VOP_DELETEEXTATTR Remove extended attribute
+.El
+.Pp
+The implementation details of the vnode operations vector are not
+quite what is described here.
+.Pp
+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.
+.Pp
+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:
+.Bd -literal
+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() */
+};
+.Ed
+.Pp
+The top half of the structure is used exclusively for the pathname
+lookups using
+.Fn VOP_LOOKUP
+and is initialized by the caller.
+The semantics of the lookup are affected by the lookup operation
+specified in
+.Em cn_nameiop
+and the flags specified in
+.Em cn_flags .
+Valid operations are:
+.Pp
+.Bl -tag -offset indent -width LOOKUP -compact
+.It LOOKUP
+perform name lookup only
+.It CREATE
+set up for file creation
+.It DELETE
+set up for file deletion
+.It RENAME
+set up for file renaming
+.It OPMASK
+mask for operation
+.El
+.Pp
+Valid values for
+.Em cn->cn_flags
+are:
+.Pp
+.Bl -tag -offset indent -width LOCKPARENT -compact
+.It LOCKLEAF
+lock inode on return
+.It LOCKPARENT
+want parent vnode returned locked
+.It NOCACHE
+name must not be left in name cache (see
+.Xr namecache 9 )
+.It FOLLOW
+follow symbolic links
+.It NOFOLLOW
+do not follow symbolic links (pseudo)
+.It MODMASK
+mask of operational modifiers
+.El
+.Pp
+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.
+.Pp
+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
+.Xr vnsubr 9 .
+.Sh FUNCTIONS
+.Bl -tag -width compact
+.It Fn VOP_LOOKUP "dvp" "vpp" "cnp"
+Lookup a single pathname component in a given directory.
+The argument
+.Fa dvp
+is the locked vnode of the directory to search and
+.Fa 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
+.Fa vpp .
+The operation specified in
+.Em cnp->cn_nameiop
+indicates
+.Fn VOP_LOOKUP
+the reason for requesting the lookup and uses it to cache
+file system type specific information in the vnode for subsequent
+operations.
+.Pp
+There are three types of lookups: ".", ".." (ISDOTDOT), and regular.
+If the pathname component being searched for is ".", then
+.Fa dvp
+has an extra reference added to it and it is returned in
+.Fa *vpp .
+For other pathname components,
+.Fn VOP_LOOKUP
+checks the accessibility of the directory and searches the name cache
+for the pathname component.
+See
+.Xr 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
+.Fa vpp .
+.Fa dvp
+is always returned locked.
+.Pp
+On failure
+.Fa *vpp
+is
+.Dv NULL ,
+and
+.Fa *dvp
+is left locked.
+If the operation is successful
+.Fa *vpp
+is unlocked and zero is returned.
+Typically, if
+.Fa *vpp
+and
+.Fa dvp
+are the same vnode the caller will need to release twice (decrement
+the reference count) and unlock once.
+.It Fn VOP_CREATE "dvp" "vpp" "cnp" "vap"
+Create a new file in a given directory.
+The argument
+.Fa dvp
+is the locked vnode of the directory to create the new file in and
+.Fa cnp
+is the pathname component of the new file.
+The argument
+.Fa 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
+.Fa vpp
+and zero is returned.
+.Pp
+This function is called after
+.Fn VOP_LOOKUP
+when a file is being created.
+Normally,
+.Fn VOP_LOOKUP
+will have set the SAVENAME flag in
+.Em cnp->cn_flags
+to keep the memory pointed to by
+.Em 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
+.Em cnp->cn_flags .
+.It Fn VOP_MKNOD "dvp" "vpp" "cnp" "vap"
+Make a new device-special file in a given directory.
+The argument
+.Fa dvp
+is the locked vnode of the directory to create the new device-special
+file in and
+.Fa cnp
+is the pathname component of the new device-special file.
+The argument
+.Fa 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
+.Fa vpp
+and zero is returned.
+.Pp
+This function is called after
+.Fn VOP_LOOKUP
+when a device-special file is being created.
+Normally,
+.Fn VOP_LOOKUP
+will have set the SAVENAME flag in
+.Em cnp->cn_flags
+to keep the memory pointed to by
+.Em 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
+.Em cnp->cn_flags .
+.It Fn VOP_OPEN "vp" "mode" "cred"
+Open a file.
+The argument
+.Fa vp
+is the vnode of the file to open and
+.Fa mode
+specifies the access mode required by the calling process.
+The calling credentials are specified by
+.Fa cred .
+The access mode is a set of flags, including FREAD, FWRITE,
+O_NONBLOCK, O_APPEND, etc.
+.Fn VOP_OPEN
+must be called before a file can be accessed by a thread.
+The vnode reference count is incremented.
+.Pp
+.Fn VOP_OPEN
+expects the vnode
+.Fa 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.
+.It Fn VOP_CLOSE "vp" "fflag" "cred"
+Close a file.
+The argument
+.Fa vp
+is the vnode of the file to close and
+.Fa fflag
+specifies the access mode by the calling process.
+The possible flags are
+.Dv FREAD ,
+.Dv FWRITE
+and
+.Dv FNONBLOCK .
+The calling credentials are specified by
+.Fa cred .
+.Fn VOP_CLOSE
+frees resources allocated by
+.Fn VOP_OPEN .
+.Pp
+The vnode
+.Fa vp
+will be locked on entry and should remain locked on return.
+.It Fn VOP_ACCESS "vp" "mode" "cred"
+Determine the accessibility (permissions) of the file against the
+specified credentials.
+The argument
+.Fa vp
+is the vnode of the file to check,
+.Fa mode
+is the type of access required and
+.Fa cred
+contains the user credentials to check.
+The argument
+.Fa 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.
+.Pp
+The vnode
+.Fa vp
+will be locked on entry and should remain locked on return.
+.It Fn VOP_GETATTR "vp" "vap" "cred"
+Get specific vnode attributes on a file.
+The argument
+.Fa vp
+is the vnode of the file to get the attributes for.
+The argument
+.Fa cred
+specifies the calling credentials.
+.Fn VOP_GETATTR
+uses the file system type specific data object
+.Em vp->v_data
+to reference the underlying file attributes.
+.\" Attributes associated with the file are collected by setting the
+.\" required attribute bits in
+.\" .Em vap->va_mask .
+The attributes are returned in
+.Fa vap .
+Attributes which are not available are set to the value VNOVAL.
+.Pp
+For more information on vnode attributes see
+.Xr vattr 9 .
+Historically it was considered acceptable to call
+.Fn VOP_GETATTR
+without first locking the vnode.
+This usage is deprecated.
+.Pp
+The vnode
+.Fa vp
+will be locked on entry and should remain locked on return.
+.It Fn VOP_SETATTR "vp" "vap" "cred"
+Set specific vnode attributes on a file.
+The argument
+.Fa vp
+is the locked vnode of the file to set the attributes for.
+The argument
+.Fa cred
+specifies the calling credentials.
+.Fn VOP_SETATTR
+uses the file system type specific data object
+.Em vp->v_data
+to reference the underlying file attributes.
+The new attributes are defined in
+.Fa vap .
+.\" Attributes associated with the file are set by setting the required
+.\" attribute bits in
+.\" .Em vap->va_mask .
+Attributes which are not being modified by
+.Fn VOP_SETATTR
+should be set to the value VNOVAL.
+If the operation is successful zero is returned, otherwise an
+appropriate error is returned.
+.Pp
+For more information on vnode attributes see
+.Xr vattr 9 .
+.It Fn VOP_READ "vp" "uio" "ioflag" "cred"
+Read the contents of a file.
+The argument
+.Fa vp
+is the vnode of the file to read from,
+.Fa uio
+is the location to read the data into,
+.Fa ioflag
+is a set of flags and
+.Fa cred
+are the credentials of the calling process.
+.Pp
+The
+.Fa 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:
+.Pp
+.Bl -tag -offset indent -width IO_ALTSEMANTICS -compact
+.It IO_UNIT
+do I/O as atomic unit
+.It IO_APPEND
+append write to end
+.It IO_SYNC
+sync I/O file integrity completion
+.It IO_NODELOCKED
+underlying node already locked
+.It IO_NDELAY
+FNDELAY flag set in file table
+.It IO_DSYNC
+sync I/O data integrity completion
+.It IO_ALTSEMANTICS
+use alternate I/O semantics
+.It IO_NORMAL
+operate on regular data
+.It IO_EXT
+operate on extended attributes
+.It IO_DIRECT
+do not buffer data in the kernel
+.El
+.Pp
+Zero is returned on success, otherwise an error is returned.
+The vnode should be locked on entry and remains locked on exit.
+.It Fn VOP_WRITE "vp" "uio" "ioflag" "cred"
+Write to a file.
+The argument
+.Fa vp
+is the vnode of the file to write to,
+.Fa uio
+is the location of the data to write,
+.Fa ioflag
+is a set of flags and
+.Fa cred
+are the credentials of the calling process.
+.Pp
+The
+.Fa 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
+.Fn VOP_READ .
+.Pp
+Zero is returned on success, otherwise an error is returned.
+The vnode should be locked on entry and remains locked on exit.
+.It Fn VOP_FALLOCATE "vp" "pos" "len"
+Allocate backing store.
+The argument
+.Fa vp
+is the vnode for the file.
+The
+.Fa pos
+and
+.Fa 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
+.Dq holes
+from files.
+.It Fn VOP_FDISCARD "vp" "pos" "len"
+Discard backing store.
+The argument
+.Fa vp
+is the vnode for the file.
+The
+.Fa pos
+and
+.Fa 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
+.Dq 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
+.Em 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.
+.\" XXX: if you discard part of a block in a regular file, should that
+.\" part be explicitly zeroed? Also, how do you find the underlying
+.\" block size?
+.It Fn VOP_IOCTL "vp" "command" "data" "fflag" "cred"
+Perform device-specific I/O.
+The argument
+.Fa vp
+is the vnode of the file, normally representing a device.
+The argument
+.Fa command
+specifies the device-specific operation to perform and
+.Fa cnp
+provides extra data for the specified operation.
+The argument
+.Fa fflags
+is a set of flags.
+The argument
+.Fa cred
+is the caller's credentials.
+If the operation is successful, zero is
+returned, otherwise an appropriate error code is returned.
+.Pp
+Most file systems do not supply a function for
+.Fn VOP_IOCTL .
+This function implements the
+.Xr ioctl 2
+system call.
+.It Fn VOP_FCNTL "vp" "command" "data" "fflag" "cred"
+Perform file control.
+The argument
+.Fa vp
+is the locked vnode of the file.
+The argument
+.Fa command
+specifies the operation to perform and
+.Fa cnp
+provides extra data for the specified operation.
+The argument
+.Fa fflags
+is a set of flags.
+The argument
+.Fa cred
+is the caller's credentials.
+If the operation is successful, zero is returned, otherwise an
+appropriate error code is returned.
+.It Fn VOP_POLL "vp" "events"
+Test if a poll event has occurred.
+The argument
+.Fa vp
+is the vnode of the file to poll.
+It returns any events of interest as specified by
+.Fa events
+that may have occurred for the file.
+The argument
+.Fa events
+is a set of flags as specified by
+.Xr poll 2 .
+.Pp
+The vnode
+.Fa vp
+remains unlocked throughout the whole operation.
+.It Fn VOP_KQFILTER "vp" "kn"
+Register a knote
+.Fa kn
+with the vnode
+.Fa vn .
+If the operation is successful zero is returned, otherwise an
+appropriate error code is returned.
+.Pp
+The vnode
+.Fa vp
+remains unlocked throughout the whole operation.
+.It Fn VOP_REVOKE "vp" "flags"
+Eliminate all activity associated with the vnode
+.Fa vp .
+The argument
+.Fa flags
+is a set of flags.
+If REVOKEALL is set in
+.Fa flags
+all vnodes aliased to the vnode
+.Fa vp
+are also eliminated.
+If the operation is successful zero is returned, otherwise an
+appropriate error is returned.
+.Pp
+The vnode
+.Fa vp
+remains unlocked throughout the whole operation.
+.It Fn VOP_MMAP "vp" "prot" "cred"
+Inform file system that
+.Fa vp
+is in the process of being memory mapped.
+The argument
+.Fa prot
+specifies the vm access protection the vnode is going to be mapped with.
+The argument
+.Fa cred
+is the caller's credentials.
+If the file system allows the memory mapping, zero is returned, otherwise
+an appropriate error code is returned.
+.Pp
+Most file systems do not supply a function for
+.Fn VOP_MMAP
+and use
+.Fn 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.
+.It Fn VOP_FSYNC "vp" "cred" "flags" "offlo" "offhi"
+Flush pending data buffers for a file to disk.
+The argument
+.Fa vp
+is the locked vnode of the file for flush.
+The argument
+.Fa cred
+is the caller's credentials.
+The argument
+.Fa flags
+is a set of flags.
+If FSYNC_WAIT is specified in
+.Fa flags ,
+the function should wait for I/O to complete before returning.
+The argument
+.Fa offlo
+and
+.Fa offhi
+specify the range of file to flush.
+If the operation is successful zero is returned, otherwise an
+appropriate error code is returned.
+.Pp
+This function implements the
+.Xr sync 2
+and
+.Xr fsync 2
+system calls.
+.It Fn VOP_SEEK "vp" "oldoff" "newoff" "cred"
+Test if the file is seekable for the specified offset
+.Fa newoff .
+The argument
+.Fa vp
+is the locked vnode of the file to test.
+For most file systems this function simply tests if
+.Fa newoff
+is valid.
+If the specified
+.Fa newoff
+is less than zero, the function returns error code EINVAL.
+.It Fn VOP_REMOVE "dvp" "vp" "cnp"
+Remove a file.
+The argument
+.Fa dvp
+is the locked vnode of the directory to remove the file from and
+.Fa vp
+is the locked vnode of the file to remove.
+The argument
+.Fa 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
+.Fa dvp
+and
+.Fa vp
+are locked on entry and are to be unlocked before returning.
+.It Fn VOP_LINK "dvp" "vp" "cnp"
+Link to a file.
+The argument
+.Fa dvp
+is the locked node of the directory to create the new link and
+.Fa vp
+is the vnode of the file to be linked.
+The argument
+.Fa 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
+.Fa dvp
+should be locked on entry and will be released and unlocked on return.
+The vnode
+.Fa vp
+should not be locked on entry and will remain unlocked on return.
+.It Fn VOP_RENAME "fdvp" "fvp" "fcnp" "tdvp" "tvp" "tcnp"
+Rename a file.
+The argument
+.Fa fdvp
+is the vnode of the old parent directory containing in the file to be
+renamed and
+.Fa fvp
+is the vnode of the file to be renamed.
+The argument
+.Fa fcnp
+is the pathname component about the file to be renamed.
+The argument
+.Fa tdvp
+is the vnode of the new directory of the target file and
+.Fa tvp
+is the vnode of the target file (if it exists).
+The argument
+.Fa 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.
+.Pp
+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.
+.Fn VOP_RENAME
+updates the reference counts prior to returning.
+.Pp
+Because of the complexity and nastiness of the interface, please do
+not write new code that calls
+.Fn VOP_RENAME
+directly until such time as ongoing cleanup work reaches a point where
+the interface has been rendered halfway sane.
+.It Fn VOP_MKDIR "dvp" "vpp" "cnp" "vap"
+Make a new directory in a given directory.
+The argument
+.Fa dvp
+is the locked vnode of the directory to create the new directory in and
+.Fa cnp
+is the pathname component of the new directory.
+The argument
+.Fa 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
+.Fa vpp
+and zero is returned.
+.Pp
+This function is called after
+.Fn VOP_LOOKUP
+when a directory is being created.
+Normally,
+.Fn VOP_LOOKUP
+will have set the SAVENAME flag in
+.Em cnp->cn_flags
+to keep the memory pointed to by
+.Em 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
+.Em cnp->cn_flags .
+.It Fn VOP_RMDIR "dvp" "vp" "cnp"
+Remove a directory in a given directory.
+The argument
+.Fa dvp
+is the locked vnode of the directory to remove the directory from and
+.Fa vp
+is the locked vnode of the directory to remove.
+The argument
+.Fa cnp
+is the pathname component of the directory.
+Zero is returned on success, otherwise an error code is returned.
+Both
+.Fa dvp
+and
+.Fa vp
+should be locked on entry and will be released and unlocked on return.
+.It Fn VOP_SYMLINK "dvp" "vpp" "cnp" "vap" "target"
+Create a symbolic link in a given directory.
+The argument
+.Fa dvp
+is the locked vnode of the directory to create the symbolic link in
+and
+.Fa cnp
+is the pathname component of the symbolic link.
+The argument
+.Fa vap
+specifies the attributes that the symbolic link should be created
+with and
+.Fa 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
+.Fa vpp
+and zero is returned.
+.Pp
+This function is called after
+.Fn VOP_LOOKUP
+when a symbolic link is being created.
+Normally,
+.Fn VOP_LOOKUP
+will have set the SAVENAME flag in
+.Em cnp->cn_flags
+to keep the memory pointed to by
+.Em 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
+.Em cnp->cn_flags .
+.It Fn VOP_READDIR "vp" "uio" "cred" "eofflag" "cookies" "ncookies"
+Read directory entry.
+The argument
+.Fa vp
+is the vnode of the directory to read the contents of and
+.Fa uio
+is the destination location to read the contents into.
+The argument
+.Fa cred
+is the caller's credentials.
+The argument
+.Fa eofflag
+is the pointer to a flag which is set by
+.Fn VOP_READDIR
+to indicate an end-of-file condition.
+If
+.Fa eofflag
+is
+.Dv NULL ,
+the end-of-file condition is not returned.
+The arguments
+.Fa cookies
+and
+.Fa ncookies
+specify the addresses for the list and number of directory seek
+cookies generated for NFS.
+Both
+.Fa cookies
+and
+.Fa ncookies
+should be
+.Dv NULL
+if they aren't required to be returned by
+.Fn VOP_READDIR .
+The directory contents are read into struct dirent structures and
+.Fa 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.
+.Pp
+The directory should be locked on entry and will remain locked on
+return.
+.Pp
+In case
+.Fa ncookies
+and
+.Fa 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
+.Fa i ,
+the corresponding cookie should refer to the offset of directory entry
+.Fa i + 1 .
+.Pp
+Note that the
+.Fa cookies
+array must be allocated by the callee using the M_TEMP malloc type as
+callers of
+.Fn VOP_READDIR
+must be able to free the allocation.
+.It Fn VOP_READLINK "vp" "uio" "cred"
+Read the contents of a symbolic link.
+The argument
+.Fa vp
+is the locked vnode of the symlink and
+.Fa uio
+is the destination location to read the contents into.
+The argument
+.Fa cred
+is the credentials of the caller.
+If the operation is successful zero is returned, otherwise an error
+code is returned.
+.Pp
+The vnode should be locked on entry and will remain locked on return.
+.It Fn VOP_ABORTOP "dvp" "cnp"
+Abort pending operation on vnode
+.Fa dvp
+and free resources allocated in
+.Fa cnp .
+.Pp
+This operation is rarely implemented in file systems and
+.Fn genfs_abortop
+is typically used instead.
+.It Fn VOP_INACTIVE "vp"
+Release the inactive vnode.
+.Fn 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
+.Fa 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
+.Fa vp
+must be locked on entry, and will remain locked on return.
+.It Fn VOP_RECLAIM "vp"
+Reclaim the vnode for another file system.
+.Fn 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
+.Fa vp
+is the vnode to be reclaimed.
+If the operation is successful zero is returned, otherwise an
+appropriate error code is returned.
+The vnode
+.Fa vp
+should be locked on entry, and will be returned unlocked.
+.It Fn VOP_LOCK "vp" "flags"
+Sleep until vnode lock is free.
+The argument
+.Fa vp
+is the vnode of the file to be locked.
+The argument
+.Fa flags
+is
+.Dv LK_EXCLUSIVE
+to take the lock exclusively or
+.Dv LK_SHARED
+to take a shared lock.
+If
+.Fa flags
+contains
+.Dv LK_NOWAIT
+and the lock is busy, the operation will return immediately with an error code.
+If
+.Fa flags
+contains
+.Dv 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.
+.Fn 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
+.Xr vn_lock 9
+to lock a vnode rather than calling
+.Fn VOP_LOCK
+directly.
+.It Fn VOP_UNLOCK "vp"
+Wake up process sleeping on lock.
+The argument
+.Fa 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.
+.Fn 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.
+.It Fn VOP_ISLOCKED "vp"
+Test if the vnode
+.Fa vp
+is locked.
+Possible return values are
+.Dv LK_EXCLUSIVE ,
+.Dv LK_SHARED
+or 0 for lock held exclusively by the calling thread, shared lock held
+by anyone or unlocked, respectively.
+.Pp
+This function must never be used to make locking decisions at run time:
+it is provided only for diagnostic purposes.
+.It Fn VOP_BMAP "vp" "bn" "vpp" "bnp" "runp"
+Convert the logical block number
+.Fa bn
+of a file specified by vnode
+.Fa vp
+to its physical block number on the disk.
+The physical block is returned in
+.Fa bnp .
+In case the logical block is not allocated, \-1 is used.
+.Pp
+If
+.Fa vpp
+is not
+.Dv NULL ,
+the vnode of the device vnode for the file system is
+returned in the address specified by
+.Fa vpp .
+If
+.Fa runp
+is not
+.Dv NULL ,
+the number of contiguous blocks starting from the next block after
+the queried block will be returned in
+.Fa runp .
+.It Fn VOP_PRINT "vp"
+Print debugging information.
+The argument
+.Fa vp
+is the vnode to print.
+If the operation is successful zero is returned, otherwise an
+appropriate error code is returned.
+.It Fn VOP_PATHCONF "vp" "name" "retval"
+Implement POSIX
+.Xr pathconf 2
+and
+.Xr fpathconf 2
+support.
+The argument
+.Fa vp
+is the locked vnode to get information about.
+The argument
+.Fa name
+specified the type of information to return.
+The information is returned in the address specified by
+.Fa retval .
+Valid values for
+.Fa name
+are:
+.Pp
+.Bl -tag -offset indent -width _PC_CHOWN_RESTRICTED -compact
+.It _PC_LINK_MAX
+return the maximum number of links to a file
+.It _PC_NAME_MAX
+return the maximum number of bytes in a file name
+.It _PC_PATH_MAX
+return the maximum number of bytes in a pathname
+.It _PC_PIPE_BUF
+return the maximum number of bytes which will be written atomically to
+a pipe
+.It _PC_CHOWN_RESTRICTED
+return 1 if appropriate privileges are required for the
+.Xr chown 2
+system call, otherwise zero
+.It _PC_NO_TRUNC
+return 0 if file names longer than
+.Brq Dv NAME_MAX
+are silently truncated
+.El
+.Pp
+If
+.Fa name
+is recognized,
+.Fa *retval
+is set to the specified value and zero is returned, otherwise an
+appropriate error is returned.
+.It Fn VOP_ADVLOCK "vp" "id" "op" "fl" "flags"
+Manipulate Advisory record locks on a vnode.
+The argument
+.Fa vp
+is the vnode on which locks are manipulated.
+The argument
+.Fa id
+is the id token which is changing the lock and
+.Fa op
+is the
+.Xr fcntl 2
+operation to perform.
+Valid values are:
+.Pp
+.Bl -tag -offset indent -width F_UNLCK -compact
+.It F_SETLK
+set lock
+.It F_GETLK
+get the first conflicted lock
+.It F_UNLCK
+clear lock
+.El
+.Pp
+The argument
+.Fa fl
+is a description of the lock.
+In the case of
+.Dv SEEK_CUR ,
+The caller should add the current file offset to
+fl->l_start beforehand.
+.Fn VOP_ADVLOCK
+treats
+.Dv SEEK_CUR
+as
+.Dv SEEK_SET .
+.Pp
+The argument
+.Fa flags
+is the set of flags.
+Valid values are:
+.Pp
+.Bl -tag -offset indent -width F_FLOCK -compact
+.It F_WAIT
+wait until lock is granted
+.It F_FLOCK
+use
+.Xr flock 2
+semantics for lock
+.It F_POSIX
+use POSIX semantics for lock
+.El
+.Pp
+If the operation is successful zero is returned, otherwise an
+appropriate error is returned.
+.It Fn VOP_WHITEOUT "dvp" "cnp" "flags"
+Whiteout pathname component in directory with vnode
+.Fa dvp .
+The argument
+.Fa cnp
+specifies the pathname component to whiteout.
+.Pp
+The vnode
+.Fa dvp
+should be locked on entry and will remain locked on return.
+.It Fn VOP_GETPAGES "vp" "offset" "m" "count" "centeridx" "access_type" "advice" "flags"
+Read VM pages from file.
+The argument
+.Fa vp
+is the locked vnode to read the VM pages from.
+The argument
+.Fa offset
+is offset in the file to start accessing and
+.Fa m
+is an array of VM pages.
+The argument
+.Fa 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
+.Em flags ,
+.Fn VOP_GETPAGES
+might return less pages than requested.
+In that case, the variable pointed to by
+.Em count
+will be updated.
+.Pp
+This function is primarily used by the page-fault handing mechanism.
+.It Fn VOP_PUTPAGES "vp" "offlo" "offhi" "flags"
+Write modified (dirty) VM pages to file.
+The argument
+.Fa vp
+is the vnode to write the VM pages to.
+The vnode's vm object lock
+.Va ( v_uobj.vmobjlock )
+must be held by the caller and will be released upon return.
+The arguments
+.Fa offlo
+and
+.Fa offhi
+specify the range of VM pages to write.
+In case
+.Fa offhi
+is given as 0, all pages at and after the start offset
+.Fa offlo
+belonging the vnode
+.Fa vp
+will be written.
+The argument
+.Fa flags
+controls the behavior of the routine and takes the vm pager's
+flags
+.Dv ( PGO_ -prefixed ) .
+If the operation is successful zero is returned, otherwise an
+appropriate error code is returned.
+.Pp
+The function is primarily used by the pageout handling mechanism and
+is commonly implemented indirectly
+by
+.Fn genfs_putpages
+with the help of
+.Fn VOP_STRATEGY
+and
+.Fn VOP_BMAP .
+.It Fn VOP_STRATEGY "vp" "bp"
+Read/write a file system buffer.
+The argument
+.Fa vp
+is the vnode to read/write to.
+The argument
+.Fa bp
+is the buffer to be read or written.
+.Fn VOP_STRATEGY
+will either read or write data to the file depending on the value of
+.Em bp->b_flags .
+If the operation is successful zero is returned, otherwise an
+appropriate error code is returned.
+.It Fn VOP_BWRITE "vp" "bp"
+Write a file system buffer.
+The argument
+.Fa vp
+is the vnode to write to.
+The argument
+.Fa bp
+specifies the buffer to be written.
+If the operation is successful zero is returned, otherwise an
+appropriate error code is returned.
+.It Fn VOP_GETEXTATTR "vp" "attrnamespace" "name" "uio" "size" "cred"
+Get an extended attribute.
+The argument
+.Fa vp
+is the locked vnode of the file or directory from which to retrieve the
+attribute.
+The argument
+.Fa attrnamespace
+specifies the extended attribute namespace.
+The argument
+.Fa name
+is a nul-terminated character string naming the attribute to retrieve.
+The argument
+.Fa uio ,
+if not
+.Dv NULL ,
+specifies where the extended attribute value is to be written.
+The argument
+.Fa size ,
+if not
+.Dv NULL ,
+will contain the number of bytes required to read all of
+the attribute data upon return.
+In most cases,
+.Fa uio
+will be
+.Dv NULL
+when
+.Fa size
+is not, and vice versa.
+The argument
+.Fa cred
+specifies the user credentials to use when authorizing the request.
+.It Fn VOP_SETEXTATTR "vp" "attrnamespace" "name" "uio" "cred"
+Set an extended attribute.
+The argument
+.Fa vp
+is the locked vnode of the file or directory to which to store the
+attribute.
+The argument
+.Fa namespace
+specifies the extended attribute namespace.
+The argument
+.Fa name
+is a nul-terminated character string naming the attribute to store.
+The argument
+.Fa uio
+specifies the source of the extended attribute data.
+The argument
+.Fa cred
+specifies the user credentials to use when authorizing the request.
+.It Fn VOP_LISTEXTATTR "vp" "attrnamespace" "uio" "size" "cred"
+Retrieve the list of extended attributes.
+The argument
+.Fa vp
+is the locked vnode of the file or directory whose attributes are to be listed.
+The argument
+.Fa attrnamespace
+specifies the extended attribute namespace.
+The argument
+.Fa uio ,
+if not
+.Dv NULL ,
+specifies where the extended attribute list is to be written.
+The argument
+.Fa size ,
+if not
+.Dv NULL ,
+will contain the number of bytes required to read all of
+the attribute names upon return.
+In most cases,
+.Fa uio
+will be
+.Dv NULL
+when
+.Fa size
+is not, and vice versa.
+The argument
+.Fa cred
+specifies the user credentials to use when authorizing the request.
+.It Fn VOP_DELETEEXTATTR "vp" "attrnamespace" "name" "cred"
+Remove attribute
+.Fa name
+from file associated with
+.Fa vp .
+The argument
+.Fa attrnamespace
+specifies the extended attribute namespace.
+If full removal is not supported, the file system should return
+.Er EOPNOTSUPP
+to allow the caller to zero out the value with
+.Fn VOP_SETEXTATTR .
+.Pp
+The vnode
+.Fa vp
+should be locked on entry and will remain locked on return.
+.El
+.Sh FILES
+.Pa src/sys/kern/vnode_if.src
+contains the list of vnode functions, their definitions and an exact locking
+protocol.
+.Sh ERRORS
+.Bl -tag -width Er
+.It Bq Er EACCES
+Access for the specified operation is denied.
+.It Bq Er EDQUOT
+Quota exceeded.
+.It Bq Er EINVAL
+attempt to read from an illegal offset in the directory; unrecognized
+input
+.It Bq Er EIO
+a read error occurred while reading the directory or reading the
+contents of a symbolic link
+.It Bq Er EJUSTRETURN
+A CREATE or RENAME operation would be successful.
+.It Bq Er ENOATTR
+The requested attribute is not defined for this vnode.
+.It Bq Er ENOENT
+The component was not found in the directory.
+.It Bq Er ENOSPC
+The file system is full.
+.It Bq Er ENOTDIR
+The vnode does not represent a directory.
+.It Bq Er ENOTEMPTY
+attempt to remove a directory which is not empty
+.It Bq Er EPERM
+an attempt was made to change an immutable file
+.It Bq Er EROFS
+the file system is read-only
+.El
+.Sh SEE ALSO
+.Xr extattr 9 ,
+.Xr intro 9 ,
+.Xr namei 9 ,
+.Xr vattr 9 ,
+.Xr vfs 9 ,
+.Xr vfsops 9 ,
+.Xr vnode 9
+.Sh HISTORY
+The vnode operations vector, its functions and the corresponding
+macros appeared in
+.Bx 4.3 .
generated by cgit v1.2.3 (git 2.46.0) at 2026-05-15 13:22:51 +0000