228 lines
5.7 KiB
Groff
228 lines
5.7 KiB
Groff
.\" -*- nroff -*-
|
|
.\"
|
|
.\" Copyright (c) 1996 Doug Rabson
|
|
.\"
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This program is free software.
|
|
.\"
|
|
.\" 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 DEVELOPERS ``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 DEVELOPERS 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.
|
|
.\"
|
|
.\" $Id: VOP_RDWR.9,v 1.4 1997/03/07 03:32:27 mpp Exp $
|
|
.\"
|
|
.Dd July 24, 1996
|
|
.Os
|
|
.Dt VOP_RDWR 9
|
|
.Sh NAME
|
|
.Nm VOP_READ ,
|
|
.Nm VOP_WRITE
|
|
.Nd read or write a file
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/param.h>
|
|
.Fd #include <sys/vnode.h>
|
|
.Fd #include <sys/uio.h>
|
|
.Ft int
|
|
.Fn VOP_READ "struct vnode *vp" "struct uio *uio" "int ioflag" "struct ucred *cred"
|
|
.Ft int
|
|
.Fn VOP_WRITE "struct vnode *vp" "struct uio *uio" "int ioflag" "struct ucred *cred"
|
|
.Sh DESCRIPTION
|
|
These entry points read or write the contents of a file
|
|
.Pp
|
|
The arguments are:
|
|
.Bl -tag -width ioflag
|
|
.It Ar vp
|
|
the vnode of the file
|
|
.It Ar uio
|
|
the location of the data to be read or written
|
|
.It Ar ioflag
|
|
various flags
|
|
.It Ar cnp
|
|
the credentials of the caller
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fa ioflag
|
|
argument is a bit mask which can contain the following flags:
|
|
.Bl -tag -width IO_NODELOCKED
|
|
.It Dv IO_UNIT
|
|
do I/O as atomic unit
|
|
.It Dv IO_APPEND
|
|
append write to end
|
|
.It Dv IO_SYNC
|
|
do I/O synchronously
|
|
.It Dv IO_NODELOCKED
|
|
underlying node already locked
|
|
.It Dv IO_NDELAY
|
|
.Dv FNDELAY
|
|
flag set in file table
|
|
.It Dv IO_VMIO
|
|
data already in VMIO space
|
|
.El
|
|
.Sh LOCKS
|
|
The file should be locked on entry and will still be locked on exit.
|
|
.Sh RETURN VALUES
|
|
Zero is returned on success, otherwise an error code is returned.
|
|
.Sh PSEUDOCODE
|
|
.Bd -literal
|
|
int
|
|
vop_read(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
|
|
{
|
|
struct buf *bp;
|
|
off_t bytesinfile;
|
|
daddr_t lbn, nextlbn;
|
|
long size, xfersize, blkoffset;
|
|
int error;
|
|
|
|
size = block size of filesystem;
|
|
|
|
for (error = 0, bp = NULL; uio->uio_resid > 0; bp = NULL) {
|
|
bytesinfile = size of file - uio->uio_offset;
|
|
if (bytesinfile <= 0)
|
|
break;
|
|
|
|
lbn = uio->uio_offset / size;
|
|
blkoffset = uio->uio_offset - lbn * size;
|
|
|
|
xfersize = size - blkoffset;
|
|
if (uio->uio_resid < xfersize)
|
|
xfersize = uio->uio_resid;
|
|
if (bytesinfile < xfersize)
|
|
xfersize = bytesinfile;
|
|
|
|
error = bread(vp, lbn, size, NOCRED, &bp);
|
|
if (error) {
|
|
brelse(bp);
|
|
bp = NULL;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* We should only get non-zero b_resid when an I/O error
|
|
* has occurred, which should cause us to break above.
|
|
* However, if the short read did not cause an error,
|
|
* then we want to ensure that we do not uiomove bad
|
|
* or uninitialized data.
|
|
*/
|
|
size -= bp->b_resid;
|
|
if (size < xfersize) {
|
|
if (size == 0)
|
|
break;
|
|
xfersize = size;
|
|
}
|
|
|
|
error = uiomove((char *)bp->b_data + blkoffset, (int)xfersize, uio);
|
|
if (error)
|
|
break;
|
|
|
|
bqrelse(bp);
|
|
}
|
|
if (bp != NULL)
|
|
bqrelse(bp);
|
|
|
|
return error;
|
|
}
|
|
|
|
int
|
|
vop_write(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
|
|
{
|
|
struct buf *bp;
|
|
off_t bytesinfile;
|
|
daddr_t lbn, nextlbn;
|
|
off_t osize;
|
|
long size, resid, xfersize, blkoffset;
|
|
int flags;
|
|
int error;
|
|
|
|
osize = size of file;
|
|
size = block size of filesystem;
|
|
resid = uio->uio_resid;
|
|
if (ioflag & IO_SYNC)
|
|
flags = B_SYNC;
|
|
else
|
|
flags = 0;
|
|
|
|
for (error = 0; uio->uio_resid > 0;) {
|
|
lbn = uio->uio_offset / size;
|
|
blkoffset = uio->uio_offset - lbn * size;
|
|
|
|
xfersize = size - blkoffset;
|
|
if (uio->uio_resid < xfersize)
|
|
xfersize = uio->uio_resid;
|
|
|
|
if (uio->uio_offset + xfersize > size of file)
|
|
vnode_pager_setsize(vp, uio->uio_offset + xfersize);
|
|
|
|
if (size > xfersize)
|
|
flags |= B_CLRBUF;
|
|
else
|
|
flags &= ~B_CLRBUF;
|
|
|
|
error = find_block_in_file(vp, lbn, blkoffset + xfersize,
|
|
cred, &bp, flags);
|
|
if (error)
|
|
break;
|
|
|
|
if (uio->uio_offset + xfersize > size of file)
|
|
set size of file to uio->uio_offset + xfersize;
|
|
|
|
error = uiomove((char *)bp->b_data + blkoffset, (int) xfersize, uio);
|
|
/* XXX ufs does not check the error here. Why? */
|
|
|
|
if (ioflag & IO_VMIO)
|
|
bp->b_flags |= B_RELBUF; /* ??? */
|
|
|
|
if (ioflag & IO_SYNC)
|
|
bwrite(bp);
|
|
else if (xfersize + blkoffset == size)
|
|
bawrite(bp);
|
|
else
|
|
bdwrite(bp);
|
|
|
|
if (error || xfersize == 0)
|
|
break;
|
|
}
|
|
|
|
if (error) {
|
|
if (ioflag & IO_UNIT) {
|
|
VOP_TRUNCATE(vp, osize, ioflag & IO_SYNC, cred, uio->uio_procp);
|
|
uio->uio_offset -= resid - uio->uio_resid;
|
|
uio->uio_resid = resid;
|
|
}
|
|
} else if (resid > uio->uio_resid && (ioflag & IO_SYNC)) {
|
|
struct timeval tv;
|
|
error = VOP_UPDATE(vp, &tv, &tv, 1); /* XXX what does this do? */
|
|
}
|
|
|
|
return error;
|
|
}
|
|
.Ed
|
|
.Sh ERRORS
|
|
.Bl -tag -width Er
|
|
.It Bq Er ENOSPC
|
|
The filesystem is full.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr vnode 9 ,
|
|
.Xr uiomove 9
|
|
.Sh AUTHORS
|
|
This man page was written by Doug Rabson.
|
|
|