Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 939 insertions, 0 deletions

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
new file mode 100644
index 000000000..47a264576
--- /dev/null
+++ b/fs/afs/cell.c
@@ -0,0 +1,939 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* AFS cell and server record management
+ *
+ * Copyright (C) 2002, 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/slab.h>
+#include <linux/key.h>
+#include <linux/ctype.h>
+#include <linux/dns_resolver.h>
+#include <linux/sched.h>
+#include <linux/inet.h>
+#include <linux/namei.h>
+#include <keys/rxrpc-type.h>
+#include "internal.h"
+
+static unsigned __read_mostly afs_cell_gc_delay = 10;
+static unsigned __read_mostly afs_cell_min_ttl = 10 * 60;
+static unsigned __read_mostly afs_cell_max_ttl = 24 * 60 * 60;
+static atomic_t cell_debug_id;
+
+static void afs_cell_timer(struct timer_list *timer);
+static void afs_destroy_cell_work(struct work_struct *work);
+static void afs_manage_cell_work(struct work_struct *work);
+
+static void afs_dec_cells_outstanding(struct afs_net *net)
+{
+	if (atomic_dec_and_test(&net->cells_outstanding))
+		wake_up_var(&net->cells_outstanding);
+}
+
+static void afs_set_cell_state(struct afs_cell *cell, enum afs_cell_state state)
+{
+	smp_store_release(&cell->state, state); /* Commit cell changes before state */
+	smp_wmb(); /* Set cell state before task state */
+	wake_up_var(&cell->state);
+}
+
+/*
+ * Look up and get an activation reference on a cell record.  The caller must
+ * hold net->cells_lock at least read-locked.
+ */
+static struct afs_cell *afs_find_cell_locked(struct afs_net *net,
+					     const char *name, unsigned int namesz,
+					     enum afs_cell_trace reason)
+{
+	struct afs_cell *cell = NULL;
+	struct rb_node *p;
+	int n;
+
+	_enter("%*.*s", namesz, namesz, name);
+
+	if (name && namesz == 0)
+		return ERR_PTR(-EINVAL);
+	if (namesz > AFS_MAXCELLNAME)
+		return ERR_PTR(-ENAMETOOLONG);
+
+	if (!name) {
+		cell = rcu_dereference_protected(net->ws_cell,
+						 lockdep_is_held(&net->cells_lock));
+		if (!cell)
+			return ERR_PTR(-EDESTADDRREQ);
+		goto found;
+	}
+
+	p = net->cells.rb_node;
+	while (p) {
+		cell = rb_entry(p, struct afs_cell, net_node);
+
+		n = strncasecmp(cell->name, name,
+				min_t(size_t, cell->name_len, namesz));
+		if (n == 0)
+			n = cell->name_len - namesz;
+		if (n < 0)
+			p = p->rb_left;
+		else if (n > 0)
+			p = p->rb_right;
+		else
+			goto found;
+	}
+
+	return ERR_PTR(-ENOENT);
+
+found:
+	return afs_use_cell(cell, reason);
+}
+
+/*
+ * Look up and get an activation reference on a cell record.
+ */
+struct afs_cell *afs_find_cell(struct afs_net *net,
+			       const char *name, unsigned int namesz,
+			       enum afs_cell_trace reason)
+{
+	struct afs_cell *cell;
+
+	down_read(&net->cells_lock);
+	cell = afs_find_cell_locked(net, name, namesz, reason);
+	up_read(&net->cells_lock);
+	return cell;
+}
+
+/*
+ * Set up a cell record and fill in its name, VL server address list and
+ * allocate an anonymous key
+ */
+static struct afs_cell *afs_alloc_cell(struct afs_net *net,
+				       const char *name, unsigned int namelen,
+				       const char *addresses)
+{
+	struct afs_vlserver_list *vllist = NULL;
+	struct afs_cell *cell;
+	int i, ret;
+
+	ASSERT(name);
+	if (namelen == 0)
+		return ERR_PTR(-EINVAL);
+	if (namelen > AFS_MAXCELLNAME) {
+		_leave(" = -ENAMETOOLONG");
+		return ERR_PTR(-ENAMETOOLONG);
+	}
+
+	/* Prohibit cell names that contain unprintable chars, '/' and '@' or
+	 * that begin with a dot.  This also precludes "@cell".
+	 */
+	if (name[0] == '.')
+		return ERR_PTR(-EINVAL);
+	for (i = 0; i < namelen; i++) {
+		char ch = name[i];
+		if (!isprint(ch) || ch == '/' || ch == '@')
+			return ERR_PTR(-EINVAL);
+	}
+
+	_enter("%*.*s,%s", namelen, namelen, name, addresses);
+
+	cell = kzalloc_obj(struct afs_cell);
+	if (!cell) {
+		_leave(" = -ENOMEM");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	/* Allocate the cell name and the key name in one go. */
+	cell->name = kmalloc(1 + namelen + 1 +
+			     4 + namelen + 1, GFP_KERNEL);
+	if (!cell->name) {
+		kfree(cell);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	cell->name[0] = '.';
+	cell->name++;
+	cell->name_len = namelen;
+	for (i = 0; i < namelen; i++)
+		cell->name[i] = tolower(name[i]);
+	cell->name[i++] = 0;
+
+	cell->key_desc = cell->name + i;
+	memcpy(cell->key_desc, "afs@", 4);
+	memcpy(cell->key_desc + 4, cell->name, cell->name_len + 1);
+
+	cell->net = net;
+	refcount_set(&cell->ref, 1);
+	atomic_set(&cell->active, 0);
+	INIT_WORK(&cell->destroyer, afs_destroy_cell_work);
+	INIT_WORK(&cell->manager, afs_manage_cell_work);
+	timer_setup(&cell->management_timer, afs_cell_timer, 0);
+	init_rwsem(&cell->vs_lock);
+	cell->volumes = RB_ROOT;
+	INIT_HLIST_HEAD(&cell->proc_volumes);
+	seqlock_init(&cell->volume_lock);
+	cell->fs_servers = RB_ROOT;
+	init_rwsem(&cell->fs_lock);
+	rwlock_init(&cell->vl_servers_lock);
+	cell->flags = (1 << AFS_CELL_FL_CHECK_ALIAS);
+
+	/* Provide a VL server list, filling it in if we were given a list of
+	 * addresses to use.
+	 */
+	if (addresses) {
+		vllist = afs_parse_text_addrs(net,
+					      addresses, strlen(addresses), ':',
+					      VL_SERVICE, AFS_VL_PORT);
+		if (IS_ERR(vllist)) {
+			ret = PTR_ERR(vllist);
+			vllist = NULL;
+			goto parse_failed;
+		}
+
+		vllist->source = DNS_RECORD_FROM_CONFIG;
+		vllist->status = DNS_LOOKUP_NOT_DONE;
+		cell->dns_expiry = TIME64_MAX;
+	} else {
+		ret = -ENOMEM;
+		vllist = afs_alloc_vlserver_list(0);
+		if (!vllist)
+			goto error;
+		vllist->source = DNS_RECORD_UNAVAILABLE;
+		vllist->status = DNS_LOOKUP_NOT_DONE;
+		cell->dns_expiry = ktime_get_real_seconds();
+	}
+
+	rcu_assign_pointer(cell->vl_servers, vllist);
+
+	cell->dns_source = vllist->source;
+	cell->dns_status = vllist->status;
+	smp_store_release(&cell->dns_lookup_count, 1); /* vs source/status */
+	atomic_inc(&net->cells_outstanding);
+	cell->debug_id = atomic_inc_return(&cell_debug_id);
+
+	trace_afs_cell(cell->debug_id, 1, 0, afs_cell_trace_alloc);
+
+	_leave(" = %p", cell);
+	return cell;
+
+parse_failed:
+	if (ret == -EINVAL)
+		printk(KERN_ERR "kAFS: bad VL server IP address\n");
+error:
+	afs_put_vlserverlist(cell->net, vllist);
+	kfree(cell->name - 1);
+	kfree(cell);
+	_leave(" = %d", ret);
+	return ERR_PTR(ret);
+}
+
+/*
+ * afs_lookup_cell - Look up or create a cell record.
+ * @net:	The network namespace
+ * @name:	The name of the cell.
+ * @namesz:	The strlen of the cell name.
+ * @vllist:	A colon/comma separated list of numeric IP addresses or NULL.
+ * @reason:	The reason we're doing the lookup
+ * @trace:	The reason to be logged if the lookup is successful.
+ *
+ * Look up a cell record by name and query the DNS for VL server addresses if
+ * needed.  Note that that actual DNS query is punted off to the manager thread
+ * so that this function can return immediately if interrupted whilst allowing
+ * cell records to be shared even if not yet fully constructed.
+ */
+struct afs_cell *afs_lookup_cell(struct afs_net *net,
+				 const char *name, unsigned int namesz,
+				 const char *vllist,
+				 enum afs_lookup_cell_for reason,
+				 enum afs_cell_trace trace)
+{
+	struct afs_cell *cell, *candidate, *cursor;
+	struct rb_node *parent, **pp;
+	enum afs_cell_state state;
+	int ret, n;
+
+	_enter("%s,%s,%u", name, vllist, reason);
+
+	if (reason != AFS_LOOKUP_CELL_PRELOAD) {
+		cell = afs_find_cell(net, name, namesz, trace);
+		if (!IS_ERR(cell)) {
+			if (reason == AFS_LOOKUP_CELL_DYNROOT)
+				goto no_wait;
+			if (cell->state == AFS_CELL_SETTING_UP ||
+			    cell->state == AFS_CELL_UNLOOKED)
+				goto lookup_cell;
+			goto wait_for_cell;
+		}
+	}
+
+	/* Assume we're probably going to create a cell and preallocate and
+	 * mostly set up a candidate record.  We can then use this to stash the
+	 * name, the net namespace and VL server addresses.
+	 *
+	 * We also want to do this before we hold any locks as it may involve
+	 * upcalling to userspace to make DNS queries.
+	 */
+	candidate = afs_alloc_cell(net, name, namesz, vllist);
+	if (IS_ERR(candidate)) {
+		_leave(" = %ld", PTR_ERR(candidate));
+		return candidate;
+	}
+
+	/* Find the insertion point and check to see if someone else added a
+	 * cell whilst we were allocating.
+	 */
+	down_write(&net->cells_lock);
+
+	pp = &net->cells.rb_node;
+	parent = NULL;
+	while (*pp) {
+		parent = *pp;
+		cursor = rb_entry(parent, struct afs_cell, net_node);
+
+		n = strncasecmp(cursor->name, name,
+				min_t(size_t, cursor->name_len, namesz));
+		if (n == 0)
+			n = cursor->name_len - namesz;
+		if (n < 0)
+			pp = &(*pp)->rb_left;
+		else if (n > 0)
+			pp = &(*pp)->rb_right;
+		else
+			goto cell_already_exists;
+	}
+
+	ret = idr_alloc_cyclic(&net->cells_dyn_ino, candidate,
+			       2, INT_MAX / 2, GFP_KERNEL);
+	if (ret < 0)
+		goto cant_alloc_ino;
+	candidate->dynroot_ino = ret;
+	set_bit(AFS_CELL_FL_HAVE_INO, &candidate->flags);
+
+	cell = candidate;
+	candidate = NULL;
+	afs_use_cell(cell, trace);
+	rb_link_node_rcu(&cell->net_node, parent, pp);
+	rb_insert_color(&cell->net_node, &net->cells);
+	up_write(&net->cells_lock);
+
+lookup_cell:
+	if (reason != AFS_LOOKUP_CELL_PRELOAD &&
+	    reason != AFS_LOOKUP_CELL_ROOTCELL) {
+		set_bit(AFS_CELL_FL_DO_LOOKUP, &cell->flags);
+		afs_queue_cell(cell, afs_cell_trace_queue_new);
+	}
+
+wait_for_cell:
+	state = smp_load_acquire(&cell->state); /* vs error */
+	switch (state) {
+	case AFS_CELL_ACTIVE:
+	case AFS_CELL_DEAD:
+		break;
+	case AFS_CELL_UNLOOKED:
+	default:
+		if (reason == AFS_LOOKUP_CELL_PRELOAD ||
+		    reason == AFS_LOOKUP_CELL_ROOTCELL)
+			break;
+		_debug("wait_for_cell");
+		afs_see_cell(cell, afs_cell_trace_wait);
+		wait_var_event(&cell->state,
+			       ({
+				       state = smp_load_acquire(&cell->state); /* vs error */
+				       state == AFS_CELL_ACTIVE || state == AFS_CELL_DEAD;
+			       }));
+		_debug("waited_for_cell %d %d", cell->state, cell->error);
+	}
+
+no_wait:
+	/* Check the state obtained from the wait check. */
+	state = smp_load_acquire(&cell->state); /* vs error */
+	if (state == AFS_CELL_DEAD) {
+		ret = cell->error;
+		goto error;
+	}
+	if (state == AFS_CELL_ACTIVE) {
+		switch (cell->dns_status) {
+		case DNS_LOOKUP_NOT_DONE:
+			if (cell->dns_source == DNS_RECORD_FROM_CONFIG) {
+				ret = 0;
+				break;
+			}
+			fallthrough;
+		default:
+			ret = -EIO;
+			goto error;
+		case DNS_LOOKUP_GOOD:
+		case DNS_LOOKUP_GOOD_WITH_BAD:
+			ret = 0;
+			break;
+		case DNS_LOOKUP_GOT_NOT_FOUND:
+			ret = -ENOENT;
+			goto error;
+		case DNS_LOOKUP_BAD:
+			ret = -EREMOTEIO;
+			goto error;
+		case DNS_LOOKUP_GOT_LOCAL_FAILURE:
+		case DNS_LOOKUP_GOT_TEMP_FAILURE:
+		case DNS_LOOKUP_GOT_NS_FAILURE:
+			ret = -EDESTADDRREQ;
+			goto error;
+		}
+	}
+
+	_leave(" = %p [cell]", cell);
+	return cell;
+
+cant_alloc_ino:
+	up_write(&net->cells_lock);
+	afs_put_cell(candidate, afs_cell_trace_put_candidate);
+	goto error_noput;
+
+cell_already_exists:
+	_debug("cell exists");
+	cell = cursor;
+	if (reason == AFS_LOOKUP_CELL_PRELOAD) {
+		ret = -EEXIST;
+	} else {
+		afs_use_cell(cursor, trace);
+		ret = 0;
+	}
+	up_write(&net->cells_lock);
+	if (candidate)
+		afs_put_cell(candidate, afs_cell_trace_put_candidate);
+	if (ret == 0)
+		goto wait_for_cell;
+	goto error_noput;
+error:
+	afs_unuse_cell(cell, afs_cell_trace_unuse_lookup_error);
+error_noput:
+	_leave(" = %d [error]", ret);
+	return ERR_PTR(ret);
+}
+
+/*
+ * set the root cell information
+ * - can be called with a module parameter string
+ * - can be called from a write to /proc/fs/afs/rootcell
+ */
+int afs_cell_init(struct afs_net *net, const char *rootcell)
+{
+	struct afs_cell *old_root, *new_root;
+	const char *cp, *vllist;
+	size_t len;
+
+	_enter("");
+
+	if (!rootcell) {
+		/* module is loaded with no parameters, or built statically.
+		 * - in the future we might initialize cell DB here.
+		 */
+		_leave(" = 0 [no root]");
+		return 0;
+	}
+
+	cp = strchr(rootcell, ':');
+	if (!cp) {
+		_debug("kAFS: no VL server IP addresses specified");
+		vllist = NULL;
+		len = strlen(rootcell);
+	} else {
+		vllist = cp + 1;
+		len = cp - rootcell;
+	}
+
+	if (len == 0 || !rootcell[0] || rootcell[0] == '.' || rootcell[len - 1] == '.')
+		return -EINVAL;
+	if (memchr(rootcell, '/', len))
+		return -EINVAL;
+	cp = strstr(rootcell, "..");
+	if (cp && cp < rootcell + len)
+		return -EINVAL;
+
+	/* allocate a cell record for the root/workstation cell */
+	new_root = afs_lookup_cell(net, rootcell, len, vllist,
+				   AFS_LOOKUP_CELL_ROOTCELL,
+				   afs_cell_trace_use_lookup_ws);
+	if (IS_ERR(new_root)) {
+		_leave(" = %ld", PTR_ERR(new_root));
+		return PTR_ERR(new_root);
+	}
+
+	if (!test_and_set_bit(AFS_CELL_FL_NO_GC, &new_root->flags))
+		afs_use_cell(new_root, afs_cell_trace_use_pin);
+
+	/* install the new cell */
+	down_write(&net->cells_lock);
+	old_root = rcu_replace_pointer(net->ws_cell, new_root,
+				       lockdep_is_held(&net->cells_lock));
+	up_write(&net->cells_lock);
+
+	afs_unuse_cell(old_root, afs_cell_trace_unuse_ws);
+	_leave(" = 0");
+	return 0;
+}
+
+/*
+ * Update a cell's VL server address list from the DNS.
+ */
+static int afs_update_cell(struct afs_cell *cell)
+{
+	struct afs_vlserver_list *vllist, *old = NULL, *p;
+	unsigned int min_ttl = READ_ONCE(afs_cell_min_ttl);
+	unsigned int max_ttl = READ_ONCE(afs_cell_max_ttl);
+	time64_t now, expiry = 0;
+	int ret = 0;
+
+	_enter("%s", cell->name);
+
+	vllist = afs_dns_query(cell, &expiry);
+	if (IS_ERR(vllist)) {
+		ret = PTR_ERR(vllist);
+
+		_debug("%s: fail %d", cell->name, ret);
+		if (ret == -ENOMEM)
+			goto out_wake;
+
+		vllist = afs_alloc_vlserver_list(0);
+		if (!vllist) {
+			if (ret >= 0)
+				ret = -ENOMEM;
+			goto out_wake;
+		}
+
+		switch (ret) {
+		case -ENODATA:
+		case -EDESTADDRREQ:
+			vllist->status = DNS_LOOKUP_GOT_NOT_FOUND;
+			break;
+		case -EAGAIN:
+		case -ECONNREFUSED:
+			vllist->status = DNS_LOOKUP_GOT_TEMP_FAILURE;
+			break;
+		default:
+			vllist->status = DNS_LOOKUP_GOT_LOCAL_FAILURE;
+			break;
+		}
+	}
+
+	_debug("%s: got list %d %d", cell->name, vllist->source, vllist->status);
+	cell->dns_status = vllist->status;
+
+	now = ktime_get_real_seconds();
+	if (min_ttl > max_ttl)
+		max_ttl = min_ttl;
+	if (expiry < now + min_ttl)
+		expiry = now + min_ttl;
+	else if (expiry > now + max_ttl)
+		expiry = now + max_ttl;
+
+	_debug("%s: status %d", cell->name, vllist->status);
+	if (vllist->source == DNS_RECORD_UNAVAILABLE) {
+		switch (vllist->status) {
+		case DNS_LOOKUP_GOT_NOT_FOUND:
+			/* The DNS said that the cell does not exist or there
+			 * weren't any addresses to be had.
+			 */
+			cell->dns_expiry = expiry;
+			break;
+
+		case DNS_LOOKUP_BAD:
+		case DNS_LOOKUP_GOT_LOCAL_FAILURE:
+		case DNS_LOOKUP_GOT_TEMP_FAILURE:
+		case DNS_LOOKUP_GOT_NS_FAILURE:
+		default:
+			cell->dns_expiry = now + 10;
+			break;
+		}
+	} else {
+		cell->dns_expiry = expiry;
+	}
+
+	/* Replace the VL server list if the new record has servers or the old
+	 * record doesn't.
+	 */
+	write_lock(&cell->vl_servers_lock);
+	p = rcu_dereference_protected(cell->vl_servers, true);
+	if (vllist->nr_servers > 0 || p->nr_servers == 0) {
+		rcu_assign_pointer(cell->vl_servers, vllist);
+		cell->dns_source = vllist->source;
+		old = p;
+	} else {
+		old = vllist;
+	}
+	write_unlock(&cell->vl_servers_lock);
+	afs_put_vlserverlist(cell->net, old);
+
+out_wake:
+	smp_store_release(&cell->dns_lookup_count,
+			  cell->dns_lookup_count + 1); /* vs source/status */
+	wake_up_var(&cell->dns_lookup_count);
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * Destroy a cell record
+ */
+static void afs_cell_destroy(struct rcu_head *rcu)
+{
+	struct afs_cell *cell = container_of(rcu, struct afs_cell, rcu);
+	struct afs_net *net = cell->net;
+	int r;
+
+	_enter("%p{%s}", cell, cell->name);
+
+	r = refcount_read(&cell->ref);
+	ASSERTCMP(r, ==, 0);
+	trace_afs_cell(cell->debug_id, r, atomic_read(&cell->active), afs_cell_trace_free);
+
+	afs_put_vlserverlist(net, rcu_access_pointer(cell->vl_servers));
+	afs_unuse_cell(cell->alias_of, afs_cell_trace_unuse_alias);
+	key_put(cell->anonymous_key);
+	kfree(cell->name - 1);
+	kfree(cell);
+
+	afs_dec_cells_outstanding(net);
+	_leave(" [destroyed]");
+}
+
+static void afs_destroy_cell_work(struct work_struct *work)
+{
+	struct afs_cell *cell = container_of(work, struct afs_cell, destroyer);
+
+	afs_see_cell(cell, afs_cell_trace_destroy);
+	timer_delete_sync(&cell->management_timer);
+	cancel_work_sync(&cell->manager);
+
+	if (test_bit(AFS_CELL_FL_HAVE_INO, &cell->flags)) {
+		down_write(&cell->net->cells_lock);
+		idr_remove(&cell->net->cells_dyn_ino, cell->dynroot_ino);
+		up_write(&cell->net->cells_lock);
+	}
+
+	call_rcu(&cell->rcu, afs_cell_destroy);
+}
+
+/*
+ * Get a reference on a cell record.
+ */
+struct afs_cell *afs_get_cell(struct afs_cell *cell, enum afs_cell_trace reason)
+{
+	int r;
+
+	__refcount_inc(&cell->ref, &r);
+	trace_afs_cell(cell->debug_id, r + 1, atomic_read(&cell->active), reason);
+	return cell;
+}
+
+/*
+ * Drop a reference on a cell record.
+ */
+void afs_put_cell(struct afs_cell *cell, enum afs_cell_trace reason)
+{
+	if (cell) {
+		unsigned int debug_id = cell->debug_id;
+		unsigned int a;
+		bool zero;
+		int r;
+
+		a = atomic_read(&cell->active);
+		zero = __refcount_dec_and_test(&cell->ref, &r);
+		trace_afs_cell(debug_id, r - 1, a, reason);
+		if (zero) {
+			a = atomic_read(&cell->active);
+			WARN(a != 0, "Cell active count %u > 0\n", a);
+			WARN_ON(!queue_work(afs_wq, &cell->destroyer));
+		}
+	}
+}
+
+/*
+ * Note a cell becoming more active.
+ */
+struct afs_cell *afs_use_cell(struct afs_cell *cell, enum afs_cell_trace reason)
+{
+	int r, a;
+
+	__refcount_inc(&cell->ref, &r);
+	a = atomic_inc_return(&cell->active);
+	trace_afs_cell(cell->debug_id, r + 1, a, reason);
+	return cell;
+}
+
+/*
+ * Record a cell becoming less active.  When the active counter reaches 1, it
+ * is scheduled for destruction, but may get reactivated.
+ */
+void afs_unuse_cell(struct afs_cell *cell, enum afs_cell_trace reason)
+{
+	unsigned int debug_id;
+	time64_t now, expire_delay;
+	bool zero;
+	int r, a;
+
+	if (!cell)
+		return;
+
+	_enter("%s", cell->name);
+
+	now = ktime_get_real_seconds();
+	cell->last_inactive = now;
+	expire_delay = 0;
+	if (cell->vl_servers->nr_servers)
+		expire_delay = afs_cell_gc_delay;
+
+	debug_id = cell->debug_id;
+	a = atomic_dec_return(&cell->active);
+	if (!a)
+		/* 'cell' may now be garbage collected. */
+		afs_set_cell_timer(cell, expire_delay);
+
+	zero = __refcount_dec_and_test(&cell->ref, &r);
+	trace_afs_cell(debug_id, r - 1, a, reason);
+	if (zero)
+		WARN_ON(!queue_work(afs_wq, &cell->destroyer));
+}
+
+/*
+ * Note that a cell has been seen.
+ */
+void afs_see_cell(struct afs_cell *cell, enum afs_cell_trace reason)
+{
+	int r, a;
+
+	r = refcount_read(&cell->ref);
+	a = atomic_read(&cell->active);
+	trace_afs_cell(cell->debug_id, r, a, reason);
+}
+
+/*
+ * Queue a cell for management, giving the workqueue a ref to hold.
+ */
+void afs_queue_cell(struct afs_cell *cell, enum afs_cell_trace reason)
+{
+	queue_work(afs_wq, &cell->manager);
+}
+
+/*
+ * Cell-specific management timer.
+ */
+static void afs_cell_timer(struct timer_list *timer)
+{
+	struct afs_cell *cell = container_of(timer, struct afs_cell, management_timer);
+
+	afs_see_cell(cell, afs_cell_trace_see_mgmt_timer);
+	if (refcount_read(&cell->ref) > 0 && cell->net->live)
+		queue_work(afs_wq, &cell->manager);
+}
+
+/*
+ * Set/reduce the cell timer.
+ */
+void afs_set_cell_timer(struct afs_cell *cell, unsigned int delay_secs)
+{
+	timer_reduce(&cell->management_timer, jiffies + delay_secs * HZ);
+}
+
+/*
+ * Activate a cell.
+ */
+static int afs_activate_cell(struct afs_net *net, struct afs_cell *cell)
+{
+	struct hlist_node **p;
+	struct afs_cell *pcell;
+	int ret;
+
+	ret = afs_proc_cell_setup(cell);
+	if (ret < 0)
+		return ret;
+
+	mutex_lock(&net->proc_cells_lock);
+	for (p = &net->proc_cells.first; *p; p = &(*p)->next) {
+		pcell = hlist_entry(*p, struct afs_cell, proc_link);
+		if (strcmp(cell->name, pcell->name) < 0)
+			break;
+	}
+
+	cell->proc_link.pprev = p;
+	cell->proc_link.next = *p;
+	rcu_assign_pointer(*p, &cell->proc_link.next);
+	if (cell->proc_link.next)
+		cell->proc_link.next->pprev = &cell->proc_link.next;
+
+	mutex_unlock(&net->proc_cells_lock);
+	return 0;
+}
+
+/*
+ * Deactivate a cell.
+ */
+static void afs_deactivate_cell(struct afs_net *net, struct afs_cell *cell)
+{
+	_enter("%s", cell->name);
+
+	afs_proc_cell_remove(cell);
+
+	mutex_lock(&net->proc_cells_lock);
+	if (!hlist_unhashed(&cell->proc_link))
+		hlist_del_rcu(&cell->proc_link);
+	mutex_unlock(&net->proc_cells_lock);
+
+	_leave("");
+}
+
+static bool afs_has_cell_expired(struct afs_cell *cell, time64_t *_next_manage)
+{
+	const struct afs_vlserver_list *vllist;
+	time64_t expire_at = cell->last_inactive;
+	time64_t now = ktime_get_real_seconds();
+
+	if (atomic_read(&cell->active))
+		return false;
+	if (!cell->net->live)
+		return true;
+
+	vllist = rcu_dereference_protected(cell->vl_servers, true);
+	if (vllist && vllist->nr_servers > 0)
+		expire_at += afs_cell_gc_delay;
+
+	if (expire_at <= now)
+		return true;
+	if (expire_at < *_next_manage)
+		*_next_manage = expire_at;
+	return false;
+}
+
+/*
+ * Manage a cell record, initialising and destroying it, maintaining its DNS
+ * records.
+ */
+static bool afs_manage_cell(struct afs_cell *cell)
+{
+	struct afs_net *net = cell->net;
+	time64_t next_manage = TIME64_MAX;
+	int ret;
+
+	_enter("%s", cell->name);
+
+	_debug("state %u", cell->state);
+	switch (cell->state) {
+	case AFS_CELL_SETTING_UP:
+		goto set_up_cell;
+	case AFS_CELL_UNLOOKED:
+	case AFS_CELL_ACTIVE:
+		goto cell_is_active;
+	case AFS_CELL_REMOVING:
+		WARN_ON_ONCE(1);
+		return false;
+	case AFS_CELL_DEAD:
+		return false;
+	default:
+		_debug("bad state %u", cell->state);
+		WARN_ON_ONCE(1); /* Unhandled state */
+		return false;
+	}
+
+set_up_cell:
+	ret = afs_activate_cell(net, cell);
+	if (ret < 0) {
+		cell->error = ret;
+		goto remove_cell;
+	}
+
+	afs_set_cell_state(cell, AFS_CELL_UNLOOKED);
+
+cell_is_active:
+	if (afs_has_cell_expired(cell, &next_manage))
+		goto remove_cell;
+
+	if (test_and_clear_bit(AFS_CELL_FL_DO_LOOKUP, &cell->flags)) {
+		ret = afs_update_cell(cell);
+		if (ret < 0)
+			cell->error = ret;
+		if (cell->state == AFS_CELL_UNLOOKED)
+			afs_set_cell_state(cell, AFS_CELL_ACTIVE);
+	}
+
+	if (next_manage < TIME64_MAX && cell->net->live) {
+		time64_t now = ktime_get_real_seconds();
+
+		if (next_manage - now <= 0)
+			afs_queue_cell(cell, afs_cell_trace_queue_again);
+		else
+			afs_set_cell_timer(cell, next_manage - now);
+	}
+	_leave(" [done %u]", cell->state);
+	return false;
+
+remove_cell:
+	down_write(&net->cells_lock);
+
+	if (atomic_read(&cell->active)) {
+		up_write(&net->cells_lock);
+		goto cell_is_active;
+	}
+
+	/* Make sure that the expiring server records are going to see the fact
+	 * that the cell is caput.
+	 */
+	afs_set_cell_state(cell, AFS_CELL_REMOVING);
+
+	afs_deactivate_cell(net, cell);
+	afs_purge_servers(cell);
+
+	rb_erase(&cell->net_node, &net->cells);
+	afs_see_cell(cell, afs_cell_trace_unuse_delete);
+	up_write(&net->cells_lock);
+
+	/* The root volume is pinning the cell */
+	afs_put_volume(cell->root_volume, afs_volume_trace_put_cell_root);
+	cell->root_volume = NULL;
+
+	afs_set_cell_state(cell, AFS_CELL_DEAD);
+	return true;
+}
+
+static void afs_manage_cell_work(struct work_struct *work)
+{
+	struct afs_cell *cell = container_of(work, struct afs_cell, manager);
+	bool final_put;
+
+	afs_see_cell(cell, afs_cell_trace_manage);
+	final_put = afs_manage_cell(cell);
+	afs_see_cell(cell, afs_cell_trace_managed);
+	if (final_put)
+		afs_put_cell(cell, afs_cell_trace_put_final);
+}
+
+/*
+ * Purge in-memory cell database.
+ */
+void afs_cell_purge(struct afs_net *net)
+{
+	struct afs_cell *ws;
+	struct rb_node *cursor;
+
+	_enter("");
+
+	down_write(&net->cells_lock);
+	ws = rcu_replace_pointer(net->ws_cell, NULL,
+				 lockdep_is_held(&net->cells_lock));
+	up_write(&net->cells_lock);
+	afs_unuse_cell(ws, afs_cell_trace_unuse_ws);
+
+	_debug("kick cells");
+	down_read(&net->cells_lock);
+	for (cursor = rb_first(&net->cells); cursor; cursor = rb_next(cursor)) {
+		struct afs_cell *cell = rb_entry(cursor, struct afs_cell, net_node);
+
+		afs_see_cell(cell, afs_cell_trace_purge);
+
+		if (test_and_clear_bit(AFS_CELL_FL_NO_GC, &cell->flags))
+			afs_unuse_cell(cell, afs_cell_trace_unuse_pin);
+
+		afs_queue_cell(cell, afs_cell_trace_queue_purge);
+	}
+	up_read(&net->cells_lock);
+
+	_debug("wait");
+	wait_var_event(&net->cells_outstanding,
+		       !atomic_read(&net->cells_outstanding));
+	_leave("");
+}