[3/7] dst: export node.

[Evgeniy Polyakov]

This patch introduces remote (export) node machinery: initialization
address/port (and other socket parameters), export block device (can be
another DST storage for example or local device like /dev/sda1), local
IO processing engine (BIO state machines, receiving/submitting logic).
Network management for the export node like accepting new client, scheduling
its command processing thread, receiving/sending IO requests, all are placed
here.

Signed-off-by: Evgeniy Polyakov <zbr@xxxxxxxxxxx>

diff --git a/drivers/block/dst/export.c b/drivers/block/dst/export.c
new file mode 100644
index 0000000..122fe75
--- /dev/null
+++ b/drivers/block/dst/export.c
@@ -0,0 +1,664 @@
+/*
+ * 2007+ Copyright (c) Evgeniy Polyakov <zbr@xxxxxxxxxxx>
+ * All rights reserved.
+ *
+ * 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.
+ */
+
+#include <linux/blkdev.h>
+#include <linux/bio.h>
+#include <linux/dst.h>
+#include <linux/in.h>
+#include <linux/in6.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/socket.h>
+
+#include <net/sock.h>
+
+/*
+ * Export bioset is used for server block IO requests.
+ */
+static struct bio_set *dst_bio_set;
+
+int __init dst_export_init(void)
+{
+	int err = -ENOMEM;
+
+	dst_bio_set = bioset_create(32, 32);
+	if (!dst_bio_set)
+		goto err_out_exit;
+
+	return 0;
+
+err_out_exit:
+	return err;
+}
+
+void dst_export_exit(void)
+{
+	bioset_free(dst_bio_set);
+}
+
+/*
+ * When client connects and autonegotiates with the server node,
+ * its permissions are checked in a security attributes and sent
+ * back.
+ */
+static unsigned int dst_check_permissions(struct dst_state *main, struct dst_state *st)
+{
+	struct dst_node *n = main->node;
+	struct dst_secure *sentry;
+	struct dst_secure_user *s;
+	struct saddr *sa = &st->ctl.addr;
+	unsigned int perm = 0;
+
+	mutex_lock(&n->security_lock);
+	list_for_each_entry(sentry, &n->security_list, sec_entry) {
+		s = &sentry->sec;
+
+		if (s->addr.sa_family != sa->sa_family)
+			continue;
+
+		if (s->addr.sa_data_len != sa->sa_data_len)
+			continue;
+
+		/*
+		 * This '2' below is a port field. This may be very wrong to do
+		 * in atalk for example though. If there will be any need to extent
+		 * protocol to something else, I can create per-family helpers and
+		 * use them instead of this memcmp.
+		 */
+		if (memcmp(s->addr.sa_data + 2, sa->sa_data + 2,
+					sa->sa_data_len - 2))
+			continue;
+
+		perm = s->permissions;
+	}
+	mutex_unlock(&n->security_lock);
+
+	return perm;
+}
+
+/*
+ * Accept new client: allocate appropriate network state and check permissions.
+ */
+static struct dst_state *dst_accept_client(struct dst_state *st)
+{
+	unsigned int revents = 0;
+	unsigned int err_mask = POLLERR | POLLHUP | POLLRDHUP;
+	unsigned int mask = err_mask | POLLIN;
+	struct dst_node *n = st->node;
+	int err = 0;
+	struct socket *sock = NULL;
+	struct dst_state *new;
+
+	while (!err && !sock) {
+		revents = dst_state_poll(st);
+
+		if (!(revents & mask)) {
+			DEFINE_WAIT(wait);
+
+			for (;;) {
+				prepare_to_wait(&st->thread_wait,
+						&wait, TASK_INTERRUPTIBLE);
+				if (!n->trans_scan_timeout || st->need_exit)
+					break;
+
+				revents = dst_state_poll(st);
+
+				if (revents & mask)
+					break;
+
+				if (signal_pending(current))
+					break;
+
+				/*
+				 * Magic HZ? Polling check above is not safe in
+				 * all cases (like socket reset in BH context),
+				 * so it is simpler just to postpone it to the
+				 * process context instead of implementing special
+				 * locking there.
+				 */
+				schedule_timeout(HZ);
+			}
+			finish_wait(&st->thread_wait, &wait);
+		}
+
+		err = -ECONNRESET;
+		dst_state_lock(st);
+
+		dprintk("%s: st: %p, revents: %x [err: %d, in: %d].\n",
+			__func__, st, revents, revents & err_mask,
+			revents & POLLIN);
+
+		if (revents & err_mask) {
+			dprintk("%s: revents: %x, socket: %p, err: %d.\n",
+					__func__, revents, st->socket, err);
+			err = -ECONNRESET;
+		}
+
+		if (!n->trans_scan_timeout || st->need_exit)
+			err = -ENODEV;
+
+		if (st->socket && (revents & POLLIN))
+			err = kernel_accept(st->socket, &sock, 0);
+
+		dst_state_unlock(st);
+	}
+
+	if (err)
+		goto err_out_exit;
+
+	new = dst_state_alloc(st->node);
+	if (!new) {
+		err = -ENOMEM;
+		goto err_out_release;
+	}
+	new->socket = sock;
+
+	new->ctl.addr.sa_data_len = sizeof(struct sockaddr);
+	err = kernel_getpeername(sock, (struct sockaddr *)&new->ctl.addr,
+			(int *)&new->ctl.addr.sa_data_len);
+	if (err)
+		goto err_out_put;
+
+	new->permissions = dst_check_permissions(st, new);
+	if (new->permissions == 0) {
+		err = -EPERM;
+		dst_dump_addr(sock, (struct sockaddr *)&new->ctl.addr,
+				"Client is not allowed to connect");
+		goto err_out_put;
+	}
+
+	err = dst_poll_init(new);
+	if (err)
+		goto err_out_put;
+
+	dst_dump_addr(sock, (struct sockaddr *)&new->ctl.addr,
+			"Connected client");
+
+	return new;
+
+err_out_put:
+	dst_state_put(new);
+err_out_release:
+	sock_release(sock);
+err_out_exit:
+	return ERR_PTR(err);
+}
+
+/*
+ * Each server's block request sometime finishes.
+ * Usually it happens in hard irq context of the appropriate controller,
+ * so to play good with all cases we just queue BIO into the queue
+ * and wake up processing thread, which gets completed request and
+ * send (encrypting if needed) it back to the client (if it was a read
+ * request), or sends back reply that writing succesfully completed.
+ */
+static int dst_export_process_request_queue(struct dst_state *st)
+{
+	unsigned long flags;
+	struct dst_export_priv *p = NULL;
+	struct bio *bio;
+	int err = 0;
+
+	while (!list_empty(&st->request_list)) {
+		spin_lock_irqsave(&st->request_lock, flags);
+		if (!list_empty(&st->request_list)) {
+			p = list_first_entry(&st->request_list,
+				struct dst_export_priv, request_entry);
+			list_del(&p->request_entry);
+		}
+		spin_unlock_irqrestore(&st->request_lock, flags);
+
+		if (!p)
+			break;
+
+		bio = p->bio;
+
+		if (dst_need_crypto(st->node) && (bio_data_dir(bio) == READ))
+			err = dst_export_crypto(st->node, bio);
+		else
+			err = dst_export_send_bio(bio);
+
+		if (err)
+			break;
+	}
+
+	return err;
+}
+
+/*
+ * Cleanup export state.
+ * It has to wait until all requests are finished,
+ * and then free them all.
+ */
+static void dst_state_cleanup_export(struct dst_state *st)
+{
+	struct dst_export_priv *p;
+	unsigned long flags;
+
+	/*
+	 * This loop waits for all pending bios to be completed and freed.
+	 */
+	while (atomic_read(&st->refcnt) > 1) {
+		dprintk("%s: st: %p, refcnt: %d, list_empty: %d.\n",
+				__func__, st, atomic_read(&st->refcnt),
+				list_empty(&st->request_list));
+		wait_event_timeout(st->thread_wait,
+				(atomic_read(&st->refcnt) == 1) ||
+				!list_empty(&st->request_list),
+				HZ/2);
+
+		while (!list_empty(&st->request_list)) {
+			p = NULL;
+			spin_lock_irqsave(&st->request_lock, flags);
+			if (!list_empty(&st->request_list)) {
+				p = list_first_entry(&st->request_list,
+					struct dst_export_priv, request_entry);
+				list_del(&p->request_entry);
+			}
+			spin_unlock_irqrestore(&st->request_lock, flags);
+
+			if (p)
+				bio_put(p->bio);
+
+			dprintk("%s: st: %p, refcnt: %d, list_empty: %d, p: %p.\n",
+				__func__, st, atomic_read(&st->refcnt),
+				list_empty(&st->request_list), p);
+		}
+	}
+
+	dst_state_put(st);
+}
+
+/*
+ * Client accepting thread.
+ * Not only accepts new connection, but also schedules receiving thread
+ * and performs request completion described above.
+ */
+static int dst_accept(void *init_data, void *schedule_data)
+{
+	struct dst_state *main_st = schedule_data;
+	struct dst_node *n = init_data;
+	struct dst_state *st;
+	int err;
+
+	while (n->trans_scan_timeout && !main_st->need_exit) {
+		dprintk("%s: main_st: %p, n: %p.\n", __func__, main_st, n);
+		st = dst_accept_client(main_st);
+		if (IS_ERR(st))
+			continue;
+
+		err = dst_state_schedule_receiver(st);
+		if (!err) {
+			while (n->trans_scan_timeout) {
+				err = wait_event_interruptible_timeout(st->thread_wait,
+						!list_empty(&st->request_list) ||
+						!n->trans_scan_timeout ||
+						st->need_exit,
+					HZ);
+
+				if (!n->trans_scan_timeout || st->need_exit)
+					break;
+
+				if (list_empty(&st->request_list))
+					continue;
+
+				err = dst_export_process_request_queue(st);
+				if (err)
+					break;
+			}
+
+			st->need_exit = 1;
+			wake_up(&st->thread_wait);
+		}
+
+		dst_state_cleanup_export(st);
+	}
+
+	dprintk("%s: freeing listening socket st: %p.\n", __func__, main_st);
+
+	dst_state_lock(main_st);
+	dst_poll_exit(main_st);
+	dst_state_socket_release(main_st);
+	dst_state_unlock(main_st);
+	dst_state_put(main_st);
+	dprintk("%s: freed listening socket st: %p.\n", __func__, main_st);
+
+	return 0;
+}
+
+int dst_start_export(struct dst_node *n)
+{
+	if (list_empty(&n->security_list)) {
+		printk(KERN_ERR "You are trying to export node '%s' without security attributes.\n"
+				"No clients will be allowed to connect. Exiting.\n", n->name);
+		return -EINVAL;
+	}
+	return dst_node_trans_init(n, sizeof(struct dst_export_priv));
+}
+
+/*
+ * Initialize listening state and schedule accepting thread.
+ */
+int dst_node_init_listened(struct dst_node *n, struct dst_export_ctl *le)
+{
+	struct dst_state *st;
+	int err = -ENOMEM;
+	struct dst_network_ctl *ctl = &le->ctl;
+
+	memcpy(&n->info->net, ctl, sizeof(struct dst_network_ctl));
+
+	st = dst_state_alloc(n);
+	if (IS_ERR(st)) {
+		err = PTR_ERR(st);
+		goto err_out_exit;
+	}
+	memcpy(&st->ctl, ctl, sizeof(struct dst_network_ctl));
+
+	err = dst_state_socket_create(st);
+	if (err)
+		goto err_out_put;
+
+	st->socket->sk->sk_reuse = 1;
+
+	err = kernel_bind(st->socket, (struct sockaddr *)&ctl->addr,
+			ctl->addr.sa_data_len);
+	if (err)
+		goto err_out_socket_release;
+
+	err = kernel_listen(st->socket, 1024);
+	if (err)
+		goto err_out_socket_release;
+	n->state = st;
+
+	err = dst_poll_init(st);
+	if (err)
+		goto err_out_socket_release;
+
+	dst_state_get(st);
+
+	err = thread_pool_schedule(n->pool, dst_thread_setup,
+			dst_accept, st, MAX_SCHEDULE_TIMEOUT);
+	if (err)
+		goto err_out_poll_exit;
+
+	return 0;
+
+err_out_poll_exit:
+	dst_poll_exit(st);
+err_out_socket_release:
+	dst_state_socket_release(st);
+err_out_put:
+	dst_state_put(st);
+err_out_exit:
+	n->state = NULL;
+	return err;
+}
+
+/*
+ * Free bio and related private data.
+ * Also drop a reference counter for appropriate state,
+ * which waits when there are no more block IOs in-flight.
+ */
+static void dst_bio_destructor(struct bio *bio)
+{
+	struct bio_vec *bv;
+	struct dst_export_priv *priv = bio->bi_private;
+	int i;
+
+	bio_for_each_segment(bv, bio, i) {
+		if (!bv->bv_page)
+			break;
+
+		__free_page(bv->bv_page);
+	}
+
+	if (priv) {
+		struct dst_node *n = priv->state->node;
+
+		dst_state_put(priv->state);
+		mempool_free(priv, n->trans_pool);
+	}
+	bio_free(bio, dst_bio_set);
+}
+
+/*
+ * Block IO completion. Queue request to be sent back to
+ * the client (or just confirmation).
+ */
+static void dst_bio_end_io(struct bio *bio, int err)
+{
+	struct dst_export_priv *p = bio->bi_private;
+	struct dst_state *st = p->state;
+	unsigned long flags;
+
+	spin_lock_irqsave(&st->request_lock, flags);
+	list_add_tail(&p->request_entry, &st->request_list);
+	spin_unlock_irqrestore(&st->request_lock, flags);
+
+	wake_up(&st->thread_wait);
+}
+
+/*
+ * Allocate read request for the server.
+ */
+static int dst_export_read_request(struct bio *bio, unsigned int total_size)
+{
+	unsigned int size;
+	struct page *page;
+	int err;
+
+	while (total_size) {
+		err = -ENOMEM;
+		page = alloc_page(GFP_KERNEL);
+		if (!page)
+			goto err_out_exit;
+
+		size = min_t(unsigned int, PAGE_SIZE, total_size);
+
+		err = bio_add_page(bio, page, size, 0);
+		dprintk("%s: bio: %llu/%u, size: %u, err: %d.\n",
+				__func__, (u64)bio->bi_sector, bio->bi_size,
+				size, err);
+		if (err <= 0)
+			goto err_out_free_page;
+
+		total_size -= size;
+	}
+
+	return 0;
+
+err_out_free_page:
+	__free_page(page);
+err_out_exit:
+	return err;
+}
+
+/*
+ * Allocate write request for the server.
+ * Should not only get pages, but also read data from the network.
+ */
+static int dst_export_write_request(struct dst_state *st,
+		struct bio *bio, unsigned int total_size)
+{
+	unsigned int size;
+	struct page *page;
+	void *data;
+	int err;
+
+	while (total_size) {
+		err = -ENOMEM;
+		page = alloc_page(GFP_KERNEL);
+		if (!page)
+			goto err_out_exit;
+
+		data = kmap(page);
+		if (!data)
+			goto err_out_free_page;
+
+		size = min_t(unsigned int, PAGE_SIZE, total_size);
+
+		err = dst_data_recv(st, data, size);
+		if (err)
+			goto err_out_unmap_page;
+
+		err = bio_add_page(bio, page, size, 0);
+		if (err <= 0)
+			goto err_out_unmap_page;
+
+		kunmap(page);
+
+		total_size -= size;
+	}
+
+	return 0;
+
+err_out_unmap_page:
+	kunmap(page);
+err_out_free_page:
+	__free_page(page);
+err_out_exit:
+	return err;
+}
+
+/*
+ * Groovy, we've gotten an IO request from the client.
+ * Allocate BIO from the bioset, private data from the mempool
+ * and lots of pages for IO.
+ */
+int dst_process_io(struct dst_state *st)
+{
+	struct dst_node *n = st->node;
+	struct dst_cmd *cmd = st->data;
+	struct bio *bio;
+	struct dst_export_priv *priv;
+	int err = -ENOMEM;
+
+	if (unlikely(!n->bdev)) {
+		err = -EINVAL;
+		goto err_out_exit;
+	}
+
+	bio = bio_alloc_bioset(GFP_KERNEL,
+			PAGE_ALIGN(cmd->size) >> PAGE_SHIFT,
+			dst_bio_set);
+	if (!bio)
+		goto err_out_exit;
+	bio->bi_private = NULL;
+
+	priv = mempool_alloc(st->node->trans_pool, GFP_KERNEL);
+	if (!priv)
+		goto err_out_free;
+
+	priv->state = dst_state_get(st);
+	priv->bio = bio;
+
+	bio->bi_private = priv;
+	bio->bi_end_io = dst_bio_end_io;
+	bio->bi_destructor = dst_bio_destructor;
+	bio->bi_bdev = n->bdev;
+
+	/*
+	 * Server side is only interested in two low bits:
+	 * uptodate (set by itself actually) and rw block
+	 */
+	bio->bi_flags |= cmd->flags & 3;
+
+	bio->bi_rw = cmd->rw;
+	bio->bi_size = 0;
+	bio->bi_sector = cmd->sector;
+
+	dst_bio_to_cmd(bio, &priv->cmd, DST_IO_RESPONSE, cmd->id);
+
+	priv->cmd.flags = 0;
+	priv->cmd.size = cmd->size;
+
+	if (bio_data_dir(bio) == WRITE) {
+		err = dst_recv_cdata(st, priv->cmd.hash);
+		if (err)
+			goto err_out_free;
+
+		err = dst_export_write_request(st, bio, cmd->size);
+		if (err)
+			goto err_out_free;
+
+		if (dst_need_crypto(n))
+			return dst_export_crypto(n, bio);
+	} else {
+		err = dst_export_read_request(bio, cmd->size);
+		if (err)
+			goto err_out_free;
+	}
+
+	dprintk("%s: bio: %llu/%u, rw: %lu, dir: %lu, flags: %lx, phys: %d.\n",
+			__func__, (u64)bio->bi_sector, bio->bi_size,
+			bio->bi_rw, bio_data_dir(bio),
+			bio->bi_flags, bio->bi_phys_segments);
+
+	generic_make_request(bio);
+
+	return 0;
+
+err_out_free:
+	bio_put(bio);
+err_out_exit:
+	return err;
+}
+
+/*
+ * Ok, block IO is ready, let's send it back to the client...
+ */
+int dst_export_send_bio(struct bio *bio)
+{
+	struct dst_export_priv *p = bio->bi_private;
+	struct dst_state *st = p->state;
+	struct dst_cmd *cmd = &p->cmd;
+	int err;
+
+	dprintk("%s: id: %llu, bio: %llu/%u, csize: %u, flags: %lu, rw: %lu.\n",
+			__func__, cmd->id, (u64)bio->bi_sector, bio->bi_size,
+			cmd->csize, bio->bi_flags, bio->bi_rw);
+
+	dst_convert_cmd(cmd);
+
+	dst_state_lock(st);
+	if (!st->socket) {
+		err = -ECONNRESET;
+		goto err_out_unlock;
+	}
+
+	if (bio_data_dir(bio) == WRITE) {
+		/* ... or just confirmation that writing has completed. */
+		cmd->size = cmd->csize = 0;
+		err = dst_data_send_header(st->socket, cmd,
+				sizeof(struct dst_cmd), 0);
+		if (err)
+			goto err_out_unlock;
+	} else {
+		err = dst_send_bio(st, cmd, bio);
+		if (err)
+			goto err_out_unlock;
+	}
+
+	dst_state_unlock(st);
+
+	bio_put(bio);
+	return 0;
+
+err_out_unlock:
+	dst_state_unlock(st);
+
+	bio_put(bio);
+	return err;
+}
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