RDS: Message parsing

Parsing of newly-received RDS message headers (including ext.
headers) and copy-to/from-user routines.

page.c implements a per-cpu page remainder cache, to reduce the
number of allocations needed for small datagrams.
Signed-off-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/message.c

+/*
+ * Copyright (c) 2006 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - 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.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+
+#include "rds.h"
+#include "rdma.h"
+
+static DECLARE_WAIT_QUEUE_HEAD(rds_message_flush_waitq);
+
+static unsigned int	rds_exthdr_size[__RDS_EXTHDR_MAX] = {
+[RDS_EXTHDR_NONE]	= 0,
+[RDS_EXTHDR_VERSION]	= sizeof(struct rds_ext_header_version),
+[RDS_EXTHDR_RDMA]	= sizeof(struct rds_ext_header_rdma),
+[RDS_EXTHDR_RDMA_DEST]	= sizeof(struct rds_ext_header_rdma_dest),
+};
+
+
+void rds_message_addref(struct rds_message *rm)
+{
+	rdsdebug("addref rm %p ref %d\n", rm, atomic_read(&rm->m_refcount));
+	atomic_inc(&rm->m_refcount);
+}
+
+/*
+ * This relies on dma_map_sg() not touching sg[].page during merging.
+ */
+static void rds_message_purge(struct rds_message *rm)
+{
+	unsigned long i;
+
+	if (unlikely(test_bit(RDS_MSG_PAGEVEC, &rm->m_flags)))
+		return;
+
+	for (i = 0; i < rm->m_nents; i++) {
+		rdsdebug("putting data page %p\n", (void *)sg_page(&rm->m_sg[i]));
+		/* XXX will have to put_page for page refs */
+		__free_page(sg_page(&rm->m_sg[i]));
+	}
+	rm->m_nents = 0;
+
+	if (rm->m_rdma_op)
+		rds_rdma_free_op(rm->m_rdma_op);
+	if (rm->m_rdma_mr)
+		rds_mr_put(rm->m_rdma_mr);
+}
+
+void rds_message_inc_purge(struct rds_incoming *inc)
+{
+	struct rds_message *rm = container_of(inc, struct rds_message, m_inc);
+	rds_message_purge(rm);
+}
+
+void rds_message_put(struct rds_message *rm)
+{
+	rdsdebug("put rm %p ref %d\n", rm, atomic_read(&rm->m_refcount));
+
+	if (atomic_dec_and_test(&rm->m_refcount)) {
+		BUG_ON(!list_empty(&rm->m_sock_item));
+		BUG_ON(!list_empty(&rm->m_conn_item));
+		rds_message_purge(rm);
+
+		kfree(rm);
+	}
+}
+
+void rds_message_inc_free(struct rds_incoming *inc)
+{
+	struct rds_message *rm = container_of(inc, struct rds_message, m_inc);
+	rds_message_put(rm);
+}
+
+void rds_message_populate_header(struct rds_header *hdr, __be16 sport,
+				 __be16 dport, u64 seq)
+{
+	hdr->h_flags = 0;
+	hdr->h_sport = sport;
+	hdr->h_dport = dport;
+	hdr->h_sequence = cpu_to_be64(seq);
+	hdr->h_exthdr[0] = RDS_EXTHDR_NONE;
+}
+
+int rds_message_add_extension(struct rds_header *hdr,
+		unsigned int type, const void *data, unsigned int len)
+{
+	unsigned int ext_len = sizeof(u8) + len;
+	unsigned char *dst;
+
+	/* For now, refuse to add more than one extension header */
+	if (hdr->h_exthdr[0] != RDS_EXTHDR_NONE)
+		return 0;
+
+	if (type >= __RDS_EXTHDR_MAX
+	 || len != rds_exthdr_size[type])
+		return 0;
+
+	if (ext_len >= RDS_HEADER_EXT_SPACE)
+		return 0;
+	dst = hdr->h_exthdr;
+
+	*dst++ = type;
+	memcpy(dst, data, len);
+
+	dst[len] = RDS_EXTHDR_NONE;
+	return 1;
+}
+
+/*
+ * If a message has extension headers, retrieve them here.
+ * Call like this:
+ *
+ * unsigned int pos = 0;
+ *
+ * while (1) {
+ *	buflen = sizeof(buffer);
+ *	type = rds_message_next_extension(hdr, &pos, buffer, &buflen);
+ *	if (type == RDS_EXTHDR_NONE)
+ *		break;
+ *	...
+ * }
+ */
+int rds_message_next_extension(struct rds_header *hdr,
+		unsigned int *pos, void *buf, unsigned int *buflen)
+{
+	unsigned int offset, ext_type, ext_len;
+	u8 *src = hdr->h_exthdr;
+
+	offset = *pos;
+	if (offset >= RDS_HEADER_EXT_SPACE)
+		goto none;
+
+	/* Get the extension type and length. For now, the
+	 * length is implied by the extension type. */
+	ext_type = src[offset++];
+
+	if (ext_type == RDS_EXTHDR_NONE || ext_type >= __RDS_EXTHDR_MAX)
+		goto none;
+	ext_len = rds_exthdr_size[ext_type];
+	if (offset + ext_len > RDS_HEADER_EXT_SPACE)
+		goto none;
+
+	*pos = offset + ext_len;
+	if (ext_len < *buflen)
+		*buflen = ext_len;
+	memcpy(buf, src + offset, *buflen);
+	return ext_type;
+
+none:
+	*pos = RDS_HEADER_EXT_SPACE;
+	*buflen = 0;
+	return RDS_EXTHDR_NONE;
+}
+
+int rds_message_add_version_extension(struct rds_header *hdr, unsigned int version)
+{
+	struct rds_ext_header_version ext_hdr;
+
+	ext_hdr.h_version = cpu_to_be32(version);
+	return rds_message_add_extension(hdr, RDS_EXTHDR_VERSION, &ext_hdr, sizeof(ext_hdr));
+}
+
+int rds_message_get_version_extension(struct rds_header *hdr, unsigned int *version)
+{
+	struct rds_ext_header_version ext_hdr;
+	unsigned int pos = 0, len = sizeof(ext_hdr);
+
+	/* We assume the version extension is the only one present */
+	if (rds_message_next_extension(hdr, &pos, &ext_hdr, &len) != RDS_EXTHDR_VERSION)
+		return 0;
+	*version = be32_to_cpu(ext_hdr.h_version);
+	return 1;
+}
+
+int rds_message_add_rdma_dest_extension(struct rds_header *hdr, u32 r_key, u32 offset)
+{
+	struct rds_ext_header_rdma_dest ext_hdr;
+
+	ext_hdr.h_rdma_rkey = cpu_to_be32(r_key);
+	ext_hdr.h_rdma_offset = cpu_to_be32(offset);
+	return rds_message_add_extension(hdr, RDS_EXTHDR_RDMA_DEST, &ext_hdr, sizeof(ext_hdr));
+}
+
+struct rds_message *rds_message_alloc(unsigned int nents, gfp_t gfp)
+{
+	struct rds_message *rm;
+
+	rm = kzalloc(sizeof(struct rds_message) +
+		     (nents * sizeof(struct scatterlist)), gfp);
+	if (!rm)
+		goto out;
+
+	if (nents)
+		sg_init_table(rm->m_sg, nents);
+	atomic_set(&rm->m_refcount, 1);
+	INIT_LIST_HEAD(&rm->m_sock_item);
+	INIT_LIST_HEAD(&rm->m_conn_item);
+	spin_lock_init(&rm->m_rs_lock);
+
+out:
+	return rm;
+}
+
+struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned int total_len)
+{
+	struct rds_message *rm;
+	unsigned int i;
+
+	rm = rds_message_alloc(ceil(total_len, PAGE_SIZE), GFP_KERNEL);
+	if (rm == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	set_bit(RDS_MSG_PAGEVEC, &rm->m_flags);
+	rm->m_inc.i_hdr.h_len = cpu_to_be32(total_len);
+	rm->m_nents = ceil(total_len, PAGE_SIZE);
+
+	for (i = 0; i < rm->m_nents; ++i) {
+		sg_set_page(&rm->m_sg[i],
+				virt_to_page(page_addrs[i]),
+				PAGE_SIZE, 0);
+	}
+
+	return rm;
+}
+
+struct rds_message *rds_message_copy_from_user(struct iovec *first_iov,
+					       size_t total_len)
+{
+	unsigned long to_copy;
+	unsigned long iov_off;
+	unsigned long sg_off;
+	struct rds_message *rm;
+	struct iovec *iov;
+	struct scatterlist *sg;
+	int ret;
+
+	rm = rds_message_alloc(ceil(total_len, PAGE_SIZE), GFP_KERNEL);
+	if (rm == NULL) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	rm->m_inc.i_hdr.h_len = cpu_to_be32(total_len);
+
+	/*
+	 * now allocate and copy in the data payload.
+	 */
+	sg = rm->m_sg;
+	iov = first_iov;
+	iov_off = 0;
+	sg_off = 0; /* Dear gcc, sg->page will be null from kzalloc. */
+
+	while (total_len) {
+		if (sg_page(sg) == NULL) {
+			ret = rds_page_remainder_alloc(sg, total_len,
+						       GFP_HIGHUSER);
+			if (ret)
+				goto out;
+			rm->m_nents++;
+			sg_off = 0;
+		}
+
+		while (iov_off == iov->iov_len) {
+			iov_off = 0;
+			iov++;
+		}
+
+		to_copy = min(iov->iov_len - iov_off, sg->length - sg_off);
+		to_copy = min_t(size_t, to_copy, total_len);
+
+		rdsdebug("copying %lu bytes from user iov [%p, %zu] + %lu to "
+			 "sg [%p, %u, %u] + %lu\n",
+			 to_copy, iov->iov_base, iov->iov_len, iov_off,
+			 (void *)sg_page(sg), sg->offset, sg->length, sg_off);
+
+		ret = rds_page_copy_from_user(sg_page(sg), sg->offset + sg_off,
+					      iov->iov_base + iov_off,
+					      to_copy);
+		if (ret)
+			goto out;
+
+		iov_off += to_copy;
+		total_len -= to_copy;
+		sg_off += to_copy;
+
+		if (sg_off == sg->length)
+			sg++;
+	}
+
+	ret = 0;
+out:
+	if (ret) {
+		if (rm)
+			rds_message_put(rm);
+		rm = ERR_PTR(ret);
+	}
+	return rm;
+}
+
+int rds_message_inc_copy_to_user(struct rds_incoming *inc,
+				 struct iovec *first_iov, size_t size)
+{
+	struct rds_message *rm;
+	struct iovec *iov;
+	struct scatterlist *sg;
+	unsigned long to_copy;
+	unsigned long iov_off;
+	unsigned long vec_off;
+	int copied;
+	int ret;
+	u32 len;
+
+	rm = container_of(inc, struct rds_message, m_inc);
+	len = be32_to_cpu(rm->m_inc.i_hdr.h_len);
+
+	iov = first_iov;
+	iov_off = 0;
+	sg = rm->m_sg;
+	vec_off = 0;
+	copied = 0;
+
+	while (copied < size && copied < len) {
+		while (iov_off == iov->iov_len) {
+			iov_off = 0;
+			iov++;
+		}
+
+		to_copy = min(iov->iov_len - iov_off, sg->length - vec_off);
+		to_copy = min_t(size_t, to_copy, size - copied);
+		to_copy = min_t(unsigned long, to_copy, len - copied);
+
+		rdsdebug("copying %lu bytes to user iov [%p, %zu] + %lu to "
+			 "sg [%p, %u, %u] + %lu\n",
+			 to_copy, iov->iov_base, iov->iov_len, iov_off,
+			 sg_page(sg), sg->offset, sg->length, vec_off);
+
+		ret = rds_page_copy_to_user(sg_page(sg), sg->offset + vec_off,
+					    iov->iov_base + iov_off,
+					    to_copy);
+		if (ret) {
+			copied = ret;
+			break;
+		}
+
+		iov_off += to_copy;
+		vec_off += to_copy;
+		copied += to_copy;
+
+		if (vec_off == sg->length) {
+			vec_off = 0;
+			sg++;
+		}
+	}
+
+	return copied;
+}
+
+/*
+ * If the message is still on the send queue, wait until the transport
+ * is done with it. This is particularly important for RDMA operations.
+ */
+void rds_message_wait(struct rds_message *rm)
+{
+	wait_event(rds_message_flush_waitq,
+			!test_bit(RDS_MSG_MAPPED, &rm->m_flags));
+}
+
+void rds_message_unmapped(struct rds_message *rm)
+{
+	clear_bit(RDS_MSG_MAPPED, &rm->m_flags);
+	if (waitqueue_active(&rds_message_flush_waitq))
+		wake_up(&rds_message_flush_waitq);
+}
+

net/rds/page.c

+/*
+ * Copyright (c) 2006 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - 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.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/highmem.h>
+
+#include "rds.h"
+
+struct rds_page_remainder {
+	struct page	*r_page;
+	unsigned long	r_offset;
+};
+
+DEFINE_PER_CPU(struct rds_page_remainder, rds_page_remainders) ____cacheline_aligned;
+
+/*
+ * returns 0 on success or -errno on failure.
+ *
+ * We don't have to worry about flush_dcache_page() as this only works
+ * with private pages.  If, say, we were to do directed receive to pinned
+ * user pages we'd have to worry more about cache coherence.  (Though
+ * the flush_dcache_page() in get_user_pages() would probably be enough).
+ */
+int rds_page_copy_user(struct page *page, unsigned long offset,
+		       void __user *ptr, unsigned long bytes,
+		       int to_user)
+{
+	unsigned long ret;
+	void *addr;
+
+	if (to_user)
+		rds_stats_add(s_copy_to_user, bytes);
+	else
+		rds_stats_add(s_copy_from_user, bytes);
+
+	addr = kmap_atomic(page, KM_USER0);
+	if (to_user)
+		ret = __copy_to_user_inatomic(ptr, addr + offset, bytes);
+	else
+		ret = __copy_from_user_inatomic(addr + offset, ptr, bytes);
+	kunmap_atomic(addr, KM_USER0);
+
+	if (ret) {
+		addr = kmap(page);
+		if (to_user)
+			ret = copy_to_user(ptr, addr + offset, bytes);
+		else
+			ret = copy_from_user(addr + offset, ptr, bytes);
+		kunmap(page);
+		if (ret)
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+/*
+ * Message allocation uses this to build up regions of a message.
+ *
+ * @bytes - the number of bytes needed.
+ * @gfp - the waiting behaviour of the allocation
+ *
+ * @gfp is always ored with __GFP_HIGHMEM.  Callers must be prepared to
+ * kmap the pages, etc.
+ *
+ * If @bytes is at least a full page then this just returns a page from
+ * alloc_page().
+ *
+ * If @bytes is a partial page then this stores the unused region of the
+ * page in a per-cpu structure.  Future partial-page allocations may be
+ * satisfied from that cached region.  This lets us waste less memory on
+ * small allocations with minimal complexity.  It works because the transmit
+ * path passes read-only page regions down to devices.  They hold a page
+ * reference until they are done with the region.
+ */
+int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes,
+			     gfp_t gfp)
+{
+	struct rds_page_remainder *rem;
+	unsigned long flags;
+	struct page *page;
+	int ret;
+
+	gfp |= __GFP_HIGHMEM;
+
+	/* jump straight to allocation if we're trying for a huge page */
+	if (bytes >= PAGE_SIZE) {
+		page = alloc_page(gfp);
+		if (page == NULL) {
+			ret = -ENOMEM;
+		} else {
+			sg_set_page(scat, page, PAGE_SIZE, 0);
+			ret = 0;
+		}
+		goto out;
+	}
+
+	rem = &per_cpu(rds_page_remainders, get_cpu());
+	local_irq_save(flags);
+
+	while (1) {
+		/* avoid a tiny region getting stuck by tossing it */
+		if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) {
+			rds_stats_inc(s_page_remainder_miss);
+			__free_page(rem->r_page);
+			rem->r_page = NULL;
+		}
+
+		/* hand out a fragment from the cached page */
+		if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) {
+			sg_set_page(scat, rem->r_page, bytes, rem->r_offset);
+			get_page(sg_page(scat));
+
+			if (rem->r_offset != 0)
+				rds_stats_inc(s_page_remainder_hit);
+
+			rem->r_offset += bytes;
+			if (rem->r_offset == PAGE_SIZE) {
+				__free_page(rem->r_page);
+				rem->r_page = NULL;
+			}
+			ret = 0;
+			break;
+		}
+
+		/* alloc if there is nothing for us to use */
+		local_irq_restore(flags);
+		put_cpu();
+
+		page = alloc_page(gfp);
+
+		rem = &per_cpu(rds_page_remainders, get_cpu());
+		local_irq_save(flags);
+
+		if (page == NULL) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		/* did someone race to fill the remainder before us? */
+		if (rem->r_page) {
+			__free_page(page);
+			continue;
+		}
+
+		/* otherwise install our page and loop around to alloc */
+		rem->r_page = page;
+		rem->r_offset = 0;
+	}
+
+	local_irq_restore(flags);
+	put_cpu();
+out:
+	rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret,
+		 ret ? NULL : sg_page(scat), ret ? 0 : scat->offset,
+		 ret ? 0 : scat->length);
+	return ret;
+}
+
+static int rds_page_remainder_cpu_notify(struct notifier_block *self,
+					 unsigned long action, void *hcpu)
+{
+	struct rds_page_remainder *rem;
+	long cpu = (long)hcpu;
+
+	rem = &per_cpu(rds_page_remainders, cpu);
+
+	rdsdebug("cpu %ld action 0x%lx\n", cpu, action);
+
+	switch (action) {
+	case CPU_DEAD:
+		if (rem->r_page)
+			__free_page(rem->r_page);
+		rem->r_page = NULL;
+		break;
+	}
+
+	return 0;
+}
+
+static struct notifier_block rds_page_remainder_nb = {
+	.notifier_call = rds_page_remainder_cpu_notify,
+};
+
+void rds_page_exit(void)
+{
+	int i;
+
+	for_each_possible_cpu(i)
+		rds_page_remainder_cpu_notify(&rds_page_remainder_nb,
+					      (unsigned long)CPU_DEAD,
+					      (void *)(long)i);
+}