Merge tag 'vfs-6.8.netfs' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs

Pull netfs updates from Christian Brauner:
 "This extends the netfs helper library that network filesystems can use
  to replace their own implementations. Both afs and 9p are ported. cifs
  is ready as well but the patches are way bigger and will be routed
  separately once this is merged. That will remove lots of code as well.

  The overal goal is to get high-level I/O and knowledge of the page
  cache and ouf of the filesystem drivers. This includes knowledge about
  the existence of pages and folios

  The pull request converts afs and 9p. This removes about 800 lines of
  code from afs and 300 from 9p. For 9p it is now possible to do writes
  in larger than a page chunks. Additionally, multipage folio support
  can be turned on for 9p. Separate patches exist for cifs removing
  another 2000+ lines. I've included detailed information in the
  individual pulls I took.

  Summary:

   - Add NFS-style (and Ceph-style) locking around DIO vs buffered I/O
     calls to prevent these from happening at the same time.

   - Support for direct and unbuffered I/O.

   - Support for write-through caching in the page cache.

   - O_*SYNC and RWF_*SYNC writes use write-through rather than writing
     to the page cache and then flushing afterwards.

   - Support for write-streaming.

   - Support for write grouping.

   - Skip reads for which the server could only return zeros or EOF.

   - The fscache module is now part of the netfs library and the
     corresponding maintainer entry is updated.

   - Some helpers from the fscache subsystem are renamed to mark them as
     belonging to the netfs library.

   - Follow-up fixes for the netfs library.

   - Follow-up fixes for the 9p conversion"

* tag 'vfs-6.8.netfs' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs: (50 commits)
  netfs: Fix wrong #ifdef hiding wait
  cachefiles: Fix signed/unsigned mixup
  netfs: Fix the loop that unmarks folios after writing to the cache
  netfs: Fix interaction between write-streaming and cachefiles culling
  netfs: Count DIO writes
  netfs: Mark netfs_unbuffered_write_iter_locked() static
  netfs: Fix proc/fs/fscache symlink to point to "netfs" not "../netfs"
  netfs: Rearrange netfs_io_subrequest to put request pointer first
  9p: Use length of data written to the server in preference to error
  9p: Do a couple of cleanups
  9p: Fix initialisation of netfs_inode for 9p
  cachefiles: Fix __cachefiles_prepare_write()
  9p: Use netfslib read/write_iter
  afs: Use the netfs write helpers
  netfs: Export the netfs_sreq tracepoint
  netfs: Optimise away reads above the point at which there can be no data
  netfs: Implement a write-through caching option
  netfs: Provide a launder_folio implementation
  netfs: Provide a writepages implementation
  netfs, cachefiles: Pass upper bound length to allow expansion
  ...

1 files changed, 1180 insertions, 0 deletions

diff --git a/fs/netfs/fscache_cookie.c b/fs/netfs/fscache_cookie.c
new file mode 100644
index 000000000000..bce2492186d0
--- /dev/null
+++ b/fs/netfs/fscache_cookie.c
@@ -0,0 +1,1180 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* netfs cookie management
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * See Documentation/filesystems/caching/netfs-api.rst for more information on
+ * the netfs API.
+ */
+
+#define FSCACHE_DEBUG_LEVEL COOKIE
+#include <linux/module.h>
+#include <linux/slab.h>
+#include "internal.h"
+
+struct kmem_cache *fscache_cookie_jar;
+
+static void fscache_cookie_lru_timed_out(struct timer_list *timer);
+static void fscache_cookie_lru_worker(struct work_struct *work);
+static void fscache_cookie_worker(struct work_struct *work);
+static void fscache_unhash_cookie(struct fscache_cookie *cookie);
+static void fscache_perform_invalidation(struct fscache_cookie *cookie);
+
+#define fscache_cookie_hash_shift 15
+static struct hlist_bl_head fscache_cookie_hash[1 << fscache_cookie_hash_shift];
+static LIST_HEAD(fscache_cookies);
+static DEFINE_RWLOCK(fscache_cookies_lock);
+static LIST_HEAD(fscache_cookie_lru);
+static DEFINE_SPINLOCK(fscache_cookie_lru_lock);
+DEFINE_TIMER(fscache_cookie_lru_timer, fscache_cookie_lru_timed_out);
+static DECLARE_WORK(fscache_cookie_lru_work, fscache_cookie_lru_worker);
+static const char fscache_cookie_states[FSCACHE_COOKIE_STATE__NR] = "-LCAIFUWRD";
+static unsigned int fscache_lru_cookie_timeout = 10 * HZ;
+
+void fscache_print_cookie(struct fscache_cookie *cookie, char prefix)
+{
+	const u8 *k;
+
+	pr_err("%c-cookie c=%08x [fl=%lx na=%u nA=%u s=%c]\n",
+	       prefix,
+	       cookie->debug_id,
+	       cookie->flags,
+	       atomic_read(&cookie->n_active),
+	       atomic_read(&cookie->n_accesses),
+	       fscache_cookie_states[cookie->state]);
+	pr_err("%c-cookie V=%08x [%s]\n",
+	       prefix,
+	       cookie->volume->debug_id,
+	       cookie->volume->key);
+
+	k = (cookie->key_len <= sizeof(cookie->inline_key)) ?
+		cookie->inline_key : cookie->key;
+	pr_err("%c-key=[%u] '%*phN'\n", prefix, cookie->key_len, cookie->key_len, k);
+}
+
+static void fscache_free_cookie(struct fscache_cookie *cookie)
+{
+	if (WARN_ON_ONCE(!list_empty(&cookie->commit_link))) {
+		spin_lock(&fscache_cookie_lru_lock);
+		list_del_init(&cookie->commit_link);
+		spin_unlock(&fscache_cookie_lru_lock);
+		fscache_stat_d(&fscache_n_cookies_lru);
+		fscache_stat(&fscache_n_cookies_lru_removed);
+	}
+
+	if (WARN_ON_ONCE(test_bit(FSCACHE_COOKIE_IS_HASHED, &cookie->flags))) {
+		fscache_print_cookie(cookie, 'F');
+		return;
+	}
+
+	write_lock(&fscache_cookies_lock);
+	list_del(&cookie->proc_link);
+	write_unlock(&fscache_cookies_lock);
+	if (cookie->aux_len > sizeof(cookie->inline_aux))
+		kfree(cookie->aux);
+	if (cookie->key_len > sizeof(cookie->inline_key))
+		kfree(cookie->key);
+	fscache_stat_d(&fscache_n_cookies);
+	kmem_cache_free(fscache_cookie_jar, cookie);
+}
+
+static void __fscache_queue_cookie(struct fscache_cookie *cookie)
+{
+	if (!queue_work(fscache_wq, &cookie->work))
+		fscache_put_cookie(cookie, fscache_cookie_put_over_queued);
+}
+
+static void fscache_queue_cookie(struct fscache_cookie *cookie,
+				 enum fscache_cookie_trace where)
+{
+	fscache_get_cookie(cookie, where);
+	__fscache_queue_cookie(cookie);
+}
+
+/*
+ * Initialise the access gate on a cookie by setting a flag to prevent the
+ * state machine from being queued when the access counter transitions to 0.
+ * We're only interested in this when we withdraw caching services from the
+ * cookie.
+ */
+static void fscache_init_access_gate(struct fscache_cookie *cookie)
+{
+	int n_accesses;
+
+	n_accesses = atomic_read(&cookie->n_accesses);
+	trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
+			     n_accesses, fscache_access_cache_pin);
+	set_bit(FSCACHE_COOKIE_NO_ACCESS_WAKE, &cookie->flags);
+}
+
+/**
+ * fscache_end_cookie_access - Unpin a cache at the end of an access.
+ * @cookie: A data file cookie
+ * @why: An indication of the circumstances of the access for tracing
+ *
+ * Unpin a cache cookie after we've accessed it and bring a deferred
+ * relinquishment or withdrawal state into effect.
+ *
+ * The @why indicator is provided for tracing purposes.
+ */
+void fscache_end_cookie_access(struct fscache_cookie *cookie,
+			       enum fscache_access_trace why)
+{
+	int n_accesses;
+
+	smp_mb__before_atomic();
+	n_accesses = atomic_dec_return(&cookie->n_accesses);
+	trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
+			     n_accesses, why);
+	if (n_accesses == 0 &&
+	    !test_bit(FSCACHE_COOKIE_NO_ACCESS_WAKE, &cookie->flags))
+		fscache_queue_cookie(cookie, fscache_cookie_get_end_access);
+}
+EXPORT_SYMBOL(fscache_end_cookie_access);
+
+/*
+ * Pin the cache behind a cookie so that we can access it.
+ */
+static void __fscache_begin_cookie_access(struct fscache_cookie *cookie,
+					  enum fscache_access_trace why)
+{
+	int n_accesses;
+
+	n_accesses = atomic_inc_return(&cookie->n_accesses);
+	smp_mb__after_atomic(); /* (Future) read state after is-caching.
+				 * Reread n_accesses after is-caching
+				 */
+	trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
+			     n_accesses, why);
+}
+
+/**
+ * fscache_begin_cookie_access - Pin a cache so data can be accessed
+ * @cookie: A data file cookie
+ * @why: An indication of the circumstances of the access for tracing
+ *
+ * Attempt to pin the cache to prevent it from going away whilst we're
+ * accessing data and returns true if successful.  This works as follows:
+ *
+ *  (1) If the cookie is not being cached (ie. FSCACHE_COOKIE_IS_CACHING is not
+ *      set), we return false to indicate access was not permitted.
+ *
+ *  (2) If the cookie is being cached, we increment its n_accesses count and
+ *      then recheck the IS_CACHING flag, ending the access if it got cleared.
+ *
+ *  (3) When we end the access, we decrement the cookie's n_accesses and wake
+ *      up the any waiters if it reaches 0.
+ *
+ *  (4) Whilst the cookie is actively being cached, its n_accesses is kept
+ *      artificially incremented to prevent wakeups from happening.
+ *
+ *  (5) When the cache is taken offline or if the cookie is culled, the flag is
+ *      cleared to prevent new accesses, the cookie's n_accesses is decremented
+ *      and we wait for it to become 0.
+ *
+ * The @why indicator are merely provided for tracing purposes.
+ */
+bool fscache_begin_cookie_access(struct fscache_cookie *cookie,
+				 enum fscache_access_trace why)
+{
+	if (!test_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags))
+		return false;
+	__fscache_begin_cookie_access(cookie, why);
+	if (!test_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags) ||
+	    !fscache_cache_is_live(cookie->volume->cache)) {
+		fscache_end_cookie_access(cookie, fscache_access_unlive);
+		return false;
+	}
+	return true;
+}
+
+static inline void wake_up_cookie_state(struct fscache_cookie *cookie)
+{
+	/* Use a barrier to ensure that waiters see the state variable
+	 * change, as spin_unlock doesn't guarantee a barrier.
+	 *
+	 * See comments over wake_up_bit() and waitqueue_active().
+	 */
+	smp_mb();
+	wake_up_var(&cookie->state);
+}
+
+/*
+ * Change the state a cookie is at and wake up anyone waiting for that.  Impose
+ * an ordering between the stuff stored in the cookie and the state member.
+ * Paired with fscache_cookie_state().
+ */
+static void __fscache_set_cookie_state(struct fscache_cookie *cookie,
+				       enum fscache_cookie_state state)
+{
+	smp_store_release(&cookie->state, state);
+}
+
+static void fscache_set_cookie_state(struct fscache_cookie *cookie,
+				     enum fscache_cookie_state state)
+{
+	spin_lock(&cookie->lock);
+	__fscache_set_cookie_state(cookie, state);
+	spin_unlock(&cookie->lock);
+	wake_up_cookie_state(cookie);
+}
+
+/**
+ * fscache_cookie_lookup_negative - Note negative lookup
+ * @cookie: The cookie that was being looked up
+ *
+ * Note that some part of the metadata path in the cache doesn't exist and so
+ * we can release any waiting readers in the certain knowledge that there's
+ * nothing for them to actually read.
+ *
+ * This function uses no locking and must only be called from the state machine.
+ */
+void fscache_cookie_lookup_negative(struct fscache_cookie *cookie)
+{
+	set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
+	fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_CREATING);
+}
+EXPORT_SYMBOL(fscache_cookie_lookup_negative);
+
+/**
+ * fscache_resume_after_invalidation - Allow I/O to resume after invalidation
+ * @cookie: The cookie that was invalidated
+ *
+ * Tell fscache that invalidation is sufficiently complete that I/O can be
+ * allowed again.
+ */
+void fscache_resume_after_invalidation(struct fscache_cookie *cookie)
+{
+	fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_ACTIVE);
+}
+EXPORT_SYMBOL(fscache_resume_after_invalidation);
+
+/**
+ * fscache_caching_failed - Report that a failure stopped caching on a cookie
+ * @cookie: The cookie that was affected
+ *
+ * Tell fscache that caching on a cookie needs to be stopped due to some sort
+ * of failure.
+ *
+ * This function uses no locking and must only be called from the state machine.
+ */
+void fscache_caching_failed(struct fscache_cookie *cookie)
+{
+	clear_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags);
+	fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_FAILED);
+	trace_fscache_cookie(cookie->debug_id, refcount_read(&cookie->ref),
+				fscache_cookie_failed);
+}
+EXPORT_SYMBOL(fscache_caching_failed);
+
+/*
+ * Set the index key in a cookie.  The cookie struct has space for a 16-byte
+ * key plus length and hash, but if that's not big enough, it's instead a
+ * pointer to a buffer containing 3 bytes of hash, 1 byte of length and then
+ * the key data.
+ */
+static int fscache_set_key(struct fscache_cookie *cookie,
+			   const void *index_key, size_t index_key_len)
+{
+	void *buf;
+	size_t buf_size;
+
+	buf_size = round_up(index_key_len, sizeof(__le32));
+
+	if (index_key_len > sizeof(cookie->inline_key)) {
+		buf = kzalloc(buf_size, GFP_KERNEL);
+		if (!buf)
+			return -ENOMEM;
+		cookie->key = buf;
+	} else {
+		buf = cookie->inline_key;
+	}
+
+	memcpy(buf, index_key, index_key_len);
+	cookie->key_hash = fscache_hash(cookie->volume->key_hash,
+					buf, buf_size);
+	return 0;
+}
+
+static bool fscache_cookie_same(const struct fscache_cookie *a,
+				const struct fscache_cookie *b)
+{
+	const void *ka, *kb;
+
+	if (a->key_hash	!= b->key_hash ||
+	    a->volume	!= b->volume ||
+	    a->key_len	!= b->key_len)
+		return false;
+
+	if (a->key_len <= sizeof(a->inline_key)) {
+		ka = &a->inline_key;
+		kb = &b->inline_key;
+	} else {
+		ka = a->key;
+		kb = b->key;
+	}
+	return memcmp(ka, kb, a->key_len) == 0;
+}
+
+static atomic_t fscache_cookie_debug_id = ATOMIC_INIT(1);
+
+/*
+ * Allocate a cookie.
+ */
+static struct fscache_cookie *fscache_alloc_cookie(
+	struct fscache_volume *volume,
+	u8 advice,
+	const void *index_key, size_t index_key_len,
+	const void *aux_data, size_t aux_data_len,
+	loff_t object_size)
+{
+	struct fscache_cookie *cookie;
+
+	/* allocate and initialise a cookie */
+	cookie = kmem_cache_zalloc(fscache_cookie_jar, GFP_KERNEL);
+	if (!cookie)
+		return NULL;
+	fscache_stat(&fscache_n_cookies);
+
+	cookie->volume		= volume;
+	cookie->advice		= advice;
+	cookie->key_len		= index_key_len;
+	cookie->aux_len		= aux_data_len;
+	cookie->object_size	= object_size;
+	if (object_size == 0)
+		__set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
+
+	if (fscache_set_key(cookie, index_key, index_key_len) < 0)
+		goto nomem;
+
+	if (cookie->aux_len <= sizeof(cookie->inline_aux)) {
+		memcpy(cookie->inline_aux, aux_data, cookie->aux_len);
+	} else {
+		cookie->aux = kmemdup(aux_data, cookie->aux_len, GFP_KERNEL);
+		if (!cookie->aux)
+			goto nomem;
+	}
+
+	refcount_set(&cookie->ref, 1);
+	cookie->debug_id = atomic_inc_return(&fscache_cookie_debug_id);
+	spin_lock_init(&cookie->lock);
+	INIT_LIST_HEAD(&cookie->commit_link);
+	INIT_WORK(&cookie->work, fscache_cookie_worker);
+	__fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
+
+	write_lock(&fscache_cookies_lock);
+	list_add_tail(&cookie->proc_link, &fscache_cookies);
+	write_unlock(&fscache_cookies_lock);
+	fscache_see_cookie(cookie, fscache_cookie_new_acquire);
+	return cookie;
+
+nomem:
+	fscache_free_cookie(cookie);
+	return NULL;
+}
+
+static inline bool fscache_cookie_is_dropped(struct fscache_cookie *cookie)
+{
+	return READ_ONCE(cookie->state) == FSCACHE_COOKIE_STATE_DROPPED;
+}
+
+static void fscache_wait_on_collision(struct fscache_cookie *candidate,
+				      struct fscache_cookie *wait_for)
+{
+	enum fscache_cookie_state *statep = &wait_for->state;
+
+	wait_var_event_timeout(statep, fscache_cookie_is_dropped(wait_for),
+			       20 * HZ);
+	if (!fscache_cookie_is_dropped(wait_for)) {
+		pr_notice("Potential collision c=%08x old: c=%08x",
+			  candidate->debug_id, wait_for->debug_id);
+		wait_var_event(statep, fscache_cookie_is_dropped(wait_for));
+	}
+}
+
+/*
+ * Attempt to insert the new cookie into the hash.  If there's a collision, we
+ * wait for the old cookie to complete if it's being relinquished and an error
+ * otherwise.
+ */
+static bool fscache_hash_cookie(struct fscache_cookie *candidate)
+{
+	struct fscache_cookie *cursor, *wait_for = NULL;
+	struct hlist_bl_head *h;
+	struct hlist_bl_node *p;
+	unsigned int bucket;
+
+	bucket = candidate->key_hash & (ARRAY_SIZE(fscache_cookie_hash) - 1);
+	h = &fscache_cookie_hash[bucket];
+
+	hlist_bl_lock(h);
+	hlist_bl_for_each_entry(cursor, p, h, hash_link) {
+		if (fscache_cookie_same(candidate, cursor)) {
+			if (!test_bit(FSCACHE_COOKIE_RELINQUISHED, &cursor->flags))
+				goto collision;
+			wait_for = fscache_get_cookie(cursor,
+						      fscache_cookie_get_hash_collision);
+			break;
+		}
+	}
+
+	fscache_get_volume(candidate->volume, fscache_volume_get_cookie);
+	atomic_inc(&candidate->volume->n_cookies);
+	hlist_bl_add_head(&candidate->hash_link, h);
+	set_bit(FSCACHE_COOKIE_IS_HASHED, &candidate->flags);
+	hlist_bl_unlock(h);
+
+	if (wait_for) {
+		fscache_wait_on_collision(candidate, wait_for);
+		fscache_put_cookie(wait_for, fscache_cookie_put_hash_collision);
+	}
+	return true;
+
+collision:
+	trace_fscache_cookie(cursor->debug_id, refcount_read(&cursor->ref),
+			     fscache_cookie_collision);
+	pr_err("Duplicate cookie detected\n");
+	fscache_print_cookie(cursor, 'O');
+	fscache_print_cookie(candidate, 'N');
+	hlist_bl_unlock(h);
+	return false;
+}
+
+/*
+ * Request a cookie to represent a data storage object within a volume.
+ *
+ * We never let on to the netfs about errors.  We may set a negative cookie
+ * pointer, but that's okay
+ */
+struct fscache_cookie *__fscache_acquire_cookie(
+	struct fscache_volume *volume,
+	u8 advice,
+	const void *index_key, size_t index_key_len,
+	const void *aux_data, size_t aux_data_len,
+	loff_t object_size)
+{
+	struct fscache_cookie *cookie;
+
+	_enter("V=%x", volume->debug_id);
+
+	if (!index_key || !index_key_len || index_key_len > 255 || aux_data_len > 255)
+		return NULL;
+	if (!aux_data || !aux_data_len) {
+		aux_data = NULL;
+		aux_data_len = 0;
+	}
+
+	fscache_stat(&fscache_n_acquires);
+
+	cookie = fscache_alloc_cookie(volume, advice,
+				      index_key, index_key_len,
+				      aux_data, aux_data_len,
+				      object_size);
+	if (!cookie) {
+		fscache_stat(&fscache_n_acquires_oom);
+		return NULL;
+	}
+
+	if (!fscache_hash_cookie(cookie)) {
+		fscache_see_cookie(cookie, fscache_cookie_discard);
+		fscache_free_cookie(cookie);
+		return NULL;
+	}
+
+	trace_fscache_acquire(cookie);
+	fscache_stat(&fscache_n_acquires_ok);
+	_leave(" = c=%08x", cookie->debug_id);
+	return cookie;
+}
+EXPORT_SYMBOL(__fscache_acquire_cookie);
+
+/*
+ * Prepare a cache object to be written to.
+ */
+static void fscache_prepare_to_write(struct fscache_cookie *cookie)
+{
+	cookie->volume->cache->ops->prepare_to_write(cookie);
+}
+
+/*
+ * Look up a cookie in the cache.
+ */
+static void fscache_perform_lookup(struct fscache_cookie *cookie)
+{
+	enum fscache_access_trace trace = fscache_access_lookup_cookie_end_failed;
+	bool need_withdraw = false;
+
+	_enter("");
+
+	if (!cookie->volume->cache_priv) {
+		fscache_create_volume(cookie->volume, true);
+		if (!cookie->volume->cache_priv) {
+			fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
+			goto out;
+		}
+	}
+
+	if (!cookie->volume->cache->ops->lookup_cookie(cookie)) {
+		if (cookie->state != FSCACHE_COOKIE_STATE_FAILED)
+			fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
+		need_withdraw = true;
+		_leave(" [fail]");
+		goto out;
+	}
+
+	fscache_see_cookie(cookie, fscache_cookie_see_active);
+	spin_lock(&cookie->lock);
+	if (test_and_clear_bit(FSCACHE_COOKIE_DO_INVALIDATE, &cookie->flags))
+		__fscache_set_cookie_state(cookie,
+					   FSCACHE_COOKIE_STATE_INVALIDATING);
+	else
+		__fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_ACTIVE);
+	spin_unlock(&cookie->lock);
+	wake_up_cookie_state(cookie);
+	trace = fscache_access_lookup_cookie_end;
+
+out:
+	fscache_end_cookie_access(cookie, trace);
+	if (need_withdraw)
+		fscache_withdraw_cookie(cookie);
+	fscache_end_volume_access(cookie->volume, cookie, trace);
+}
+
+/*
+ * Begin the process of looking up a cookie.  We offload the actual process to
+ * a worker thread.
+ */
+static bool fscache_begin_lookup(struct fscache_cookie *cookie, bool will_modify)
+{
+	if (will_modify) {
+		set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags);
+		set_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags);
+	}
+	if (!fscache_begin_volume_access(cookie->volume, cookie,
+					 fscache_access_lookup_cookie))
+		return false;
+
+	__fscache_begin_cookie_access(cookie, fscache_access_lookup_cookie);
+	__fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_LOOKING_UP);
+	set_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags);
+	set_bit(FSCACHE_COOKIE_HAS_BEEN_CACHED, &cookie->flags);
+	return true;
+}
+
+/*
+ * Start using the cookie for I/O.  This prevents the backing object from being
+ * reaped by VM pressure.
+ */
+void __fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify)
+{
+	enum fscache_cookie_state state;
+	bool queue = false;
+	int n_active;
+
+	_enter("c=%08x", cookie->debug_id);
+
+	if (WARN(test_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags),
+		 "Trying to use relinquished cookie\n"))
+		return;
+
+	spin_lock(&cookie->lock);
+
+	n_active = atomic_inc_return(&cookie->n_active);
+	trace_fscache_active(cookie->debug_id, refcount_read(&cookie->ref),
+			     n_active, atomic_read(&cookie->n_accesses),
+			     will_modify ?
+			     fscache_active_use_modify : fscache_active_use);
+
+again:
+	state = fscache_cookie_state(cookie);
+	switch (state) {
+	case FSCACHE_COOKIE_STATE_QUIESCENT:
+		queue = fscache_begin_lookup(cookie, will_modify);
+		break;
+
+	case FSCACHE_COOKIE_STATE_LOOKING_UP:
+	case FSCACHE_COOKIE_STATE_CREATING:
+		if (will_modify)
+			set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags);
+		break;
+	case FSCACHE_COOKIE_STATE_ACTIVE:
+	case FSCACHE_COOKIE_STATE_INVALIDATING:
+		if (will_modify &&
+		    !test_and_set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags)) {
+			set_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags);
+			queue = true;
+		}
+		/*
+		 * We could race with cookie_lru which may set LRU_DISCARD bit
+		 * but has yet to run the cookie state machine.  If this happens
+		 * and another thread tries to use the cookie, clear LRU_DISCARD
+		 * so we don't end up withdrawing the cookie while in use.
+		 */
+		if (test_and_clear_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags))
+			fscache_see_cookie(cookie, fscache_cookie_see_lru_discard_clear);
+		break;
+
+	case FSCACHE_COOKIE_STATE_FAILED:
+	case FSCACHE_COOKIE_STATE_WITHDRAWING:
+		break;
+
+	case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
+		spin_unlock(&cookie->lock);
+		wait_var_event(&cookie->state,
+			       fscache_cookie_state(cookie) !=
+			       FSCACHE_COOKIE_STATE_LRU_DISCARDING);
+		spin_lock(&cookie->lock);
+		goto again;
+
+	case FSCACHE_COOKIE_STATE_DROPPED:
+	case FSCACHE_COOKIE_STATE_RELINQUISHING:
+		WARN(1, "Can't use cookie in state %u\n", state);
+		break;
+	}
+
+	spin_unlock(&cookie->lock);
+	if (queue)
+		fscache_queue_cookie(cookie, fscache_cookie_get_use_work);
+	_leave("");
+}
+EXPORT_SYMBOL(__fscache_use_cookie);
+
+static void fscache_unuse_cookie_locked(struct fscache_cookie *cookie)
+{
+	clear_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags);
+	if (!test_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags))
+		return;
+
+	cookie->unused_at = jiffies;
+	spin_lock(&fscache_cookie_lru_lock);
+	if (list_empty(&cookie->commit_link)) {
+		fscache_get_cookie(cookie, fscache_cookie_get_lru);
+		fscache_stat(&fscache_n_cookies_lru);
+	}
+	list_move_tail(&cookie->commit_link, &fscache_cookie_lru);
+
+	spin_unlock(&fscache_cookie_lru_lock);
+	timer_reduce(&fscache_cookie_lru_timer,
+		     jiffies + fscache_lru_cookie_timeout);
+}
+
+/*
+ * Stop using the cookie for I/O.
+ */
+void __fscache_unuse_cookie(struct fscache_cookie *cookie,
+			    const void *aux_data, const loff_t *object_size)
+{
+	unsigned int debug_id = cookie->debug_id;
+	unsigned int r = refcount_read(&cookie->ref);
+	unsigned int a = atomic_read(&cookie->n_accesses);
+	unsigned int c;
+
+	if (aux_data || object_size)
+		__fscache_update_cookie(cookie, aux_data, object_size);
+
+	/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
+	c = atomic_fetch_add_unless(&cookie->n_active, -1, 1);
+	if (c != 1) {
+		trace_fscache_active(debug_id, r, c - 1, a, fscache_active_unuse);
+		return;
+	}
+
+	spin_lock(&cookie->lock);
+	r = refcount_read(&cookie->ref);
+	a = atomic_read(&cookie->n_accesses);
+	c = atomic_dec_return(&cookie->n_active);
+	trace_fscache_active(debug_id, r, c, a, fscache_active_unuse);
+	if (c == 0)
+		fscache_unuse_cookie_locked(cookie);
+	spin_unlock(&cookie->lock);
+}
+EXPORT_SYMBOL(__fscache_unuse_cookie);
+
+/*
+ * Perform work upon the cookie, such as committing its cache state,
+ * relinquishing it or withdrawing the backing cache.  We're protected from the
+ * cache going away under us as object withdrawal must come through this
+ * non-reentrant work item.
+ */
+static void fscache_cookie_state_machine(struct fscache_cookie *cookie)
+{
+	enum fscache_cookie_state state;
+	bool wake = false;
+
+	_enter("c=%x", cookie->debug_id);
+
+again:
+	spin_lock(&cookie->lock);
+again_locked:
+	state = cookie->state;
+	switch (state) {
+	case FSCACHE_COOKIE_STATE_QUIESCENT:
+		/* The QUIESCENT state is jumped to the LOOKING_UP state by
+		 * fscache_use_cookie().
+		 */
+
+		if (atomic_read(&cookie->n_accesses) == 0 &&
+		    test_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags)) {
+			__fscache_set_cookie_state(cookie,
+						   FSCACHE_COOKIE_STATE_RELINQUISHING);
+			wake = true;
+			goto again_locked;
+		}
+		break;
+
+	case FSCACHE_COOKIE_STATE_LOOKING_UP:
+		spin_unlock(&cookie->lock);
+		fscache_init_access_gate(cookie);
+		fscache_perform_lookup(cookie);
+		goto again;
+
+	case FSCACHE_COOKIE_STATE_INVALIDATING:
+		spin_unlock(&cookie->lock);
+		fscache_perform_invalidation(cookie);
+		goto again;
+
+	case FSCACHE_COOKIE_STATE_ACTIVE:
+		if (test_and_clear_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags)) {
+			spin_unlock(&cookie->lock);
+			fscache_prepare_to_write(cookie);
+			spin_lock(&cookie->lock);
+		}
+		if (test_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags)) {
+			__fscache_set_cookie_state(cookie,
+						   FSCACHE_COOKIE_STATE_LRU_DISCARDING);
+			wake = true;
+			goto again_locked;
+		}
+		fallthrough;
+
+	case FSCACHE_COOKIE_STATE_FAILED:
+		if (test_and_clear_bit(FSCACHE_COOKIE_DO_INVALIDATE, &cookie->flags))
+			fscache_end_cookie_access(cookie, fscache_access_invalidate_cookie_end);
+
+		if (atomic_read(&cookie->n_accesses) != 0)
+			break;
+		if (test_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags)) {
+			__fscache_set_cookie_state(cookie,
+						   FSCACHE_COOKIE_STATE_RELINQUISHING);
+			wake = true;
+			goto again_locked;
+		}
+		if (test_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags)) {
+			__fscache_set_cookie_state(cookie,
+						   FSCACHE_COOKIE_STATE_WITHDRAWING);
+			wake = true;
+			goto again_locked;
+		}
+		break;
+
+	case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
+	case FSCACHE_COOKIE_STATE_RELINQUISHING:
+	case FSCACHE_COOKIE_STATE_WITHDRAWING:
+		if (cookie->cache_priv) {
+			spin_unlock(&cookie->lock);
+			cookie->volume->cache->ops->withdraw_cookie(cookie);
+			spin_lock(&cookie->lock);
+		}
+
+		if (test_and_clear_bit(FSCACHE_COOKIE_DO_INVALIDATE, &cookie->flags))
+			fscache_end_cookie_access(cookie, fscache_access_invalidate_cookie_end);
+
+		switch (state) {
+		case FSCACHE_COOKIE_STATE_RELINQUISHING:
+			fscache_see_cookie(cookie, fscache_cookie_see_relinquish);
+			fscache_unhash_cookie(cookie);
+			__fscache_set_cookie_state(cookie,
+						   FSCACHE_COOKIE_STATE_DROPPED);
+			wake = true;
+			goto out;
+		case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
+			fscache_see_cookie(cookie, fscache_cookie_see_lru_discard);
+			break;
+		case FSCACHE_COOKIE_STATE_WITHDRAWING:
+			fscache_see_cookie(cookie, fscache_cookie_see_withdraw);
+			break;
+		default:
+			BUG();
+		}
+
+		clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);
+		clear_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags);
+		clear_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags);
+		clear_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags);
+		set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
+		__fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT);
+		wake = true;
+		goto again_locked;
+
+	case FSCACHE_COOKIE_STATE_DROPPED:
+		break;
+
+	default:
+		WARN_ONCE(1, "Cookie %x in unexpected state %u\n",
+			  cookie->debug_id, state);
+		break;
+	}
+
+out:
+	spin_unlock(&cookie->lock);
+	if (wake)
+		wake_up_cookie_state(cookie);
+	_leave("");
+}
+
+static void fscache_cookie_worker(struct work_struct *work)
+{
+	struct fscache_cookie *cookie = container_of(work, struct fscache_cookie, work);
+
+	fscache_see_cookie(cookie, fscache_cookie_see_work);
+	fscache_cookie_state_machine(cookie);
+	fscache_put_cookie(cookie, fscache_cookie_put_work);
+}
+
+/*
+ * Wait for the object to become inactive.  The cookie's work item will be
+ * scheduled when someone transitions n_accesses to 0 - but if someone's
+ * already done that, schedule it anyway.
+ */
+static void __fscache_withdraw_cookie(struct fscache_cookie *cookie)
+{
+	int n_accesses;
+	bool unpinned;
+
+	unpinned = test_and_clear_bit(FSCACHE_COOKIE_NO_ACCESS_WAKE, &cookie->flags);
+
+	/* Need to read the access count after unpinning */
+	n_accesses = atomic_read(&cookie->n_accesses);
+	if (unpinned)
+		trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
+				     n_accesses, fscache_access_cache_unpin);
+	if (n_accesses == 0)
+		fscache_queue_cookie(cookie, fscache_cookie_get_end_access);
+}
+
+static void fscache_cookie_lru_do_one(struct fscache_cookie *cookie)
+{
+	fscache_see_cookie(cookie, fscache_cookie_see_lru_do_one);
+
+	spin_lock(&cookie->lock);
+	if (cookie->state != FSCACHE_COOKIE_STATE_ACTIVE ||
+	    time_before(jiffies, cookie->unused_at + fscache_lru_cookie_timeout) ||
+	    atomic_read(&cookie->n_active) > 0) {
+		spin_unlock(&cookie->lock);
+		fscache_stat(&fscache_n_cookies_lru_removed);
+	} else {
+		set_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags);
+		spin_unlock(&cookie->lock);
+		fscache_stat(&fscache_n_cookies_lru_expired);
+		_debug("lru c=%x", cookie->debug_id);
+		__fscache_withdraw_cookie(cookie);
+	}
+
+	fscache_put_cookie(cookie, fscache_cookie_put_lru);
+}
+
+static void fscache_cookie_lru_worker(struct work_struct *work)
+{
+	struct fscache_cookie *cookie;
+	unsigned long unused_at;
+
+	spin_lock(&fscache_cookie_lru_lock);
+
+	while (!list_empty(&fscache_cookie_lru)) {
+		cookie = list_first_entry(&fscache_cookie_lru,
+					  struct fscache_cookie, commit_link);
+		unused_at = cookie->unused_at + fscache_lru_cookie_timeout;
+		if (time_before(jiffies, unused_at)) {
+			timer_reduce(&fscache_cookie_lru_timer, unused_at);
+			break;
+		}
+
+		list_del_init(&cookie->commit_link);
+		fscache_stat_d(&fscache_n_cookies_lru);
+		spin_unlock(&fscache_cookie_lru_lock);
+		fscache_cookie_lru_do_one(cookie);
+		spin_lock(&fscache_cookie_lru_lock);
+	}
+
+	spin_unlock(&fscache_cookie_lru_lock);
+}
+
+static void fscache_cookie_lru_timed_out(struct timer_list *timer)
+{
+	queue_work(fscache_wq, &fscache_cookie_lru_work);
+}
+
+static void fscache_cookie_drop_from_lru(struct fscache_cookie *cookie)
+{
+	bool need_put = false;
+
+	if (!list_empty(&cookie->commit_link)) {
+		spin_lock(&fscache_cookie_lru_lock);
+		if (!list_empty(&cookie->commit_link)) {
+			list_del_init(&cookie->commit_link);
+			fscache_stat_d(&fscache_n_cookies_lru);
+			fscache_stat(&fscache_n_cookies_lru_dropped);
+			need_put = true;
+		}
+		spin_unlock(&fscache_cookie_lru_lock);
+		if (need_put)
+			fscache_put_cookie(cookie, fscache_cookie_put_lru);
+	}
+}
+
+/*
+ * Remove a cookie from the hash table.
+ */
+static void fscache_unhash_cookie(struct fscache_cookie *cookie)
+{
+	struct hlist_bl_head *h;
+	unsigned int bucket;
+
+	bucket = cookie->key_hash & (ARRAY_SIZE(fscache_cookie_hash) - 1);
+	h = &fscache_cookie_hash[bucket];
+
+	hlist_bl_lock(h);
+	hlist_bl_del(&cookie->hash_link);
+	clear_bit(FSCACHE_COOKIE_IS_HASHED, &cookie->flags);
+	hlist_bl_unlock(h);
+	fscache_stat(&fscache_n_relinquishes_dropped);
+}
+
+static void fscache_drop_withdraw_cookie(struct fscache_cookie *cookie)
+{
+	fscache_cookie_drop_from_lru(cookie);
+	__fscache_withdraw_cookie(cookie);
+}
+
+/**
+ * fscache_withdraw_cookie - Mark a cookie for withdrawal
+ * @cookie: The cookie to be withdrawn.
+ *
+ * Allow the cache backend to withdraw the backing for a cookie for its own
+ * reasons, even if that cookie is in active use.
+ */
+void fscache_withdraw_cookie(struct fscache_cookie *cookie)
+{
+	set_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags);
+	fscache_drop_withdraw_cookie(cookie);
+}
+EXPORT_SYMBOL(fscache_withdraw_cookie);
+
+/*
+ * Allow the netfs to release a cookie back to the cache.
+ * - the object will be marked as recyclable on disk if retire is true
+ */
+void __fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
+{
+	fscache_stat(&fscache_n_relinquishes);
+	if (retire)
+		fscache_stat(&fscache_n_relinquishes_retire);
+
+	_enter("c=%08x{%d},%d",
+	       cookie->debug_id, atomic_read(&cookie->n_active), retire);
+
+	if (WARN(test_and_set_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags),
+		 "Cookie c=%x already relinquished\n", cookie->debug_id))
+		return;
+
+	if (retire)
+		set_bit(FSCACHE_COOKIE_RETIRED, &cookie->flags);
+	trace_fscache_relinquish(cookie, retire);
+
+	ASSERTCMP(atomic_read(&cookie->n_active), ==, 0);
+	ASSERTCMP(atomic_read(&cookie->volume->n_cookies), >, 0);
+	atomic_dec(&cookie->volume->n_cookies);
+
+	if (test_bit(FSCACHE_COOKIE_HAS_BEEN_CACHED, &cookie->flags)) {
+		set_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags);
+		fscache_drop_withdraw_cookie(cookie);
+	} else {
+		fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_DROPPED);
+		fscache_unhash_cookie(cookie);
+	}
+	fscache_put_cookie(cookie, fscache_cookie_put_relinquish);
+}
+EXPORT_SYMBOL(__fscache_relinquish_cookie);
+
+/*
+ * Drop a reference to a cookie.
+ */
+void fscache_put_cookie(struct fscache_cookie *cookie,
+			enum fscache_cookie_trace where)
+{
+	struct fscache_volume *volume = cookie->volume;
+	unsigned int cookie_debug_id = cookie->debug_id;
+	bool zero;
+	int ref;
+
+	zero = __refcount_dec_and_test(&cookie->ref, &ref);
+	trace_fscache_cookie(cookie_debug_id, ref - 1, where);
+	if (zero) {
+		fscache_free_cookie(cookie);
+		fscache_put_volume(volume, fscache_volume_put_cookie);
+	}
+}
+EXPORT_SYMBOL(fscache_put_cookie);
+
+/*
+ * Get a reference to a cookie.
+ */
+struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie,
+					  enum fscache_cookie_trace where)
+{
+	int ref;
+
+	__refcount_inc(&cookie->ref, &ref);
+	trace_fscache_cookie(cookie->debug_id, ref + 1, where);
+	return cookie;
+}
+EXPORT_SYMBOL(fscache_get_cookie);
+
+/*
+ * Ask the cache to effect invalidation of a cookie.
+ */
+static void fscache_perform_invalidation(struct fscache_cookie *cookie)
+{
+	if (!cookie->volume->cache->ops->invalidate_cookie(cookie))
+		fscache_caching_failed(cookie);
+	fscache_end_cookie_access(cookie, fscache_access_invalidate_cookie_end);
+}
+
+/*
+ * Invalidate an object.
+ */
+void __fscache_invalidate(struct fscache_cookie *cookie,
+			  const void *aux_data, loff_t new_size,
+			  unsigned int flags)
+{
+	bool is_caching;
+
+	_enter("c=%x", cookie->debug_id);
+
+	fscache_stat(&fscache_n_invalidates);
+
+	if (WARN(test_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags),
+		 "Trying to invalidate relinquished cookie\n"))
+		return;
+
+	if ((flags & FSCACHE_INVAL_DIO_WRITE) &&
+	    test_and_set_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags))
+		return;
+
+	spin_lock(&cookie->lock);
+	set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
+	fscache_update_aux(cookie, aux_data, &new_size);
+	cookie->inval_counter++;
+	trace_fscache_invalidate(cookie, new_size);
+
+	switch (cookie->state) {
+	case FSCACHE_COOKIE_STATE_INVALIDATING: /* is_still_valid will catch it */
+	default:
+		spin_unlock(&cookie->lock);
+		_leave(" [no %u]", cookie->state);
+		return;
+
+	case FSCACHE_COOKIE_STATE_LOOKING_UP:
+		if (!test_and_set_bit(FSCACHE_COOKIE_DO_INVALIDATE, &cookie->flags))
+			__fscache_begin_cookie_access(cookie, fscache_access_invalidate_cookie);
+		fallthrough;
+	case FSCACHE_COOKIE_STATE_CREATING:
+		spin_unlock(&cookie->lock);
+		_leave(" [look %x]", cookie->inval_counter);
+		return;
+
+	case FSCACHE_COOKIE_STATE_ACTIVE:
+		is_caching = fscache_begin_cookie_access(
+			cookie, fscache_access_invalidate_cookie);
+		if (is_caching)
+			__fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_INVALIDATING);
+		spin_unlock(&cookie->lock);
+		wake_up_cookie_state(cookie);
+
+		if (is_caching)
+			fscache_queue_cookie(cookie, fscache_cookie_get_inval_work);
+		_leave(" [inv]");
+		return;
+	}
+}
+EXPORT_SYMBOL(__fscache_invalidate);
+
+#ifdef CONFIG_PROC_FS
+/*
+ * Generate a list of extant cookies in /proc/fs/fscache/cookies
+ */
+static int fscache_cookies_seq_show(struct seq_file *m, void *v)
+{
+	struct fscache_cookie *cookie;
+	unsigned int keylen = 0, auxlen = 0;
+	u8 *p;
+
+	if (v == &fscache_cookies) {
+		seq_puts(m,
+			 "COOKIE   VOLUME   REF ACT ACC S FL DEF             \n"
+			 "======== ======== === === === = == ================\n"
+			 );
+		return 0;
+	}
+
+	cookie = list_entry(v, struct fscache_cookie, proc_link);
+
+	seq_printf(m,
+		   "%08x %08x %3d %3d %3d %c %02lx",
+		   cookie->debug_id,
+		   cookie->volume->debug_id,
+		   refcount_read(&cookie->ref),
+		   atomic_read(&cookie->n_active),
+		   atomic_read(&cookie->n_accesses),
+		   fscache_cookie_states[cookie->state],
+		   cookie->flags);
+
+	keylen = cookie->key_len;
+	auxlen = cookie->aux_len;
+
+	if (keylen > 0 || auxlen > 0) {
+		seq_puts(m, " ");
+		p = keylen <= sizeof(cookie->inline_key) ?
+			cookie->inline_key : cookie->key;
+		for (; keylen > 0; keylen--)
+			seq_printf(m, "%02x", *p++);
+		if (auxlen > 0) {
+			seq_puts(m, ", ");
+			p = auxlen <= sizeof(cookie->inline_aux) ?
+				cookie->inline_aux : cookie->aux;
+			for (; auxlen > 0; auxlen--)
+				seq_printf(m, "%02x", *p++);
+		}
+	}
+
+	seq_puts(m, "\n");
+	return 0;
+}
+
+static void *fscache_cookies_seq_start(struct seq_file *m, loff_t *_pos)
+	__acquires(fscache_cookies_lock)
+{
+	read_lock(&fscache_cookies_lock);
+	return seq_list_start_head(&fscache_cookies, *_pos);
+}
+
+static void *fscache_cookies_seq_next(struct seq_file *m, void *v, loff_t *_pos)
+{
+	return seq_list_next(v, &fscache_cookies, _pos);
+}
+
+static void fscache_cookies_seq_stop(struct seq_file *m, void *v)
+	__releases(rcu)
+{
+	read_unlock(&fscache_cookies_lock);
+}
+
+
+const struct seq_operations fscache_cookies_seq_ops = {
+	.start  = fscache_cookies_seq_start,
+	.next   = fscache_cookies_seq_next,
+	.stop   = fscache_cookies_seq_stop,
+	.show   = fscache_cookies_seq_show,
+};
+#endif