CONTENTS

SYNOPSIS

DESCRIPTION

The arguments are:

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 units of file system blocks) that the file system should attempt. The low 16 bits are a bit mask which can contain the following flags:

LOCKS

RETURN VALUES

PSEUDOCODE

size = block size of file system;

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 file system;
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) {
/* call private routine to truncate file. */
your_truncate(vp, osize, ioflag & IO_SYNC, cred, uio->uio_td);
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? */
}

SEE ALSO

AUTHORS