[PATCH] Pull in FreeBSD's sglist

[Tim <bissont@xxxxxxx>]

---
 sys/conf/files         |    1 +
 sys/kern/subr_sglist.c |  711 ++++++++++++++++++++++++++++++++++++++++++++++++
 sys/sys/sglist.h       |  104 +++++++
 3 files changed, 816 insertions(+), 0 deletions(-)
 create mode 100644 sys/kern/subr_sglist.c
 create mode 100644 sys/sys/sglist.h

diff --git a/sys/conf/files b/sys/conf/files
index 3707744..e62dcf0 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -978,6 +978,7 @@ kern/subr_alist.c	standard
 kern/subr_blist.c	standard
 kern/subr_sbuf.c	standard
 kern/subr_scanf.c	standard
+kern/subr_sglist.c	standard
 kern/subr_taskqueue.c	standard
 kern/sys_generic.c	standard
 kern/sys_pipe.c		standard
diff --git a/sys/kern/subr_sglist.c b/sys/kern/subr_sglist.c
new file mode 100644
index 0000000..0d1bb80
--- /dev/null
+++ b/sys/kern/subr_sglist.c
@@ -0,0 +1,711 @@
+/*-
+ * 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>
+
+#include <sys/param.h>
+#include <sys/kernel.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/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);
+}
+
+/*
+ * 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 = kmalloc(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 (refcount_release(&sg->sg_refs))
+		kfree(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 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 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) {
+			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 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 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);
+}
diff --git a/sys/sys/sglist.h b/sys/sys/sglist.h
new file mode 100644
index 0000000..95d6dfa
--- /dev/null
+++ b/sys/sys/sglist.h
@@ -0,0 +1,104 @@
+/*-
+ * 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.
+ *
+ * $FreeBSD: src/sys/sys/sglist.h,v 1.1.2.2.4.1 2010/06/14 02:09:06 kensmith Exp $
+ */
+
+/*
+ * A scatter/gather list describes a group of physical address ranges.
+ * Each physical address range consists of a starting address and a
+ * length.
+ */
+
+#ifndef __SGLIST_H__
+#define	__SGLIST_H__
+
+#include <sys/refcount.h>
+
+struct sglist_seg {
+	vm_paddr_t	ss_paddr;
+	size_t		ss_len;
+};
+
+struct sglist {
+	struct sglist_seg *sg_segs;
+	int		sg_refs;
+	u_short		sg_nseg;
+	u_short		sg_maxseg;
+};
+
+struct mbuf;
+struct uio;
+
+static __inline void
+sglist_init(struct sglist *sg, u_short maxsegs, struct sglist_seg *segs)
+{
+
+	sg->sg_segs = segs;
+	sg->sg_nseg = 0;
+	sg->sg_maxseg = maxsegs;
+	refcount_init(&sg->sg_refs, 1);
+}
+
+static __inline void
+sglist_reset(struct sglist *sg)
+{
+
+	sg->sg_nseg = 0;
+}
+
+static __inline struct sglist *
+sglist_hold(struct sglist *sg)
+{
+
+	refcount_acquire(&sg->sg_refs);
+	return (sg);
+}
+
+struct sglist *sglist_alloc(int nsegs, int mflags);
+int	sglist_append(struct sglist *sg, void *buf, size_t len);
+int	sglist_append_mbuf(struct sglist *sg, struct mbuf *m0);
+int	sglist_append_phys(struct sglist *sg, vm_paddr_t paddr,
+	    size_t len);
+int	sglist_append_uio(struct sglist *sg, struct uio *uio);
+int	sglist_append_user(struct sglist *sg, void *buf, size_t len,
+	    struct thread *td);
+struct sglist *sglist_build(void *buf, size_t len, int mflags);
+struct sglist *sglist_clone(struct sglist *sg, int mflags);
+int	sglist_consume_uio(struct sglist *sg, struct uio *uio, size_t resid);
+int	sglist_count(void *buf, size_t len);
+void	sglist_free(struct sglist *sg);
+int	sglist_join(struct sglist *first, struct sglist *second);
+size_t	sglist_length(struct sglist *sg);
+int	sglist_slice(struct sglist *original, struct sglist **slice,
+	    size_t offset, size_t length, int mflags);
+int	sglist_split(struct sglist *original, struct sglist **head,
+	    size_t length, int mflags);
+
+#endif	/* !__SGLIST_H__ */
-- 
1.7.0.4


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