fs: use RCU in shrink_dentry_list to reduce lock nesting
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
diff --git a/fs/dcache.c b/fs/dcache.c
index fe8f28a..d1840b3 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -615,16 +615,16 @@
{
struct dentry *dentry;
- while (!list_empty(list)) {
+ rcu_read_lock();
+ for (;;) {
struct dentry *parent;
- dentry = list_entry(list->prev, struct dentry, d_lru);
-
- if (!spin_trylock(&dentry->d_lock)) {
-relock1:
- spin_unlock(&dcache_lru_lock);
- cpu_relax();
- spin_lock(&dcache_lru_lock);
+ dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
+ if (&dentry->d_lru == list)
+ break; /* empty */
+ spin_lock(&dentry->d_lock);
+ if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
+ spin_unlock(&dentry->d_lock);
continue;
}
@@ -634,14 +634,16 @@
* it - just keep it off the LRU list.
*/
if (dentry->d_count) {
- __dentry_lru_del(dentry);
+ dentry_lru_del(dentry);
spin_unlock(&dentry->d_lock);
continue;
}
+
if (!spin_trylock(&dcache_inode_lock)) {
-relock2:
+relock:
spin_unlock(&dentry->d_lock);
- goto relock1;
+ cpu_relax();
+ continue;
}
if (IS_ROOT(dentry))
parent = NULL;
@@ -649,15 +651,15 @@
parent = dentry->d_parent;
if (parent && !spin_trylock(&parent->d_lock)) {
spin_unlock(&dcache_inode_lock);
- goto relock2;
+ goto relock;
}
- __dentry_lru_del(dentry);
- spin_unlock(&dcache_lru_lock);
+ dentry_lru_del(dentry);
+ rcu_read_unlock();
prune_one_dentry(dentry, parent);
- /* dcache_inode_lock and dentry->d_lock dropped */
- spin_lock(&dcache_lru_lock);
+ rcu_read_lock();
}
+ rcu_read_unlock();
}
/**
@@ -705,15 +707,15 @@
if (!--cnt)
break;
}
- /* XXX: re-add cond_resched_lock when dcache_lock goes away */
+ cond_resched_lock(&dcache_lru_lock);
}
-
- *count = cnt;
- shrink_dentry_list(&tmp);
-
if (!list_empty(&referenced))
list_splice(&referenced, &sb->s_dentry_lru);
spin_unlock(&dcache_lru_lock);
+
+ shrink_dentry_list(&tmp);
+
+ *count = cnt;
}
/**
@@ -805,7 +807,9 @@
spin_lock(&dcache_lru_lock);
while (!list_empty(&sb->s_dentry_lru)) {
list_splice_init(&sb->s_dentry_lru, &tmp);
+ spin_unlock(&dcache_lru_lock);
shrink_dentry_list(&tmp);
+ spin_lock(&dcache_lru_lock);
}
spin_unlock(&dcache_lru_lock);
}