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Subject[PATCH 4/8] [I/OAT] Utility functions for offloading sk_buff to iovec copies
Date
Provides for pinning user space pages in memory, copying to iovecs,
and copying from sk_buffs including fragmented and chained sk_buffs.

Signed-off-by: Chris Leech <christopher.leech@intel.com>
---
drivers/dma/Makefile | 1
drivers/dma/iovlock.c | 320 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/dmaengine.h | 24 +++
include/net/netdma.h | 5 +
net/core/Makefile | 3
net/core/user_dma.c | 133 +++++++++++++++++++
6 files changed, 485 insertions(+), 1 deletions(-)
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index c8a5f56..ea2f110 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -1,2 +1,3 @@
obj-y += dmaengine.o
+obj-$(CONFIG_NET_DMA) += iovlock.o
obj-$(CONFIG_INTEL_IOATDMA) += ioatdma.o
diff --git a/drivers/dma/iovlock.c b/drivers/dma/iovlock.c
new file mode 100644
index 0000000..edbf581
--- /dev/null
+++ b/drivers/dma/iovlock.c
@@ -0,0 +1,320 @@
+/*****************************************************************************
+Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
+Portions based on net/core/datagram.c and copyrighted by their authors.
+
+This program is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2 of the License, or (at your option)
+any later version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc., 59
+Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+The full GNU General Public License is included in this distribution in the
+file called LICENSE.
+*****************************************************************************/
+
+/*
+ * This code allows the net stack to make use of a DMA engine for
+ * skb to iovec copies.
+ */
+
+#include <linux/dmaengine.h>
+#include <linux/pagemap.h>
+#include <net/tcp.h> /* for memcpy_toiovec */
+#include <asm/io.h>
+#include <asm/uaccess.h>
+
+#ifdef CONFIG_DMA_ENGINE
+
+#define NUM_PAGES_SPANNED(start, length) \
+ ((PAGE_ALIGN((unsigned long)start + length) - \
+ ((unsigned long)start & PAGE_MASK)) >> PAGE_SHIFT)
+
+/*
+ * Lock down all the iovec pages needed for len bytes.
+ * Return a struct dma_locked_list to keep track of pages locked down.
+ *
+ * We are allocating a single chunk of memory, and then carving it up into
+ * 3 sections, the latter 2 whose size depends on the number of iovecs and the
+ * total number of pages, respectively.
+ */
+int dma_lock_iovec_pages(struct iovec *iov, size_t len, struct dma_locked_list
+ **locked_list)
+{
+ struct dma_locked_list *local_list;
+ struct page **pages;
+ int i;
+ int ret;
+
+ int nr_iovecs = 0;
+ int iovec_len_used = 0;
+ int iovec_pages_used = 0;
+
+ /* don't lock down non-user-based iovecs */
+ if (segment_eq(get_fs(), KERNEL_DS)) {
+ *locked_list = NULL;
+ return 0;
+ }
+
+ /* determine how many iovecs/pages there are, up front */
+ do {
+ iovec_len_used += iov[nr_iovecs].iov_len;
+ iovec_pages_used += NUM_PAGES_SPANNED(iov[nr_iovecs].iov_base,
+ iov[nr_iovecs].iov_len);
+ nr_iovecs++;
+ } while (iovec_len_used < len);
+
+ /* single kmalloc for locked list, page_list[], and the page arrays */
+ local_list = kmalloc(sizeof(*local_list)
+ + (nr_iovecs * sizeof (struct dma_page_list))
+ + (iovec_pages_used * sizeof (struct page*)), GFP_KERNEL);
+ if (!local_list)
+ return -ENOMEM;
+
+ /* list of pages starts right after the page list array */
+ pages = (struct page **) &local_list->page_list[nr_iovecs];
+
+ /* it's a userspace pointer */
+ might_sleep();
+
+ for (i = 0; i < nr_iovecs; i++) {
+ struct dma_page_list *page_list = &local_list->page_list[i];
+
+ len -= iov[i].iov_len;
+
+ if (!access_ok(VERIFY_WRITE, iov[i].iov_base, iov[i].iov_len)) {
+ dma_unlock_iovec_pages(local_list);
+ return -EFAULT;
+ }
+
+ page_list->nr_pages = NUM_PAGES_SPANNED(iov[i].iov_base,
+ iov[i].iov_len);
+ page_list->base_address = iov[i].iov_base;
+
+ page_list->pages = pages;
+ pages += page_list->nr_pages;
+
+ /* lock pages down */
+ down_read(&current->mm->mmap_sem);
+ ret = get_user_pages(
+ current,
+ current->mm,
+ (unsigned long) iov[i].iov_base,
+ page_list->nr_pages,
+ 1,
+ 0,
+ page_list->pages,
+ NULL);
+ up_read(&current->mm->mmap_sem);
+
+ if (ret != page_list->nr_pages) {
+ goto mem_error;
+ }
+
+ local_list->nr_iovecs = i + 1;
+ }
+
+ *locked_list = local_list;
+ return 0;
+
+mem_error:
+ dma_unlock_iovec_pages(local_list);
+ return -ENOMEM;
+}
+
+void dma_unlock_iovec_pages(struct dma_locked_list *locked_list)
+{
+ int i, j;
+
+ if (!locked_list)
+ return;
+
+ for (i = 0; i < locked_list->nr_iovecs; i++) {
+ struct dma_page_list *page_list = &locked_list->page_list[i];
+ for (j = 0; j < page_list->nr_pages; j++) {
+ SetPageDirty(page_list->pages[j]);
+ page_cache_release(page_list->pages[j]);
+ }
+ }
+
+ kfree(locked_list);
+}
+
+static dma_cookie_t dma_memcpy_tokerneliovec(struct dma_chan *chan, struct
+ iovec *iov, unsigned char *kdata, size_t len)
+{
+ dma_cookie_t dma_cookie = 0;
+
+ while (len > 0) {
+ if (iov->iov_len) {
+ int copy = min_t(unsigned int, iov->iov_len, len);
+ dma_cookie = dma_async_memcpy_buf_to_buf(
+ chan,
+ iov->iov_base,
+ kdata,
+ copy);
+ kdata += copy;
+ len -= copy;
+ iov->iov_len -= copy;
+ iov->iov_base += copy;
+ }
+ iov++;
+ }
+
+ return dma_cookie;
+}
+
+/*
+ * We have already locked down the pages we will be using in the iovecs.
+ * Each entry in iov array has corresponding entry in locked_list->page_list.
+ * Using array indexing to keep iov[] and page_list[] in sync.
+ * Initial elements in iov array's iov->iov_len will be 0 if already copied into
+ * by another call.
+ * iov array length remaining guaranteed to be bigger than len.
+ */
+dma_cookie_t dma_memcpy_toiovec(struct dma_chan *chan, struct iovec *iov,
+ struct dma_locked_list *locked_list, unsigned char *kdata, size_t len)
+{
+ int iov_byte_offset;
+ int copy;
+ dma_cookie_t dma_cookie = 0;
+ int iovec_idx;
+ int page_idx;
+
+ if (!chan)
+ return memcpy_toiovec(iov, kdata, len);
+
+ /* -> kernel copies (e.g. smbfs) */
+ if (!locked_list)
+ return dma_memcpy_tokerneliovec(chan, iov, kdata, len);
+
+ iovec_idx = 0;
+ while (iovec_idx < locked_list->nr_iovecs) {
+ struct dma_page_list *page_list;
+
+ /* skip already used-up iovecs */
+ while (!iov[iovec_idx].iov_len)
+ iovec_idx++;
+
+ page_list = &locked_list->page_list[iovec_idx];
+
+ iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
+ page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
+ - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;
+
+ /* break up copies to not cross page boundary */
+ while (iov[iovec_idx].iov_len) {
+ copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
+ copy = min_t(int, copy, iov[iovec_idx].iov_len);
+
+ dma_cookie = dma_async_memcpy_buf_to_pg(chan,
+ page_list->pages[page_idx],
+ iov_byte_offset,
+ kdata,
+ copy);
+
+ len -= copy;
+ iov[iovec_idx].iov_len -= copy;
+ iov[iovec_idx].iov_base += copy;
+
+ if (!len)
+ return dma_cookie;
+
+ kdata += copy;
+ iov_byte_offset = 0;
+ page_idx++;
+ }
+ iovec_idx++;
+ }
+
+ /* really bad if we ever run out of iovecs */
+ BUG();
+ return -EFAULT;
+}
+
+dma_cookie_t dma_memcpy_pg_toiovec(struct dma_chan *chan, struct iovec *iov,
+ struct dma_locked_list *locked_list, struct page *page,
+ unsigned int offset, size_t len)
+{
+ int iov_byte_offset;
+ int copy;
+ dma_cookie_t dma_cookie = 0;
+ int iovec_idx;
+ int page_idx;
+ int err;
+
+ /* this needs as-yet-unimplemented buf-to-buff, so punt. */
+ /* TODO: use dma for this */
+ if (!chan || !locked_list) {
+ u8 *vaddr = kmap(page);
+ err = memcpy_toiovec(iov, vaddr + offset, len);
+ kunmap(page);
+ return err;
+ }
+
+ iovec_idx = 0;
+ while (iovec_idx < locked_list->nr_iovecs) {
+ struct dma_page_list *page_list;
+
+ /* skip already used-up iovecs */
+ while (!iov[iovec_idx].iov_len)
+ iovec_idx++;
+
+ page_list = &locked_list->page_list[iovec_idx];
+
+ iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
+ page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
+ - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;
+
+ /* break up copies to not cross page boundary */
+ while (iov[iovec_idx].iov_len) {
+ copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
+ copy = min_t(int, copy, iov[iovec_idx].iov_len);
+
+ dma_cookie = dma_async_memcpy_pg_to_pg(chan,
+ page_list->pages[page_idx],
+ iov_byte_offset,
+ page,
+ offset,
+ copy);
+
+ len -= copy;
+ iov[iovec_idx].iov_len -= copy;
+ iov[iovec_idx].iov_base += copy;
+
+ if (!len)
+ return dma_cookie;
+
+ offset += copy;
+ iov_byte_offset = 0;
+ page_idx++;
+ }
+ iovec_idx++;
+ }
+
+ /* really bad if we ever run out of iovecs */
+ BUG();
+ return -EFAULT;
+}
+
+#else
+
+int dma_lock_iovec_pages(struct iovec *iov, size_t len, struct dma_locked_list
+ **locked_list)
+{
+ *locked_list = NULL;
+
+ return 0;
+}
+
+void dma_unlock_iovec_pages(struct dma_locked_list* locked_list)
+{ }
+
+#endif
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index f8a77ab..e198712 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -319,4 +319,28 @@ static inline enum dma_status dma_async_
int dma_async_device_register(struct dma_device *device);
void dma_async_device_unregister(struct dma_device *device);

+/* --- Helper iov-locking functions --- */
+
+struct dma_page_list
+{
+ char *base_address;
+ int nr_pages;
+ struct page **pages;
+};
+
+struct dma_locked_list
+{
+ int nr_iovecs;
+ struct dma_page_list page_list[0];
+};
+
+int dma_lock_iovec_pages(struct iovec *iov, size_t len,
+ struct dma_locked_list **locked_list);
+void dma_unlock_iovec_pages(struct dma_locked_list* locked_list);
+dma_cookie_t dma_memcpy_toiovec(struct dma_chan *chan, struct iovec *iov,
+ struct dma_locked_list *locked_list, unsigned char *kdata, size_t len);
+dma_cookie_t dma_memcpy_pg_toiovec(struct dma_chan *chan, struct iovec *iov,
+ struct dma_locked_list *locked_list, struct page *page,
+ unsigned int offset, size_t len);
+
#endif /* DMAENGINE_H */
diff --git a/include/net/netdma.h b/include/net/netdma.h
index 3cd9e6d..415d74c 100644
--- a/include/net/netdma.h
+++ b/include/net/netdma.h
@@ -21,6 +21,7 @@ file called LICENSE.
#ifndef NETDMA_H
#define NETDMA_H
#include <linux/dmaengine.h>
+#include <linux/skbuff.h>

static inline struct dma_chan *get_softnet_dma(void)
{
@@ -33,4 +34,8 @@ static inline struct dma_chan *get_softn
return chan;
}

+int dma_skb_copy_datagram_iovec(struct dma_chan* chan,
+ const struct sk_buff *skb, int offset, struct iovec *to,
+ size_t len, struct dma_locked_list *locked_list);
+
#endif /* NETDMA_H */
diff --git a/net/core/Makefile b/net/core/Makefile
index 630da0f..d02132b 100644
--- a/net/core/Makefile
+++ b/net/core/Makefile
@@ -8,7 +8,8 @@ obj-y := sock.o request_sock.o skbuff.o
obj-$(CONFIG_SYSCTL) += sysctl_net_core.o

obj-y += dev.o ethtool.o dev_mcast.o dst.o \
- neighbour.o rtnetlink.o utils.o link_watch.o filter.o
+ neighbour.o rtnetlink.o utils.o link_watch.o filter.o \
+ user_dma.o

obj-$(CONFIG_XFRM) += flow.o
obj-$(CONFIG_SYSFS) += net-sysfs.o
diff --git a/net/core/user_dma.c b/net/core/user_dma.c
new file mode 100644
index 0000000..1e1aae5
--- /dev/null
+++ b/net/core/user_dma.c
@@ -0,0 +1,133 @@
+/*****************************************************************************
+Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
+Portions based on net/core/datagram.c and copyrighted by their authors.
+
+This program is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2 of the License, or (at your option)
+any later version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc., 59
+Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+The full GNU General Public License is included in this distribution in the
+file called LICENSE.
+*****************************************************************************/
+
+/*
+ * This code allows the net stack to make use of a DMA engine for
+ * skb to iovec copies.
+ */
+
+#include <linux/dmaengine.h>
+#include <linux/socket.h>
+#include <linux/rtnetlink.h> /* for BUG_TRAP */
+#include <net/tcp.h>
+
+
+#ifdef CONFIG_NET_DMA
+
+/**
+ * dma_skb_copy_datagram_iovec - Copy a datagram to an iovec.
+ * @skb - buffer to copy
+ * @offset - offset in the buffer to start copying from
+ * @iovec - io vector to copy to
+ * @len - amount of data to copy from buffer to iovec
+ * @locked_list - locked iovec buffer data
+ *
+ * Note: the iovec is modified during the copy.
+ */
+int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
+ struct sk_buff *skb, int offset, struct iovec *to,
+ size_t len, struct dma_locked_list *locked_list)
+{
+ int start = skb_headlen(skb);
+ int i, copy = start - offset;
+ dma_cookie_t cookie = 0;
+
+ /* Copy header. */
+ if (copy > 0) {
+ if (copy > len)
+ copy = len;
+ if ((cookie = dma_memcpy_toiovec(chan, to, locked_list,
+ skb->data + offset, copy)) < 0)
+ goto fault;
+ if ((len -= copy) == 0)
+ goto end;
+ offset += copy;
+ }
+
+ /* Copy paged appendix. Hmm... why does this look so complicated? */
+ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+ int end;
+
+ BUG_TRAP(start <= offset + len);
+
+ end = start + skb_shinfo(skb)->frags[i].size;
+ if ((copy = end - offset) > 0) {
+ skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+ struct page *page = frag->page;
+
+ if (copy > len)
+ copy = len;
+
+ cookie = dma_memcpy_pg_toiovec(chan, to, locked_list, page,
+ frag->page_offset + offset - start, copy);
+ if (cookie < 0)
+ goto fault;
+ if (!(len -= copy))
+ goto end;
+ offset += copy;
+ }
+ start = end;
+ }
+
+ if (skb_shinfo(skb)->frag_list) {
+ struct sk_buff *list = skb_shinfo(skb)->frag_list;
+
+ for (; list; list = list->next) {
+ int end;
+
+ BUG_TRAP(start <= offset + len);
+
+ end = start + list->len;
+ if ((copy = end - offset) > 0) {
+ if (copy > len)
+ copy = len;
+ if ((cookie = dma_skb_copy_datagram_iovec(chan, list,
+ offset - start, to, copy, locked_list)) < 0)
+ goto fault;
+ if ((len -= copy) == 0)
+ goto end;
+ offset += copy;
+ }
+ start = end;
+ }
+ }
+
+end:
+ if (!len) {
+ skb->dma_cookie = cookie;
+ return cookie;
+ }
+
+fault:
+ return -EFAULT;
+}
+
+#else
+
+int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
+ const struct sk_buff *skb, int offset, struct iovec *to,
+ size_t len, struct dma_locked_list *locked_list)
+{
+ return skb_copy_datagram_iovec(skb, offset, to, len);
+}
+
+#endif
-
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