/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 2008 Yahoo!, Inc.
* All rights reserved.
* Written by: John Baldwin <jhb@FreeBSD.org>
*
* 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.
* 3. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* 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 <sys/param.h>
#include <sys/kernel.h>
#include <sys/bio.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/proc.h>
#include <sys/sglist.h>
#include <sys/uio.h>
#include <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <sys/ktr.h>
static MALLOC_DEFINE(M_SGLIST, "sglist", "scatter/gather lists");
/*
* Convenience macros to save the state of an sglist so it can be restored
* if an append attempt fails. Since sglist's only grow we only need to
* save the current count of segments and the length of the ending segment.
* Earlier segments will not be changed by an append, and the only change
* that can occur to the ending segment is that it can be extended.
*/
struct sgsave {
u_short sg_nseg;
size_t ss_len;
};
#define SGLIST_SAVE(sg, sgsave) do { \
(sgsave).sg_nseg = (sg)->sg_nseg; \
if ((sgsave).sg_nseg > 0) \
(sgsave).ss_len = (sg)->sg_segs[(sgsave).sg_nseg - 1].ss_len; \
else \
(sgsave).ss_len = 0; \
} while (0)
#define SGLIST_RESTORE(sg, sgsave) do { \
(sg)->sg_nseg = (sgsave).sg_nseg; \
if ((sgsave).sg_nseg > 0) \
(sg)->sg_segs[(sgsave).sg_nseg - 1].ss_len = (sgsave).ss_len; \
} while (0)
/*
* Append a single (paddr, len) to a sglist. sg is the list and ss is
* the current segment in the list. If we run out of segments then
* EFBIG will be returned.
*/
static __inline int
_sglist_append_range(struct sglist *sg, struct sglist_seg **ssp,
vm_paddr_t paddr, size_t len)
{
struct sglist_seg *ss;
ss = *ssp;
if (ss->ss_paddr + ss->ss_len == paddr)
ss->ss_len += len;
else {
if (sg->sg_nseg == sg->sg_maxseg)
return (EFBIG);
ss++;
ss->ss_paddr = paddr;
ss->ss_len = len;
sg->sg_nseg++;
*ssp = ss;
}
return (0);
}
/*
* Worker routine to append a virtual address range (either kernel or
* user) to a scatter/gather list.
*/
static __inline int
_sglist_append_buf(struct sglist *sg, void *buf, size_t len, pmap_t pmap,
size_t *donep)
{
struct sglist_seg *ss;
vm_offset_t vaddr, offset;
vm_paddr_t paddr;
size_t seglen;
int error;
if (donep)
*donep = 0;
if (len == 0)
return (0);
/* Do the first page. It may have an offset. */
vaddr = (vm_offset_t)buf;
offset = vaddr & PAGE_MASK;
if (pmap != NULL)
paddr = pmap_extract(pmap, vaddr);
else
paddr = pmap_kextract(vaddr);
seglen = MIN(len, PAGE_SIZE - offset);
if (sg->sg_nseg == 0) {
ss = sg->sg_segs;
ss->ss_paddr = paddr;
ss->ss_len = seglen;
sg->sg_nseg = 1;
} else {
ss = &sg->sg_segs[sg->sg_nseg - 1];
error = _sglist_append_range(sg, &ss, paddr, seglen);
if (error)
return (error);
}
vaddr += seglen;
len -= seglen;
if (donep)
*donep += seglen;
while (len > 0) {
seglen = MIN(len, PAGE_SIZE);
if (pmap != NULL)
paddr = pmap_extract(pmap, vaddr);
else
paddr = pmap_kextract(vaddr);
error = _sglist_append_range(sg, &ss, paddr, seglen);
if (error)
return (error);
vaddr += seglen;
len -= seglen;
if (donep)
*donep += seglen;
}
return (0);
}
/*
* Determine the number of scatter/gather list elements needed to
* describe a kernel virtual address range.
*/
int
sglist_count(void *buf, size_t len)
{
vm_offset_t vaddr, vendaddr;
vm_paddr_t lastaddr, paddr;
int nsegs;
if (len == 0)
return (0);
vaddr = trunc_page((vm_offset_t)buf);
vendaddr = (vm_offset_t)buf + len;
nsegs = 1;
lastaddr = pmap_kextract(vaddr);
vaddr += PAGE_SIZE;
while (vaddr < vendaddr) {
paddr = pmap_kextract(vaddr);
if (lastaddr + PAGE_SIZE != paddr)
nsegs++;
lastaddr = paddr;
vaddr += PAGE_SIZE;
}
return (nsegs);
}
/*
* Determine the number of scatter/gather list elements needed to
* describe a buffer backed by an array of VM pages.
*/
int
sglist_count_vmpages(vm_page_t *m, size_t pgoff, size_t len)
{
vm_paddr_t lastaddr, paddr;
int i, nsegs;
if (len == 0)
return (0);
len += pgoff;
nsegs = 1;
lastaddr = VM_PAGE_TO_PHYS(m[0]);
for (i = 1; len > PAGE_SIZE; len -= PAGE_SIZE, i++) {
paddr = VM_PAGE_TO_PHYS(m[i]);
if (lastaddr + PAGE_SIZE != paddr)
nsegs++;
lastaddr = paddr;
}
return (nsegs);
}
/*
* Determine the number of scatter/gather list elements needed to
* describe an M_EXTPG mbuf.
*/
int
sglist_count_mbuf_epg(struct mbuf *m, size_t off, size_t len)
{
vm_paddr_t nextaddr, paddr;
size_t seglen, segoff;
int i, nsegs, pglen, pgoff;
if (len == 0)
return (0);
nsegs = 0;
if (m->m_epg_hdrlen != 0) {
if (off >= m->m_epg_hdrlen) {
off -= m->m_epg_hdrlen;
} else {
seglen = m->m_epg_hdrlen - off;
segoff = off;
seglen = MIN(seglen, len);
off = 0;
len -= seglen;
nsegs += sglist_count(&m->m_epg_hdr[segoff],
seglen);
}
}
nextaddr = 0;
pgoff = m->m_epg_1st_off;
for (i = 0; i < m->m_epg_npgs && len > 0; i++) {
pglen = m_epg_pagelen(m, i, pgoff);
if (off >= pglen) {
off -= pglen;
pgoff = 0;
continue;
}
seglen = pglen - off;
segoff = pgoff + off;
off = 0;
seglen = MIN(seglen, len);
len -= seglen;
paddr = m->m_epg_pa[i] + segoff;
if (paddr != nextaddr)
nsegs++;
nextaddr = paddr + seglen;
pgoff = 0;
};
if (len != 0) {
seglen = MIN(len, m->m_epg_trllen - off);
len -= seglen;
nsegs += sglist_count(&m->m_epg_trail[off], seglen);
}
KASSERT(len == 0, ("len != 0"));
return (nsegs);
}
/*
* Allocate a scatter/gather list along with 'nsegs' segments. The
* 'mflags' parameters are the same as passed to malloc(9). The caller
* should use sglist_free() to free this list.
*/
struct sglist *
sglist_alloc(int nsegs, int mflags)
{
struct sglist *sg;
sg = malloc(sizeof(struct sglist) + nsegs * sizeof(struct sglist_seg),
M_SGLIST, mflags);
if (sg == NULL)
return (NULL);
sglist_init(sg, nsegs, (struct sglist_seg *)(sg + 1));
return (sg);
}
/*
* Free a scatter/gather list allocated via sglist_allc().
*/
void
sglist_free(struct sglist *sg)
{
if (sg == NULL)
return;
if (refcount_release(&sg->sg_refs))
free(sg, M_SGLIST);
}
/*
* Append the segments to describe a single kernel virtual address
* range to a scatter/gather list. If there are insufficient
* segments, then this fails with EFBIG.
*/
int
sglist_append(struct sglist *sg, void *buf, size_t len)
{
struct sgsave save;
int error;
if (sg->sg_maxseg == 0)
return (EINVAL);
SGLIST_SAVE(sg, save);
error = _sglist_append_buf(sg, buf, len, NULL, NULL);
if (error)
SGLIST_RESTORE(sg, save);
return (error);
}
/*
* Append the segments to describe a bio's data to a scatter/gather list.
* If there are insufficient segments, then this fails with EFBIG.
*
* NOTE: This function expects bio_bcount to be initialized.
*/
int
sglist_append_bio(struct sglist *sg, struct bio *bp)
{
int error;
if ((bp->bio_flags & BIO_UNMAPPED) == 0)
error = sglist_append(sg, bp->bio_data, bp->bio_bcount);
else
error = sglist_append_vmpages(sg, bp->bio_ma,
bp->bio_ma_offset, bp->bio_bcount);
return (error);
}
/*
* Append a single physical address range to a scatter/gather list.
* If there are insufficient segments, then this fails with EFBIG.
*/
int
sglist_append_phys(struct sglist *sg, vm_paddr_t paddr, size_t len)
{
struct sglist_seg *ss;
struct sgsave save;
int error;
if (sg->sg_maxseg == 0)
return (EINVAL);
if (len == 0)
return (0);
if (sg->sg_nseg == 0) {
sg->sg_segs[0].ss_paddr = paddr;
sg->sg_segs[0].ss_len = len;
sg->sg_nseg = 1;
return (0);
}
ss = &sg->sg_segs[sg->sg_nseg - 1];
SGLIST_SAVE(sg, save);
error = _sglist_append_range(sg, &ss, paddr, len);
if (error)
SGLIST_RESTORE(sg, save);
return (error);
}
/*
* Append the segments of single multi-page mbuf.
* If there are insufficient segments, then this fails with EFBIG.
*/
int
sglist_append_mbuf_epg(struct sglist *sg, struct mbuf *m, size_t off,
size_t len)
{
size_t seglen, segoff;
vm_paddr_t paddr;
int error, i, pglen, pgoff;
M_ASSERTEXTPG(m);
error = 0;
if (m->m_epg_hdrlen != 0) {
if (off >= m->m_epg_hdrlen) {
off -= m->m_epg_hdrlen;
} else {
seglen = m->m_epg_hdrlen - off;
segoff = off;
seglen = MIN(seglen, len);
off = 0;
len -= seglen;
error = sglist_append(sg,
&m->m_epg_hdr[segoff], seglen);
}
}
pgoff = m->m_epg_1st_off;
for (i = 0; i < m->m_epg_npgs && error == 0 && len > 0; i++) {
pglen = m_epg_pagelen(m, i, pgoff);
if (off >= pglen) {
off -= pglen;
pgoff = 0;
continue;
}
seglen = pglen - off;
segoff = pgoff + off;
off = 0;
seglen = MIN(seglen, len);
len -= seglen;
paddr = m->m_epg_pa[i] + segoff;
error = sglist_append_phys(sg, paddr, seglen);
pgoff = 0;
};
if (error == 0 && len > 0) {
seglen = MIN(len, m->m_epg_trllen - off);
len -= seglen;
error = sglist_append(sg,
&m->m_epg_trail[off], seglen);
}
if (error == 0)
KASSERT(len == 0, ("len != 0"));
return (error);
}
/*
* Append the segments that describe a single mbuf chain to a
* scatter/gather list. If there are insufficient segments, then this
* fails with EFBIG.
*/
int
sglist_append_mbuf(struct sglist *sg, struct mbuf *m0)
{
struct sgsave save;
struct mbuf *m;
int error;
if (sg->sg_maxseg == 0)
return (EINVAL);
error = 0;
SGLIST_SAVE(sg, save);
for (m = m0; m != NULL; m = m->m_next) {
if (m->m_len > 0) {
if ((m->m_flags & M_EXTPG) != 0)
error = sglist_append_mbuf_epg(sg, m,
mtod(m, vm_offset_t), m->m_len);
else
error = sglist_append(sg, m->m_data,
m->m_len);
if (error) {
SGLIST_RESTORE(sg, save);
return (error);
}
}
}
return (0);
}
/*
* Append the segments that describe a buffer spanning an array of VM
* pages. The buffer begins at an offset of 'pgoff' in the first
* page.
*/
int
sglist_append_vmpages(struct sglist *sg, vm_page_t *m, size_t pgoff,
size_t len)
{
struct sgsave save;
struct sglist_seg *ss;
vm_paddr_t paddr;
size_t seglen;
int error, i;
if (sg->sg_maxseg == 0)
return (EINVAL);
if (len == 0)
return (0);
SGLIST_SAVE(sg, save);
i = 0;
if (sg->sg_nseg == 0) {
seglen = min(PAGE_SIZE - pgoff, len);
sg->sg_segs[0].ss_paddr = VM_PAGE_TO_PHYS(m[0]) + pgoff;
sg->sg_segs[0].ss_len = seglen;
sg->sg_nseg = 1;
pgoff = 0;
len -= seglen;
i++;
}
ss = &sg->sg_segs[sg->sg_nseg - 1];
for (; len > 0; i++, len -= seglen) {
seglen = min(PAGE_SIZE - pgoff, len);
paddr = VM_PAGE_TO_PHYS(m[i]) + pgoff;
error = _sglist_append_range(sg, &ss, paddr, seglen);
if (error) {
SGLIST_RESTORE(sg, save);
return (error);
}
pgoff = 0;
}
return (0);
}
/*
* Append the segments that describe a single user address range to a
* scatter/gather list. If there are insufficient segments, then this
* fails with EFBIG.
*/
int
sglist_append_user(struct sglist *sg, void *buf, size_t len, struct thread *td)
{
struct sgsave save;
int error;
if (sg->sg_maxseg == 0)
return (EINVAL);
SGLIST_SAVE(sg, save);
error = _sglist_append_buf(sg, buf, len,
vmspace_pmap(td->td_proc->p_vmspace), NULL);
if (error)
SGLIST_RESTORE(sg, save);
return (error);
}
/*
* Append a subset of an existing scatter/gather list 'source' to a
* the scatter/gather list 'sg'. If there are insufficient segments,
* then this fails with EFBIG.
*/
int
sglist_append_sglist(struct sglist *sg, struct sglist *source, size_t offset,
size_t length)
{
struct sgsave save;
struct sglist_seg *ss;
size_t seglen;
int error, i;
if (sg->sg_maxseg == 0 || length == 0)
return (EINVAL);
SGLIST_SAVE(sg, save);
error = EINVAL;
ss = &sg->sg_segs[sg->sg_nseg - 1];
for (i = 0; i < source->sg_nseg; i++) {
if (offset >= source->sg_segs[i].ss_len) {
offset -= source->sg_segs[i].ss_len;
continue;
}
seglen = source->sg_segs[i].ss_len - offset;
if (seglen > length)
seglen = length;
error = _sglist_append_range(sg, &ss,
source->sg_segs[i].ss_paddr + offset, seglen);
if (error)
break;
offset = 0;
length -= seglen;
if (length == 0)
break;
}
if (length != 0)
error = EINVAL;
if (error)
SGLIST_RESTORE(sg, save);
return (error);
}
/*
* Append the segments that describe a single uio to a scatter/gather
* list. If there are insufficient segments, then this fails with
* EFBIG.
*/
int
sglist_append_uio(struct sglist *sg, struct uio *uio)
{
struct iovec *iov;
struct sgsave save;
size_t resid, minlen;
pmap_t pmap;
int error, i;
if (sg->sg_maxseg == 0)
return (EINVAL);
resid = uio->uio_resid;
iov = uio->uio_iov;
if (uio->uio_segflg == UIO_USERSPACE) {
KASSERT(uio->uio_td != NULL,
("sglist_append_uio: USERSPACE but no thread"));
pmap = vmspace_pmap(uio->uio_td->td_proc->p_vmspace);
} else
pmap = NULL;
error = 0;
SGLIST_SAVE(sg, save);
for (i = 0; i < uio->uio_iovcnt && resid != 0; i++) {
/*
* Now at the first iovec to load. Load each iovec
* until we have exhausted the residual count.
*/
minlen = MIN(resid, iov[i].iov_len);
if (minlen > 0) {
error = _sglist_append_buf(sg, iov[i].iov_base, minlen,
pmap, NULL);
if (error) {
SGLIST_RESTORE(sg, save);
return (error);
}
resid -= minlen;
}
}
return (0);
}
/*
* Append the segments that describe at most 'resid' bytes from a
* single uio to a scatter/gather list. If there are insufficient
* segments, then only the amount that fits is appended.
*/
int
sglist_consume_uio(struct sglist *sg, struct uio *uio, size_t resid)
{
struct iovec *iov;
size_t done;
pmap_t pmap;
int error, len;
if (sg->sg_maxseg == 0)
return (EINVAL);
if (uio->uio_segflg == UIO_USERSPACE) {
KASSERT(uio->uio_td != NULL,
("sglist_consume_uio: USERSPACE but no thread"));
pmap = vmspace_pmap(uio->uio_td->td_proc->p_vmspace);
} else
pmap = NULL;
error = 0;
while (resid > 0 && uio->uio_resid) {
iov = uio->uio_iov;
len = iov->iov_len;
if (len == 0) {
uio->uio_iov++;
uio->uio_iovcnt--;
continue;
}
if (len > resid)
len = resid;
/*
* Try to append this iovec. If we run out of room,
* then break out of the loop.
*/
error = _sglist_append_buf(sg, iov->iov_base, len, pmap, &done);
iov->iov_base = (char *)iov->iov_base + done;
iov->iov_len -= done;
uio->uio_resid -= done;
uio->uio_offset += done;
resid -= done;
if (error)
break;
}
return (0);
}
/*
* Allocate and populate a scatter/gather list to describe a single
* kernel virtual address range.
*/
struct sglist *
sglist_build(void *buf, size_t len, int mflags)
{
struct sglist *sg;
int nsegs;
if (len == 0)
return (NULL);
nsegs = sglist_count(buf, len);
sg = sglist_alloc(nsegs, mflags);
if (sg == NULL)
return (NULL);
if (sglist_append(sg, buf, len) != 0) {
sglist_free(sg);
return (NULL);
}
return (sg);
}
/*
* Clone a new copy of a scatter/gather list.
*/
struct sglist *
sglist_clone(struct sglist *sg, int mflags)
{
struct sglist *new;
if (sg == NULL)
return (NULL);
new = sglist_alloc(sg->sg_maxseg, mflags);
if (new == NULL)
return (NULL);
new->sg_nseg = sg->sg_nseg;
bcopy(sg->sg_segs, new->sg_segs, sizeof(struct sglist_seg) *
sg->sg_nseg);
return (new);
}
/*
* Calculate the total length of the segments described in a
* scatter/gather list.
*/
size_t
sglist_length(struct sglist *sg)
{
size_t space;
int i;
space = 0;
for (i = 0; i < sg->sg_nseg; i++)
space += sg->sg_segs[i].ss_len;
return (space);
}
/*
* Split a scatter/gather list into two lists. The scatter/gather
* entries for the first 'length' bytes of the 'original' list are
* stored in the '*head' list and are removed from 'original'.
*
* If '*head' is NULL, then a new list will be allocated using
* 'mflags'. If M_NOWAIT is specified and the allocation fails,
* ENOMEM will be returned.
*
* If '*head' is not NULL, it should point to an empty sglist. If it
* does not have enough room for the remaining space, then EFBIG will
* be returned. If '*head' is not empty, then EINVAL will be
* returned.
*
* If 'original' is shared (refcount > 1), then EDOOFUS will be
* returned.
*/
int
sglist_split(struct sglist *original, struct sglist **head, size_t length,
int mflags)
{
struct sglist *sg;
size_t space, split;
int count, i;
if (original->sg_refs > 1)
return (EDOOFUS);
/* Figure out how big of a sglist '*head' has to hold. */
count = 0;
space = 0;
split = 0;
for (i = 0; i < original->sg_nseg; i++) {
space += original->sg_segs[i].ss_len;
count++;
if (space >= length) {
/*
* If 'length' falls in the middle of a
* scatter/gather list entry, then 'split'
* holds how much of that entry will remain in
* 'original'.
*/
split = space - length;
break;
}
}
/* Nothing to do, so leave head empty. */
if (count == 0)
return (0);
if (*head == NULL) {
sg = sglist_alloc(count, mflags);
if (sg == NULL)
return (ENOMEM);
*head = sg;
} else {
sg = *head;
if (sg->sg_maxseg < count)
return (EFBIG);
if (sg->sg_nseg != 0)
return (EINVAL);
}
/* Copy 'count' entries to 'sg' from 'original'. */
bcopy(original->sg_segs, sg->sg_segs, count *
sizeof(struct sglist_seg));
sg->sg_nseg = count;
/*
* If we had to split a list entry, fixup the last entry in
* 'sg' and the new first entry in 'original'. We also
* decrement 'count' by 1 since we will only be removing
* 'count - 1' segments from 'original' now.
*/
if (split != 0) {
count--;
sg->sg_segs[count].ss_len -= split;
original->sg_segs[count].ss_paddr =
sg->sg_segs[count].ss_paddr + split;
original->sg_segs[count].ss_len = split;
}
/* Trim 'count' entries from the front of 'original'. */
original->sg_nseg -= count;
bcopy(original->sg_segs + count, original->sg_segs, count *
sizeof(struct sglist_seg));
return (0);
}
/*
* Append the scatter/gather list elements in 'second' to the
* scatter/gather list 'first'. If there is not enough space in
* 'first', EFBIG is returned.
*/
int
sglist_join(struct sglist *first, struct sglist *second)
{
struct sglist_seg *flast, *sfirst;
int append;
/* If 'second' is empty, there is nothing to do. */
if (second->sg_nseg == 0)
return (0);
/*
* If the first entry in 'second' can be appended to the last entry
* in 'first' then set append to '1'.
*/
append = 0;
flast = &first->sg_segs[first->sg_nseg - 1];
sfirst = &second->sg_segs[0];
if (first->sg_nseg != 0 &&
flast->ss_paddr + flast->ss_len == sfirst->ss_paddr)
append = 1;
/* Make sure 'first' has enough room. */
if (first->sg_nseg + second->sg_nseg - append > first->sg_maxseg)
return (EFBIG);
/* Merge last in 'first' and first in 'second' if needed. */
if (append)
flast->ss_len += sfirst->ss_len;
/* Append new segments from 'second' to 'first'. */
bcopy(first->sg_segs + first->sg_nseg, second->sg_segs + append,
(second->sg_nseg - append) * sizeof(struct sglist_seg));
first->sg_nseg += second->sg_nseg - append;
sglist_reset(second);
return (0);
}
/*
* Generate a new scatter/gather list from a range of an existing
* scatter/gather list. The 'offset' and 'length' parameters specify
* the logical range of the 'original' list to extract. If that range
* is not a subset of the length of 'original', then EINVAL is
* returned. The new scatter/gather list is stored in '*slice'.
*
* If '*slice' is NULL, then a new list will be allocated using
* 'mflags'. If M_NOWAIT is specified and the allocation fails,
* ENOMEM will be returned.
*
* If '*slice' is not NULL, it should point to an empty sglist. If it
* does not have enough room for the remaining space, then EFBIG will
* be returned. If '*slice' is not empty, then EINVAL will be
* returned.
*/
int
sglist_slice(struct sglist *original, struct sglist **slice, size_t offset,
size_t length, int mflags)
{
struct sglist *sg;
size_t space, end, foffs, loffs;
int count, i, fseg;
/* Nothing to do. */
if (length == 0)
return (0);
/* Figure out how many segments '*slice' needs to have. */
end = offset + length;
space = 0;
count = 0;
fseg = 0;
foffs = loffs = 0;
for (i = 0; i < original->sg_nseg; i++) {
space += original->sg_segs[i].ss_len;
if (space > offset) {
/*
* When we hit the first segment, store its index
* in 'fseg' and the offset into the first segment
* of 'offset' in 'foffs'.
*/
if (count == 0) {
fseg = i;
foffs = offset - (space -
original->sg_segs[i].ss_len);
CTR1(KTR_DEV, "sglist_slice: foffs = %08lx",
foffs);
}
count++;
/*
* When we hit the last segment, break out of
* the loop. Store the amount of extra space
* at the end of this segment in 'loffs'.
*/
if (space >= end) {
loffs = space - end;
CTR1(KTR_DEV, "sglist_slice: loffs = %08lx",
loffs);
break;
}
}
}
/* If we never hit 'end', then 'length' ran off the end, so fail. */
if (space < end)
return (EINVAL);
if (*slice == NULL) {
sg = sglist_alloc(count, mflags);
if (sg == NULL)
return (ENOMEM);
*slice = sg;
} else {
sg = *slice;
if (sg->sg_maxseg < count)
return (EFBIG);
if (sg->sg_nseg != 0)
return (EINVAL);
}
/*
* Copy over 'count' segments from 'original' starting at
* 'fseg' to 'sg'.
*/
bcopy(original->sg_segs + fseg, sg->sg_segs,
count * sizeof(struct sglist_seg));
sg->sg_nseg = count;
/* Fixup first and last segments if needed. */
if (foffs != 0) {
sg->sg_segs[0].ss_paddr += foffs;
sg->sg_segs[0].ss_len -= foffs;
CTR2(KTR_DEV, "sglist_slice seg[0]: %08lx:%08lx",
(long)sg->sg_segs[0].ss_paddr, sg->sg_segs[0].ss_len);
}
if (loffs != 0) {
sg->sg_segs[count - 1].ss_len -= loffs;
CTR2(KTR_DEV, "sglist_slice seg[%d]: len %08x", count - 1,
sg->sg_segs[count - 1].ss_len);
}
return (0);
}
