RDS: RDMA support

/*

 * Copyright (c) 2007 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/pagemap.h>

#include <linux/rbtree.h>

#include <linux/dma-mapping.h> /* for DMA_*_DEVICE */

#include "rdma.h"

/*

 * XXX

 *  - build with sparse

 *  - should we limit the size of a mr region?  let transport return failure?

 *  - should we detect duplicate keys on a socket?  hmm.

 *  - an rdma is an mlock, apply rlimit?

 */

/*

 * get the number of pages by looking at the page indices that the start and

 * end addresses fall in.

 *

 * Returns 0 if the vec is invalid.  It is invalid if the number of bytes

 * causes the address to wrap or overflows an unsigned int.  This comes

 * from being stored in the 'length' member of 'struct scatterlist'.

 */

static unsigned int rds_pages_in_vec(struct rds_iovec *vec)

{

	if ((vec->addr + vec->bytes <= vec->addr) ||

	    (vec->bytes > (u64)UINT_MAX))

		return 0;

	return ((vec->addr + vec->bytes + PAGE_SIZE - 1) >> PAGE_SHIFT) -

		(vec->addr >> PAGE_SHIFT);

}

static struct rds_mr *rds_mr_tree_walk(struct rb_root *root, u64 key,

				       struct rds_mr *insert)

{

	struct rb_node **p = &root->rb_node;

	struct rb_node *parent = NULL;

	struct rds_mr *mr;

	while (*p) {

		parent = *p;

		mr = rb_entry(parent, struct rds_mr, r_rb_node);

		if (key < mr->r_key)

			p = &(*p)->rb_left;

		else if (key > mr->r_key)

			p = &(*p)->rb_right;

		else

			return mr;

	}

	if (insert) {

		rb_link_node(&insert->r_rb_node, parent, p);

		rb_insert_color(&insert->r_rb_node, root);

		atomic_inc(&insert->r_refcount);

	}

	return NULL;

}

/*

 * Destroy the transport-specific part of a MR.

 */

static void rds_destroy_mr(struct rds_mr *mr)

{

	struct rds_sock *rs = mr->r_sock;

	void *trans_private = NULL;

	unsigned long flags;

	rdsdebug("RDS: destroy mr key is %x refcnt %u\n",

			mr->r_key, atomic_read(&mr->r_refcount));

	if (test_and_set_bit(RDS_MR_DEAD, &mr->r_state))

		return;

	spin_lock_irqsave(&rs->rs_rdma_lock, flags);

	if (!RB_EMPTY_NODE(&mr->r_rb_node))

		rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys);

	trans_private = mr->r_trans_private;

	mr->r_trans_private = NULL;

	spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);

	if (trans_private)

		mr->r_trans->free_mr(trans_private, mr->r_invalidate);

}

void __rds_put_mr_final(struct rds_mr *mr)

{

	rds_destroy_mr(mr);

	kfree(mr);

}

/*

 * By the time this is called we can't have any more ioctls called on

 * the socket so we don't need to worry about racing with others.

 */

void rds_rdma_drop_keys(struct rds_sock *rs)

{

	struct rds_mr *mr;

	struct rb_node *node;

	/* Release any MRs associated with this socket */

	while ((node = rb_first(&rs->rs_rdma_keys))) {

		mr = container_of(node, struct rds_mr, r_rb_node);

		if (mr->r_trans == rs->rs_transport)

			mr->r_invalidate = 0;

		rds_mr_put(mr);

	}

	if (rs->rs_transport && rs->rs_transport->flush_mrs)

		rs->rs_transport->flush_mrs();

}

/*

 * Helper function to pin user pages.

 */

static int rds_pin_pages(unsigned long user_addr, unsigned int nr_pages,

			struct page **pages, int write)

{

	int ret;

	down_read(&current->mm->mmap_sem);

	ret = get_user_pages(current, current->mm, user_addr,

			     nr_pages, write, 0, pages, NULL);

	up_read(&current->mm->mmap_sem);

	if (0 <= ret && (unsigned) ret < nr_pages) {

		while (ret--)

			put_page(pages[ret]);

		ret = -EFAULT;

	}

	return ret;

}

static int __rds_rdma_map(struct rds_sock *rs, struct rds_get_mr_args *args,

				u64 *cookie_ret, struct rds_mr **mr_ret)

{

	struct rds_mr *mr = NULL, *found;

	unsigned int nr_pages;

	struct page **pages = NULL;

	struct scatterlist *sg;

	void *trans_private;

	unsigned long flags;

	rds_rdma_cookie_t cookie;

	unsigned int nents;

	long i;

	int ret;

	if (rs->rs_bound_addr == 0) {

		ret = -ENOTCONN; /* XXX not a great errno */

		goto out;

	}

	if (rs->rs_transport->get_mr == NULL) {

		ret = -EOPNOTSUPP;

		goto out;

	}

	nr_pages = rds_pages_in_vec(&args->vec);

	if (nr_pages == 0) {

		ret = -EINVAL;

		goto out;

	}

	rdsdebug("RDS: get_mr addr %llx len %llu nr_pages %u\n",

		args->vec.addr, args->vec.bytes, nr_pages);

	/* XXX clamp nr_pages to limit the size of this alloc? */

	pages = kcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL);

	if (pages == NULL) {

		ret = -ENOMEM;

		goto out;

	}

	mr = kzalloc(sizeof(struct rds_mr), GFP_KERNEL);

	if (mr == NULL) {

		ret = -ENOMEM;

		goto out;

	}

	atomic_set(&mr->r_refcount, 1);

	RB_CLEAR_NODE(&mr->r_rb_node);

	mr->r_trans = rs->rs_transport;

	mr->r_sock = rs;

	if (args->flags & RDS_RDMA_USE_ONCE)

		mr->r_use_once = 1;

	if (args->flags & RDS_RDMA_INVALIDATE)

		mr->r_invalidate = 1;

	if (args->flags & RDS_RDMA_READWRITE)

		mr->r_write = 1;

	/*

	 * Pin the pages that make up the user buffer and transfer the page

	 * pointers to the mr's sg array.  We check to see if we've mapped

	 * the whole region after transferring the partial page references

	 * to the sg array so that we can have one page ref cleanup path.

	 *

	 * For now we have no flag that tells us whether the mapping is

	 * r/o or r/w. We need to assume r/w, or we'll do a lot of RDMA to

	 * the zero page.

	 */

	ret = rds_pin_pages(args->vec.addr & PAGE_MASK, nr_pages, pages, 1);

	if (ret < 0)

		goto out;

	nents = ret;

	sg = kcalloc(nents, sizeof(*sg), GFP_KERNEL);

	if (sg == NULL) {

		ret = -ENOMEM;

		goto out;

	}

	WARN_ON(!nents);

	sg_init_table(sg, nents);

	/* Stick all pages into the scatterlist */

	for (i = 0 ; i < nents; i++)

		sg_set_page(&sg[i], pages[i], PAGE_SIZE, 0);

	rdsdebug("RDS: trans_private nents is %u\n", nents);

	/* Obtain a transport specific MR. If this succeeds, the

	 * s/g list is now owned by the MR.

	 * Note that dma_map() implies that pending writes are

	 * flushed to RAM, so no dma_sync is needed here. */

	trans_private = rs->rs_transport->get_mr(sg, nents, rs,

						 &mr->r_key);

	if (IS_ERR(trans_private)) {

		for (i = 0 ; i < nents; i++)

			put_page(sg_page(&sg[i]));

		kfree(sg);

		ret = PTR_ERR(trans_private);

		goto out;

	}

	mr->r_trans_private = trans_private;

	rdsdebug("RDS: get_mr put_user key is %x cookie_addr %p\n",

	       mr->r_key, (void *)(unsigned long) args->cookie_addr);

	/* The user may pass us an unaligned address, but we can only

	 * map page aligned regions. So we keep the offset, and build

	 * a 64bit cookie containing <R_Key, offset> and pass that

	 * around. */

	cookie = rds_rdma_make_cookie(mr->r_key, args->vec.addr & ~PAGE_MASK);

	if (cookie_ret)

		*cookie_ret = cookie;

	if (args->cookie_addr && put_user(cookie, (u64 __user *)(unsigned long) args->cookie_addr)) {

		ret = -EFAULT;

		goto out;

	}

	/* Inserting the new MR into the rbtree bumps its

	 * reference count. */

	spin_lock_irqsave(&rs->rs_rdma_lock, flags);

	found = rds_mr_tree_walk(&rs->rs_rdma_keys, mr->r_key, mr);

	spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);

	BUG_ON(found && found != mr);

	rdsdebug("RDS: get_mr key is %x\n", mr->r_key);

	if (mr_ret) {

		atomic_inc(&mr->r_refcount);

		*mr_ret = mr;

	}

	ret = 0;

out:

	kfree(pages);

	if (mr)

		rds_mr_put(mr);

	return ret;

}

int rds_get_mr(struct rds_sock *rs, char __user *optval, int optlen)

{

	struct rds_get_mr_args args;

	if (optlen != sizeof(struct rds_get_mr_args))

		return -EINVAL;

	if (copy_from_user(&args, (struct rds_get_mr_args __user *)optval,

			   sizeof(struct rds_get_mr_args)))

		return -EFAULT;

	return __rds_rdma_map(rs, &args, NULL, NULL);

}

/*

 * Free the MR indicated by the given R_Key

 */

int rds_free_mr(struct rds_sock *rs, char __user *optval, int optlen)

{

	struct rds_free_mr_args args;

	struct rds_mr *mr;

	unsigned long flags;

	if (optlen != sizeof(struct rds_free_mr_args))

		return -EINVAL;

	if (copy_from_user(&args, (struct rds_free_mr_args __user *)optval,

			   sizeof(struct rds_free_mr_args)))

		return -EFAULT;

	/* Special case - a null cookie means flush all unused MRs */

	if (args.cookie == 0) {

		if (!rs->rs_transport || !rs->rs_transport->flush_mrs)

			return -EINVAL;

		rs->rs_transport->flush_mrs();

		return 0;

	}

	/* Look up the MR given its R_key and remove it from the rbtree

	 * so nobody else finds it.

	 * This should also prevent races with rds_rdma_unuse.

	 */

	spin_lock_irqsave(&rs->rs_rdma_lock, flags);

	mr = rds_mr_tree_walk(&rs->rs_rdma_keys, rds_rdma_cookie_key(args.cookie), NULL);

	if (mr) {

		rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys);

		RB_CLEAR_NODE(&mr->r_rb_node);

		if (args.flags & RDS_RDMA_INVALIDATE)

			mr->r_invalidate = 1;

	}

	spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);

	if (!mr)

		return -EINVAL;

	/*

	 * call rds_destroy_mr() ourselves so that we're sure it's done by the time

	 * we return.  If we let rds_mr_put() do it it might not happen until

	 * someone else drops their ref.

	 */

	rds_destroy_mr(mr);

	rds_mr_put(mr);

	return 0;

}

/*

 * This is called when we receive an extension header that

 * tells us this MR was used. It allows us to implement

 * use_once semantics

 */

void rds_rdma_unuse(struct rds_sock *rs, u32 r_key, int force)

{

	struct rds_mr *mr;

	unsigned long flags;

	int zot_me = 0;

	spin_lock_irqsave(&rs->rs_rdma_lock, flags);

	mr = rds_mr_tree_walk(&rs->rs_rdma_keys, r_key, NULL);

	if (mr && (mr->r_use_once || force)) {

		rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys);

		RB_CLEAR_NODE(&mr->r_rb_node);

		zot_me = 1;

	} else if (mr)

		atomic_inc(&mr->r_refcount);

	spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);

	/* May have to issue a dma_sync on this memory region.

	 * Note we could avoid this if the operation was a RDMA READ,

	 * but at this point we can't tell. */

	if (mr != NULL) {

		if (mr->r_trans->sync_mr)

			mr->r_trans->sync_mr(mr->r_trans_private, DMA_FROM_DEVICE);

		/* If the MR was marked as invalidate, this will

		 * trigger an async flush. */

		if (zot_me)

			rds_destroy_mr(mr);

		rds_mr_put(mr);

	}

}

void rds_rdma_free_op(struct rds_rdma_op *ro)

{

	unsigned int i;

	for (i = 0; i < ro->r_nents; i++) {

		struct page *page = sg_page(&ro->r_sg[i]);

		/* Mark page dirty if it was possibly modified, which

		 * is the case for a RDMA_READ which copies from remote

		 * to local memory */

		if (!ro->r_write)

			set_page_dirty(page);

		put_page(page);

	}

	kfree(ro->r_notifier);

	kfree(ro);

}

/*

 * args is a pointer to an in-kernel copy in the sendmsg cmsg.

 */

static struct rds_rdma_op *rds_rdma_prepare(struct rds_sock *rs,

					    struct rds_rdma_args *args)

{

	struct rds_iovec vec;

	struct rds_rdma_op *op = NULL;

	unsigned int nr_pages;

	unsigned int max_pages;

	unsigned int nr_bytes;

	struct page **pages = NULL;

	struct rds_iovec __user *local_vec;

	struct scatterlist *sg;

	unsigned int nr;

	unsigned int i, j;

	int ret;

	if (rs->rs_bound_addr == 0) {

		ret = -ENOTCONN; /* XXX not a great errno */

		goto out;

	}

	if (args->nr_local > (u64)UINT_MAX) {

		ret = -EMSGSIZE;

		goto out;

	}

	nr_pages = 0;

	max_pages = 0;

	local_vec = (struct rds_iovec __user *)(unsigned long) args->local_vec_addr;

	/* figure out the number of pages in the vector */

	for (i = 0; i < args->nr_local; i++) {

		if (copy_from_user(&vec, &local_vec[i],

				   sizeof(struct rds_iovec))) {

			ret = -EFAULT;

			goto out;

		}

		nr = rds_pages_in_vec(&vec);

		if (nr == 0) {

			ret = -EINVAL;

			goto out;

		}

		max_pages = max(nr, max_pages);

		nr_pages += nr;

	}

	pages = kcalloc(max_pages, sizeof(struct page *), GFP_KERNEL);

	if (pages == NULL) {

		ret = -ENOMEM;

		goto out;

	}

	op = kzalloc(offsetof(struct rds_rdma_op, r_sg[nr_pages]), GFP_KERNEL);

	if (op == NULL) {

		ret = -ENOMEM;

		goto out;

	}

	op->r_write = !!(args->flags & RDS_RDMA_READWRITE);

	op->r_fence = !!(args->flags & RDS_RDMA_FENCE);

	op->r_notify = !!(args->flags & RDS_RDMA_NOTIFY_ME);

	op->r_recverr = rs->rs_recverr;

	WARN_ON(!nr_pages);

	sg_init_table(op->r_sg, nr_pages);

	if (op->r_notify || op->r_recverr) {

		/* We allocate an uninitialized notifier here, because

		 * we don't want to do that in the completion handler. We

		 * would have to use GFP_ATOMIC there, and don't want to deal

		 * with failed allocations.

		 */

		op->r_notifier = kmalloc(sizeof(struct rds_notifier), GFP_KERNEL);

		if (!op->r_notifier) {

			ret = -ENOMEM;

			goto out;

		}

		op->r_notifier->n_user_token = args->user_token;

		op->r_notifier->n_status = RDS_RDMA_SUCCESS;

	}

	/* The cookie contains the R_Key of the remote memory region, and

	 * optionally an offset into it. This is how we implement RDMA into

	 * unaligned memory.

	 * When setting up the RDMA, we need to add that offset to the

	 * destination address (which is really an offset into the MR)

	 * FIXME: We may want to move this into ib_rdma.c

	 */

	op->r_key = rds_rdma_cookie_key(args->cookie);

	op->r_remote_addr = args->remote_vec.addr + rds_rdma_cookie_offset(args->cookie);

	nr_bytes = 0;

	rdsdebug("RDS: rdma prepare nr_local %llu rva %llx rkey %x\n",

	       (unsigned long long)args->nr_local,

	       (unsigned long long)args->remote_vec.addr,

	       op->r_key);

	for (i = 0; i < args->nr_local; i++) {

		if (copy_from_user(&vec, &local_vec[i],

				   sizeof(struct rds_iovec))) {

			ret = -EFAULT;

			goto out;

		}

		nr = rds_pages_in_vec(&vec);

		if (nr == 0) {

			ret = -EINVAL;

			goto out;

		}

		rs->rs_user_addr = vec.addr;

		rs->rs_user_bytes = vec.bytes;

		/* did the user change the vec under us? */

		if (nr > max_pages || op->r_nents + nr > nr_pages) {

			ret = -EINVAL;

			goto out;

		}

		/* If it's a WRITE operation, we want to pin the pages for reading.

		 * If it's a READ operation, we need to pin the pages for writing.

		 */

		ret = rds_pin_pages(vec.addr & PAGE_MASK, nr, pages, !op->r_write);

		if (ret < 0)

			goto out;

		rdsdebug("RDS: nr_bytes %u nr %u vec.bytes %llu vec.addr %llx\n",

		       nr_bytes, nr, vec.bytes, vec.addr);

		nr_bytes += vec.bytes;

		for (j = 0; j < nr; j++) {

			unsigned int offset = vec.addr & ~PAGE_MASK;

			sg = &op->r_sg[op->r_nents + j];

			sg_set_page(sg, pages[j],

					min_t(unsigned int, vec.bytes, PAGE_SIZE - offset),

					offset);

			rdsdebug("RDS: sg->offset %x sg->len %x vec.addr %llx vec.bytes %llu\n",

			       sg->offset, sg->length, vec.addr, vec.bytes);

			vec.addr += sg->length;

			vec.bytes -= sg->length;

		}

		op->r_nents += nr;

	}

	if (nr_bytes > args->remote_vec.bytes) {

		rdsdebug("RDS nr_bytes %u remote_bytes %u do not match\n",

				nr_bytes,

				(unsigned int) args->remote_vec.bytes);

		ret = -EINVAL;

		goto out;

	}

	op->r_bytes = nr_bytes;

	ret = 0;

out:

	kfree(pages);

	if (ret) {

		if (op)

			rds_rdma_free_op(op);

		op = ERR_PTR(ret);

	}

	return op;

}

/*

 * The application asks for a RDMA transfer.

 * Extract all arguments and set up the rdma_op

 */

int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,

			  struct cmsghdr *cmsg)

{

	struct rds_rdma_op *op;

	if (cmsg->cmsg_len < CMSG_LEN(sizeof(struct rds_rdma_args))

	 || rm->m_rdma_op != NULL)

		return -EINVAL;

	op = rds_rdma_prepare(rs, CMSG_DATA(cmsg));

	if (IS_ERR(op))

		return PTR_ERR(op);

	rds_stats_inc(s_send_rdma);

	rm->m_rdma_op = op;

	return 0;

}

/*

 * The application wants us to pass an RDMA destination (aka MR)

 * to the remote

 */

int rds_cmsg_rdma_dest(struct rds_sock *rs, struct rds_message *rm,

			  struct cmsghdr *cmsg)

{

	unsigned long flags;

	struct rds_mr *mr;

	u32 r_key;

	int err = 0;

	if (cmsg->cmsg_len < CMSG_LEN(sizeof(rds_rdma_cookie_t))

	 || rm->m_rdma_cookie != 0)

		return -EINVAL;

	memcpy(&rm->m_rdma_cookie, CMSG_DATA(cmsg), sizeof(rm->m_rdma_cookie));