51ea7bea91
The current scheme of calling VOP_GETATTR adds avoidable overhead. An example with tmpfs doing fstat (ops/s): before: 7488958 after: 7913833 Reviewed by: kib (previous version) Differential Revision: https://reviews.freebsd.org/D25910
140 lines
4.0 KiB
Groff
140 lines
4.0 KiB
Groff
.\" -*- nroff -*-
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.\"
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.\" Copyright (c) 1996 Doug Rabson
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.\"
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.\" All rights reserved.
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.\"
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.\" This program is free software.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 8, 2020
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.Dt VOP_ATTRIB 9
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.Os
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.Sh NAME
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.Nm VOP_GETATTR ,
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.Nm VOP_SETATTR
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.Nd get and set attributes on a file or directory
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/vnode.h
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.Ft int
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.Fn VOP_GETATTR "struct vnode *vp" "struct vattr *vap" "struct ucred *cred"
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.Ft int
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.Fn VOP_SETATTR "struct vnode *vp" "struct vattr *vap" "struct ucred *cred"
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.Ft int
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.Fn VOP_STAT "struct vnode *vp" "struct stat *sb" "struct ucred *active_cred" \
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"struct ucred *file_cred" "struct thread *td"
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.Sh DESCRIPTION
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These entry points manipulate various attributes of a file or directory,
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including file permissions, owner, group, size,
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access time and modification time.
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.Pp
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.Fn VOP_STAT
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returns data in a format suitable for the
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.Xr stat 2
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system call and by default is implemented as a wrapper around
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.Fn VOP_GETATTR .
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Filesystems may want to implement their own variant for performance reasons.
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.Pp
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For
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.Fn VOP_GETATTR
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and
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.Fn VOP_SETATTR
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the arguments are:
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.Bl -tag -width cred
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.It Fa vp
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The vnode of the file.
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.It Fa vap
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The attributes of the file.
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.It Fa cred
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The user credentials of the calling thread.
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.El
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.Pp
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For
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.Fn VOP_STAT
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the arguments are:
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.Bl -tag -width active_cred
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.It Fa vp
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The vnode of the file.
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.It Fa sb
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The attributes of the file.
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.It Fa active_cred
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The user credentials of the calling thread.
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.It Fa file_cred
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The credentials installed on the file description pointing to the vnode or NOCRED.
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.It Fa td
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The calling thread.
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.El
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.Pp
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Attributes which are not being modified by
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.Fn VOP_SETATTR
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should be set to the value
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.Dv VNOVAL ;
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.Fn VATTR_NULL
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may be used to clear all the values, and should generally be used to reset
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the contents of
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.Fa *vap
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prior to setting specific values.
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.Sh LOCKS
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Both
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.Fn VOP_GETATTR
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and
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.Fn VOP_STAT
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expect the vnode to be locked on entry and will leave the vnode locked on
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return.
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The lock type can be either shared or exclusive.
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.Pp
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.Fn VOP_SETATTR
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expects the vnode to be locked on entry and will leave the vnode locked on
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return.
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The lock type must be exclusive.
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.Sh RETURN VALUES
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.Fn VOP_GETATTR
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returns 0 if it was able to retrieve the attribute data via
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.Fa *vap ,
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otherwise an appropriate error is returned.
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.Fn VOP_SETATTR
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returns zero if the attributes were changed successfully, otherwise an
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appropriate error is returned.
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.Fn VOP_STAT
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returns 0 if it was able to retrieve the attribute data
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.Fa *sb ,
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otherwise an appropriate error is returned.
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EPERM
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The file is immutable.
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.It Bq Er EACCES
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The caller does not have permission to modify the file or directory attributes.
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.It Bq Er EROFS
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The file system is read-only.
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.El
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.Sh SEE ALSO
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.Xr VFS 9 ,
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.Xr vnode 9 ,
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.Xr VOP_ACCESS 9
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.Sh AUTHORS
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This manual page was written by
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.An Doug Rabson .
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