--- /dev/null
+diff --git a/fs/dcookies.c b/fs/dcookies.c
+index a21cabd..1e95c94 100644
+--- a/fs/dcookies.c
++++ b/fs/dcookies.c
+@@ -25,6 +25,7 @@
+ #include <linux/dcookies.h>
+ #include <linux/mutex.h>
+ #include <linux/path.h>
++#include <linux/spinlock.h>
+ #include <asm/uaccess.h>
+
+ /* The dcookies are allocated from a kmem_cache and
+@@ -38,15 +39,21 @@ struct dcookie_struct {
+
+ static LIST_HEAD(dcookie_users);
+ static DEFINE_MUTEX(dcookie_mutex);
++spinlock_t dcookie_hash_write_lock = SPIN_LOCK_UNLOCKED;
+ static struct kmem_cache *dcookie_cache __read_mostly;
+-static struct list_head *dcookie_hashtable __read_mostly;
++static struct list_head *dcookie_hashtable[3] __read_mostly;
+ static size_t hash_size __read_mostly;
++unsigned int current_hash = 1, old_hash = 0;
+
+ static inline int is_live(void)
+ {
+ return !(list_empty(&dcookie_users));
+ }
+
++static inline int is_shared(void)
++{
++ return !(list_empty(&dcookie_users)) && !(list_empty(dcookie_users.next));
++}
+
+ /* The dentry is locked, its address will do for the cookie */
+ static inline unsigned long dcookie_value(struct dcookie_struct * dcs)
+@@ -68,7 +75,7 @@ static struct dcookie_struct * find_dcookie(unsigned long dcookie)
+ struct list_head * pos;
+ struct list_head * list;
+
+- list = dcookie_hashtable + dcookie_hash(dcookie);
++ list = dcookie_hashtable[current_hash] + dcookie_hash(dcookie);
+
+ list_for_each(pos, list) {
+ dcs = list_entry(pos, struct dcookie_struct, hash_list);
+@@ -78,21 +85,33 @@ static struct dcookie_struct * find_dcookie(unsigned long dcookie)
+ }
+ }
+
++ if (!found) {
++ list = dcookie_hashtable[old_hash] + dcookie_hash(dcookie);
++
++ list_for_each(pos, list) {
++ dcs = list_entry(pos, struct dcookie_struct, hash_list);
++ if (dcookie_value(dcs) == dcookie) {
++ found = dcs;
++ break;
++ }
++ }
++ }
++
+ return found;
+ }
+
+
+ static void hash_dcookie(struct dcookie_struct * dcs)
+ {
+- struct list_head * list = dcookie_hashtable + dcookie_hash(dcookie_value(dcs));
++ struct list_head * list = dcookie_hashtable[current_hash] + dcookie_hash(dcookie_value(dcs));
+ list_add(&dcs->hash_list, list);
+ }
+
+
+ static struct dcookie_struct *alloc_dcookie(struct path *path)
+ {
+- struct dcookie_struct *dcs = kmem_cache_alloc(dcookie_cache,
+- GFP_KERNEL);
++ struct dcookie_struct *dcs = kmem_cache_alloc(dcookie_cache, GFP_ATOMIC);
++
+ struct dentry *d;
+ if (!dcs)
+ return NULL;
+@@ -117,7 +136,7 @@ int get_dcookie(struct path *path, unsigned long *cookie)
+ int err = 0;
+ struct dcookie_struct * dcs;
+
+- mutex_lock(&dcookie_mutex);
++ spin_lock(&dcookie_hash_write_lock);
+
+ if (!is_live()) {
+ err = -EINVAL;
+@@ -137,7 +156,7 @@ int get_dcookie(struct path *path, unsigned long *cookie)
+ *cookie = dcookie_value(dcs);
+
+ out:
+- mutex_unlock(&dcookie_mutex);
++ spin_unlock(&dcookie_hash_write_lock);
+ return err;
+ }
+
+@@ -209,7 +228,7 @@ SYSCALL_ALIAS(sys_lookup_dcookie, SyS_lookup_dcookie);
+ static int dcookie_init(void)
+ {
+ struct list_head * d;
+- unsigned int i, hash_bits;
++ unsigned int i, j, hash_bits;
+ int err = -ENOMEM;
+
+ dcookie_cache = kmem_cache_create("dcookie_cache",
+@@ -219,9 +238,11 @@ static int dcookie_init(void)
+ if (!dcookie_cache)
+ goto out;
+
+- dcookie_hashtable = kmalloc(PAGE_SIZE, GFP_KERNEL);
+- if (!dcookie_hashtable)
++ for (i=0; i<3; i++) {
++ dcookie_hashtable[i] = kmalloc(PAGE_SIZE, GFP_KERNEL);
++ if (!dcookie_hashtable[i])
+ goto out_kmem;
++ }
+
+ err = 0;
+
+@@ -244,13 +265,15 @@ static int dcookie_init(void)
+ hash_size = 1UL << hash_bits;
+
+ /* And initialize the newly allocated array */
+- d = dcookie_hashtable;
+- i = hash_size;
++ for (i=0; i<3; i++) {
++ d = dcookie_hashtable[i];
++ j = hash_size;
+ do {
+ INIT_LIST_HEAD(d);
+ d++;
+- i--;
+- } while (i);
++ j--;
++ } while (j);
++ }
+
+ out:
+ return err;
+@@ -272,17 +295,31 @@ static void free_dcookie(struct dcookie_struct * dcs)
+ kmem_cache_free(dcookie_cache, dcs);
+ }
+
++int dcookie_swap(void) {
++ if (is_shared())
++ return -EAGAIN;
++
++ old_hash=current_hash;
++ current_hash = (current_hash + 1) % 3;
++ return 0;
++}
+
+-static void dcookie_exit(void)
+-{
++/* Switch to the second hash */
++int dcookie_garbage_collect(void) {
+ struct list_head * list;
+ struct list_head * pos;
+ struct list_head * pos2;
+ struct dcookie_struct * dcs;
+ size_t i;
++
++ int next_hash=(current_hash + 1) % 3;
++
++ if (is_shared())
++ return -EAGAIN;
+
++ /* XXX consider the consequence of dcookie allocation concurring with this cleanup */
+ for (i = 0; i < hash_size; ++i) {
+- list = dcookie_hashtable + i;
++ list = dcookie_hashtable[next_hash] + i;
+ list_for_each_safe(pos, pos2, list) {
+ dcs = list_entry(pos, struct dcookie_struct, hash_list);
+ list_del(&dcs->hash_list);
+@@ -290,7 +327,29 @@ static void dcookie_exit(void)
+ }
+ }
+
+- kfree(dcookie_hashtable);
++ return 0;
++}
++
++static void dcookie_exit(void)
++{
++ struct list_head * list;
++ struct list_head * pos;
++ struct list_head * pos2;
++ struct dcookie_struct * dcs;
++ size_t j;
++ unsigned int i;
++
++ for (i = 0; i < 3; ++i) {
++ for (j = 0; j < hash_size; ++j) {
++ list = dcookie_hashtable[i] + j;
++ list_for_each_safe(pos, pos2, list) {
++ dcs = list_entry(pos, struct dcookie_struct, hash_list);
++ list_del(&dcs->hash_list);
++ free_dcookie(dcs);
++ }
++ }
++ kfree(dcookie_hashtable[i]);
++ }
+ kmem_cache_destroy(dcookie_cache);
+ }
+
+@@ -340,3 +399,5 @@ void dcookie_unregister(struct dcookie_user * user)
+ EXPORT_SYMBOL_GPL(dcookie_register);
+ EXPORT_SYMBOL_GPL(dcookie_unregister);
+ EXPORT_SYMBOL_GPL(get_dcookie);
++EXPORT_SYMBOL_GPL(dcookie_garbage_collect);
++EXPORT_SYMBOL_GPL(dcookie_swap);
+diff --git a/include/linux/dcookies.h b/include/linux/dcookies.h
+index 24c806f..3c1d2b2 100644
+--- a/include/linux/dcookies.h
++++ b/include/linux/dcookies.h
+@@ -46,6 +46,27 @@ void dcookie_unregister(struct dcookie_user * user);
+ */
+ int get_dcookie(struct path *path, unsigned long *cookie);
+
++/**
++ * dcookie_swap - switch to the next dcookie epoch
++ *
++ * Deactivate the current dcookie hash table and activate
++ * the next one
++ *
++ * Returns 0 on success
++ */
++
++int dcookie_swap(void);
++
++/**
++ * dcookie_garbage_collect - clear the hash table next in line
++ *
++ * Clear the hash table to be activated in the next epoch.
++ *
++ * Returns 0 on success
++ */
++
++int dcookie_garbage_collect(void);
++
+ #else
+
+ static inline struct dcookie_user * dcookie_register(void)
git://git.onelab.eu / linux-2.6.git / commitdiff