SELinux: code readability with avc_cache

The code making use of struct avc_cache was not easy to read thanks to liberal
use of &avc_cache.{slots_lock,slots}[hvalue] throughout.  This patch simply
creates local pointers and uses those instead of the long global names.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index 326aa78..9dd5c50 100644 (file)
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -92,12 +92,12 @@ struct avc_entry {
 
 struct avc_node {
        struct avc_entry        ae;
-       struct list_head        list;
+       struct list_head        list; /* anchored in avc_cache->slots[i] */
        struct rcu_head         rhead;
 };
 
 struct avc_cache {
-       struct list_head        slots[AVC_CACHE_SLOTS];
+       struct list_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;
@@ -249,16 +249,18 @@ int avc_get_hash_stats(char *page)
 {
        int i, chain_len, max_chain_len, slots_used;
        struct avc_node *node;
+       struct list_head *head;
 
        rcu_read_lock();
 
        slots_used = 0;
        max_chain_len = 0;
        for (i = 0; i < AVC_CACHE_SLOTS; i++) {
-               if (!list_empty(&avc_cache.slots[i])) {
+               head = &avc_cache.slots[i];
+               if (!list_empty(head)) {
                        slots_used++;
                        chain_len = 0;
-                       list_for_each_entry_rcu(node, &avc_cache.slots[i], list)
+                       list_for_each_entry_rcu(node, head, list)
                                chain_len++;
                        if (chain_len > max_chain_len)
                                max_chain_len = chain_len;
@@ -306,26 +308,30 @@ static inline int avc_reclaim_node(void)
        struct avc_node *node;
        int hvalue, try, ecx;
        unsigned long flags;
+       struct list_head *head;
+       spinlock_t *lock;
 
        for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
                hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
+               head = &avc_cache.slots[hvalue];
+               lock = &avc_cache.slots_lock[hvalue];
 
-               if (!spin_trylock_irqsave(&avc_cache.slots_lock[hvalue], flags))
+               if (!spin_trylock_irqsave(lock, flags))
                        continue;
 
                rcu_read_lock();
-               list_for_each_entry(node, &avc_cache.slots[hvalue], list) {
+               list_for_each_entry(node, head, list) {
                        avc_node_delete(node);
                        avc_cache_stats_incr(reclaims);
                        ecx++;
                        if (ecx >= AVC_CACHE_RECLAIM) {
                                rcu_read_unlock();
-                               spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flags);
+                               spin_unlock_irqrestore(lock, flags);
                                goto out;
                        }
                }
                rcu_read_unlock();
-               spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flags);
+               spin_unlock_irqrestore(lock, flags);
        }
 out:
        return ecx;
@@ -362,9 +368,11 @@ 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;
 
        hvalue = avc_hash(ssid, tsid, tclass);
-       list_for_each_entry_rcu(node, &avc_cache.slots[hvalue], list) {
+       head = &avc_cache.slots[hvalue];
+       list_for_each_entry_rcu(node, head, list) {
                if (ssid == node->ae.ssid &&
                    tclass == node->ae.tclass &&
                    tsid == node->ae.tsid) {
@@ -453,11 +461,17 @@ 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;
+               spinlock_t *lock;
+
                hvalue = avc_hash(ssid, tsid, tclass);
                avc_node_populate(node, ssid, tsid, tclass, avd);
 
-               spin_lock_irqsave(&avc_cache.slots_lock[hvalue], flag);
-               list_for_each_entry(pos, &avc_cache.slots[hvalue], list) {
+               head = &avc_cache.slots[hvalue];
+               lock = &avc_cache.slots_lock[hvalue];
+
+               spin_lock_irqsave(lock, flag);
+               list_for_each_entry(pos, head, list) {
                        if (pos->ae.ssid == ssid &&
                            pos->ae.tsid == tsid &&
                            pos->ae.tclass == tclass) {
@@ -465,9 +479,9 @@ static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_dec
                                goto found;
                        }
                }
-               list_add_rcu(&node->list, &avc_cache.slots[hvalue]);
+               list_add_rcu(&node->list, head);
 found:
-               spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flag);
+               spin_unlock_irqrestore(lock, flag);
        }
 out:
        return node;
@@ -736,6 +750,8 @@ 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;
+       spinlock_t *lock;
 
        node = avc_alloc_node();
        if (!node) {
@@ -745,9 +761,13 @@ static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
 
        /* Lock the target slot */
        hvalue = avc_hash(ssid, tsid, tclass);
-       spin_lock_irqsave(&avc_cache.slots_lock[hvalue], flag);
 
-       list_for_each_entry(pos, &avc_cache.slots[hvalue], list) {
+       head = &avc_cache.slots[hvalue];
+       lock = &avc_cache.slots_lock[hvalue];
+
+       spin_lock_irqsave(lock, flag);
+
+       list_for_each_entry(pos, head, list) {
                if (ssid == pos->ae.ssid &&
                    tsid == pos->ae.tsid &&
                    tclass == pos->ae.tclass &&
@@ -792,7 +812,7 @@ static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
        }
        avc_node_replace(node, orig);
 out_unlock:
-       spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flag);
+       spin_unlock_irqrestore(lock, flag);
 out:
        return rc;
 }
@@ -807,18 +827,23 @@ int avc_ss_reset(u32 seqno)
        int i, rc = 0, tmprc;
        unsigned long flag;
        struct avc_node *node;
+       struct list_head *head;
+       spinlock_t *lock;
 
        for (i = 0; i < AVC_CACHE_SLOTS; i++) {
-               spin_lock_irqsave(&avc_cache.slots_lock[i], flag);
+               head = &avc_cache.slots[i];
+               lock = &avc_cache.slots_lock[i];
+
+               spin_lock_irqsave(lock, flag);
                /*
                 * With preemptable RCU, the outer spinlock does not
                 * prevent RCU grace periods from ending.
                 */
                rcu_read_lock();
-               list_for_each_entry(node, &avc_cache.slots[i], list)
+               list_for_each_entry(node, head, list)
                        avc_node_delete(node);
                rcu_read_unlock();
-               spin_unlock_irqrestore(&avc_cache.slots_lock[i], flag);
+               spin_unlock_irqrestore(lock, flag);
        }
 
        for (c = avc_callbacks; c; c = c->next) {