1 files changed, 513 insertions, 0 deletions

diff --git a/fs/afs/rotate.c b/fs/afs/rotate.c
new file mode 100644
index 000000000..d83f13c44
--- /dev/null
+++ b/fs/afs/rotate.c
@@ -0,0 +1,513 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Handle fileserver selection and rotation.
+ *
+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/delay.h>
+#include <linux/sched/signal.h>
+#include "internal.h"
+#include "afs_fs.h"
+
+/*
+ * Begin iteration through a server list, starting with the vnode's last used
+ * server if possible, or the last recorded good server if not.
+ */
+static bool afs_start_fs_iteration(struct afs_operation *op,
+				   struct afs_vnode *vnode)
+{
+	struct afs_server *server;
+	void *cb_server;
+	int i;
+
+	read_lock(&op->volume->servers_lock);
+	op->server_list = afs_get_serverlist(
+		rcu_dereference_protected(op->volume->servers,
+					  lockdep_is_held(&op->volume->servers_lock)));
+	read_unlock(&op->volume->servers_lock);
+
+	op->untried = (1UL << op->server_list->nr_servers) - 1;
+	op->index = READ_ONCE(op->server_list->preferred);
+
+	cb_server = vnode->cb_server;
+	if (cb_server) {
+		/* See if the vnode's preferred record is still available */
+		for (i = 0; i < op->server_list->nr_servers; i++) {
+			server = op->server_list->servers[i].server;
+			if (server == cb_server) {
+				op->index = i;
+				goto found_interest;
+			}
+		}
+
+		/* If we have a lock outstanding on a server that's no longer
+		 * serving this vnode, then we can't switch to another server
+		 * and have to return an error.
+		 */
+		if (op->flags & AFS_OPERATION_CUR_ONLY) {
+			op->error = -ESTALE;
+			return false;
+		}
+
+		/* Note that the callback promise is effectively broken */
+		write_seqlock(&vnode->cb_lock);
+		ASSERTCMP(cb_server, ==, vnode->cb_server);
+		vnode->cb_server = NULL;
+		if (test_and_clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags))
+			vnode->cb_break++;
+		write_sequnlock(&vnode->cb_lock);
+	}
+
+found_interest:
+	return true;
+}
+
+/*
+ * Post volume busy note.
+ */
+static void afs_busy(struct afs_volume *volume, u32 abort_code)
+{
+	const char *m;
+
+	switch (abort_code) {
+	case VOFFLINE:		m = "offline";		break;
+	case VRESTARTING:	m = "restarting";	break;
+	case VSALVAGING:	m = "being salvaged";	break;
+	default:		m = "busy";		break;
+	}
+
+	pr_notice("kAFS: Volume %llu '%s' is %s\n", volume->vid, volume->name, m);
+}
+
+/*
+ * Sleep and retry the operation to the same fileserver.
+ */
+static bool afs_sleep_and_retry(struct afs_operation *op)
+{
+	if (!(op->flags & AFS_OPERATION_UNINTR)) {
+		msleep_interruptible(1000);
+		if (signal_pending(current)) {
+			op->error = -ERESTARTSYS;
+			return false;
+		}
+	} else {
+		msleep(1000);
+	}
+
+	return true;
+}
+
+/*
+ * Select the fileserver to use.  May be called multiple times to rotate
+ * through the fileservers.
+ */
+bool afs_select_fileserver(struct afs_operation *op)
+{
+	struct afs_addr_list *alist;
+	struct afs_server *server;
+	struct afs_vnode *vnode = op->file[0].vnode;
+	struct afs_error e;
+	u32 rtt;
+	int error = op->ac.error, i;
+
+	_enter("%lx[%d],%lx[%d],%d,%d",
+	       op->untried, op->index,
+	       op->ac.tried, op->ac.index,
+	       error, op->ac.abort_code);
+
+	if (op->flags & AFS_OPERATION_STOP) {
+		_leave(" = f [stopped]");
+		return false;
+	}
+
+	op->nr_iterations++;
+
+	/* Evaluate the result of the previous operation, if there was one. */
+	switch (error) {
+	case SHRT_MAX:
+		goto start;
+
+	case 0:
+	default:
+		/* Success or local failure.  Stop. */
+		op->error = error;
+		op->flags |= AFS_OPERATION_STOP;
+		_leave(" = f [okay/local %d]", error);
+		return false;
+
+	case -ECONNABORTED:
+		/* The far side rejected the operation on some grounds.  This
+		 * might involve the server being busy or the volume having been moved.
+		 */
+		switch (op->ac.abort_code) {
+		case VNOVOL:
+			/* This fileserver doesn't know about the volume.
+			 * - May indicate that the VL is wrong - retry once and compare
+			 *   the results.
+			 * - May indicate that the fileserver couldn't attach to the vol.
+			 */
+			if (op->flags & AFS_OPERATION_VNOVOL) {
+				op->error = -EREMOTEIO;
+				goto next_server;
+			}
+
+			write_lock(&op->volume->servers_lock);
+			op->server_list->vnovol_mask |= 1 << op->index;
+			write_unlock(&op->volume->servers_lock);
+
+			set_bit(AFS_VOLUME_NEEDS_UPDATE, &op->volume->flags);
+			error = afs_check_volume_status(op->volume, op);
+			if (error < 0)
+				goto failed_set_error;
+
+			if (test_bit(AFS_VOLUME_DELETED, &op->volume->flags)) {
+				op->error = -ENOMEDIUM;
+				goto failed;
+			}
+
+			/* If the server list didn't change, then assume that
+			 * it's the fileserver having trouble.
+			 */
+			if (rcu_access_pointer(op->volume->servers) == op->server_list) {
+				op->error = -EREMOTEIO;
+				goto next_server;
+			}
+
+			/* Try again */
+			op->flags |= AFS_OPERATION_VNOVOL;
+			_leave(" = t [vnovol]");
+			return true;
+
+		case VSALVAGE: /* TODO: Should this return an error or iterate? */
+		case VVOLEXISTS:
+		case VNOSERVICE:
+		case VONLINE:
+		case VDISKFULL:
+		case VOVERQUOTA:
+			op->error = afs_abort_to_error(op->ac.abort_code);
+			goto next_server;
+
+		case VOFFLINE:
+			if (!test_and_set_bit(AFS_VOLUME_OFFLINE, &op->volume->flags)) {
+				afs_busy(op->volume, op->ac.abort_code);
+				clear_bit(AFS_VOLUME_BUSY, &op->volume->flags);
+			}
+			if (op->flags & AFS_OPERATION_NO_VSLEEP) {
+				op->error = -EADV;
+				goto failed;
+			}
+			if (op->flags & AFS_OPERATION_CUR_ONLY) {
+				op->error = -ESTALE;
+				goto failed;
+			}
+			goto busy;
+
+		case VSALVAGING:
+		case VRESTARTING:
+		case VBUSY:
+			/* Retry after going round all the servers unless we
+			 * have a file lock we need to maintain.
+			 */
+			if (op->flags & AFS_OPERATION_NO_VSLEEP) {
+				op->error = -EBUSY;
+				goto failed;
+			}
+			if (!test_and_set_bit(AFS_VOLUME_BUSY, &op->volume->flags)) {
+				afs_busy(op->volume, op->ac.abort_code);
+				clear_bit(AFS_VOLUME_OFFLINE, &op->volume->flags);
+			}
+		busy:
+			if (op->flags & AFS_OPERATION_CUR_ONLY) {
+				if (!afs_sleep_and_retry(op))
+					goto failed;
+
+				 /* Retry with same server & address */
+				_leave(" = t [vbusy]");
+				return true;
+			}
+
+			op->flags |= AFS_OPERATION_VBUSY;
+			goto next_server;
+
+		case VMOVED:
+			/* The volume migrated to another server.  We consider
+			 * consider all locks and callbacks broken and request
+			 * an update from the VLDB.
+			 *
+			 * We also limit the number of VMOVED hops we will
+			 * honour, just in case someone sets up a loop.
+			 */
+			if (op->flags & AFS_OPERATION_VMOVED) {
+				op->error = -EREMOTEIO;
+				goto failed;
+			}
+			op->flags |= AFS_OPERATION_VMOVED;
+
+			set_bit(AFS_VOLUME_WAIT, &op->volume->flags);
+			set_bit(AFS_VOLUME_NEEDS_UPDATE, &op->volume->flags);
+			error = afs_check_volume_status(op->volume, op);
+			if (error < 0)
+				goto failed_set_error;
+
+			/* If the server list didn't change, then the VLDB is
+			 * out of sync with the fileservers.  This is hopefully
+			 * a temporary condition, however, so we don't want to
+			 * permanently block access to the file.
+			 *
+			 * TODO: Try other fileservers if we can.
+			 *
+			 * TODO: Retry a few times with sleeps.
+			 */
+			if (rcu_access_pointer(op->volume->servers) == op->server_list) {
+				op->error = -ENOMEDIUM;
+				goto failed;
+			}
+
+			goto restart_from_beginning;
+
+		default:
+			clear_bit(AFS_VOLUME_OFFLINE, &op->volume->flags);
+			clear_bit(AFS_VOLUME_BUSY, &op->volume->flags);
+			op->error = afs_abort_to_error(op->ac.abort_code);
+			goto failed;
+		}
+
+	case -ETIMEDOUT:
+	case -ETIME:
+		if (op->error != -EDESTADDRREQ)
+			goto iterate_address;
+		fallthrough;
+	case -ERFKILL:
+	case -EADDRNOTAVAIL:
+	case -ENETUNREACH:
+	case -EHOSTUNREACH:
+	case -EHOSTDOWN:
+	case -ECONNREFUSED:
+		_debug("no conn");
+		op->error = error;
+		goto iterate_address;
+
+	case -ECONNRESET:
+		_debug("call reset");
+		op->error = error;
+		goto failed;
+	}
+
+restart_from_beginning:
+	_debug("restart");
+	afs_end_cursor(&op->ac);
+	op->server = NULL;
+	afs_put_serverlist(op->net, op->server_list);
+	op->server_list = NULL;
+start:
+	_debug("start");
+	/* See if we need to do an update of the volume record.  Note that the
+	 * volume may have moved or even have been deleted.
+	 */
+	error = afs_check_volume_status(op->volume, op);
+	if (error < 0)
+		goto failed_set_error;
+
+	if (!afs_start_fs_iteration(op, vnode))
+		goto failed;
+
+	_debug("__ VOL %llx __", op->volume->vid);
+
+pick_server:
+	_debug("pick [%lx]", op->untried);
+
+	error = afs_wait_for_fs_probes(op->server_list, op->untried);
+	if (error < 0)
+		goto failed_set_error;
+
+	/* Pick the untried server with the lowest RTT.  If we have outstanding
+	 * callbacks, we stick with the server we're already using if we can.
+	 */
+	if (op->server) {
+		_debug("server %u", op->index);
+		if (test_bit(op->index, &op->untried))
+			goto selected_server;
+		op->server = NULL;
+		_debug("no server");
+	}
+
+	op->index = -1;
+	rtt = U32_MAX;
+	for (i = 0; i < op->server_list->nr_servers; i++) {
+		struct afs_server *s = op->server_list->servers[i].server;
+
+		if (!test_bit(i, &op->untried) ||
+		    !test_bit(AFS_SERVER_FL_RESPONDING, &s->flags))
+			continue;
+		if (s->probe.rtt < rtt) {
+			op->index = i;
+			rtt = s->probe.rtt;
+		}
+	}
+
+	if (op->index == -1)
+		goto no_more_servers;
+
+selected_server:
+	_debug("use %d", op->index);
+	__clear_bit(op->index, &op->untried);
+
+	/* We're starting on a different fileserver from the list.  We need to
+	 * check it, create a callback intercept, find its address list and
+	 * probe its capabilities before we use it.
+	 */
+	ASSERTCMP(op->ac.alist, ==, NULL);
+	server = op->server_list->servers[op->index].server;
+
+	if (!afs_check_server_record(op, server))
+		goto failed;
+
+	_debug("USING SERVER: %pU", &server->uuid);
+
+	op->flags |= AFS_OPERATION_RETRY_SERVER;
+	op->server = server;
+	if (vnode->cb_server != server) {
+		vnode->cb_server = server;
+		vnode->cb_s_break = server->cb_s_break;
+		vnode->cb_v_break = vnode->volume->cb_v_break;
+		clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
+	}
+
+	read_lock(&server->fs_lock);
+	alist = rcu_dereference_protected(server->addresses,
+					  lockdep_is_held(&server->fs_lock));
+	afs_get_addrlist(alist);
+	read_unlock(&server->fs_lock);
+
+retry_server:
+	memset(&op->ac, 0, sizeof(op->ac));
+
+	if (!op->ac.alist)
+		op->ac.alist = alist;
+	else
+		afs_put_addrlist(alist);
+
+	op->ac.index = -1;
+
+iterate_address:
+	ASSERT(op->ac.alist);
+	/* Iterate over the current server's address list to try and find an
+	 * address on which it will respond to us.
+	 */
+	if (!afs_iterate_addresses(&op->ac))
+		goto out_of_addresses;
+
+	_debug("address [%u] %u/%u %pISp",
+	       op->index, op->ac.index, op->ac.alist->nr_addrs,
+	       &op->ac.alist->addrs[op->ac.index].transport);
+
+	_leave(" = t");
+	return true;
+
+out_of_addresses:
+	/* We've now had a failure to respond on all of a server's addresses -
+	 * immediately probe them again and consider retrying the server.
+	 */
+	afs_probe_fileserver(op->net, op->server);
+	if (op->flags & AFS_OPERATION_RETRY_SERVER) {
+		alist = op->ac.alist;
+		error = afs_wait_for_one_fs_probe(
+			op->server, !(op->flags & AFS_OPERATION_UNINTR));
+		switch (error) {
+		case 0:
+			op->flags &= ~AFS_OPERATION_RETRY_SERVER;
+			goto retry_server;
+		case -ERESTARTSYS:
+			goto failed_set_error;
+		case -ETIME:
+		case -EDESTADDRREQ:
+			goto next_server;
+		}
+	}
+
+next_server:
+	_debug("next");
+	afs_end_cursor(&op->ac);
+	goto pick_server;
+
+no_more_servers:
+	/* That's all the servers poked to no good effect.  Try again if some
+	 * of them were busy.
+	 */
+	if (op->flags & AFS_OPERATION_VBUSY)
+		goto restart_from_beginning;
+
+	e.error = -EDESTADDRREQ;
+	e.responded = false;
+	for (i = 0; i < op->server_list->nr_servers; i++) {
+		struct afs_server *s = op->server_list->servers[i].server;
+
+		afs_prioritise_error(&e, READ_ONCE(s->probe.error),
+				     s->probe.abort_code);
+	}
+
+	error = e.error;
+
+failed_set_error:
+	op->error = error;
+failed:
+	op->flags |= AFS_OPERATION_STOP;
+	afs_end_cursor(&op->ac);
+	_leave(" = f [failed %d]", op->error);
+	return false;
+}
+
+/*
+ * Dump cursor state in the case of the error being EDESTADDRREQ.
+ */
+void afs_dump_edestaddrreq(const struct afs_operation *op)
+{
+	static int count;
+	int i;
+
+	if (!IS_ENABLED(CONFIG_AFS_DEBUG_CURSOR) || count > 3)
+		return;
+	count++;
+
+	rcu_read_lock();
+
+	pr_notice("EDESTADDR occurred\n");
+	pr_notice("FC: cbb=%x cbb2=%x fl=%x err=%hd\n",
+		  op->file[0].cb_break_before,
+		  op->file[1].cb_break_before, op->flags, op->error);
+	pr_notice("FC: ut=%lx ix=%d ni=%u\n",
+		  op->untried, op->index, op->nr_iterations);
+
+	if (op->server_list) {
+		const struct afs_server_list *sl = op->server_list;
+		pr_notice("FC: SL nr=%u pr=%u vnov=%hx\n",
+			  sl->nr_servers, sl->preferred, sl->vnovol_mask);
+		for (i = 0; i < sl->nr_servers; i++) {
+			const struct afs_server *s = sl->servers[i].server;
+			pr_notice("FC: server fl=%lx av=%u %pU\n",
+				  s->flags, s->addr_version, &s->uuid);
+			if (s->addresses) {
+				const struct afs_addr_list *a =
+					rcu_dereference(s->addresses);
+				pr_notice("FC:  - av=%u nr=%u/%u/%u pr=%u\n",
+					  a->version,
+					  a->nr_ipv4, a->nr_addrs, a->max_addrs,
+					  a->preferred);
+				pr_notice("FC:  - R=%lx F=%lx\n",
+					  a->responded, a->failed);
+				if (a == op->ac.alist)
+					pr_notice("FC:  - current\n");
+			}
+		}
+	}
+
+	pr_notice("AC: t=%lx ax=%u ac=%d er=%d r=%u ni=%u\n",
+		  op->ac.tried, op->ac.index, op->ac.abort_code, op->ac.error,
+		  op->ac.responded, op->ac.nr_iterations);
+	rcu_read_unlock();
+}