14 files changed, 578 insertions, 3 deletions

diff --git a/Documentation/filesystems/caching/fscache.txt b/Documentation/filesystems/caching/fscache.txt
index 9e94b9491d8..cac09e11ca3 100644
--- a/Documentation/filesystems/caching/fscache.txt
+++ b/Documentation/filesystems/caching/fscache.txt
@@ -299,6 +299,87 @@ proc files.
      jiffy range covered, and the SECS field the equivalent number of seconds.
 
 
+===========
+OBJECT LIST
+===========
+
+If CONFIG_FSCACHE_OBJECT_LIST is enabled, the FS-Cache facility will maintain a
+list of all the objects currently allocated and allow them to be viewed
+through:
+
+        /proc/fs/fscache/objects
+
+This will look something like:
+
+        [root@andromeda ~]# head /proc/fs/fscache/objects
+        OBJECT   PARENT   STAT CHLDN OPS OOP IPR EX READS EM EV F S | NETFS_COOKIE_DEF TY FL NETFS_DATA       OBJECT_KEY, AUX_DATA
+        ======== ======== ==== ===== === === === == ===== == == = = | ================ == == ================ ================
+           17e4b        2 ACTV     0   0   0   0  0     0 7b  4 0 8 | NFS.fh           DT  0 ffff88001dd82820 010006017edcf8bbc93b43298fdfbe71e50b57b13a172c0117f38472, e567634700000000000000000000000063f2404a000000000000000000000000c9030000000000000000000063f2404a
+           1693a        2 ACTV     0   0   0   0  0     0 7b  4 0 8 | NFS.fh           DT  0 ffff88002db23380 010006017edcf8bbc93b43298fdfbe71e50b57b1e0162c01a2df0ea6, 420ebc4a000000000000000000000000420ebc4a0000000000000000000000000e1801000000000000000000420ebc4a
+
+where the first set of columns before the '|' describe the object:
+
+        COLUMN  DESCRIPTION
+        ======= ===============================================================
+        OBJECT  Object debugging ID (appears as OBJ%x in some debug messages)
+        PARENT  Debugging ID of parent object
+        STAT    Object state
+        CHLDN   Number of child objects of this object
+        OPS     Number of outstanding operations on this object
+        OOP     Number of outstanding child object management operations
+        IPR
+        EX      Number of outstanding exclusive operations
+        READS   Number of outstanding read operations
+        EM      Object's event mask
+        EV      Events raised on this object
+        F       Object flags
+        S       Object slow-work work item flags
+
+and the second set of columns describe the object's cookie, if present:
+
+        COLUMN          DESCRIPTION
+        =============== =======================================================
+        NETFS_COOKIE_DEF Name of netfs cookie definition
+        TY              Cookie type (IX - index, DT - data, hex - special)
+        FL              Cookie flags
+        NETFS_DATA      Netfs private data stored in the cookie
+        OBJECT_KEY      Object key      } 1 column, with separating comma
+        AUX_DATA        Object aux data } presence may be configured
+
+The data shown may be filtered by attaching the a key to an appropriate keyring
+before viewing the file.  Something like:
+
+                keyctl add user fscache:objlist <restrictions> @s
+
+where <restrictions> are a selection of the following letters:
+
+        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 the following paired letters:
+
+        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 letter 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.
+
+By default all objects and all fields will be shown.
+
+
 =========
 DEBUGGING
 =========
diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index 431accd475a..dd7f852746c 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -331,6 +331,7 @@ static void cachefiles_put_object(struct fscache_object *_object)
                 }
 
                 cache = object->fscache.cache;
+                fscache_object_destroy(&object->fscache);
                 kmem_cache_free(cachefiles_object_jar, object);
                 fscache_object_destroyed(cache);
         }
diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c
index a69787e7dd9..3304646dae8 100644
--- a/fs/cachefiles/rdwr.c
+++ b/fs/cachefiles/rdwr.c
@@ -333,7 +333,8 @@ int cachefiles_read_or_alloc_page(struct fscache_retrieval *op,
 
         shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits;
 
-        op->op.flags = FSCACHE_OP_FAST;
+        op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
+        op->op.flags |= FSCACHE_OP_FAST;
         op->op.processor = cachefiles_read_copier;
 
         pagevec_init(&pagevec, 0);
@@ -639,7 +640,8 @@ int cachefiles_read_or_alloc_pages(struct fscache_retrieval *op,
 
         pagevec_init(&pagevec, 0);
 
-        op->op.flags = FSCACHE_OP_FAST;
+        op->op.flags &= FSCACHE_OP_KEEP_FLAGS;
+        op->op.flags |= FSCACHE_OP_FAST;
         op->op.processor = cachefiles_read_copier;
 
         INIT_LIST_HEAD(&backpages);
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
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index 7a9847ccd19..184cbdfbcc9 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -91,6 +91,8 @@ struct fscache_operation {
 #define FSCACHE_OP_WAITING      4       /* cleared when op is woken */
 #define FSCACHE_OP_EXCLUSIVE    5       /* exclusive op, other ops must wait */
 #define FSCACHE_OP_DEAD         6       /* op is now dead */
+#define FSCACHE_OP_DEC_READ_CNT 7       /* decrement object->n_reads on destruction */
+#define FSCACHE_OP_KEEP_FLAGS   0xc0    /* flags to keep when repurposing an op */
 
         atomic_t                usage;
         unsigned                debug_id;       /* debugging ID */
@@ -357,6 +359,7 @@ struct fscache_object {
         int                     n_obj_ops;      /* number of object ops outstanding on object */
         int                     n_in_progress;  /* number of ops in progress */
         int                     n_exclusive;    /* number of exclusive ops queued */
+        atomic_t                n_reads;        /* number of read ops in progress */
         spinlock_t              lock;           /* state and operations lock */
 
         unsigned long           lookup_jif;     /* time at which lookup started */
@@ -370,6 +373,7 @@ struct fscache_object {
 #define FSCACHE_OBJECT_EV_RELEASE       4       /* T if netfs requested object release */
 #define FSCACHE_OBJECT_EV_RETIRE        5       /* T if netfs requested object retirement */
 #define FSCACHE_OBJECT_EV_WITHDRAW      6       /* T if cache requested object withdrawal */
+#define FSCACHE_OBJECT_EVENTS_MASK      0x7f    /* mask of all events*/
 
         unsigned long           flags;
 #define FSCACHE_OBJECT_LOCK             0       /* T if object is busy being processed */
@@ -385,6 +389,9 @@ struct fscache_object {
         struct list_head        dependents;     /* FIFO of dependent objects */
         struct list_head        dep_link;       /* link in parent's dependents list */
         struct list_head        pending_ops;    /* unstarted operations on this object */
+#ifdef CONFIG_FSCACHE_OBJECT_LIST
+        struct rb_node          objlist_link;   /* link in global object list */
+#endif
         pgoff_t                 store_limit;    /* current storage limit */
 };
 
@@ -434,6 +441,12 @@ void fscache_object_init(struct fscache_object *object,
 extern void fscache_object_lookup_negative(struct fscache_object *object);
 extern void fscache_obtained_object(struct fscache_object *object);
 
+#ifdef CONFIG_FSCACHE_OBJECT_LIST
+extern void fscache_object_destroy(struct fscache_object *object);
+#else
+#define fscache_object_destroy(object) do {} while(0)
+#endif
+
 /**
  * fscache_object_destroyed - Note destruction of an object in a cache
  * @cache: The cache from which the object came