FS-Cache: Allow the current state of all objects to be dumped

Allow the current state of all fscache objects to be dumped by doing:

	cat /proc/fs/fscache/objects

By default, all objects and all fields will be shown.  This can be restricted
by adding a suitable key to one of the caller's keyrings (such as the session
keyring):

	keyctl add user fscache:objlist "<restrictions>" @s

The <restrictions> are:

	K	Show hexdump of object key (don't show if not given)
	A	Show hexdump of object aux data (don't show if not given)

And paired restrictions:

	C	Show objects that have a cookie
	c	Show objects that don't have a cookie
	B	Show objects that are busy
	b	Show objects that aren't busy
	W	Show objects that have pending writes
	w	Show objects that don't have pending writes
	R	Show objects that have outstanding reads
	r	Show objects that don't have outstanding reads
	S	Show objects that have slow work queued
	s	Show objects that don't have slow work queued

If neither side of a restriction pair is given, then both are implied.  For
example:

	keyctl add user fscache:objlist KB @s

shows objects that are busy, and lists their object keys, but does not dump
their auxiliary data.  It also implies "CcWwRrSs", but as 'B' is given, 'b' is
not implied.

Signed-off-by: David Howells <dhowells@redhat.com>

10 files changed, 479 insertions, 1 deletions

diff --git a/fs/fscache/Kconfig b/fs/fscache/Kconfig
index 9bbb8ce7bea..864dac20a24 100644
--- a/fs/fscache/Kconfig
+++ b/fs/fscache/Kconfig
@@ -54,3 +54,10 @@ config FSCACHE_DEBUG
 	  enabled by setting bits in /sys/modules/fscache/parameter/debug.
 
 	  See Documentation/filesystems/caching/fscache.txt for more information.
+
+config FSCACHE_OBJECT_LIST
+	bool "Maintain global object list for debugging purposes"
+	depends on FSCACHE && PROC_FS
+	help
+	  Maintain a global list of active fscache objects that can be
+	  retrieved through /proc/fs/fscache/objects for debugging purposes
diff --git a/fs/fscache/Makefile b/fs/fscache/Makefile
index 91571b95aac..6d561531cb3 100644
--- a/fs/fscache/Makefile
+++ b/fs/fscache/Makefile
@@ -15,5 +15,6 @@ fscache-y := \
 fscache-$(CONFIG_PROC_FS) += proc.o
 fscache-$(CONFIG_FSCACHE_STATS) += stats.o
 fscache-$(CONFIG_FSCACHE_HISTOGRAM) += histogram.o
+fscache-$(CONFIG_FSCACHE_OBJECT_LIST) += object-list.o
 
 obj-$(CONFIG_FSCACHE) := fscache.o
diff --git a/fs/fscache/cache.c b/fs/fscache/cache.c
index e21985bbb1f..724384ef96d 100644
--- a/fs/fscache/cache.c
+++ b/fs/fscache/cache.c
@@ -263,6 +263,7 @@ int fscache_add_cache(struct fscache_cache *cache,
 	spin_lock(&cache->object_list_lock);
 	list_add_tail(&ifsdef->cache_link, &cache->object_list);
 	spin_unlock(&cache->object_list_lock);
+	fscache_objlist_add(ifsdef);
 
 	/* add the cache's netfs definition index object to the top level index
 	 * cookie as a known backing object */
diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index 72fd18f6c71..9b518732823 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -349,6 +349,8 @@ static int fscache_attach_object(struct fscache_cookie *cookie,
 	object->cookie = cookie;
 	atomic_inc(&cookie->usage);
 	hlist_add_head(&object->cookie_link, &cookie->backing_objects);
+
+	fscache_objlist_add(object);
 	ret = 0;
 
 cant_attach_object:
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index 1c341304621..fe02973a951 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -88,11 +88,24 @@ extern int fscache_wait_bit_interruptible(void *);
 /*
  * object.c
  */
+extern const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5];
+
 extern void fscache_withdrawing_object(struct fscache_cache *,
 				       struct fscache_object *);
 extern void fscache_enqueue_object(struct fscache_object *);
 
 /*
+ * object-list.c
+ */
+#ifdef CONFIG_FSCACHE_OBJECT_LIST
+extern const struct file_operations fscache_objlist_fops;
+
+extern void fscache_objlist_add(struct fscache_object *);
+#else
+#define fscache_objlist_add(object) do {} while(0)
+#endif
+
+/*
  * operation.c
  */
 extern int fscache_submit_exclusive_op(struct fscache_object *,
diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c
new file mode 100644
index 00000000000..e590242fa41
--- /dev/null
+++ b/fs/fscache/object-list.c
@@ -0,0 +1,432 @@
+/* Global fscache object list maintainer and viewer
+ *
+ * Copyright (C) 2009 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.
+ */
+
+#define FSCACHE_DEBUG_LEVEL COOKIE
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/key.h>
+#include <keys/user-type.h>
+#include "internal.h"
+
+static struct rb_root fscache_object_list;
+static DEFINE_RWLOCK(fscache_object_list_lock);
+
+struct fscache_objlist_data {
+	unsigned long	config;		/* display configuration */
+#define FSCACHE_OBJLIST_CONFIG_KEY	0x00000001	/* show object keys */
+#define FSCACHE_OBJLIST_CONFIG_AUX	0x00000002	/* show object auxdata */
+#define FSCACHE_OBJLIST_CONFIG_COOKIE	0x00000004	/* show objects with cookies */
+#define FSCACHE_OBJLIST_CONFIG_NOCOOKIE	0x00000008	/* show objects without cookies */
+#define FSCACHE_OBJLIST_CONFIG_BUSY	0x00000010	/* show busy objects */
+#define FSCACHE_OBJLIST_CONFIG_IDLE	0x00000020	/* show idle objects */
+#define FSCACHE_OBJLIST_CONFIG_PENDWR	0x00000040	/* show objects with pending writes */
+#define FSCACHE_OBJLIST_CONFIG_NOPENDWR	0x00000080	/* show objects without pending writes */
+#define FSCACHE_OBJLIST_CONFIG_READS	0x00000100	/* show objects with active reads */
+#define FSCACHE_OBJLIST_CONFIG_NOREADS	0x00000200	/* show objects without active reads */
+#define FSCACHE_OBJLIST_CONFIG_EVENTS	0x00000400	/* show objects with events */
+#define FSCACHE_OBJLIST_CONFIG_NOEVENTS	0x00000800	/* show objects without no events */
+#define FSCACHE_OBJLIST_CONFIG_WORK	0x00001000	/* show objects with slow work */
+#define FSCACHE_OBJLIST_CONFIG_NOWORK	0x00002000	/* show objects without slow work */
+
+	u8		buf[512];	/* key and aux data buffer */
+};
+
+/*
+ * Add an object to the object list
+ * - we use the address of the fscache_object structure as the key into the
+ *   tree
+ */
+void fscache_objlist_add(struct fscache_object *obj)
+{
+	struct fscache_object *xobj;
+	struct rb_node **p = &fscache_object_list.rb_node, *parent = NULL;
+
+	write_lock(&fscache_object_list_lock);
+
+	while (*p) {
+		parent = *p;
+		xobj = rb_entry(parent, struct fscache_object, objlist_link);
+
+		if (obj < xobj)
+			p = &(*p)->rb_left;
+		else if (obj > xobj)
+			p = &(*p)->rb_right;
+		else
+			BUG();
+	}
+
+	rb_link_node(&obj->objlist_link, parent, p);
+	rb_insert_color(&obj->objlist_link, &fscache_object_list);
+
+	write_unlock(&fscache_object_list_lock);
+}
+
+/**
+ * fscache_object_destroy - Note that a cache object is about to be destroyed
+ * @object: The object to be destroyed
+ *
+ * Note the imminent destruction and deallocation of a cache object record.
+ */
+void fscache_object_destroy(struct fscache_object *obj)
+{
+	write_lock(&fscache_object_list_lock);
+
+	BUG_ON(RB_EMPTY_ROOT(&fscache_object_list));
+	rb_erase(&obj->objlist_link, &fscache_object_list);
+
+	write_unlock(&fscache_object_list_lock);
+}
+EXPORT_SYMBOL(fscache_object_destroy);
+
+/*
+ * find the object in the tree on or after the specified index
+ */
+static struct fscache_object *fscache_objlist_lookup(loff_t *_pos)
+{
+	struct fscache_object *pobj, *obj, *minobj = NULL;
+	struct rb_node *p;
+	unsigned long pos;
+
+	if (*_pos >= (unsigned long) ERR_PTR(-ENOENT))
+		return NULL;
+	pos = *_pos;
+
+	/* banners (can't represent line 0 by pos 0 as that would involve
+	 * returning a NULL pointer) */
+	if (pos == 0)
+		return (struct fscache_object *) ++(*_pos);
+	if (pos < 3)
+		return (struct fscache_object *)pos;
+
+	pobj = (struct fscache_object *)pos;
+	p = fscache_object_list.rb_node;
+	while (p) {
+		obj = rb_entry(p, struct fscache_object, objlist_link);
+		if (pobj < obj) {
+			if (!minobj || minobj > obj)
+				minobj = obj;
+			p = p->rb_left;
+		} else if (pobj > obj) {
+			p = p->rb_right;
+		} else {
+			minobj = obj;
+			break;
+		}
+		obj = NULL;
+	}
+
+	if (!minobj)
+		*_pos = (unsigned long) ERR_PTR(-ENOENT);
+	else if (minobj != obj)
+		*_pos = (unsigned long) minobj;
+	return minobj;
+}
+
+/*
+ * set up the iterator to start reading from the first line
+ */
+static void *fscache_objlist_start(struct seq_file *m, loff_t *_pos)
+	__acquires(&fscache_object_list_lock)
+{
+	read_lock(&fscache_object_list_lock);
+	return fscache_objlist_lookup(_pos);
+}
+
+/*
+ * move to the next line
+ */
+static void *fscache_objlist_next(struct seq_file *m, void *v, loff_t *_pos)
+{
+	(*_pos)++;
+	return fscache_objlist_lookup(_pos);
+}
+
+/*
+ * clean up after reading
+ */
+static void fscache_objlist_stop(struct seq_file *m, void *v)
+	__releases(&fscache_object_list_lock)
+{
+	read_unlock(&fscache_object_list_lock);
+}
+
+/*
+ * display an object
+ */
+static int fscache_objlist_show(struct seq_file *m, void *v)
+{
+	struct fscache_objlist_data *data = m->private;
+	struct fscache_object *obj = v;
+	unsigned long config = data->config;
+	uint16_t keylen, auxlen;
+	char _type[3], *type;
+	bool no_cookie;
+	u8 *buf = data->buf, *p;
+
+	if ((unsigned long) v == 1) {
+		seq_puts(m, "OBJECT   PARENT   STAT CHLDN OPS OOP IPR EX READS"
+			 " EM EV F S"
+			 " | NETFS_COOKIE_DEF TY FL NETFS_DATA");
+		if (config & (FSCACHE_OBJLIST_CONFIG_KEY |
+			      FSCACHE_OBJLIST_CONFIG_AUX))
+			seq_puts(m, "       ");
+		if (config & FSCACHE_OBJLIST_CONFIG_KEY)
+			seq_puts(m, "OBJECT_KEY");
+		if ((config & (FSCACHE_OBJLIST_CONFIG_KEY |
+			       FSCACHE_OBJLIST_CONFIG_AUX)) ==
+		    (FSCACHE_OBJLIST_CONFIG_KEY | FSCACHE_OBJLIST_CONFIG_AUX))
+			seq_puts(m, ", ");
+		if (config & FSCACHE_OBJLIST_CONFIG_AUX)
+			seq_puts(m, "AUX_DATA");
+		seq_puts(m, "\n");
+		return 0;
+	}
+
+	if ((unsigned long) v == 2) {
+		seq_puts(m, "======== ======== ==== ===== === === === == ====="
+			 " == == = ="
+			 " | ================ == == ================");
+		if (config & (FSCACHE_OBJLIST_CONFIG_KEY |
+			      FSCACHE_OBJLIST_CONFIG_AUX))
+			seq_puts(m, " ================");
+		seq_puts(m, "\n");
+		return 0;
+	}
+
+	/* filter out any unwanted objects */
+#define FILTER(criterion, _yes, _no)					\
+	do {								\
+		unsigned long yes = FSCACHE_OBJLIST_CONFIG_##_yes;	\
+		unsigned long no = FSCACHE_OBJLIST_CONFIG_##_no;	\
+		if (criterion) {					\
+			if (!(config & yes))				\
+				return 0;				\
+		} else {						\
+			if (!(config & no))				\
+				return 0;				\
+		}							\
+	} while(0)
+
+	if (~config) {
+		FILTER(obj->cookie,
+		       COOKIE, NOCOOKIE);
+		FILTER(obj->state != FSCACHE_OBJECT_ACTIVE ||
+		       obj->n_ops != 0 ||
+		       obj->n_obj_ops != 0 ||
+		       obj->flags ||
+		       !list_empty(&obj->dependents),
+		       BUSY, IDLE);
+		FILTER(test_bit(FSCACHE_OBJECT_PENDING_WRITE, &obj->flags),
+		       PENDWR, NOPENDWR);
+		FILTER(atomic_read(&obj->n_reads),
+		       READS, NOREADS);
+		FILTER(obj->events & obj->event_mask,
+		       EVENTS, NOEVENTS);
+		FILTER(obj->work.flags & ~(1UL << SLOW_WORK_VERY_SLOW),
+		       WORK, NOWORK);
+	}
+
+	seq_printf(m,
+		   "%8x %8x %s %5u %3u %3u %3u %2u %5u %2lx %2lx %1lx %1lx | ",
+		   obj->debug_id,
+		   obj->parent ? obj->parent->debug_id : -1,
+		   fscache_object_states_short[obj->state],
+		   obj->n_children,
+		   obj->n_ops,
+		   obj->n_obj_ops,
+		   obj->n_in_progress,
+		   obj->n_exclusive,
+		   atomic_read(&obj->n_reads),
+		   obj->event_mask & FSCACHE_OBJECT_EVENTS_MASK,
+		   obj->events,
+		   obj->flags,
+		   obj->work.flags);
+
+	no_cookie = true;
+	keylen = auxlen = 0;
+	if (obj->cookie) {
+		spin_lock(&obj->lock);
+		if (obj->cookie) {
+			switch (obj->cookie->def->type) {
+			case 0:
+				type = "IX";
+				break;
+			case 1:
+				type = "DT";
+				break;
+			default:
+				sprintf(_type, "%02u",
+					obj->cookie->def->type);
+				type = _type;
+				break;
+			}
+
+			seq_printf(m, "%-16s %s %2lx %16p",
+				   obj->cookie->def->name,
+				   type,
+				   obj->cookie->flags,
+				   obj->cookie->netfs_data);
+
+			if (obj->cookie->def->get_key &&
+			    config & FSCACHE_OBJLIST_CONFIG_KEY)
+				keylen = obj->cookie->def->get_key(
+					obj->cookie->netfs_data,
+					buf, 400);
+
+			if (obj->cookie->def->get_aux &&
+			    config & FSCACHE_OBJLIST_CONFIG_AUX)
+				auxlen = obj->cookie->def->get_aux(
+					obj->cookie->netfs_data,
+					buf + keylen, 512 - keylen);
+
+			no_cookie = false;
+		}
+		spin_unlock(&obj->lock);
+
+		if (!no_cookie && (keylen > 0 || auxlen > 0)) {
+			seq_printf(m, " ");
+			for (p = buf; keylen > 0; keylen--)
+				seq_printf(m, "%02x", *p++);
+			if (auxlen > 0) {
+				if (config & FSCACHE_OBJLIST_CONFIG_KEY)
+					seq_printf(m, ", ");
+				for (; auxlen > 0; auxlen--)
+					seq_printf(m, "%02x", *p++);
+			}
+		}
+	}
+
+	if (no_cookie)
+		seq_printf(m, "<no_cookie>\n");
+	else
+		seq_printf(m, "\n");
+	return 0;
+}
+
+static const struct seq_operations fscache_objlist_ops = {
+	.start		= fscache_objlist_start,
+	.stop		= fscache_objlist_stop,
+	.next		= fscache_objlist_next,
+	.show		= fscache_objlist_show,
+};
+
+/*
+ * get the configuration for filtering the list
+ */
+static void fscache_objlist_config(struct fscache_objlist_data *data)
+{
+#ifdef CONFIG_KEYS
+	struct user_key_payload *confkey;
+	unsigned long config;
+	struct key *key;
+	const char *buf;
+	int len;
+
+	key = request_key(&key_type_user, "fscache:objlist", NULL);
+	if (IS_ERR(key))
+		goto no_config;
+
+	config = 0;
+	rcu_read_lock();
+
+	confkey = key->payload.data;
+	buf = confkey->data;
+
+	for (len = confkey->datalen - 1; len >= 0; len--) {
+		switch (buf[len]) {
+		case 'K': config |= FSCACHE_OBJLIST_CONFIG_KEY;		break;
+		case 'A': config |= FSCACHE_OBJLIST_CONFIG_AUX;		break;
+		case 'C': config |= FSCACHE_OBJLIST_CONFIG_COOKIE;	break;
+		case 'c': config |= FSCACHE_OBJLIST_CONFIG_NOCOOKIE;	break;
+		case 'B': config |= FSCACHE_OBJLIST_CONFIG_BUSY;	break;
+		case 'b': config |= FSCACHE_OBJLIST_CONFIG_IDLE;	break;
+		case 'W': config |= FSCACHE_OBJLIST_CONFIG_PENDWR;	break;
+		case 'w': config |= FSCACHE_OBJLIST_CONFIG_NOPENDWR;	break;
+		case 'R': config |= FSCACHE_OBJLIST_CONFIG_READS;	break;
+		case 'r': config |= FSCACHE_OBJLIST_CONFIG_NOREADS;	break;
+		case 'S': config |= FSCACHE_OBJLIST_CONFIG_WORK;	break;
+		case 's': config |= FSCACHE_OBJLIST_CONFIG_NOWORK;	break;
+		}
+	}
+
+	rcu_read_unlock();
+	key_put(key);
+
+	if (!(config & (FSCACHE_OBJLIST_CONFIG_COOKIE | FSCACHE_OBJLIST_CONFIG_NOCOOKIE)))
+	    config   |= FSCACHE_OBJLIST_CONFIG_COOKIE | FSCACHE_OBJLIST_CONFIG_NOCOOKIE;
+	if (!(config & (FSCACHE_OBJLIST_CONFIG_BUSY | FSCACHE_OBJLIST_CONFIG_IDLE)))
+	    config   |= FSCACHE_OBJLIST_CONFIG_BUSY | FSCACHE_OBJLIST_CONFIG_IDLE;
+	if (!(config & (FSCACHE_OBJLIST_CONFIG_PENDWR | FSCACHE_OBJLIST_CONFIG_NOPENDWR)))
+	    config   |= FSCACHE_OBJLIST_CONFIG_PENDWR | FSCACHE_OBJLIST_CONFIG_NOPENDWR;
+	if (!(config & (FSCACHE_OBJLIST_CONFIG_READS | FSCACHE_OBJLIST_CONFIG_NOREADS)))
+	    config   |= FSCACHE_OBJLIST_CONFIG_READS | FSCACHE_OBJLIST_CONFIG_NOREADS;
+	if (!(config & (FSCACHE_OBJLIST_CONFIG_EVENTS | FSCACHE_OBJLIST_CONFIG_NOEVENTS)))
+	    config   |= FSCACHE_OBJLIST_CONFIG_EVENTS | FSCACHE_OBJLIST_CONFIG_NOEVENTS;
+	if (!(config & (FSCACHE_OBJLIST_CONFIG_WORK | FSCACHE_OBJLIST_CONFIG_NOWORK)))
+	    config   |= FSCACHE_OBJLIST_CONFIG_WORK | FSCACHE_OBJLIST_CONFIG_NOWORK;
+
+	data->config = config;
+	return;
+
+no_config:
+#endif
+	data->config = ULONG_MAX;
+}
+
+/*
+ * open "/proc/fs/fscache/objects" to provide a list of active objects
+ * - can be configured by a user-defined key added to the caller's keyrings
+ */
+static int fscache_objlist_open(struct inode *inode, struct file *file)
+{
+	struct fscache_objlist_data *data;
+	struct seq_file *m;
+	int ret;
+
+	ret = seq_open(file, &fscache_objlist_ops);
+	if (ret < 0)
+		return ret;
+
+	m = file->private_data;
+
+	/* buffer for key extraction */
+	data = kmalloc(sizeof(struct fscache_objlist_data), GFP_KERNEL);
+	if (!data) {
+		seq_release(inode, file);
+		return -ENOMEM;
+	}
+
+	/* get the configuration key */
+	fscache_objlist_config(data);
+
+	m->private = data;
+	return 0;
+}
+
+/*
+ * clean up on close
+ */
+static int fscache_objlist_release(struct inode *inode, struct file *file)
+{
+	struct seq_file *m = file->private_data;
+
+	kfree(m->private);
+	m->private = NULL;
+	return seq_release(inode, file);
+}
+
+const struct file_operations fscache_objlist_fops = {
+	.owner		= THIS_MODULE,
+	.open		= fscache_objlist_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= fscache_objlist_release,
+};
diff --git a/fs/fscache/object.c b/fs/fscache/object.c
index 615b63dd9ec..ad1644f073b 100644
--- a/fs/fscache/object.c
+++ b/fs/fscache/object.c
@@ -34,7 +34,7 @@ const char *fscache_object_states[FSCACHE_OBJECT__NSTATES] = {
 };
 EXPORT_SYMBOL(fscache_object_states);
 
-static const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5] = {
+const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5] = {
 	[FSCACHE_OBJECT_INIT]		= "INIT",
 	[FSCACHE_OBJECT_LOOKING_UP]	= "LOOK",
 	[FSCACHE_OBJECT_CREATING]	= "CRTN",
diff --git a/fs/fscache/operation.c b/fs/fscache/operation.c
index 91bbe6f0377..09e43b6e822 100644
--- a/fs/fscache/operation.c
+++ b/fs/fscache/operation.c
@@ -322,6 +322,9 @@ void fscache_put_operation(struct fscache_operation *op)
 
 	object = op->object;
 
+	if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
+		atomic_dec(&object->n_reads);
+
 	/* now... we may get called with the object spinlock held, so we
 	 * complete the cleanup here only if we can immediately acquire the
 	 * lock, and defer it otherwise */
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index e8bbc395cef..c5973e38ce3 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -275,6 +275,9 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 
 	ASSERTCMP(object->state, >, FSCACHE_OBJECT_LOOKING_UP);
 
+	atomic_inc(&object->n_reads);
+	set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
+
 	if (fscache_submit_op(object, &op->op) < 0)
 		goto nobufs_unlock;
 	spin_unlock(&cookie->lock);
@@ -386,6 +389,9 @@ int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
 	object = hlist_entry(cookie->backing_objects.first,
 			     struct fscache_object, cookie_link);
 
+	atomic_inc(&object->n_reads);
+	set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
+
 	if (fscache_submit_op(object, &op->op) < 0)
 		goto nobufs_unlock;
 	spin_unlock(&cookie->lock);
diff --git a/fs/fscache/proc.c b/fs/fscache/proc.c
index beeab44bc31..1d9e4951a59 100644
--- a/fs/fscache/proc.c
+++ b/fs/fscache/proc.c
@@ -37,10 +37,20 @@ int __init fscache_proc_init(void)
 		goto error_histogram;
 #endif
 
+#ifdef CONFIG_FSCACHE_OBJECT_LIST
+	if (!proc_create("fs/fscache/objects", S_IFREG | 0444, NULL,
+			 &fscache_objlist_fops))
+		goto error_objects;
+#endif
+
 	_leave(" = 0");
 	return 0;
 
+#ifdef CONFIG_FSCACHE_OBJECT_LIST
+error_objects:
+#endif
 #ifdef CONFIG_FSCACHE_HISTOGRAM
+	remove_proc_entry("fs/fscache/histogram", NULL);
 error_histogram:
 #endif
 #ifdef CONFIG_FSCACHE_STATS
@@ -58,6 +68,9 @@ error_dir:
  */
 void fscache_proc_cleanup(void)
 {
+#ifdef CONFIG_FSCACHE_OBJECT_LIST
+	remove_proc_entry("fs/fscache/objects", NULL);
+#endif
 #ifdef CONFIG_FSCACHE_HISTOGRAM
 	remove_proc_entry("fs/fscache/histogram", NULL);
 #endif