freebsd-dev/sys/kern/subr_bus_dma.c
Andrew Gallatin 23feb56348 KTLS: Re-work unmapped mbufs to carry ext_pgs in the mbuf itself.
While the original implementation of unmapped mbufs was a large
step forward in terms of reducing cache misses by enabling mbufs
to carry more than a single page for sendfile, they are rather
cache unfriendly when accessing the ext_pgs metadata and
data. This is because the ext_pgs part of the mbuf is allocated
separately, and almost guaranteed to be cold in cache.

This change takes advantage of the fact that unmapped mbufs
are never used at the same time as pkthdr mbufs. Given this
fact, we can overlap the ext_pgs metadata with the mbuf
pkthdr, and carry the ext_pgs meta directly in the mbuf itself.
Similarly, we can carry the ext_pgs data (TLS hdr/trailer/array
of pages) directly after the existing m_ext.

In order to be able to carry 5 pages (which is the minimum
required for a 16K TLS record which is not perfectly aligned) on
LP64, I've had to steal ext_arg2. The only user of this in the
xmit path is sendfile, and I've adjusted it to use arg1 when
using unmapped mbufs.

This change is almost entirely mechanical, except that we
change mb_alloc_ext_pgs() to no longer allow allocating
pkthdrs, the change to avoid ext_arg2 as mentioned above,
and the removal of the ext_pgs zone,

This change saves roughly 2% "raw" CPU (~59% -> 57%), or over
3% "scaled" CPU on a Netflix 100% software kTLS workload at
90+ Gb/s on Broadwell Xeons.

In a follow-on commit, I plan to remove some hacks to avoid
access ext_pgs fields of mbufs, since they will now be in
cache.

Many thanks to glebius for helping to make this better in
the Netflix tree.

Reviewed by:	hselasky, jhb, rrs, glebius (early version)
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D24213
2020-04-14 14:46:06 +00:00

689 lines
17 KiB
C

/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2012 EMC Corp.
* All rights reserved.
*
* Copyright (c) 1997, 1998 Justin T. Gibbs.
* All rights reserved.
*
* 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 AUTHOR 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 AUTHOR 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_bus.h"
#include <sys/param.h>
#include <sys/conf.h>
#include <sys/systm.h>
#include <sys/bio.h>
#include <sys/bus.h>
#include <sys/callout.h>
#include <sys/ktr.h>
#include <sys/mbuf.h>
#include <sys/memdesc.h>
#include <sys/proc.h>
#include <sys/uio.h>
#include <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/pmap.h>
#include <cam/cam.h>
#include <cam/cam_ccb.h>
#include <opencrypto/cryptodev.h>
#include <machine/bus.h>
/*
* Load up data starting at offset within a region specified by a
* list of virtual address ranges until either length or the region
* are exhausted.
*/
static int
_bus_dmamap_load_vlist(bus_dma_tag_t dmat, bus_dmamap_t map,
bus_dma_segment_t *list, int sglist_cnt, struct pmap *pmap, int *nsegs,
int flags, size_t offset, size_t length)
{
int error;
error = 0;
for (; sglist_cnt > 0 && length != 0; sglist_cnt--, list++) {
char *addr;
size_t ds_len;
KASSERT((offset < list->ds_len),
("Invalid mid-segment offset"));
addr = (char *)(uintptr_t)list->ds_addr + offset;
ds_len = list->ds_len - offset;
offset = 0;
if (ds_len > length)
ds_len = length;
length -= ds_len;
KASSERT((ds_len != 0), ("Segment length is zero"));
error = _bus_dmamap_load_buffer(dmat, map, addr, ds_len, pmap,
flags, NULL, nsegs);
if (error)
break;
}
return (error);
}
/*
* Load a list of physical addresses.
*/
static int
_bus_dmamap_load_plist(bus_dma_tag_t dmat, bus_dmamap_t map,
bus_dma_segment_t *list, int sglist_cnt, int *nsegs, int flags)
{
int error;
error = 0;
for (; sglist_cnt > 0; sglist_cnt--, list++) {
error = _bus_dmamap_load_phys(dmat, map,
(vm_paddr_t)list->ds_addr, list->ds_len, flags, NULL,
nsegs);
if (error)
break;
}
return (error);
}
/*
* Load an unmapped mbuf
*/
static int
_bus_dmamap_load_unmapped_mbuf_sg(bus_dma_tag_t dmat, bus_dmamap_t map,
struct mbuf *m, bus_dma_segment_t *segs, int *nsegs, int flags)
{
struct mbuf_ext_pgs *ext_pgs;
int error, i, off, len, pglen, pgoff, seglen, segoff;
MBUF_EXT_PGS_ASSERT(m);
ext_pgs = &m->m_ext_pgs;
len = m->m_len;
error = 0;
/* Skip over any data removed from the front. */
off = mtod(m, vm_offset_t);
if (ext_pgs->hdr_len != 0) {
if (off >= ext_pgs->hdr_len) {
off -= ext_pgs->hdr_len;
} else {
seglen = ext_pgs->hdr_len - off;
segoff = off;
seglen = min(seglen, len);
off = 0;
len -= seglen;
error = _bus_dmamap_load_buffer(dmat, map,
&ext_pgs->m_epg_hdr[segoff], seglen, kernel_pmap,
flags, segs, nsegs);
}
}
pgoff = ext_pgs->first_pg_off;
for (i = 0; i < ext_pgs->npgs && error == 0 && len > 0; i++) {
pglen = mbuf_ext_pg_len(ext_pgs, i, pgoff);
if (off >= pglen) {
off -= pglen;
pgoff = 0;
continue;
}
seglen = pglen - off;
segoff = pgoff + off;
off = 0;
seglen = min(seglen, len);
len -= seglen;
error = _bus_dmamap_load_phys(dmat, map,
ext_pgs->m_epg_pa[i] + segoff, seglen, flags, segs, nsegs);
pgoff = 0;
};
if (len != 0 && error == 0) {
KASSERT((off + len) <= ext_pgs->trail_len,
("off + len > trail (%d + %d > %d)", off, len,
ext_pgs->trail_len));
error = _bus_dmamap_load_buffer(dmat, map,
&ext_pgs->m_epg_trail[off], len, kernel_pmap, flags, segs,
nsegs);
}
return (error);
}
/*
* Load an mbuf chain.
*/
static int
_bus_dmamap_load_mbuf_sg(bus_dma_tag_t dmat, bus_dmamap_t map,
struct mbuf *m0, bus_dma_segment_t *segs, int *nsegs, int flags)
{
struct mbuf *m;
int error;
error = 0;
for (m = m0; m != NULL && error == 0; m = m->m_next) {
if (m->m_len > 0) {
if ((m->m_flags & M_NOMAP) != 0)
error = _bus_dmamap_load_unmapped_mbuf_sg(dmat,
map, m, segs, nsegs, flags);
else
error = _bus_dmamap_load_buffer(dmat, map,
m->m_data, m->m_len, kernel_pmap,
flags | BUS_DMA_LOAD_MBUF, segs, nsegs);
}
}
CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
__func__, dmat, flags, error, *nsegs);
return (error);
}
/*
* Load from block io.
*/
static int
_bus_dmamap_load_bio(bus_dma_tag_t dmat, bus_dmamap_t map, struct bio *bio,
int *nsegs, int flags)
{
if ((bio->bio_flags & BIO_VLIST) != 0) {
bus_dma_segment_t *segs = (bus_dma_segment_t *)bio->bio_data;
return (_bus_dmamap_load_vlist(dmat, map, segs, bio->bio_ma_n,
kernel_pmap, nsegs, flags, bio->bio_ma_offset,
bio->bio_bcount));
}
if ((bio->bio_flags & BIO_UNMAPPED) != 0)
return (_bus_dmamap_load_ma(dmat, map, bio->bio_ma,
bio->bio_bcount, bio->bio_ma_offset, flags, NULL, nsegs));
return (_bus_dmamap_load_buffer(dmat, map, bio->bio_data,
bio->bio_bcount, kernel_pmap, flags, NULL, nsegs));
}
int
bus_dmamap_load_ma_triv(bus_dma_tag_t dmat, bus_dmamap_t map,
struct vm_page **ma, bus_size_t tlen, int ma_offs, int flags,
bus_dma_segment_t *segs, int *segp)
{
vm_paddr_t paddr;
bus_size_t len;
int error, i;
error = 0;
for (i = 0; tlen > 0; i++, tlen -= len) {
len = min(PAGE_SIZE - ma_offs, tlen);
paddr = VM_PAGE_TO_PHYS(ma[i]) + ma_offs;
error = _bus_dmamap_load_phys(dmat, map, paddr, len,
flags, segs, segp);
if (error != 0)
break;
ma_offs = 0;
}
return (error);
}
/*
* Load a cam control block.
*/
static int
_bus_dmamap_load_ccb(bus_dma_tag_t dmat, bus_dmamap_t map, union ccb *ccb,
int *nsegs, int flags)
{
struct ccb_hdr *ccb_h;
void *data_ptr;
int error;
uint32_t dxfer_len;
uint16_t sglist_cnt;
error = 0;
ccb_h = &ccb->ccb_h;
switch (ccb_h->func_code) {
case XPT_SCSI_IO: {
struct ccb_scsiio *csio;
csio = &ccb->csio;
data_ptr = csio->data_ptr;
dxfer_len = csio->dxfer_len;
sglist_cnt = csio->sglist_cnt;
break;
}
case XPT_CONT_TARGET_IO: {
struct ccb_scsiio *ctio;
ctio = &ccb->ctio;
data_ptr = ctio->data_ptr;
dxfer_len = ctio->dxfer_len;
sglist_cnt = ctio->sglist_cnt;
break;
}
case XPT_ATA_IO: {
struct ccb_ataio *ataio;
ataio = &ccb->ataio;
data_ptr = ataio->data_ptr;
dxfer_len = ataio->dxfer_len;
sglist_cnt = 0;
break;
}
case XPT_NVME_IO:
case XPT_NVME_ADMIN: {
struct ccb_nvmeio *nvmeio;
nvmeio = &ccb->nvmeio;
data_ptr = nvmeio->data_ptr;
dxfer_len = nvmeio->dxfer_len;
sglist_cnt = nvmeio->sglist_cnt;
break;
}
default:
panic("_bus_dmamap_load_ccb: Unsupported func code %d",
ccb_h->func_code);
}
switch ((ccb_h->flags & CAM_DATA_MASK)) {
case CAM_DATA_VADDR:
error = _bus_dmamap_load_buffer(dmat, map, data_ptr, dxfer_len,
kernel_pmap, flags, NULL, nsegs);
break;
case CAM_DATA_PADDR:
error = _bus_dmamap_load_phys(dmat, map,
(vm_paddr_t)(uintptr_t)data_ptr, dxfer_len, flags, NULL,
nsegs);
break;
case CAM_DATA_SG:
error = _bus_dmamap_load_vlist(dmat, map,
(bus_dma_segment_t *)data_ptr, sglist_cnt, kernel_pmap,
nsegs, flags, 0, dxfer_len);
break;
case CAM_DATA_SG_PADDR:
error = _bus_dmamap_load_plist(dmat, map,
(bus_dma_segment_t *)data_ptr, sglist_cnt, nsegs, flags);
break;
case CAM_DATA_BIO:
error = _bus_dmamap_load_bio(dmat, map, (struct bio *)data_ptr,
nsegs, flags);
break;
default:
panic("_bus_dmamap_load_ccb: flags 0x%X unimplemented",
ccb_h->flags);
}
return (error);
}
/*
* Load a uio.
*/
static int
_bus_dmamap_load_uio(bus_dma_tag_t dmat, bus_dmamap_t map, struct uio *uio,
int *nsegs, int flags)
{
bus_size_t resid;
bus_size_t minlen;
struct iovec *iov;
pmap_t pmap;
caddr_t addr;
int error, i;
if (uio->uio_segflg == UIO_USERSPACE) {
KASSERT(uio->uio_td != NULL,
("bus_dmamap_load_uio: USERSPACE but no proc"));
pmap = vmspace_pmap(uio->uio_td->td_proc->p_vmspace);
} else
pmap = kernel_pmap;
resid = uio->uio_resid;
iov = uio->uio_iov;
error = 0;
for (i = 0; i < uio->uio_iovcnt && resid != 0 && !error; i++) {
/*
* Now at the first iovec to load. Load each iovec
* until we have exhausted the residual count.
*/
addr = (caddr_t) iov[i].iov_base;
minlen = resid < iov[i].iov_len ? resid : iov[i].iov_len;
if (minlen > 0) {
error = _bus_dmamap_load_buffer(dmat, map, addr,
minlen, pmap, flags, NULL, nsegs);
resid -= minlen;
}
}
return (error);
}
/*
* Map the buffer buf into bus space using the dmamap map.
*/
int
bus_dmamap_load(bus_dma_tag_t dmat, bus_dmamap_t map, void *buf,
bus_size_t buflen, bus_dmamap_callback_t *callback,
void *callback_arg, int flags)
{
bus_dma_segment_t *segs;
struct memdesc mem;
int error;
int nsegs;
if ((flags & BUS_DMA_NOWAIT) == 0) {
mem = memdesc_vaddr(buf, buflen);
_bus_dmamap_waitok(dmat, map, &mem, callback, callback_arg);
}
nsegs = -1;
error = _bus_dmamap_load_buffer(dmat, map, buf, buflen, kernel_pmap,
flags, NULL, &nsegs);
nsegs++;
CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
__func__, dmat, flags, error, nsegs);
if (error == EINPROGRESS)
return (error);
segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
if (error)
(*callback)(callback_arg, segs, 0, error);
else
(*callback)(callback_arg, segs, nsegs, 0);
/*
* Return ENOMEM to the caller so that it can pass it up the stack.
* This error only happens when NOWAIT is set, so deferral is disabled.
*/
if (error == ENOMEM)
return (error);
return (0);
}
int
bus_dmamap_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map, struct mbuf *m0,
bus_dmamap_callback2_t *callback, void *callback_arg, int flags)
{
bus_dma_segment_t *segs;
int nsegs, error;
M_ASSERTPKTHDR(m0);
flags |= BUS_DMA_NOWAIT;
nsegs = -1;
error = _bus_dmamap_load_mbuf_sg(dmat, map, m0, NULL, &nsegs, flags);
++nsegs;
segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
if (error)
(*callback)(callback_arg, segs, 0, 0, error);
else
(*callback)(callback_arg, segs, nsegs, m0->m_pkthdr.len, error);
CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
__func__, dmat, flags, error, nsegs);
return (error);
}
int
bus_dmamap_load_mbuf_sg(bus_dma_tag_t dmat, bus_dmamap_t map, struct mbuf *m0,
bus_dma_segment_t *segs, int *nsegs, int flags)
{
int error;
flags |= BUS_DMA_NOWAIT;
*nsegs = -1;
error = _bus_dmamap_load_mbuf_sg(dmat, map, m0, segs, nsegs, flags);
++*nsegs;
_bus_dmamap_complete(dmat, map, segs, *nsegs, error);
return (error);
}
int
bus_dmamap_load_uio(bus_dma_tag_t dmat, bus_dmamap_t map, struct uio *uio,
bus_dmamap_callback2_t *callback, void *callback_arg, int flags)
{
bus_dma_segment_t *segs;
int nsegs, error;
flags |= BUS_DMA_NOWAIT;
nsegs = -1;
error = _bus_dmamap_load_uio(dmat, map, uio, &nsegs, flags);
nsegs++;
segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
if (error)
(*callback)(callback_arg, segs, 0, 0, error);
else
(*callback)(callback_arg, segs, nsegs, uio->uio_resid, error);
CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
__func__, dmat, flags, error, nsegs);
return (error);
}
int
bus_dmamap_load_ccb(bus_dma_tag_t dmat, bus_dmamap_t map, union ccb *ccb,
bus_dmamap_callback_t *callback, void *callback_arg,
int flags)
{
bus_dma_segment_t *segs;
struct ccb_hdr *ccb_h;
struct memdesc mem;
int error;
int nsegs;
ccb_h = &ccb->ccb_h;
if ((ccb_h->flags & CAM_DIR_MASK) == CAM_DIR_NONE) {
callback(callback_arg, NULL, 0, 0);
return (0);
}
if ((flags & BUS_DMA_NOWAIT) == 0) {
mem = memdesc_ccb(ccb);
_bus_dmamap_waitok(dmat, map, &mem, callback, callback_arg);
}
nsegs = -1;
error = _bus_dmamap_load_ccb(dmat, map, ccb, &nsegs, flags);
nsegs++;
CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
__func__, dmat, flags, error, nsegs);
if (error == EINPROGRESS)
return (error);
segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
if (error)
(*callback)(callback_arg, segs, 0, error);
else
(*callback)(callback_arg, segs, nsegs, error);
/*
* Return ENOMEM to the caller so that it can pass it up the stack.
* This error only happens when NOWAIT is set, so deferral is disabled.
*/
if (error == ENOMEM)
return (error);
return (0);
}
int
bus_dmamap_load_bio(bus_dma_tag_t dmat, bus_dmamap_t map, struct bio *bio,
bus_dmamap_callback_t *callback, void *callback_arg,
int flags)
{
bus_dma_segment_t *segs;
struct memdesc mem;
int error;
int nsegs;
if ((flags & BUS_DMA_NOWAIT) == 0) {
mem = memdesc_bio(bio);
_bus_dmamap_waitok(dmat, map, &mem, callback, callback_arg);
}
nsegs = -1;
error = _bus_dmamap_load_bio(dmat, map, bio, &nsegs, flags);
nsegs++;
CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
__func__, dmat, flags, error, nsegs);
if (error == EINPROGRESS)
return (error);
segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
if (error)
(*callback)(callback_arg, segs, 0, error);
else
(*callback)(callback_arg, segs, nsegs, error);
/*
* Return ENOMEM to the caller so that it can pass it up the stack.
* This error only happens when NOWAIT is set, so deferral is disabled.
*/
if (error == ENOMEM)
return (error);
return (0);
}
int
bus_dmamap_load_mem(bus_dma_tag_t dmat, bus_dmamap_t map,
struct memdesc *mem, bus_dmamap_callback_t *callback,
void *callback_arg, int flags)
{
bus_dma_segment_t *segs;
int error;
int nsegs;
if ((flags & BUS_DMA_NOWAIT) == 0)
_bus_dmamap_waitok(dmat, map, mem, callback, callback_arg);
nsegs = -1;
error = 0;
switch (mem->md_type) {
case MEMDESC_VADDR:
error = _bus_dmamap_load_buffer(dmat, map, mem->u.md_vaddr,
mem->md_opaque, kernel_pmap, flags, NULL, &nsegs);
break;
case MEMDESC_PADDR:
error = _bus_dmamap_load_phys(dmat, map, mem->u.md_paddr,
mem->md_opaque, flags, NULL, &nsegs);
break;
case MEMDESC_VLIST:
error = _bus_dmamap_load_vlist(dmat, map, mem->u.md_list,
mem->md_opaque, kernel_pmap, &nsegs, flags, 0, SIZE_T_MAX);
break;
case MEMDESC_PLIST:
error = _bus_dmamap_load_plist(dmat, map, mem->u.md_list,
mem->md_opaque, &nsegs, flags);
break;
case MEMDESC_BIO:
error = _bus_dmamap_load_bio(dmat, map, mem->u.md_bio,
&nsegs, flags);
break;
case MEMDESC_UIO:
error = _bus_dmamap_load_uio(dmat, map, mem->u.md_uio,
&nsegs, flags);
break;
case MEMDESC_MBUF:
error = _bus_dmamap_load_mbuf_sg(dmat, map, mem->u.md_mbuf,
NULL, &nsegs, flags);
break;
case MEMDESC_CCB:
error = _bus_dmamap_load_ccb(dmat, map, mem->u.md_ccb, &nsegs,
flags);
break;
}
nsegs++;
CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
__func__, dmat, flags, error, nsegs);
if (error == EINPROGRESS)
return (error);
segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
if (error)
(*callback)(callback_arg, segs, 0, error);
else
(*callback)(callback_arg, segs, nsegs, 0);
/*
* Return ENOMEM to the caller so that it can pass it up the stack.
* This error only happens when NOWAIT is set, so deferral is disabled.
*/
if (error == ENOMEM)
return (error);
return (0);
}
int
bus_dmamap_load_crp(bus_dma_tag_t dmat, bus_dmamap_t map, struct cryptop *crp,
bus_dmamap_callback_t *callback, void *callback_arg, int flags)
{
bus_dma_segment_t *segs;
int error;
int nsegs;
flags |= BUS_DMA_NOWAIT;
nsegs = -1;
error = 0;
switch (crp->crp_buf_type) {
case CRYPTO_BUF_CONTIG:
error = _bus_dmamap_load_buffer(dmat, map, crp->crp_buf,
crp->crp_ilen, kernel_pmap, flags, NULL, &nsegs);
break;
case CRYPTO_BUF_MBUF:
error = _bus_dmamap_load_mbuf_sg(dmat, map, crp->crp_mbuf,
NULL, &nsegs, flags);
break;
case CRYPTO_BUF_UIO:
error = _bus_dmamap_load_uio(dmat, map, crp->crp_uio, &nsegs,
flags);
break;
}
nsegs++;
CTR5(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d nsegs %d",
__func__, dmat, flags, error, nsegs);
if (error == EINPROGRESS)
return (error);
segs = _bus_dmamap_complete(dmat, map, NULL, nsegs, error);
if (error)
(*callback)(callback_arg, segs, 0, error);
else
(*callback)(callback_arg, segs, nsegs, 0);
/*
* Return ENOMEM to the caller so that it can pass it up the stack.
* This error only happens when NOWAIT is set, so deferral is disabled.
*/
if (error == ENOMEM)
return (error);
return (0);
}