fs/mbcache.c: doucple the locking of local from global data (1f3e55fe) · Commits · e / devices / android_kernel_xiaomi_markw

fs/mbcache.c

+301 −116

Original line number	Diff line number	Diff line
		@@ -26,6 +26,41 @@
		* back on the lru list.
		*/

		/*
		* Lock descriptions and usage:
		*
		* Each hash chain of both the block and index hash tables now contains
		* a built-in lock used to serialize accesses to the hash chain.
		*
		* Accesses to global data structures mb_cache_list and mb_cache_lru_list
		* are serialized via the global spinlock mb_cache_spinlock.
		*
		* Each mb_cache_entry contains a spinlock, e_entry_lock, to serialize
		* accesses to its local data, such as e_used and e_queued.
		*
		* Lock ordering:
		*
		* Each block hash chain's lock has the highest lock order, followed by an
		* index hash chain's lock, mb_cache_bg_lock (used to implement mb_cache_entry's
		* lock), and mb_cach_spinlock, with the lowest order. While holding
		* either a block or index hash chain lock, a thread can acquire an
		* mc_cache_bg_lock, which in turn can also acquire mb_cache_spinlock.
		*
		* Synchronization:
		*
		* Since both mb_cache_entry_get and mb_cache_entry_find scan the block and
		* index hash chian, it needs to lock the corresponding hash chain. For each
		* mb_cache_entry within the chain, it needs to lock the mb_cache_entry to
		* prevent either any simultaneous release or free on the entry and also
		* to serialize accesses to either the e_used or e_queued member of the entry.
		*
		* To avoid having a dangling reference to an already freed
		* mb_cache_entry, an mb_cache_entry is only freed when it is not on a
		* block hash chain and also no longer being referenced, both e_used,
		* and e_queued are 0's. When an mb_cache_entry is explicitly freed it is
		* first removed from a block hash chain.
		*/

		#include <linux/kernel.h>
		#include <linux/module.h>

		@@ -37,6 +72,7 @@
		#include <linux/list_bl.h>
		#include <linux/mbcache.h>
		#include <linux/init.h>
		#include <linux/blockgroup_lock.h>

		#ifdef MB_CACHE_DEBUG
		# define mb_debug(f...) do { \
		@@ -57,7 +93,12 @@

		#define MB_CACHE_WRITER ((unsigned short)~0U >> 1)

		#define MB_CACHE_ENTRY_LOCK_BITS __builtin_log2(NR_BG_LOCKS)
		#define MB_CACHE_ENTRY_LOCK_INDEX(ce) \
		(hash_long((unsigned long)ce, MB_CACHE_ENTRY_LOCK_BITS))

		static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue);
		static struct blockgroup_lock *mb_cache_bg_lock;

		MODULE_AUTHOR("Andreas Gruenbacher <a.gruenbacher@computer.org>");
		MODULE_DESCRIPTION("Meta block cache (for extended attributes)");
		@@ -86,6 +127,20 @@ static LIST_HEAD(mb_cache_list);
		static LIST_HEAD(mb_cache_lru_list);
		static DEFINE_SPINLOCK(mb_cache_spinlock);

		static inline void
		__spin_lock_mb_cache_entry(struct mb_cache_entry *ce)
		{
		spin_lock(bgl_lock_ptr(mb_cache_bg_lock,
		MB_CACHE_ENTRY_LOCK_INDEX(ce)));
		}

		static inline void
		__spin_unlock_mb_cache_entry(struct mb_cache_entry *ce)
		{
		spin_unlock(bgl_lock_ptr(mb_cache_bg_lock,
		MB_CACHE_ENTRY_LOCK_INDEX(ce)));
		}

		static inline int
		__mb_cache_entry_is_block_hashed(struct mb_cache_entry *ce)
		{
		@@ -113,11 +168,21 @@ __mb_cache_entry_unhash_index(struct mb_cache_entry *ce)
		hlist_bl_del_init(&ce->e_index.o_list);
		}

		/*
		* __mb_cache_entry_unhash_unlock()
		*
		* This function is called to unhash both the block and index hash
		* chain.
		* It assumes both the block and index hash chain is locked upon entry.
		* It also unlock both hash chains both exit
		*/
		static inline void
		__mb_cache_entry_unhash(struct mb_cache_entry *ce)
		__mb_cache_entry_unhash_unlock(struct mb_cache_entry *ce)
		{
		__mb_cache_entry_unhash_index(ce);
		hlist_bl_unlock(ce->e_index_hash_p);
		__mb_cache_entry_unhash_block(ce);
		hlist_bl_unlock(ce->e_block_hash_p);
		}

		static void
		@@ -125,36 +190,47 @@ __mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask)
		{
		struct mb_cache *cache = ce->e_cache;

		mb_assert(!(ce->e_used \|\| ce->e_queued));
		mb_assert(!(ce->e_used \|\| ce->e_queued \|\| atomic_read(&ce->e_refcnt)));
		kmem_cache_free(cache->c_entry_cache, ce);
		atomic_dec(&cache->c_entry_count);
		}


		static void
		__mb_cache_entry_release_unlock(struct mb_cache_entry *ce)
		__releases(mb_cache_spinlock)
		__mb_cache_entry_release(struct mb_cache_entry *ce)
		{
		/* First lock the entry to serialize access to its local data. */
		__spin_lock_mb_cache_entry(ce);
		/* Wake up all processes queuing for this cache entry. */
		if (ce->e_queued)
		wake_up_all(&mb_cache_queue);
		if (ce->e_used >= MB_CACHE_WRITER)
		ce->e_used -= MB_CACHE_WRITER;
		/*
		* Make sure that all cache entries on lru_list have
		* both e_used and e_qued of 0s.
		*/
		ce->e_used--;
		if (!(ce->e_used \|\| ce->e_queued)) {
		if (!__mb_cache_entry_is_block_hashed(ce))
		if (!(ce->e_used \|\| ce->e_queued \|\| atomic_read(&ce->e_refcnt))) {
		if (!__mb_cache_entry_is_block_hashed(ce)) {
		__spin_unlock_mb_cache_entry(ce);
		goto forget;
		mb_assert(list_empty(&ce->e_lru_list));
		list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
		}
		/*
		* Need access to lru list, first drop entry lock,
		* then reacquire the lock in the proper order.
		*/
		spin_lock(&mb_cache_spinlock);
		if (list_empty(&ce->e_lru_list))
		list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
		spin_unlock(&mb_cache_spinlock);
		}
		__spin_unlock_mb_cache_entry(ce);
		return;
		forget:
		spin_unlock(&mb_cache_spinlock);
		mb_assert(list_empty(&ce->e_lru_list));
		__mb_cache_entry_forget(ce, GFP_KERNEL);
		}


		/*
		* mb_cache_shrink_scan() memory pressure callback
		*
		@@ -177,17 +253,34 @@ mb_cache_shrink_scan(struct shrinker shrink, struct shrink_control sc)

		mb_debug("trying to free %d entries", nr_to_scan);
		spin_lock(&mb_cache_spinlock);
		while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) {
		while ((nr_to_scan-- > 0) && !list_empty(&mb_cache_lru_list)) {
		struct mb_cache_entry *ce =
		list_entry(mb_cache_lru_list.next,
		struct mb_cache_entry, e_lru_list);
		list_move_tail(&ce->e_lru_list, &free_list);
		__mb_cache_entry_unhash(ce);
		freed++;
		list_del_init(&ce->e_lru_list);
		if (ce->e_used \|\| ce->e_queued \|\| atomic_read(&ce->e_refcnt))
		continue;
		spin_unlock(&mb_cache_spinlock);
		/* Prevent any find or get operation on the entry */
		hlist_bl_lock(ce->e_block_hash_p);
		hlist_bl_lock(ce->e_index_hash_p);
		/* Ignore if it is touched by a find/get */
		if (ce->e_used \|\| ce->e_queued \|\| atomic_read(&ce->e_refcnt) \|\|
		!list_empty(&ce->e_lru_list)) {
		hlist_bl_unlock(ce->e_index_hash_p);
		hlist_bl_unlock(ce->e_block_hash_p);
		spin_lock(&mb_cache_spinlock);
		continue;
		}
		__mb_cache_entry_unhash_unlock(ce);
		list_add_tail(&ce->e_lru_list, &free_list);
		spin_lock(&mb_cache_spinlock);
		}
		spin_unlock(&mb_cache_spinlock);

		list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) {
		__mb_cache_entry_forget(entry, gfp_mask);
		freed++;
		}
		return freed;
		}
		@@ -232,6 +325,14 @@ mb_cache_create(const char *name, int bucket_bits)
		int n, bucket_count = 1 << bucket_bits;
		struct mb_cache *cache = NULL;

		if (!mb_cache_bg_lock) {
		mb_cache_bg_lock = kmalloc(sizeof(struct blockgroup_lock),
		GFP_KERNEL);
		if (!mb_cache_bg_lock)
		return NULL;
		bgl_lock_init(mb_cache_bg_lock);
		}

		cache = kmalloc(sizeof(struct mb_cache), GFP_KERNEL);
		if (!cache)
		return NULL;
		@@ -290,21 +391,47 @@ void
		mb_cache_shrink(struct block_device *bdev)
		{
		LIST_HEAD(free_list);
		struct list_head l, ltmp;
		struct list_head *l;
		struct mb_cache_entry ce, tmp;

		l = &mb_cache_lru_list;
		spin_lock(&mb_cache_spinlock);
		list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
		struct mb_cache_entry *ce =
		list_entry(l, struct mb_cache_entry, e_lru_list);
		while (!list_is_last(l, &mb_cache_lru_list)) {
		l = l->next;
		ce = list_entry(l, struct mb_cache_entry, e_lru_list);
		if (ce->e_bdev == bdev) {
		list_move_tail(&ce->e_lru_list, &free_list);
		__mb_cache_entry_unhash(ce);
		list_del_init(&ce->e_lru_list);
		if (ce->e_used \|\| ce->e_queued \|\|
		atomic_read(&ce->e_refcnt))
		continue;
		spin_unlock(&mb_cache_spinlock);
		/*
		* Prevent any find or get operation on the entry.
		*/
		hlist_bl_lock(ce->e_block_hash_p);
		hlist_bl_lock(ce->e_index_hash_p);
		/* Ignore if it is touched by a find/get */
		if (ce->e_used \|\| ce->e_queued \|\|
		atomic_read(&ce->e_refcnt) \|\|
		!list_empty(&ce->e_lru_list)) {
		hlist_bl_unlock(ce->e_index_hash_p);
		hlist_bl_unlock(ce->e_block_hash_p);
		l = &mb_cache_lru_list;
		spin_lock(&mb_cache_spinlock);
		continue;
		}
		__mb_cache_entry_unhash_unlock(ce);
		mb_assert(!(ce->e_used \|\| ce->e_queued \|\|
		atomic_read(&ce->e_refcnt)));
		list_add_tail(&ce->e_lru_list, &free_list);
		l = &mb_cache_lru_list;
		spin_lock(&mb_cache_spinlock);
		}
		}
		spin_unlock(&mb_cache_spinlock);
		list_for_each_safe(l, ltmp, &free_list) {
		__mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
		e_lru_list), GFP_KERNEL);

		list_for_each_entry_safe(ce, tmp, &free_list, e_lru_list) {
		__mb_cache_entry_forget(ce, GFP_KERNEL);
		}
		}

		@@ -320,23 +447,27 @@ void
		mb_cache_destroy(struct mb_cache *cache)
		{
		LIST_HEAD(free_list);
		struct list_head l, ltmp;
		struct mb_cache_entry ce, tmp;

		spin_lock(&mb_cache_spinlock);
		list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
		struct mb_cache_entry *ce =
		list_entry(l, struct mb_cache_entry, e_lru_list);
		if (ce->e_cache == cache) {
		list_for_each_entry_safe(ce, tmp, &mb_cache_lru_list, e_lru_list) {
		if (ce->e_cache == cache)
		list_move_tail(&ce->e_lru_list, &free_list);
		__mb_cache_entry_unhash(ce);
		}
		}
		list_del(&cache->c_cache_list);
		spin_unlock(&mb_cache_spinlock);

		list_for_each_safe(l, ltmp, &free_list) {
		__mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
		e_lru_list), GFP_KERNEL);
		list_for_each_entry_safe(ce, tmp, &free_list, e_lru_list) {
		list_del_init(&ce->e_lru_list);
		/*
		* Prevent any find or get operation on the entry.
		*/
		hlist_bl_lock(ce->e_block_hash_p);
		hlist_bl_lock(ce->e_index_hash_p);
		mb_assert(!(ce->e_used \|\| ce->e_queued \|\|
		atomic_read(&ce->e_refcnt)));
		__mb_cache_entry_unhash_unlock(ce);
		__mb_cache_entry_forget(ce, GFP_KERNEL);
		}

		if (atomic_read(&cache->c_entry_count) > 0) {
		@@ -345,8 +476,6 @@ mb_cache_destroy(struct mb_cache *cache)
		atomic_read(&cache->c_entry_count));
		}

		kmem_cache_destroy(cache->c_entry_cache);

		kfree(cache->c_index_hash);
		kfree(cache->c_block_hash);
		kfree(cache);
		@@ -363,19 +492,48 @@ mb_cache_destroy(struct mb_cache *cache)
		struct mb_cache_entry *
		mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
		{
		struct mb_cache_entry *ce = NULL;
		struct mb_cache_entry *ce;

		if (atomic_read(&cache->c_entry_count) >= cache->c_max_entries) {
		struct list_head *l;

		l = &mb_cache_lru_list;
		spin_lock(&mb_cache_spinlock);
		if (!list_empty(&mb_cache_lru_list)) {
		ce = list_entry(mb_cache_lru_list.next,
		struct mb_cache_entry, e_lru_list);
		while (!list_is_last(l, &mb_cache_lru_list)) {
		l = l->next;
		ce = list_entry(l, struct mb_cache_entry, e_lru_list);
		if (ce->e_cache == cache) {
		list_del_init(&ce->e_lru_list);
		__mb_cache_entry_unhash(ce);
		if (ce->e_used \|\| ce->e_queued \|\|
		atomic_read(&ce->e_refcnt))
		continue;
		spin_unlock(&mb_cache_spinlock);
		/*
		* Prevent any find or get operation on the
		* entry.
		*/
		hlist_bl_lock(ce->e_block_hash_p);
		hlist_bl_lock(ce->e_index_hash_p);
		/* Ignore if it is touched by a find/get */
		if (ce->e_used \|\| ce->e_queued \|\|
		atomic_read(&ce->e_refcnt) \|\|
		!list_empty(&ce->e_lru_list)) {
		hlist_bl_unlock(ce->e_index_hash_p);
		hlist_bl_unlock(ce->e_block_hash_p);
		l = &mb_cache_lru_list;
		spin_lock(&mb_cache_spinlock);
		continue;
		}
		mb_assert(list_empty(&ce->e_lru_list));
		mb_assert(!(ce->e_used \|\| ce->e_queued \|\|
		atomic_read(&ce->e_refcnt)));
		__mb_cache_entry_unhash_unlock(ce);
		goto found;
		}
		}
		spin_unlock(&mb_cache_spinlock);
		}
		if (!ce) {

		ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);
		if (!ce)
		return NULL;
		@@ -385,7 +543,8 @@ mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
		INIT_HLIST_BL_NODE(&ce->e_index.o_list);
		ce->e_cache = cache;
		ce->e_queued = 0;
		}
		atomic_set(&ce->e_refcnt, 0);
		found:
		ce->e_block_hash_p = &cache->c_block_hash[0];
		ce->e_index_hash_p = &cache->c_index_hash[0];
		ce->e_used = 1 + MB_CACHE_WRITER;
		@@ -414,7 +573,6 @@ mb_cache_entry_insert(struct mb_cache_entry ce, struct block_device bdev,
		struct mb_cache *cache = ce->e_cache;
		unsigned int bucket;
		struct hlist_bl_node *l;
		int error = -EBUSY;
		struct hlist_bl_head *block_hash_p;
		struct hlist_bl_head *index_hash_p;
		struct mb_cache_entry *lce;
		@@ -423,26 +581,29 @@ mb_cache_entry_insert(struct mb_cache_entry ce, struct block_device bdev,
		bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
		cache->c_bucket_bits);
		block_hash_p = &cache->c_block_hash[bucket];
		spin_lock(&mb_cache_spinlock);
		hlist_bl_lock(block_hash_p);
		hlist_bl_for_each_entry(lce, l, block_hash_p, e_block_list) {
		if (lce->e_bdev == bdev && lce->e_block == block)
		goto out;
		if (lce->e_bdev == bdev && lce->e_block == block) {
		hlist_bl_unlock(block_hash_p);
		return -EBUSY;
		}
		}
		mb_assert(!__mb_cache_entry_is_block_hashed(ce));
		__mb_cache_entry_unhash(ce);
		__mb_cache_entry_unhash_block(ce);
		__mb_cache_entry_unhash_index(ce);
		ce->e_bdev = bdev;
		ce->e_block = block;
		ce->e_block_hash_p = block_hash_p;
		ce->e_index.o_key = key;
		hlist_bl_add_head(&ce->e_block_list, block_hash_p);
		hlist_bl_unlock(block_hash_p);
		bucket = hash_long(key, cache->c_bucket_bits);
		index_hash_p = &cache->c_index_hash[bucket];
		hlist_bl_lock(index_hash_p);
		ce->e_index_hash_p = index_hash_p;
		hlist_bl_add_head(&ce->e_index.o_list, index_hash_p);
		hlist_bl_add_head(&ce->e_block_list, block_hash_p);
		error = 0;
		out:
		spin_unlock(&mb_cache_spinlock);
		return error;
		hlist_bl_unlock(index_hash_p);
		return 0;
		}


		@@ -456,24 +617,26 @@ out:
		void
		mb_cache_entry_release(struct mb_cache_entry *ce)
		{
		spin_lock(&mb_cache_spinlock);
		__mb_cache_entry_release_unlock(ce);
		__mb_cache_entry_release(ce);
		}


		/*
		* mb_cache_entry_free()
		*
		* This is equivalent to the sequence mb_cache_entry_takeout() --
		* mb_cache_entry_release().
		*/
		void
		mb_cache_entry_free(struct mb_cache_entry *ce)
		{
		spin_lock(&mb_cache_spinlock);
		mb_assert(ce);
		mb_assert(list_empty(&ce->e_lru_list));
		__mb_cache_entry_unhash(ce);
		__mb_cache_entry_release_unlock(ce);
		hlist_bl_lock(ce->e_index_hash_p);
		__mb_cache_entry_unhash_index(ce);
		hlist_bl_unlock(ce->e_index_hash_p);
		hlist_bl_lock(ce->e_block_hash_p);
		__mb_cache_entry_unhash_block(ce);
		hlist_bl_unlock(ce->e_block_hash_p);
		__mb_cache_entry_release(ce);
		}


		@@ -497,39 +660,48 @@ mb_cache_entry_get(struct mb_cache cache, struct block_device bdev,
		bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
		cache->c_bucket_bits);
		block_hash_p = &cache->c_block_hash[bucket];
		spin_lock(&mb_cache_spinlock);
		/* First serialize access to the block corresponding hash chain. */
		hlist_bl_lock(block_hash_p);
		hlist_bl_for_each_entry(ce, l, block_hash_p, e_block_list) {
		mb_assert(ce->e_block_hash_p == block_hash_p);
		if (ce->e_bdev == bdev && ce->e_block == block) {
		/*
		* Prevent a free from removing the entry.
		*/
		atomic_inc(&ce->e_refcnt);
		hlist_bl_unlock(block_hash_p);
		__spin_lock_mb_cache_entry(ce);
		atomic_dec(&ce->e_refcnt);
		if (ce->e_used > 0) {
		DEFINE_WAIT(wait);

		if (!list_empty(&ce->e_lru_list))
		list_del_init(&ce->e_lru_list);

		while (ce->e_used > 0) {
		ce->e_queued++;
		prepare_to_wait(&mb_cache_queue, &wait,
		TASK_UNINTERRUPTIBLE);
		spin_unlock(&mb_cache_spinlock);
		__spin_unlock_mb_cache_entry(ce);
		schedule();
		spin_lock(&mb_cache_spinlock);
		__spin_lock_mb_cache_entry(ce);
		ce->e_queued--;
		}
		finish_wait(&mb_cache_queue, &wait);
		}
		ce->e_used += 1 + MB_CACHE_WRITER;
		__spin_unlock_mb_cache_entry(ce);

		if (!list_empty(&ce->e_lru_list)) {
		spin_lock(&mb_cache_spinlock);
		list_del_init(&ce->e_lru_list);
		spin_unlock(&mb_cache_spinlock);
		}
		if (!__mb_cache_entry_is_block_hashed(ce)) {
		__mb_cache_entry_release_unlock(ce);
		__mb_cache_entry_release(ce);
		return NULL;
		}
		goto cleanup;
		return ce;
		}
		}
		ce = NULL;

		cleanup:
		spin_unlock(&mb_cache_spinlock);
		return ce;
		hlist_bl_unlock(block_hash_p);
		return NULL;
		}

		#if !defined(MB_CACHE_INDEXES_COUNT) \|\| (MB_CACHE_INDEXES_COUNT > 0)
		@@ -538,40 +710,53 @@ static struct mb_cache_entry *
		__mb_cache_entry_find(struct hlist_bl_node l, struct hlist_bl_head head,
		struct block_device *bdev, unsigned int key)
		{

		/* The index hash chain is alredy acquire by caller. */
		while (l != NULL) {
		struct mb_cache_entry *ce =
		hlist_bl_entry(l, struct mb_cache_entry,
		e_index.o_list);
		mb_assert(ce->e_index_hash_p == head);
		if (ce->e_bdev == bdev && ce->e_index.o_key == key) {
		DEFINE_WAIT(wait);

		if (!list_empty(&ce->e_lru_list))
		list_del_init(&ce->e_lru_list);

		/*
		* Prevent a free from removing the entry.
		*/
		atomic_inc(&ce->e_refcnt);
		hlist_bl_unlock(head);
		__spin_lock_mb_cache_entry(ce);
		atomic_dec(&ce->e_refcnt);
		ce->e_used++;
		/* Incrementing before holding the lock gives readers
		priority over writers. */
		ce->e_used++;
		if (ce->e_used >= MB_CACHE_WRITER) {
		DEFINE_WAIT(wait);

		while (ce->e_used >= MB_CACHE_WRITER) {
		ce->e_queued++;
		prepare_to_wait(&mb_cache_queue, &wait,
		TASK_UNINTERRUPTIBLE);
		spin_unlock(&mb_cache_spinlock);
		__spin_unlock_mb_cache_entry(ce);
		schedule();
		spin_lock(&mb_cache_spinlock);
		__spin_lock_mb_cache_entry(ce);
		ce->e_queued--;
		}
		finish_wait(&mb_cache_queue, &wait);

		if (!__mb_cache_entry_is_block_hashed(ce)) {
		__mb_cache_entry_release_unlock(ce);
		}
		__spin_unlock_mb_cache_entry(ce);
		if (!list_empty(&ce->e_lru_list)) {
		spin_lock(&mb_cache_spinlock);
		list_del_init(&ce->e_lru_list);
		spin_unlock(&mb_cache_spinlock);
		}
		if (!__mb_cache_entry_is_block_hashed(ce)) {
		__mb_cache_entry_release(ce);
		return ERR_PTR(-EAGAIN);
		}
		return ce;
		}
		l = l->next;
		}
		hlist_bl_unlock(head);
		return NULL;
		}

		@@ -598,12 +783,12 @@ mb_cache_entry_find_first(struct mb_cache cache, struct block_device bdev,
		struct hlist_bl_head *index_hash_p;

		index_hash_p = &cache->c_index_hash[bucket];
		spin_lock(&mb_cache_spinlock);
		hlist_bl_lock(index_hash_p);
		if (!hlist_bl_empty(index_hash_p)) {
		l = hlist_bl_first(index_hash_p);
		ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
		}
		spin_unlock(&mb_cache_spinlock);
		} else
		hlist_bl_unlock(index_hash_p);
		return ce;
		}

		@@ -638,11 +823,11 @@ mb_cache_entry_find_next(struct mb_cache_entry *prev,

		index_hash_p = &cache->c_index_hash[bucket];
		mb_assert(prev->e_index_hash_p == index_hash_p);
		spin_lock(&mb_cache_spinlock);
		hlist_bl_lock(index_hash_p);
		mb_assert(!hlist_bl_empty(index_hash_p));
		l = prev->e_index.o_list.next;
		ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
		__mb_cache_entry_release_unlock(prev);
		__mb_cache_entry_release(prev);
		return ce;
		}