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SELinux: convert the avc cache hash list to an hlist
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We do not need O(1) access to the tail of the avc cache lists and so we are
wasting lots of space using struct list_head instead of struct hlist_head.
This patch converts the avc cache to use hlists in which there is a single
pointer from the head which saves us about 4k of global memory.

Resulted in about a 1.5% decrease in time spent in avc_has_perm_noaudit based
on oprofile sampling of tbench.  Although likely within the noise....

Signed-off-by: Eric Paris <eparis@redhat.com>
Reviewed-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>
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Eric Paris authored and James Morris committed Feb 13, 2009
1 parent edf3d1a commit 2603665
Showing 1 changed file with 27 additions and 20 deletions.
47 changes: 27 additions & 20 deletions security/selinux/avc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -92,12 +92,12 @@ struct avc_entry {

struct avc_node {
struct avc_entry ae;
struct list_head list; /* anchored in avc_cache->slots[i] */
struct hlist_node list; /* anchored in avc_cache->slots[i] */
struct rcu_head rhead;
};

struct avc_cache {
struct list_head slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
struct hlist_head slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
spinlock_t slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
atomic_t lru_hint; /* LRU hint for reclaim scan */
atomic_t active_nodes;
Expand Down Expand Up @@ -233,7 +233,7 @@ void __init avc_init(void)
int i;

for (i = 0; i < AVC_CACHE_SLOTS; i++) {
INIT_LIST_HEAD(&avc_cache.slots[i]);
INIT_HLIST_HEAD(&avc_cache.slots[i]);
spin_lock_init(&avc_cache.slots_lock[i]);
}
atomic_set(&avc_cache.active_nodes, 0);
Expand All @@ -249,18 +249,20 @@ int avc_get_hash_stats(char *page)
{
int i, chain_len, max_chain_len, slots_used;
struct avc_node *node;
struct list_head *head;
struct hlist_head *head;

rcu_read_lock();

slots_used = 0;
max_chain_len = 0;
for (i = 0; i < AVC_CACHE_SLOTS; i++) {
head = &avc_cache.slots[i];
if (!list_empty(head)) {
if (!hlist_empty(head)) {
struct hlist_node *next;

slots_used++;
chain_len = 0;
list_for_each_entry_rcu(node, head, list)
hlist_for_each_entry_rcu(node, next, head, list)
chain_len++;
if (chain_len > max_chain_len)
max_chain_len = chain_len;
Expand All @@ -284,7 +286,7 @@ static void avc_node_free(struct rcu_head *rhead)

static void avc_node_delete(struct avc_node *node)
{
list_del_rcu(&node->list);
hlist_del_rcu(&node->list);
call_rcu(&node->rhead, avc_node_free);
atomic_dec(&avc_cache.active_nodes);
}
Expand All @@ -298,7 +300,7 @@ static void avc_node_kill(struct avc_node *node)

static void avc_node_replace(struct avc_node *new, struct avc_node *old)
{
list_replace_rcu(&old->list, &new->list);
hlist_replace_rcu(&old->list, &new->list);
call_rcu(&old->rhead, avc_node_free);
atomic_dec(&avc_cache.active_nodes);
}
Expand All @@ -308,7 +310,8 @@ static inline int avc_reclaim_node(void)
struct avc_node *node;
int hvalue, try, ecx;
unsigned long flags;
struct list_head *head;
struct hlist_head *head;
struct hlist_node *next;
spinlock_t *lock;

for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
Expand All @@ -320,7 +323,7 @@ static inline int avc_reclaim_node(void)
continue;

rcu_read_lock();
list_for_each_entry(node, head, list) {
hlist_for_each_entry(node, next, head, list) {
avc_node_delete(node);
avc_cache_stats_incr(reclaims);
ecx++;
Expand All @@ -346,7 +349,7 @@ static struct avc_node *avc_alloc_node(void)
goto out;

INIT_RCU_HEAD(&node->rhead);
INIT_LIST_HEAD(&node->list);
INIT_HLIST_NODE(&node->list);
avc_cache_stats_incr(allocations);

if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
Expand All @@ -368,11 +371,12 @@ static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
{
struct avc_node *node, *ret = NULL;
int hvalue;
struct list_head *head;
struct hlist_head *head;
struct hlist_node *next;

hvalue = avc_hash(ssid, tsid, tclass);
head = &avc_cache.slots[hvalue];
list_for_each_entry_rcu(node, head, list) {
hlist_for_each_entry_rcu(node, next, head, list) {
if (ssid == node->ae.ssid &&
tclass == node->ae.tclass &&
tsid == node->ae.tsid) {
Expand Down Expand Up @@ -461,7 +465,8 @@ static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_dec

node = avc_alloc_node();
if (node) {
struct list_head *head;
struct hlist_head *head;
struct hlist_node *next;
spinlock_t *lock;

hvalue = avc_hash(ssid, tsid, tclass);
Expand All @@ -471,15 +476,15 @@ static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_dec
lock = &avc_cache.slots_lock[hvalue];

spin_lock_irqsave(lock, flag);
list_for_each_entry(pos, head, list) {
hlist_for_each_entry(pos, next, head, list) {
if (pos->ae.ssid == ssid &&
pos->ae.tsid == tsid &&
pos->ae.tclass == tclass) {
avc_node_replace(node, pos);
goto found;
}
}
list_add_rcu(&node->list, head);
hlist_add_head_rcu(&node->list, head);
found:
spin_unlock_irqrestore(lock, flag);
}
Expand Down Expand Up @@ -750,7 +755,8 @@ static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
int hvalue, rc = 0;
unsigned long flag;
struct avc_node *pos, *node, *orig = NULL;
struct list_head *head;
struct hlist_head *head;
struct hlist_node *next;
spinlock_t *lock;

node = avc_alloc_node();
Expand All @@ -767,7 +773,7 @@ static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,

spin_lock_irqsave(lock, flag);

list_for_each_entry(pos, head, list) {
hlist_for_each_entry(pos, next, head, list) {
if (ssid == pos->ae.ssid &&
tsid == pos->ae.tsid &&
tclass == pos->ae.tclass &&
Expand Down Expand Up @@ -827,7 +833,8 @@ int avc_ss_reset(u32 seqno)
int i, rc = 0, tmprc;
unsigned long flag;
struct avc_node *node;
struct list_head *head;
struct hlist_head *head;
struct hlist_node *next;
spinlock_t *lock;

for (i = 0; i < AVC_CACHE_SLOTS; i++) {
Expand All @@ -840,7 +847,7 @@ int avc_ss_reset(u32 seqno)
* prevent RCU grace periods from ending.
*/
rcu_read_lock();
list_for_each_entry(node, head, list)
hlist_for_each_entry(node, next, head, list)
avc_node_delete(node);
rcu_read_unlock();
spin_unlock_irqrestore(lock, flag);
Expand Down

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