1 files changed, 528 insertions, 0 deletions

diff --git a/fs/afs/rotate.c b/fs/afs/rotate.c
new file mode 100644
index 000000000..1faef56b1
--- /dev/null
+++ b/fs/afs/rotate.c
@@ -0,0 +1,528 @@
+/* Handle fileserver selection and rotation.
+ *
+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#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"
+
+/*
+ * Initialise a filesystem server cursor for iterating over FS servers.
+ */
+static void afs_init_fs_cursor(struct afs_fs_cursor *fc, struct afs_vnode *vnode)
+{
+	memset(fc, 0, sizeof(*fc));
+}
+
+/*
+ * Begin an operation on the fileserver.
+ *
+ * Fileserver operations are serialised on the server by vnode, so we serialise
+ * them here also using the io_lock.
+ */
+bool afs_begin_vnode_operation(struct afs_fs_cursor *fc, struct afs_vnode *vnode,
+			       struct key *key)
+{
+	afs_init_fs_cursor(fc, vnode);
+	fc->vnode = vnode;
+	fc->key = key;
+	fc->ac.error = SHRT_MAX;
+
+	if (mutex_lock_interruptible(&vnode->io_lock) < 0) {
+		fc->ac.error = -EINTR;
+		fc->flags |= AFS_FS_CURSOR_STOP;
+		return false;
+	}
+
+	if (vnode->lock_state != AFS_VNODE_LOCK_NONE)
+		fc->flags |= AFS_FS_CURSOR_CUR_ONLY;
+	return true;
+}
+
+/*
+ * 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_fs_cursor *fc,
+				   struct afs_vnode *vnode)
+{
+	struct afs_cb_interest *cbi;
+	int i;
+
+	read_lock(&vnode->volume->servers_lock);
+	fc->server_list = afs_get_serverlist(vnode->volume->servers);
+	read_unlock(&vnode->volume->servers_lock);
+
+	cbi = vnode->cb_interest;
+	if (cbi) {
+		/* See if the vnode's preferred record is still available */
+		for (i = 0; i < fc->server_list->nr_servers; i++) {
+			if (fc->server_list->servers[i].cb_interest == cbi) {
+				fc->start = 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 (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
+			fc->ac.error = -ESTALE;
+			return false;
+		}
+
+		/* Note that the callback promise is effectively broken */
+		write_seqlock(&vnode->cb_lock);
+		ASSERTCMP(cbi, ==, vnode->cb_interest);
+		vnode->cb_interest = NULL;
+		if (test_and_clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags))
+			vnode->cb_break++;
+		write_sequnlock(&vnode->cb_lock);
+
+		afs_put_cb_interest(afs_v2net(vnode), cbi);
+		cbi = NULL;
+	} else {
+		fc->start = READ_ONCE(fc->server_list->index);
+	}
+
+found_interest:
+	fc->index = fc->start;
+	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 %u '%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_fs_cursor *fc)
+{
+	msleep_interruptible(1000);
+	if (signal_pending(current)) {
+		fc->ac.error = -ERESTARTSYS;
+		return false;
+	}
+
+	return true;
+}
+
+/*
+ * Select the fileserver to use.  May be called multiple times to rotate
+ * through the fileservers.
+ */
+bool afs_select_fileserver(struct afs_fs_cursor *fc)
+{
+	struct afs_addr_list *alist;
+	struct afs_server *server;
+	struct afs_vnode *vnode = fc->vnode;
+
+	_enter("%u/%u,%u/%u,%d,%d",
+	       fc->index, fc->start,
+	       fc->ac.index, fc->ac.start,
+	       fc->ac.error, fc->ac.abort_code);
+
+	if (fc->flags & AFS_FS_CURSOR_STOP) {
+		_leave(" = f [stopped]");
+		return false;
+	}
+
+	/* Evaluate the result of the previous operation, if there was one. */
+	switch (fc->ac.error) {
+	case SHRT_MAX:
+		goto start;
+
+	case 0:
+	default:
+		/* Success or local failure.  Stop. */
+		fc->flags |= AFS_FS_CURSOR_STOP;
+		_leave(" = f [okay/local %d]", fc->ac.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 (fc->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 (fc->flags & AFS_FS_CURSOR_VNOVOL) {
+				fc->ac.error = -EREMOTEIO;
+				goto next_server;
+			}
+
+			write_lock(&vnode->volume->servers_lock);
+			fc->server_list->vnovol_mask |= 1 << fc->index;
+			write_unlock(&vnode->volume->servers_lock);
+
+			set_bit(AFS_VOLUME_NEEDS_UPDATE, &vnode->volume->flags);
+			fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
+			if (fc->ac.error < 0)
+				goto failed;
+
+			if (test_bit(AFS_VOLUME_DELETED, &vnode->volume->flags)) {
+				fc->ac.error = -ENOMEDIUM;
+				goto failed;
+			}
+
+			/* If the server list didn't change, then assume that
+			 * it's the fileserver having trouble.
+			 */
+			if (vnode->volume->servers == fc->server_list) {
+				fc->ac.error = -EREMOTEIO;
+				goto next_server;
+			}
+
+			/* Try again */
+			fc->flags |= AFS_FS_CURSOR_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:
+			fc->ac.error = afs_abort_to_error(fc->ac.abort_code);
+			goto next_server;
+
+		case VOFFLINE:
+			if (!test_and_set_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags)) {
+				afs_busy(vnode->volume, fc->ac.abort_code);
+				clear_bit(AFS_VOLUME_BUSY, &vnode->volume->flags);
+			}
+			if (fc->flags & AFS_FS_CURSOR_NO_VSLEEP) {
+				fc->ac.error = -EADV;
+				goto failed;
+			}
+			if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
+				fc->ac.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 (fc->flags & AFS_FS_CURSOR_NO_VSLEEP) {
+				fc->ac.error = -EBUSY;
+				goto failed;
+			}
+			if (!test_and_set_bit(AFS_VOLUME_BUSY, &vnode->volume->flags)) {
+				afs_busy(vnode->volume, fc->ac.abort_code);
+				clear_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags);
+			}
+		busy:
+			if (fc->flags & AFS_FS_CURSOR_CUR_ONLY) {
+				if (!afs_sleep_and_retry(fc))
+					goto failed;
+
+				 /* Retry with same server & address */
+				_leave(" = t [vbusy]");
+				return true;
+			}
+
+			fc->flags |= AFS_FS_CURSOR_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 (fc->flags & AFS_FS_CURSOR_VMOVED) {
+				fc->ac.error = -EREMOTEIO;
+				goto failed;
+			}
+			fc->flags |= AFS_FS_CURSOR_VMOVED;
+
+			set_bit(AFS_VOLUME_WAIT, &vnode->volume->flags);
+			set_bit(AFS_VOLUME_NEEDS_UPDATE, &vnode->volume->flags);
+			fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
+			if (fc->ac.error < 0)
+				goto failed;
+
+			/* 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 (vnode->volume->servers == fc->server_list) {
+				fc->ac.error = -ENOMEDIUM;
+				goto failed;
+			}
+
+			goto restart_from_beginning;
+
+		default:
+			clear_bit(AFS_VOLUME_OFFLINE, &vnode->volume->flags);
+			clear_bit(AFS_VOLUME_BUSY, &vnode->volume->flags);
+			fc->ac.error = afs_abort_to_error(fc->ac.abort_code);
+			goto failed;
+		}
+
+	case -ENETUNREACH:
+	case -EHOSTUNREACH:
+	case -ECONNREFUSED:
+	case -ETIMEDOUT:
+	case -ETIME:
+		_debug("no conn");
+		goto iterate_address;
+
+	case -ECONNRESET:
+		_debug("call reset");
+		goto failed;
+	}
+
+restart_from_beginning:
+	_debug("restart");
+	afs_end_cursor(&fc->ac);
+	afs_put_cb_interest(afs_v2net(vnode), fc->cbi);
+	fc->cbi = NULL;
+	afs_put_serverlist(afs_v2net(vnode), fc->server_list);
+	fc->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.
+	 */
+	fc->ac.error = afs_check_volume_status(vnode->volume, fc->key);
+	if (fc->ac.error < 0)
+		goto failed;
+
+	if (!afs_start_fs_iteration(fc, vnode))
+		goto failed;
+
+use_server:
+	_debug("use");
+	/* 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(fc->ac.alist, ==, NULL);
+	server = fc->server_list->servers[fc->index].server;
+
+	if (!afs_check_server_record(fc, server))
+		goto failed;
+
+	_debug("USING SERVER: %pU", &server->uuid);
+
+	/* Make sure we've got a callback interest record for this server.  We
+	 * have to link it in before we send the request as we can be sent a
+	 * break request before we've finished decoding the reply and
+	 * installing the vnode.
+	 */
+	fc->ac.error = afs_register_server_cb_interest(vnode, fc->server_list,
+						       fc->index);
+	if (fc->ac.error < 0)
+		goto failed;
+
+	fc->cbi = afs_get_cb_interest(vnode->cb_interest);
+
+	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);
+
+	memset(&fc->ac, 0, sizeof(fc->ac));
+
+	/* Probe the current fileserver if we haven't done so yet. */
+	if (!test_bit(AFS_SERVER_FL_PROBED, &server->flags)) {
+		fc->ac.alist = afs_get_addrlist(alist);
+
+		if (!afs_probe_fileserver(fc)) {
+			switch (fc->ac.error) {
+			case -ENOMEM:
+			case -ERESTARTSYS:
+			case -EINTR:
+				goto failed;
+			default:
+				goto next_server;
+			}
+		}
+	}
+
+	if (!fc->ac.alist)
+		fc->ac.alist = alist;
+	else
+		afs_put_addrlist(alist);
+
+	fc->ac.start = READ_ONCE(alist->index);
+	fc->ac.index = fc->ac.start;
+
+iterate_address:
+	ASSERT(fc->ac.alist);
+	_debug("iterate %d/%d", fc->ac.index, fc->ac.alist->nr_addrs);
+	/* 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(&fc->ac))
+		goto next_server;
+
+	_leave(" = t");
+	return true;
+
+next_server:
+	_debug("next");
+	afs_end_cursor(&fc->ac);
+	afs_put_cb_interest(afs_v2net(vnode), fc->cbi);
+	fc->cbi = NULL;
+	fc->index++;
+	if (fc->index >= fc->server_list->nr_servers)
+		fc->index = 0;
+	if (fc->index != fc->start)
+		goto use_server;
+
+	/* That's all the servers poked to no good effect.  Try again if some
+	 * of them were busy.
+	 */
+	if (fc->flags & AFS_FS_CURSOR_VBUSY)
+		goto restart_from_beginning;
+
+	fc->ac.error = -EDESTADDRREQ;
+	goto failed;
+
+failed:
+	fc->flags |= AFS_FS_CURSOR_STOP;
+	afs_end_cursor(&fc->ac);
+	_leave(" = f [failed %d]", fc->ac.error);
+	return false;
+}
+
+/*
+ * Select the same fileserver we used for a vnode before and only that
+ * fileserver.  We use this when we have a lock on that file, which is backed
+ * only by the fileserver we obtained it from.
+ */
+bool afs_select_current_fileserver(struct afs_fs_cursor *fc)
+{
+	struct afs_vnode *vnode = fc->vnode;
+	struct afs_cb_interest *cbi = vnode->cb_interest;
+	struct afs_addr_list *alist;
+
+	_enter("");
+
+	switch (fc->ac.error) {
+	case SHRT_MAX:
+		if (!cbi) {
+			fc->ac.error = -ESTALE;
+			fc->flags |= AFS_FS_CURSOR_STOP;
+			return false;
+		}
+
+		fc->cbi = afs_get_cb_interest(vnode->cb_interest);
+
+		read_lock(&cbi->server->fs_lock);
+		alist = rcu_dereference_protected(cbi->server->addresses,
+						  lockdep_is_held(&cbi->server->fs_lock));
+		afs_get_addrlist(alist);
+		read_unlock(&cbi->server->fs_lock);
+		if (!alist) {
+			fc->ac.error = -ESTALE;
+			fc->flags |= AFS_FS_CURSOR_STOP;
+			return false;
+		}
+
+		memset(&fc->ac, 0, sizeof(fc->ac));
+		fc->ac.alist = alist;
+		fc->ac.start = READ_ONCE(alist->index);
+		fc->ac.index = fc->ac.start;
+		goto iterate_address;
+
+	case 0:
+	default:
+		/* Success or local failure.  Stop. */
+		fc->flags |= AFS_FS_CURSOR_STOP;
+		_leave(" = f [okay/local %d]", fc->ac.error);
+		return false;
+
+	case -ECONNABORTED:
+		fc->flags |= AFS_FS_CURSOR_STOP;
+		_leave(" = f [abort]");
+		return false;
+
+	case -ENETUNREACH:
+	case -EHOSTUNREACH:
+	case -ECONNREFUSED:
+	case -ETIMEDOUT:
+	case -ETIME:
+		_debug("no conn");
+		goto iterate_address;
+	}
+
+iterate_address:
+	/* 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(&fc->ac)) {
+		_leave(" = t");
+		return true;
+	}
+
+	afs_end_cursor(&fc->ac);
+	return false;
+}
+
+/*
+ * Tidy up a filesystem cursor and unlock the vnode.
+ */
+int afs_end_vnode_operation(struct afs_fs_cursor *fc)
+{
+	struct afs_net *net = afs_v2net(fc->vnode);
+	int ret;
+
+	mutex_unlock(&fc->vnode->io_lock);
+
+	afs_end_cursor(&fc->ac);
+	afs_put_cb_interest(net, fc->cbi);
+	afs_put_serverlist(net, fc->server_list);
+
+	ret = fc->ac.error;
+	if (ret == -ECONNABORTED)
+		afs_abort_to_error(fc->ac.abort_code);
+
+	return fc->ac.error;
+}