Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec

[GitHub/LineageOS/android_kernel_motorola_exynos9610.git] / net / rds / rdma.c

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

#include "rds.h"

/*
 * XXX
 *  - build with sparse
 *  - 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);
                refcount_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, refcount_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;
        unsigned long flags;

        /* Release any MRs associated with this socket */
        spin_lock_irqsave(&rs->rs_rdma_lock, flags);
        while ((node = rb_first(&rs->rs_rdma_keys))) {
                mr = rb_entry(node, struct rds_mr, r_rb_node);
                if (mr->r_trans == rs->rs_transport)
                        mr->r_invalidate = 0;
                rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys);
                RB_CLEAR_NODE(&mr->r_rb_node);
                spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);
                rds_destroy_mr(mr);
                rds_mr_put(mr);
                spin_lock_irqsave(&rs->rs_rdma_lock, flags);
        }
        spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);

        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;

        ret = get_user_pages_fast(user_addr, nr_pages, write, pages);

        if (ret >= 0 && 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) {
                ret = -EOPNOTSUPP;
                goto out;
        }

        nr_pages = rds_pages_in_vec(&args->vec);
        if (nr_pages == 0) {
                ret = -EINVAL;
                goto out;
        }

        /* Restrict the size of mr irrespective of underlying transport
         * To account for unaligned mr regions, subtract one from nr_pages
         */
        if ((nr_pages - 1) > (RDS_MAX_MSG_SIZE >> PAGE_SHIFT)) {
                ret = -EMSGSIZE;
                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) {
                ret = -ENOMEM;
                goto out;
        }

        mr = kzalloc(sizeof(struct rds_mr), GFP_KERNEL);
        if (!mr) {
                ret = -ENOMEM;
                goto out;
        }

        refcount_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, nr_pages, pages, 1);
        if (ret < 0)
                goto out;

        nents = ret;
        sg = kcalloc(nents, sizeof(*sg), GFP_KERNEL);
        if (!sg) {
                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) {
                refcount_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);
}

int rds_get_mr_for_dest(struct rds_sock *rs, char __user *optval, int optlen)
{
        struct rds_get_mr_for_dest_args args;
        struct rds_get_mr_args new_args;

        if (optlen != sizeof(struct rds_get_mr_for_dest_args))
                return -EINVAL;

        if (copy_from_user(&args, (struct rds_get_mr_for_dest_args __user *)optval,
                           sizeof(struct rds_get_mr_for_dest_args)))
                return -EFAULT;

        /*
         * Initially, just behave like get_mr().
         * TODO: Implement get_mr as wrapper around this
         *       and deprecate it.
         */
        new_args.vec = args.vec;
        new_args.cookie_addr = args.cookie_addr;
        new_args.flags = args.flags;

        return __rds_rdma_map(rs, &new_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) {
                pr_debug("rds: trying to unuse MR with unknown r_key %u!\n",
                         r_key);
                spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);
                return;
        }

        if (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;
        }
        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->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 rm_rdma_op *ro)
{
        unsigned int i;

        for (i = 0; i < ro->op_nents; i++) {
                struct page *page = sg_page(&ro->op_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->op_write) {
                        WARN_ON(!page->mapping && irqs_disabled());
                        set_page_dirty(page);
                }
                put_page(page);
        }

        kfree(ro->op_notifier);
        ro->op_notifier = NULL;
        ro->op_active = 0;
}

void rds_atomic_free_op(struct rm_atomic_op *ao)
{
        struct page *page = sg_page(ao->op_sg);

        /* Mark page dirty if it was possibly modified, which
         * is the case for a RDMA_READ which copies from remote
         * to local memory */
        set_page_dirty(page);
        put_page(page);

        kfree(ao->op_notifier);
        ao->op_notifier = NULL;
        ao->op_active = 0;
}


/*
 * Count the number of pages needed to describe an incoming iovec array.
 */
static int rds_rdma_pages(struct rds_iovec iov[], int nr_iovecs)
{
        int tot_pages = 0;
        unsigned int nr_pages;
        unsigned int i;

        /* figure out the number of pages in the vector */
        for (i = 0; i < nr_iovecs; i++) {
                nr_pages = rds_pages_in_vec(&iov[i]);
                if (nr_pages == 0)
                        return -EINVAL;

                tot_pages += nr_pages;

                /*
                 * nr_pages for one entry is limited to (UINT_MAX>>PAGE_SHIFT)+1,
                 * so tot_pages cannot overflow without first going negative.
                 */
                if (tot_pages < 0)
                        return -EINVAL;
        }

        return tot_pages;
}

int rds_rdma_extra_size(struct rds_rdma_args *args)
{
        struct rds_iovec vec;
        struct rds_iovec __user *local_vec;
        int tot_pages = 0;
        unsigned int nr_pages;
        unsigned int i;

        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)))
                        return -EFAULT;

                nr_pages = rds_pages_in_vec(&vec);
                if (nr_pages == 0)
                        return -EINVAL;

                tot_pages += nr_pages;

                /*
                 * nr_pages for one entry is limited to (UINT_MAX>>PAGE_SHIFT)+1,
                 * so tot_pages cannot overflow without first going negative.
                 */
                if (tot_pages < 0)
                        return -EINVAL;
        }

        return tot_pages * sizeof(struct scatterlist);
}

/*
 * 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_args *args;
        struct rm_rdma_op *op = &rm->rdma;
        int nr_pages;
        unsigned int nr_bytes;
        struct page **pages = NULL;
        struct rds_iovec iovstack[UIO_FASTIOV], *iovs = iovstack;
        int iov_size;
        unsigned int i, j;
        int ret = 0;

        if (cmsg->cmsg_len < CMSG_LEN(sizeof(struct rds_rdma_args))
            || rm->rdma.op_active)
                return -EINVAL;

        args = CMSG_DATA(cmsg);

        if (rs->rs_bound_addr == 0) {
                ret = -ENOTCONN; /* XXX not a great errno */
                goto out_ret;
        }

        if (args->nr_local > UIO_MAXIOV) {
                ret = -EMSGSIZE;
                goto out_ret;
        }

        /* Check whether to allocate the iovec area */
        iov_size = args->nr_local * sizeof(struct rds_iovec);
        if (args->nr_local > UIO_FASTIOV) {
                iovs = sock_kmalloc(rds_rs_to_sk(rs), iov_size, GFP_KERNEL);
                if (!iovs) {
                        ret = -ENOMEM;
                        goto out_ret;
                }
        }

        if (copy_from_user(iovs, (struct rds_iovec __user *)(unsigned long) args->local_vec_addr, iov_size)) {
                ret = -EFAULT;
                goto out;
        }

        nr_pages = rds_rdma_pages(iovs, args->nr_local);
        if (nr_pages < 0) {
                ret = -EINVAL;
                goto out;
        }

        pages = kcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL);
        if (!pages) {
                ret = -ENOMEM;
                goto out;
        }

        op->op_write = !!(args->flags & RDS_RDMA_READWRITE);
        op->op_fence = !!(args->flags & RDS_RDMA_FENCE);
        op->op_notify = !!(args->flags & RDS_RDMA_NOTIFY_ME);
        op->op_silent = !!(args->flags & RDS_RDMA_SILENT);
        op->op_active = 1;
        op->op_recverr = rs->rs_recverr;
        WARN_ON(!nr_pages);
        op->op_sg = rds_message_alloc_sgs(rm, nr_pages);
        if (!op->op_sg) {
                ret = -ENOMEM;
                goto out;
        }

        if (op->op_notify || op->op_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->op_notifier = kmalloc(sizeof(struct rds_notifier), GFP_KERNEL);
                if (!op->op_notifier) {
                        ret = -ENOMEM;
                        goto out;
                }
                op->op_notifier->n_user_token = args->user_token;
                op->op_notifier->n_status = RDS_RDMA_SUCCESS;

                /* Enable rmda notification on data operation for composite
                 * rds messages and make sure notification is enabled only
                 * for the data operation which follows it so that application
                 * gets notified only after full message gets delivered.
                 */
                if (rm->data.op_sg) {
                        rm->rdma.op_notify = 0;
                        rm->data.op_notify = !!(args->flags & RDS_RDMA_NOTIFY_ME);
                }
        }

        /* 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->op_rkey = rds_rdma_cookie_key(args->cookie);
        op->op_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->op_rkey);

        for (i = 0; i < args->nr_local; i++) {
                struct rds_iovec *iov = &iovs[i];
                /* don't need to check, rds_rdma_pages() verified nr will be +nonzero */
                unsigned int nr = rds_pages_in_vec(iov);

                rs->rs_user_addr = iov->addr;
                rs->rs_user_bytes = iov->bytes;

                /* 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(iov->addr, nr, pages, !op->op_write);
                if (ret < 0)
                        goto out;
                else
                        ret = 0;

                rdsdebug("RDS: nr_bytes %u nr %u iov->bytes %llu iov->addr %llx\n",
                         nr_bytes, nr, iov->bytes, iov->addr);

                nr_bytes += iov->bytes;

                for (j = 0; j < nr; j++) {
                        unsigned int offset = iov->addr & ~PAGE_MASK;
                        struct scatterlist *sg;

                        sg = &op->op_sg[op->op_nents + j];
                        sg_set_page(sg, pages[j],
                                        min_t(unsigned int, iov->bytes, PAGE_SIZE - offset),
                                        offset);

                        rdsdebug("RDS: sg->offset %x sg->len %x iov->addr %llx iov->bytes %llu\n",
                               sg->offset, sg->length, iov->addr, iov->bytes);

                        iov->addr += sg->length;
                        iov->bytes -= sg->length;
                }

                op->op_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->op_bytes = nr_bytes;

out:
        if (iovs != iovstack)
                sock_kfree_s(rds_rs_to_sk(rs), iovs, iov_size);
        kfree(pages);
out_ret:
        if (ret)
                rds_rdma_free_op(op);
        else
                rds_stats_inc(s_send_rdma);

        return ret;
}

/*
 * 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));

        /* We are reusing a previously mapped MR here. Most likely, the
         * application has written to the buffer, so we need to explicitly
         * flush those writes to RAM. Otherwise the HCA may not see them
         * when doing a DMA from that buffer.
         */
        r_key = rds_rdma_cookie_key(rm->m_rdma_cookie);

        spin_lock_irqsave(&rs->rs_rdma_lock, flags);
        mr = rds_mr_tree_walk(&rs->rs_rdma_keys, r_key, NULL);
        if (!mr)
                err = -EINVAL;  /* invalid r_key */
        else
                refcount_inc(&mr->r_refcount);
        spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);

        if (mr) {
                mr->r_trans->sync_mr(mr->r_trans_private, DMA_TO_DEVICE);
                rm->rdma.op_rdma_mr = mr;
        }
        return err;
}

/*
 * The application passes us an address range it wants to enable RDMA
 * to/from. We map the area, and save the <R_Key,offset> pair
 * in rm->m_rdma_cookie. This causes it to be sent along to the peer
 * in an extension header.
 */
int rds_cmsg_rdma_map(struct rds_sock *rs, struct rds_message *rm,
                          struct cmsghdr *cmsg)
{
        if (cmsg->cmsg_len < CMSG_LEN(sizeof(struct rds_get_mr_args)) ||
            rm->m_rdma_cookie != 0)
                return -EINVAL;

        return __rds_rdma_map(rs, CMSG_DATA(cmsg), &rm->m_rdma_cookie, &rm->rdma.op_rdma_mr);
}

/*
 * Fill in rds_message for an atomic request.
 */
int rds_cmsg_atomic(struct rds_sock *rs, struct rds_message *rm,
                    struct cmsghdr *cmsg)
{
        struct page *page = NULL;
        struct rds_atomic_args *args;
        int ret = 0;

        if (cmsg->cmsg_len < CMSG_LEN(sizeof(struct rds_atomic_args))
         || rm->atomic.op_active)
                return -EINVAL;

        args = CMSG_DATA(cmsg);

        /* Nonmasked & masked cmsg ops converted to masked hw ops */
        switch (cmsg->cmsg_type) {
        case RDS_CMSG_ATOMIC_FADD:
                rm->atomic.op_type = RDS_ATOMIC_TYPE_FADD;
                rm->atomic.op_m_fadd.add = args->fadd.add;
                rm->atomic.op_m_fadd.nocarry_mask = 0;
                break;
        case RDS_CMSG_MASKED_ATOMIC_FADD:
                rm->atomic.op_type = RDS_ATOMIC_TYPE_FADD;
                rm->atomic.op_m_fadd.add = args->m_fadd.add;
                rm->atomic.op_m_fadd.nocarry_mask = args->m_fadd.nocarry_mask;
                break;
        case RDS_CMSG_ATOMIC_CSWP:
                rm->atomic.op_type = RDS_ATOMIC_TYPE_CSWP;
                rm->atomic.op_m_cswp.compare = args->cswp.compare;
                rm->atomic.op_m_cswp.swap = args->cswp.swap;
                rm->atomic.op_m_cswp.compare_mask = ~0;
                rm->atomic.op_m_cswp.swap_mask = ~0;
                break;
        case RDS_CMSG_MASKED_ATOMIC_CSWP:
                rm->atomic.op_type = RDS_ATOMIC_TYPE_CSWP;
                rm->atomic.op_m_cswp.compare = args->m_cswp.compare;
                rm->atomic.op_m_cswp.swap = args->m_cswp.swap;
                rm->atomic.op_m_cswp.compare_mask = args->m_cswp.compare_mask;
                rm->atomic.op_m_cswp.swap_mask = args->m_cswp.swap_mask;
                break;
        default:
                BUG(); /* should never happen */
        }

        rm->atomic.op_notify = !!(args->flags & RDS_RDMA_NOTIFY_ME);
        rm->atomic.op_silent = !!(args->flags & RDS_RDMA_SILENT);
        rm->atomic.op_active = 1;
        rm->atomic.op_recverr = rs->rs_recverr;
        rm->atomic.op_sg = rds_message_alloc_sgs(rm, 1);
        if (!rm->atomic.op_sg) {
                ret = -ENOMEM;
                goto err;
        }

        /* verify 8 byte-aligned */
        if (args->local_addr & 0x7) {
                ret = -EFAULT;
                goto err;
        }

        ret = rds_pin_pages(args->local_addr, 1, &page, 1);
        if (ret != 1)
                goto err;
        ret = 0;

        sg_set_page(rm->atomic.op_sg, page, 8, offset_in_page(args->local_addr));

        if (rm->atomic.op_notify || rm->atomic.op_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.
                 */
                rm->atomic.op_notifier = kmalloc(sizeof(*rm->atomic.op_notifier), GFP_KERNEL);
                if (!rm->atomic.op_notifier) {
                        ret = -ENOMEM;
                        goto err;
                }

                rm->atomic.op_notifier->n_user_token = args->user_token;
                rm->atomic.op_notifier->n_status = RDS_RDMA_SUCCESS;
        }

        rm->atomic.op_rkey = rds_rdma_cookie_key(args->cookie);
        rm->atomic.op_remote_addr = args->remote_addr + rds_rdma_cookie_offset(args->cookie);

        return ret;
err:
        if (page)
                put_page(page);
        kfree(rm->atomic.op_notifier);

        return ret;
}