[Devel] [PATCH RHEL9 COMMIT] fs/fuse kio: implement pcs_krpc - export kernel RPC to userspace

Konstantin Khorenko khorenko at virtuozzo.com
Fri Jul 12 18:59:48 MSK 2024


The commit is pushed to "branch-rh9-5.14.0-427.22.1.vz9.62.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh9-5.14.0-427.22.1.vz9.62.3
------>
commit bce4de9b195e0d66dffd8a39b6a955e99c15171c
Author: Liu Kui <kui.liu at virtuozzo.com>
Date:   Tue Jul 2 23:26:07 2024 +0800

    fs/fuse kio: implement pcs_krpc - export kernel RPC to userspace
    
    Currently there are 2 connections for every RPC, one in userspace,
    one in kernel. This wastes a lot of resources on client hosts from
    a huge cluster. It's therefore desirable to eliminate the connection
    in userspace by using kernel RPC directly from userspace.
    
    The newly implemented pcs_krpc serves as the glue layer between
    userspace RPC and kernel RPC. It provides execution context for
    forwarding messages from/to userspace RPC to/from kernel RPC.
    It also provides APIs for userspace to send/receive RPC messages.
    
    https://pmc.acronis.work/browse/VSTOR-82613
    
    Signed-off-by: Liu Kui <kui.liu at virtuozzo.com>
    
    ======
    Patchset description:
    fs/fuse kio: introduce pcs_krpc for merging userspace RPC in vstorage-mount with kernel RPC
    
    Implement pcs_krpc in kio module to support using kernel RPC directly
    from userspace.
    
    https://pmc.acronis.work/browse/VSTOR-82613
    
    Liu Kui (4):
      fs/fuse kio: implement memory region to support zero-copy between
        userspace and kernel.
      fs/fuse kio: implement pcs_krpc - export kernel RPC to userspace
      fs/fuse kio: adapt pcs_rpc to support pcs_krpc.
      fs/fuse kio: integrate pcs_krpc to kio module
    
    Feature: fuse: kRPC - single RPC for kernel and userspace
---
 fs/fuse/kio/pcs/pcs_krpc.c      | 815 ++++++++++++++++++++++++++++++++++++++++
 fs/fuse/kio/pcs/pcs_krpc.h      | 144 +++++++
 fs/fuse/kio/pcs/pcs_krpc_prot.h |  44 +++
 3 files changed, 1003 insertions(+)

diff --git a/fs/fuse/kio/pcs/pcs_krpc.c b/fs/fuse/kio/pcs/pcs_krpc.c
new file mode 100644
index 000000000000..3169c54a2a8b
--- /dev/null
+++ b/fs/fuse/kio/pcs/pcs_krpc.c
@@ -0,0 +1,815 @@
+/*
+ * Copyright (c) 2018-2021 Virtuozzo International GmbH. All rights reserved.
+ */
+
+#include <linux/types.h>
+#include <linux/list.h>
+#include <linux/rbtree.h>
+#include <linux/refcount.h>
+#include <linux/file.h>
+#include <linux/anon_inodes.h>
+
+#include "pcs_types.h"
+#include "pcs_cluster.h"
+#include "pcs_cs_prot.h"
+#include "pcs_req.h"
+#include "pcs_krpc.h"
+
+struct kmem_cache *krpc_req_cachep;
+
+static int krpc_completion_post(struct pcs_krpc *krpc, struct krpc_completion *comp)
+__releases(krpc->lock)
+{
+	/* post complete only when connected */
+	if (krpc->state != PCS_KRPC_STATE_CONNECTED) {
+		spin_unlock(&krpc->lock);
+		return -1;
+	}
+	list_add_tail(&comp->link, &krpc->completion_queue);
+	krpc->nr_completion++;
+	spin_unlock(&krpc->lock);
+
+	wake_up_poll(&krpc->poll_wait, EPOLLIN);
+	return 0;
+}
+
+static struct krpc_req *krpc_req_alloc(void)
+{
+	struct krpc_req *kreq;
+
+	kreq = kmem_cache_alloc(krpc_req_cachep, GFP_NOIO);
+	if (!kreq)
+		return NULL;
+
+	spin_lock_init(&kreq->lock);
+	kreq->flags = 0;
+	memset(&kreq->completion, 0, sizeof(struct krpc_completion));
+
+	return kreq;
+}
+
+static void krpc_req_free(struct krpc_req *kreq)
+{
+	kmem_cache_free(krpc_req_cachep, kreq);
+}
+
+static void krpc_completion_free(struct krpc_completion *comp)
+{
+	if (comp->private)
+		krpc_req_free((struct krpc_req *)comp->private);
+	else
+		kfree(comp);
+}
+
+static void krpc_req_complete(struct krpc_req *kreq, int error)
+{
+	struct krpc_completion *comp = &kreq->completion;
+	struct pcs_krpc *krpc = kreq->krpc;
+	int i;
+
+	BUG_ON(!comp->xid);
+
+	comp->result = error;
+
+	pcs_mr_put(kreq->hdr_chunk.mr);
+
+	for (i = 0; i < kreq->nr_data_chunks; i++) {
+		struct krpc_chunk *chunk;
+
+		chunk = &kreq->data_chunks[i];
+		if (chunk->type == KRPC_CHUNK_TYPE_UMEM)
+			pcs_umem_release(chunk->umem);
+		else
+			pcs_mr_put(chunk->mr);
+	}
+
+	if (kreq->data_chunks != &kreq->inline_data_chunks[0])
+		kfree(kreq->data_chunks);
+
+	spin_lock(&krpc->lock);
+	list_del(&kreq->link);
+
+	if (kreq->flags & KRPC_REQ_F_ABORTED) {
+		krpc_req_free(kreq);
+		spin_unlock(&krpc->lock);
+	} else if (krpc_completion_post(krpc, comp)) {
+		krpc_req_free(kreq);
+	}
+
+	pcs_krpc_put(krpc);
+}
+
+static void krpc_msg_get_response_iter(struct pcs_msg *msg, int offset,
+			struct iov_iter *it, unsigned int direction)
+{
+	struct pcs_msg *req = msg->private;
+	struct krpc_req *kreq = req->private2;
+
+	if (!(kreq->flags & KRPC_REQ_F_RESP_BUFF)) {
+		/* No data payload */
+		BUG_ON(msg->size > PAGE_SIZE);
+
+		kreq->hdr_kv.iov_base = (void *)kreq->hdr_buf;
+		kreq->hdr_kv.iov_len = msg->size;
+
+		iov_iter_kvec(it, direction, &kreq->hdr_kv, 1, msg->size);
+		iov_iter_advance(it, offset);
+	} else {
+		/* With data payload */
+		int hdr_size = sizeof(struct pcs_cs_iohdr);
+
+		if (offset < hdr_size) {
+			kreq->hdr_kv.iov_base = (void *)kreq->hdr_buf;
+			kreq->hdr_kv.iov_len = hdr_size;
+			iov_iter_kvec(it, direction, &kreq->hdr_kv, 1, hdr_size);
+			iov_iter_advance(it, offset);
+		} else {
+			BUG_ON((offset - hdr_size) > kreq->data_len);
+			BUG_ON(msg->size - hdr_size > kreq->data_len);
+
+			iov_iter_bvec(it, direction, &kreq->data_bvecs[0],
+						kreq->nr_data_bvecs, kreq->data_len);
+			iov_iter_truncate(it, msg->size - hdr_size);
+			iov_iter_advance(it, offset - hdr_size);
+		}
+	}
+}
+
+struct pcs_msg *krpc_get_hdr(struct pcs_rpc *ep, struct pcs_rpc_hdr *h)
+{
+	struct pcs_msg *msg, *resp;
+	struct pcs_rpc_hdr *req_h;
+	struct krpc_req *kreq;
+
+	if (!RPC_IS_RESPONSE(h->type))
+		return NULL;
+
+	msg = pcs_rpc_lookup_xid(ep, &h->xid);
+	if (msg == NULL)
+		return NULL;
+
+	req_h = (struct pcs_rpc_hdr *)msg_inline_head(msg);
+	if (req_h->type != (h->type & ~PCS_RPC_DIRECTION))
+		return NULL;
+
+	kreq = msg->private2;
+
+	resp = pcs_rpc_alloc_input_msg(ep, sizeof(struct pcs_rpc_hdr));
+	if (!resp)
+		return NULL;
+
+	memcpy(resp->_inline_buffer, h, sizeof(struct pcs_rpc_hdr));
+	memcpy(kreq->hdr_buf, h, sizeof(struct pcs_rpc_hdr));
+	resp->size = h->len;
+	resp->private = msg;
+	resp->get_iter = krpc_msg_get_response_iter;
+	resp->done = rpc_work_input;
+	pcs_msg_del_calendar(msg);
+
+	return resp;
+}
+
+/*
+ * All request type message from cs are forwarded to userspace directly. The PCS KRPC
+ * layer cannot process these request on its own.
+ */
+static void krpc_handle_request(struct pcs_krpc *krpc, struct pcs_msg *msg)
+{
+	struct krpc_completion *comp;
+
+	if (krpc->state != PCS_KRPC_STATE_CONNECTED)
+		return;
+
+	comp = kzalloc(sizeof(*comp) + msg->size, GFP_NOIO);
+	if (!comp)
+		return;
+
+	memcpy(comp->_data_buf, msg->_inline_buffer, msg->size);
+	comp->data_len = msg->size;
+
+	spin_lock(&krpc->lock);
+	if (krpc_completion_post(krpc, comp))
+		kfree(comp);
+}
+
+/*
+ * Let userspace to handle cs_congestion_notify request.
+ */
+void krpc_handle_congestion(struct pcs_rpc *ep, struct pcs_msg *msg)
+{
+	krpc_handle_request(ep->clnt_krpc, msg);
+}
+
+/*
+ * Let userspace to handle the keep_waiting request.
+ */
+void krpc_keep_waiting(struct pcs_rpc *ep, struct pcs_msg *req, struct pcs_msg *msg)
+{
+	krpc_handle_request(ep->clnt_krpc, msg);
+}
+
+unsigned int pcs_krpc_hash(PCS_NODE_ID_T *id)
+{
+	return *(unsigned int *)id % PCS_KRPC_HASH_SIZE;
+}
+
+static void krpc_msg_get_data(struct pcs_msg *msg, int offset,
+		struct iov_iter *it, unsigned int direction)
+{
+	struct krpc_req *kreq = msg->private2;
+	int hdr_size = pcs_krpc_msg_size(kreq->hdr_chunk.len, kreq->flags);
+	int data_size = pcs_krpc_msg_size(kreq->data_len, kreq->flags);
+	struct pcs_krpc *krpc = kreq->krpc;
+
+	if (offset < kreq->hdr_chunk.len) {
+		iov_iter_kvec(it, direction, &kreq->hdr_kv, 1, kreq->hdr_chunk.len);
+		iov_iter_advance(it, offset);
+		return;
+	}
+
+	if (offset < hdr_size) {
+		iov_iter_kvec(it, direction, &(cc_from_krpcset(krpc->krpcs))->nilbuffer_kv,
+						 1, hdr_size - offset);
+		return;
+	}
+
+	if (offset < hdr_size + kreq->data_len) {
+		iov_iter_bvec(it, direction, &kreq->data_bvecs[0],
+				kreq->nr_data_bvecs, kreq->data_len);
+		iov_iter_advance(it, offset - hdr_size);
+		return;
+	}
+
+	BUG_ON(offset >= hdr_size + data_size);
+
+	iov_iter_kvec(it, direction, &(cc_from_krpcset(krpc->krpcs))->nilbuffer_kv,
+					1, (hdr_size + data_size - offset));
+}
+
+static void pcs_krpc_response_done(struct pcs_msg *msg)
+{
+	struct krpc_req *kreq = msg->private2;
+
+	if (msg->rpc) {
+		pcs_rpc_put(msg->rpc);
+		msg->rpc = NULL;
+	}
+
+	krpc_req_complete(kreq, msg->error.value);
+}
+
+static void pcs_krpc_msg_sent(struct pcs_msg *msg)
+{
+	msg->done = pcs_krpc_response_done;
+	if (pcs_if_error(&msg->error)) {
+		msg->done(msg);
+		return;
+	}
+	pcs_rpc_sent(msg);
+}
+
+static int pcs_krpc_ioctl_recv_msg(struct pcs_krpc *krpc, struct pcs_krpc_ioc_recvmsg *iocmsg)
+{
+	struct krpc_completion *comp;
+	int res = 0;
+
+	spin_lock(&krpc->lock);
+	if (list_empty(&krpc->completion_queue)) {
+		spin_unlock(&krpc->lock);
+		return 0;
+	}
+
+	comp = list_first_entry(&krpc->completion_queue, struct krpc_completion, link);
+	list_del(&comp->link);
+	krpc->nr_completion--;
+	spin_unlock(&krpc->lock);
+
+	if (comp->result) {
+		res -= comp->result;
+		goto out;
+	}
+
+	res = 1;
+	iocmsg->xid = comp->xid;
+	if (comp->xid == 0) {
+		BUG_ON(!comp->data_len);
+		BUG_ON(iocmsg->buf.len < comp->data_len);
+		if (copy_to_user((void __user *)iocmsg->buf.addr, comp->_data_buf, comp->data_len))
+			res = -EFAULT;
+	}
+
+out:
+	krpc_completion_free(comp);
+	return res;
+}
+
+static int pcs_krpc_ioctl_send_msg(struct pcs_krpc *krpc, struct pcs_krpc_ioc_sendmsg *iocmsg)
+{
+	struct krpc_req *kreq;
+	struct pcs_msg *msg;
+	struct pcs_krpc_buf_desc *chunk_bd;
+	struct krpc_chunk *chunk;
+	int res, i;
+	struct bio_vec *bvec;
+
+	kreq = krpc_req_alloc();
+	if (!kreq)
+		return -ENOMEM;
+
+	if (iocmsg->nr_data_chunks > NR_KRPC_DATA_CHUNKS_INLINE) {
+		kreq->data_chunks = kzalloc(iocmsg->nr_data_chunks, GFP_NOIO);
+		if (!kreq->data_chunks) {
+			res = -ENOMEM;
+			goto err_free_kreq;
+		}
+	} else {
+		kreq->data_chunks = &kreq->inline_data_chunks[0];
+	}
+
+	/*
+	 * Header buff is exactly one page, used for staging message header. Will be used for
+	 * receiving header of response message as well.
+	 */
+	BUG_ON(iocmsg->hdr_chunk.addr & (PAGE_SIZE - 1));
+
+	chunk_bd = &iocmsg->hdr_chunk;
+	chunk = &kreq->hdr_chunk;
+
+	chunk->addr = chunk_bd->addr;
+	chunk->len = chunk_bd->len;
+	chunk->type = KRPC_CHUNK_TYPE_MR;
+
+	chunk->mr = pcs_mr_get(&cc_from_krpc(krpc)->mrs, iocmsg->hdr_chunk.mr_id);
+	BUG_ON(!chunk->mr);
+
+	kreq->hdr_buf = (char *) kmap(pcs_umem_page(chunk->mr->umem, chunk->addr));
+	kreq->hdr_kv.iov_base = kreq->hdr_buf;
+	kreq->hdr_kv.iov_len = chunk->len;
+
+	/* data chunk buf descriptors are placed at end of header buf, grow backwards */
+	kreq->data_len = 0;
+	kreq->nr_data_chunks = 0;
+	kreq->nr_data_bvecs = 0;
+
+	chunk_bd = (struct pcs_krpc_buf_desc *)(kreq->hdr_buf + PAGE_SIZE) - 1;
+	chunk = kreq->data_chunks;
+	bvec = &kreq->data_bvecs[0];
+
+	for (i = 0; i < iocmsg->nr_data_chunks; i++) {
+		struct page *page;
+		u64 addr;
+		int offset, len;
+
+		chunk->addr = chunk_bd->addr;
+		chunk->len = chunk_bd->len;
+		if (chunk_bd->mr_id) {
+			chunk->mr = pcs_mr_get(&cc_from_krpc(krpc)->mrs, chunk_bd->mr_id);
+			chunk->type = KRPC_CHUNK_TYPE_MR;
+			if (!chunk->mr) {
+				res = -ENXIO;
+				goto err_free_data_chunk;
+			}
+		} else {
+			/* unregistered memory buf */
+			chunk->umem = pcs_umem_get(chunk->addr, chunk->len);
+			if (IS_ERR(chunk->umem)) {
+				res = PTR_ERR(chunk->umem);
+				goto err_free_data_chunk;
+			}
+
+			chunk->type = KRPC_CHUNK_TYPE_UMEM;
+		}
+
+		/* build the bvecs for the data chunk*/
+		addr = chunk->addr;
+		len = chunk->len;
+
+		while (len) {
+			/* data bvec array overflow? */
+			BUG_ON(kreq->nr_data_bvecs >= KRPC_MAX_DATA_PAGES);
+
+			if (chunk->type == KRPC_CHUNK_TYPE_MR)
+				page = pcs_umem_page(chunk->mr->umem, addr);
+			else
+				page = pcs_umem_page(chunk->umem, addr);
+
+			BUG_ON(!page);
+
+			offset = addr & (PAGE_SIZE - 1);
+
+			bvec->bv_page = page;
+			bvec->bv_offset = offset;
+
+			bvec->bv_len = len < (PAGE_SIZE - offset) ? len : (PAGE_SIZE - offset);
+
+			addr += bvec->bv_len;
+			len -= bvec->bv_len;
+			bvec++;
+			kreq->nr_data_bvecs++;
+		}
+		BUG_ON(len != 0);
+
+		kreq->data_len += chunk->len;
+		chunk++;
+		chunk_bd--;
+		kreq->nr_data_chunks++;
+	}
+
+	kreq->completion.xid = iocmsg->xid;
+	kreq->completion.private = kreq;
+
+	kreq->flags = iocmsg->flags;
+
+	msg = &kreq->msg;
+	msg->private = krpc;
+	msg->private2 = kreq;
+
+	INIT_HLIST_NODE(&msg->kill_link);
+	pcs_clear_error(&msg->error);
+
+	msg->size = iocmsg->msg_size;
+	msg->timeout = iocmsg->timeout;
+
+	msg->rpc = NULL;
+	msg->done = pcs_krpc_msg_sent;
+	msg->get_iter = krpc_msg_get_data;
+
+	spin_lock(&krpc->lock);
+	kreq->krpc = pcs_krpc_get(krpc);
+	list_add_tail(&kreq->link, &krpc->pending_queue);
+	spin_unlock(&krpc->lock);
+	/* DTRACE to be added */
+	pcs_rpc_queue(krpc->rpc, msg);
+
+	return 0;
+
+err_free_data_chunk:
+	for (i = 0; i < kreq->nr_data_chunks; i++) {
+		chunk = &kreq->data_chunks[i];
+		if (chunk->type == KRPC_CHUNK_TYPE_UMEM)
+			pcs_umem_release(chunk->umem);
+		else
+			pcs_mr_put(chunk->mr);
+	}
+	pcs_mr_put(kreq->hdr_chunk.mr);
+
+	if (kreq->data_chunks != &kreq->inline_data_chunks[0])
+		kfree(kreq->data_chunks);
+
+err_free_kreq:
+	krpc_req_free(kreq);
+	return res;
+}
+
+static int pcs_krpc_abort(struct pcs_krpc *krpc)
+{
+	struct list_head dispose_list;
+	struct krpc_req *kreq;
+	struct krpc_completion *comp;
+
+	INIT_LIST_HEAD(&dispose_list);
+
+	spin_lock(&krpc->lock);
+
+	if (krpc->state != PCS_KRPC_STATE_CONNECTED) {
+		spin_unlock(&krpc->lock);
+		return 0;
+	}
+
+	krpc->state = PCS_KRPC_STATE_ABORTED;
+
+	/* abort incompleted requests */
+	list_splice_tail_init(&krpc->pending_queue, &krpc->dispose_queue);
+	list_for_each_entry(kreq, &krpc->dispose_queue, link)
+		kreq->flags |= KRPC_REQ_F_ABORTED;
+
+	list_splice_tail_init(&krpc->completion_queue, &dispose_list);
+	krpc->nr_completion = 0;
+
+	spin_unlock(&krpc->lock);
+
+	/* dispose all unprocessed completions */
+	while (!list_empty(&dispose_list)) {
+		comp = list_first_entry(&dispose_list, struct krpc_completion, link);
+		list_del(&comp->link);
+		krpc_completion_free(comp);
+	}
+
+	return 0;
+}
+
+static long pcs_krpc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct pcs_krpc_context *ctx = file->private_data;
+	struct pcs_krpc *krpc = ctx->krpc;
+	int res = 0;
+
+	if (unlikely(ctx->gen != krpc->gen))
+		return -EFAULT;
+
+	switch (cmd) {
+	case PCS_KRPC_IOC_SEND_MSG: {
+		struct pcs_krpc_ioc_sendmsg req;
+
+		if (copy_from_user(&req, (void __user *)arg, sizeof(req)))
+			return -EFAULT;
+
+		res = pcs_krpc_ioctl_send_msg(krpc, &req);
+		break;
+	}
+	case PCS_KRPC_IOC_RECV_MSG: {
+		struct pcs_krpc_ioc_recvmsg req;
+
+		res = pcs_krpc_ioctl_recv_msg(krpc, &req);
+
+		if (copy_to_user((void __user *)arg, &req, sizeof(req)))
+			return -EFAULT;
+		break;
+	}
+	case PCS_KRPC_IOC_ABORT:
+		res = pcs_krpc_abort(krpc);
+		break;
+	default:
+		res = -ENOTTY;
+		break;
+	}
+
+	return res;
+}
+
+static __poll_t pcs_krpc_poll(struct file *file, poll_table *wait)
+{
+	struct pcs_krpc_context *ctx = file->private_data;
+	struct pcs_krpc *krpc = ctx->krpc;
+	__poll_t pollflags = 0;
+
+	poll_wait(file, &krpc->poll_wait, wait);
+
+	if (unlikely(ctx->gen != krpc->gen)) {
+		pollflags |= EPOLLERR;
+		return pollflags;
+	}
+
+	spin_lock(&krpc->lock);
+
+	if (krpc->state == PCS_KRPC_STATE_ABORTED)
+		pollflags |= EPOLLERR;
+	else if (krpc->state == PCS_KRPC_STATE_CONNECTED) {
+		pollflags |= EPOLLOUT;
+		if (!list_empty(&krpc->completion_queue))
+			pollflags |= EPOLLIN;
+	}
+
+	spin_unlock(&krpc->lock);
+
+	return pollflags;
+}
+
+/*
+ * Close connection
+ */
+static int pcs_krpc_release(struct inode *inode, struct file *file)
+{
+	struct pcs_krpc_context *ctx = file->private_data;
+	struct pcs_krpc *krpc = ctx->krpc;
+
+	/* User may have started a new connection before close the old one */
+	if (ctx->gen == krpc->gen)
+		pcs_krpc_abort(krpc);
+
+	pcs_krpc_put(krpc);
+	kfree(ctx);
+
+	return 0;
+}
+
+static const struct file_operations pcs_krpc_fops = {
+	.owner = THIS_MODULE,
+	.release = pcs_krpc_release,
+	.poll	= pcs_krpc_poll,
+	.unlocked_ioctl = pcs_krpc_ioctl,
+	.llseek		= no_llseek,
+};
+
+struct pcs_krpc *pcs_krpc_lookup(struct pcs_krpc_set *krpcs, PCS_NODE_ID_T *id)
+{
+	struct pcs_krpc *krpc;
+
+	hlist_for_each_entry(krpc, &krpcs->ht[pcs_krpc_hash(id)], hlist) {
+		if (memcmp(&krpc->id, id, sizeof(krpc->id)) == 0)
+			return krpc;
+	}
+	return NULL;
+}
+
+struct pcs_krpc *pcs_krpc_get(struct pcs_krpc *krpc)
+{
+	refcount_inc(&krpc->refcnt);
+	return krpc;
+}
+
+void pcs_krpc_put(struct pcs_krpc *krpc)
+{
+	if (refcount_dec_and_test(&krpc->refcnt))
+		kfree(krpc);
+}
+
+/*
+ * Create a new pcs_krpc
+ */
+int pcs_krpc_create(struct pcs_krpc_set *krpcs, PCS_NODE_ID_T *id,
+		PCS_NET_ADDR_T *addr, int cs_flags)
+{
+	struct pcs_krpc *krpc;
+
+	krpc = kzalloc(sizeof(struct pcs_krpc), GFP_NOIO);
+	if (!krpc)
+		return -ENOMEM;
+
+	INIT_HLIST_NODE(&krpc->hlist);
+	INIT_LIST_HEAD(&krpc->link);
+	spin_lock_init(&krpc->lock);
+	refcount_set(&krpc->refcnt, 1);
+	INIT_LIST_HEAD(&krpc->pending_queue);
+	INIT_LIST_HEAD(&krpc->dispose_queue);
+	INIT_LIST_HEAD(&krpc->completion_queue);
+	init_waitqueue_head(&krpc->poll_wait);
+
+	krpc->krpcs = krpcs;
+	krpc->id = *id;
+	krpc->gen = 0;
+	krpc->state = PCS_KRPC_STATE_UNCONN;
+
+	krpc->rpc = pcs_rpc_clnt_create(&cc_from_krpcset(krpcs)->eng, id, addr, cs_flags);
+	if (!krpc->rpc) {
+		kfree(krpc);
+		return -ENOMEM;
+	}
+
+	krpc->rpc->clnt_krpc = krpc;
+
+	spin_lock(&krpc->lock);
+	spin_lock(&krpcs->lock);
+	hlist_add_head(&krpc->hlist, &krpcs->ht[pcs_krpc_hash(&krpc->id)]);
+	list_add_tail(&krpc->link, &krpcs->list);
+	krpcs->nkrpc++;
+	spin_unlock(&krpcs->lock);
+	spin_unlock(&krpc->lock);
+
+	return 0;
+}
+
+int pcs_krpc_update_addr(struct pcs_krpc_set *krpcs, PCS_NODE_ID_T *id,
+		PCS_NET_ADDR_T *addr, int flags)
+{
+	struct pcs_krpc *krpc;
+
+	krpc = pcs_krpc_lookup(krpcs, id);
+	if (!krpc)
+		return -ENXIO;
+
+	pcs_rpc_set_address(krpc->rpc, addr);
+
+	if (flags & CS_FL_LOCAL_SOCK)
+		krpc->rpc->flags |= PCS_RPC_F_LOCAL;
+	else
+		krpc->rpc->flags &= ~PCS_RPC_F_LOCAL;
+
+	return 0;
+}
+/*
+ * Connect to a pcs_krpc, return a valid fd on success.
+ */
+int pcs_krpc_connect(struct pcs_krpc_set *krpcs, PCS_NODE_ID_T *id)
+{
+	struct pcs_krpc *krpc;
+	int fd;
+	struct file *file;
+	struct pcs_krpc_context *ctx;
+
+	krpc = pcs_krpc_lookup(krpcs, id);
+	if (!krpc)
+		return -ENXIO;
+
+	if (krpc->state == PCS_KRPC_STATE_CONNECTED ||
+		krpc->state == PCS_KRPC_STATE_DESTROYED)
+		return -EPERM;
+
+	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	fd = get_unused_fd_flags(O_CLOEXEC);
+	if (fd < 0) {
+		kfree(ctx);
+		return fd;
+	}
+
+	file = anon_inode_getfile("[pcs_krpc]", &pcs_krpc_fops, ctx, 0);
+	if (IS_ERR(file)) {
+		kfree(ctx);
+		put_unused_fd(fd);
+		fd = PTR_ERR(file);
+		return fd;
+	}
+
+	fd_install(fd, file);
+
+	spin_lock(&krpc->lock);
+	ctx->gen = ++krpc->gen;
+	ctx->krpc = pcs_krpc_get(krpc);
+	/*
+	 * the krpc should always be connected regardless state of
+	 * underlying RPC
+	 */
+	krpc->state = PCS_KRPC_STATE_CONNECTED;
+	spin_unlock(&krpc->lock);
+
+	return fd;
+}
+
+static void __pcs_krpc_destroy(struct pcs_krpc *krpc)
+{
+	spin_lock(&krpc->lock);
+
+	krpc->state = PCS_KRPC_STATE_DESTROYED;
+
+	/*Remove from krpc set*/
+	spin_lock(&krpc->krpcs->lock);
+	hlist_del(&krpc->hlist);
+	list_del(&krpc->link);
+	krpc->krpcs->nkrpc--;
+	spin_unlock(&krpc->krpcs->lock);
+
+	spin_unlock(&krpc->lock);
+
+	if (krpc->rpc) {
+		krpc->rpc->clnt_krpc = NULL;
+		pcs_rpc_clnt_close(krpc->rpc);
+		krpc->rpc = NULL;
+	}
+	pcs_krpc_put(krpc);
+}
+
+int pcs_krpc_destroy(struct pcs_krpc_set *krpcs, PCS_NODE_ID_T *id)
+{
+	struct pcs_krpc *krpc;
+
+	krpc = pcs_krpc_lookup(krpcs, id);
+	BUG_ON(!krpc);
+
+	/* Abort current connection */
+	pcs_krpc_abort(krpc);
+
+	__pcs_krpc_destroy(krpc);
+
+	return 0;
+}
+
+void pcs_krpcset_init(struct pcs_krpc_set *krpcs)
+{
+	unsigned int i;
+
+	for (i = 0; i < PCS_KRPC_HASH_SIZE; i++)
+		INIT_HLIST_HEAD(&krpcs->ht[i]);
+
+	INIT_LIST_HEAD(&krpcs->list);
+	krpcs->nkrpc = 0;
+
+	spin_lock_init(&krpcs->lock);
+}
+
+void pcs_krpcset_fini(struct pcs_krpc_set *krpcs)
+{
+	spin_lock(&krpcs->lock);
+	while (!list_empty(&krpcs->list)) {
+		struct pcs_krpc *krpc;
+
+		krpc = list_first_entry(&krpcs->list, struct pcs_krpc, link);
+		spin_unlock(&krpcs->lock);
+		pcs_krpc_abort(krpc);
+		__pcs_krpc_destroy(krpc);
+		spin_lock(&krpcs->lock);
+	}
+	spin_unlock(&krpcs->lock);
+
+	BUG_ON(!list_empty(&krpcs->list));
+	BUG_ON(krpcs->nkrpc != 0);
+}
+
+int __init pcs_krpc_init(void)
+{
+	krpc_req_cachep = kmem_cache_create("pcs_krpc_req",
+							sizeof(struct krpc_req), 0,
+							SLAB_RECLAIM_ACCOUNT|SLAB_ACCOUNT, NULL);
+
+	if (!krpc_req_cachep)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void pcs_krpc_fini(void)
+{
+	kmem_cache_destroy(krpc_req_cachep);
+}
diff --git a/fs/fuse/kio/pcs/pcs_krpc.h b/fs/fuse/kio/pcs/pcs_krpc.h
new file mode 100644
index 000000000000..6c0ef20ebc99
--- /dev/null
+++ b/fs/fuse/kio/pcs/pcs_krpc.h
@@ -0,0 +1,144 @@
+/*
+ *  Copyright (c) 2018-2021 Virtuozzo International GmbH. All rights reserved.
+ */
+
+#ifndef _PCS_KRPC_H_
+#define _PCS_KRPC_H_ 1
+#include <linux/types.h>
+#include <linux/bvec.h>
+
+#include "pcs_prot_types.h"
+#include "pcs_perfcounters.h"
+#include "pcs_rpc_clnt.h"
+#include "pcs_krpc_prot.h"
+#include "pcs_mr.h"
+
+struct krpc_chunk {
+	u64		addr;
+	u32		len;
+	u32		type;
+#define KRPC_CHUNK_TYPE_MR		0
+#define KRPC_CHUNK_TYPE_UMEM	1
+	union {
+		struct pcs_mr *mr;
+		struct pcs_umem *umem;
+	};
+};
+
+#define PCS_KRPC_HASH_SIZE	1024
+struct pcs_krpc_set {
+	/* Set of krpcs */
+	struct hlist_head		ht[PCS_KRPC_HASH_SIZE];
+	struct list_head		list;
+	unsigned int			nkrpc;
+
+	spinlock_t				lock;
+};
+
+enum {
+	PCS_KRPC_STATE_UNCONN,
+	PCS_KRPC_STATE_CONNECTED,
+	PCS_KRPC_STATE_ABORTED,
+	PCS_KRPC_STATE_DESTROYED,
+};
+
+struct pcs_krpc {
+	struct hlist_node		hlist;
+	struct list_head		link;
+	spinlock_t				lock;
+	refcount_t				refcnt;
+
+	struct pcs_rpc			*rpc;
+
+	struct pcs_krpc_set		*krpcs;
+
+	PCS_NODE_ID_T			id;
+
+	u32	state;
+	u32	gen;
+
+	struct list_head		pending_queue;
+	struct list_head		dispose_queue;
+	struct list_head		completion_queue;
+	int nr_completion;
+
+	/** Wait queue head for poll */
+	wait_queue_head_t		poll_wait;
+};
+
+struct pcs_krpc_context {
+	struct pcs_krpc *krpc;
+	u32 gen;
+};
+/*
+ * Completion message to be received by userspace
+ */
+struct krpc_completion {
+	struct list_head	link;		/* in krpc->completion_queue */
+
+	u64			xid;
+	int			result;
+
+	void		*private;
+	int			data_len;
+	u8			_data_buf[0];
+};
+
+#define KRPC_MAX_DATA_PAGES			256
+#define NR_KRPC_DATA_CHUNKS_INLINE	4
+struct krpc_req {
+	struct list_head	link;
+	spinlock_t			lock;
+	struct pcs_krpc		*krpc;
+
+#define KRPC_REQ_F_ALIGNMENT	PCS_KRPC_MSG_F_ALIGNMENT
+#define KRPC_REQ_F_RESP_BUFF	PCS_KRPC_MSG_F_RESP_BUFF	/* data buff is for read response */
+#define KRPC_REQ_F_ABORTED		0x10000
+	int flags;
+
+	struct pcs_msg		msg;
+
+	char				*hdr_buf;
+	struct kvec			hdr_kv;
+	struct krpc_chunk	hdr_chunk;
+
+	int					nr_data_chunks;
+	struct krpc_chunk	*data_chunks;
+	struct krpc_chunk	inline_data_chunks[NR_KRPC_DATA_CHUNKS_INLINE];
+
+	int data_len;
+	int nr_data_bvecs;
+	struct bio_vec data_bvecs[KRPC_MAX_DATA_PAGES];
+
+	struct krpc_completion completion;
+};
+
+static inline u32 pcs_krpc_msg_size(u32 size, u8 flags)
+{
+	if (flags & PCS_KRPC_MSG_F_ALIGNMENT)
+		size = ALIGN(size, PCS_KRPC_MSG_ALIGNMENT);
+
+	return size;
+}
+
+int pcs_krpc_init(void);
+void pcs_krpc_fini(void);
+
+void pcs_krpcset_init(struct pcs_krpc_set *krpcs);
+void pcs_krpcset_fini(struct pcs_krpc_set *krpcs);
+
+struct pcs_krpc *pcs_krpc_lookup(struct pcs_krpc_set *krpcs, PCS_NODE_ID_T *id);
+int pcs_krpc_create(struct pcs_krpc_set *krpcs, PCS_NODE_ID_T *id,
+		PCS_NET_ADDR_T *addr, int cs_flags);
+int pcs_krpc_update_addr(struct pcs_krpc_set *krpcs, PCS_NODE_ID_T *id,
+		PCS_NET_ADDR_T *addr, int flags);
+int pcs_krpc_connect(struct pcs_krpc_set *krpcs, PCS_NODE_ID_T *id);
+int pcs_krpc_destroy(struct pcs_krpc_set *krpcs, PCS_NODE_ID_T *id);
+
+void pcs_krpc_put(struct pcs_krpc *krpc);
+struct pcs_krpc *pcs_krpc_get(struct pcs_krpc *krpc);
+
+struct pcs_msg *krpc_get_hdr(struct pcs_rpc *ep, struct pcs_rpc_hdr *h);
+void krpc_keep_waiting(struct pcs_rpc *ep, struct pcs_msg *req, struct pcs_msg *msg);
+void krpc_handle_congestion(struct pcs_rpc *ep, struct pcs_msg *msg);
+#endif
diff --git a/fs/fuse/kio/pcs/pcs_krpc_prot.h b/fs/fuse/kio/pcs/pcs_krpc_prot.h
new file mode 100644
index 000000000000..4c5bbf4492d1
--- /dev/null
+++ b/fs/fuse/kio/pcs/pcs_krpc_prot.h
@@ -0,0 +1,44 @@
+#ifndef _PCS_KRPC_PROT_H_
+#define _PCS_KRPC_PROT_H_
+#include <linux/ioctl.h>
+
+#include "pcs_prot_types.h"
+
+/* Device ioctls: */
+#define PCS_KRPC_IOC_MAGIC  255
+
+/* ioctl cmds supported by the '[pcs_krpc]' anonymous inode */
+#define PCS_KRPC_IOC_SEND_MSG	_IO(PCS_KRPC_IOC_MAGIC, 10)
+#define PCS_KRPC_IOC_RECV_MSG	_IO(PCS_KRPC_IOC_MAGIC, 11)
+#define PCS_KRPC_IOC_ABORT		_IO(PCS_KRPC_IOC_MAGIC, 12)
+
+struct pcs_krpc_buf_desc {
+	u64  addr;		/* buf address in userspace. */
+	u32  len;		/* size of the buf */
+	u32  mr_id;		/* mr id */
+};
+
+#define PCS_KRPC_MSG_ALIGNMENT		(512ULL)
+
+#define PCS_KRPC_MSG_F_ALIGNMENT	0x01
+#define PCS_KRPC_MSG_F_RESP_BUFF	0x02
+/*
+ * To avoid copying, a msg is sent to kernel in an array of buffer descriptor.
+ * Each buffer descriptor points to a buf contains a chunk of the msg. And all
+ * chunk buffers are from registered MRs
+ */
+struct pcs_krpc_ioc_sendmsg {
+	u64		xid;				/* context id */
+	u32		msg_size;			/* total size of the msg */
+	u16		timeout;			/* timeout */
+	u8		flags;				/* alignment,  */
+	u8		nr_data_chunks;		/* total number of data chunks */
+	struct pcs_krpc_buf_desc hdr_chunk;	/* the buf holding msg header */
+};
+
+struct pcs_krpc_ioc_recvmsg {
+	u64		xid;	/* context id */
+	struct pcs_krpc_buf_desc buf;	/* for cs congestion notification and rpc keep waiting msg.*/
+};
+
+#endif


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