[I/OAT]: Utility functions for offloading sk_buff to iovec copies

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 301 insertions, 0 deletions

diff --git a/drivers/dma/iovlock.c b/drivers/dma/iovlock.c
new file mode 100644
index 000000000000..5ed327e453a2
--- /dev/null
+++ b/drivers/dma/iovlock.c
@@ -0,0 +1,301 @@
+/*
+ * 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 COPYING.
+ */
+
+/*
+ * 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>
+
+int num_pages_spanned(struct iovec *iov)
+{
+        return
+        ((PAGE_ALIGN((unsigned long)iov->iov_base + iov->iov_len) -
+        ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT);
+}
+
+/*
+ * Pin down all the iovec pages needed for len bytes.
+ * Return a struct dma_pinned_list to keep track of pages pinned 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.
+ */
+struct dma_pinned_list *dma_pin_iovec_pages(struct iovec *iov, size_t len)
+{
+        struct dma_pinned_list *local_list;
+        struct page **pages;
+        int i;
+        int ret;
+        int nr_iovecs = 0;
+        int iovec_len_used = 0;
+        int iovec_pages_used = 0;
+        long err;
+
+        /* don't pin down non-user-based iovecs */
+        if (segment_eq(get_fs(), KERNEL_DS))
+                return NULL;
+
+        /* 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]);
+                nr_iovecs++;
+        } while (iovec_len_used < len);
+
+        /* single kmalloc for pinned 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) {
+                err = -ENOMEM;
+                goto out;
+        }
+
+        /* list of pages starts right after the page list array */
+        pages = (struct page **) &local_list->page_list[nr_iovecs];
+
+        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)) {
+                        err = -EFAULT;
+                        goto unpin;
+                }
+
+                page_list->nr_pages = num_pages_spanned(&iov[i]);
+                page_list->base_address = iov[i].iov_base;
+
+                page_list->pages = pages;
+                pages += page_list->nr_pages;
+
+                /* pin 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,      /* write */
+                        0,      /* force */
+                        page_list->pages,
+                        NULL);
+                up_read(&current->mm->mmap_sem);
+
+                if (ret != page_list->nr_pages) {
+                        err = -ENOMEM;
+                        goto unpin;
+                }
+
+                local_list->nr_iovecs = i + 1;
+        }
+
+        return local_list;
+
+unpin:
+        dma_unpin_iovec_pages(local_list);
+out:
+        return ERR_PTR(err);
+}
+
+void dma_unpin_iovec_pages(struct dma_pinned_list *pinned_list)
+{
+        int i, j;
+
+        if (!pinned_list)
+                return;
+
+        for (i = 0; i < pinned_list->nr_iovecs; i++) {
+                struct dma_page_list *page_list = &pinned_list->page_list[i];
+                for (j = 0; j < page_list->nr_pages; j++) {
+                        set_page_dirty_lock(page_list->pages[j]);
+                        page_cache_release(page_list->pages[j]);
+                }
+        }
+
+        kfree(pinned_list);
+}
+
+static dma_cookie_t dma_memcpy_to_kernel_iovec(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 pinned down the pages we will be using in the iovecs.
+ * Each entry in iov array has corresponding entry in pinned_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_to_iovec(struct dma_chan *chan, struct iovec *iov,
+        struct dma_pinned_list *pinned_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 (!pinned_list)
+                return dma_memcpy_to_kernel_iovec(chan, iov, kdata, len);
+
+        iovec_idx = 0;
+        while (iovec_idx < pinned_list->nr_iovecs) {
+                struct dma_page_list *page_list;
+
+                /* skip already used-up iovecs */
+                while (!iov[iovec_idx].iov_len)
+                        iovec_idx++;
+
+                page_list = &pinned_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_to_iovec(struct dma_chan *chan, struct iovec *iov,
+        struct dma_pinned_list *pinned_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 || !pinned_list) {
+                u8 *vaddr = kmap(page);
+                err = memcpy_toiovec(iov, vaddr + offset, len);
+                kunmap(page);
+                return err;
+        }
+
+        iovec_idx = 0;
+        while (iovec_idx < pinned_list->nr_iovecs) {
+                struct dma_page_list *page_list;
+
+                /* skip already used-up iovecs */
+                while (!iov[iovec_idx].iov_len)
+                        iovec_idx++;
+
+                page_list = &pinned_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;
+}