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fs: use RCU in shrink_dentry_list to reduce lock nesting 

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin 2011-01-07 17:49:47 +11:00
parent be182bff72
commit ec33679d78
1 changed files with 25 additions and 21 deletions
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46
fs/dcache.c
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@ -615,16 +615,16 @@ static void shrink_dentry_list(struct list_head *list)
{ {
struct dentry *dentry; struct dentry *dentry;
while (!list_empty(list)) { rcu_read_lock();
for (;;) {
struct dentry *parent; struct dentry *parent;
dentry = list_entry(list->prev, struct dentry, d_lru); dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
if (&dentry->d_lru == list)
if (!spin_trylock(&dentry->d_lock)) { break; /* empty */
relock1: spin_lock(&dentry->d_lock);
spin_unlock(&dcache_lru_lock); if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
cpu_relax(); spin_unlock(&dentry->d_lock);
spin_lock(&dcache_lru_lock);
continue; continue;
} }
@ -634,14 +634,16 @@ relock1:
* it - just keep it off the LRU list. * it - just keep it off the LRU list.
*/ */
if (dentry->d_count) { if (dentry->d_count) {
__dentry_lru_del(dentry); dentry_lru_del(dentry);
spin_unlock(&dentry->d_lock); spin_unlock(&dentry->d_lock);
continue; continue;
} }
if (!spin_trylock(&dcache_inode_lock)) { if (!spin_trylock(&dcache_inode_lock)) {
relock2: relock:
spin_unlock(&dentry->d_lock); spin_unlock(&dentry->d_lock);
goto relock1; cpu_relax();
continue;
} }
if (IS_ROOT(dentry)) if (IS_ROOT(dentry))
parent = NULL; parent = NULL;
@ -649,15 +651,15 @@ relock2:
parent = dentry->d_parent; parent = dentry->d_parent;
if (parent && !spin_trylock(&parent->d_lock)) { if (parent && !spin_trylock(&parent->d_lock)) {
spin_unlock(&dcache_inode_lock); spin_unlock(&dcache_inode_lock);
goto relock2; goto relock;
} }
__dentry_lru_del(dentry); dentry_lru_del(dentry);
spin_unlock(&dcache_lru_lock);
rcu_read_unlock();
prune_one_dentry(dentry, parent); prune_one_dentry(dentry, parent);
/* dcache_inode_lock and dentry->d_lock dropped */ rcu_read_lock();
spin_lock(&dcache_lru_lock);
} }
rcu_read_unlock();
} }
/** /**
@ -705,15 +707,15 @@ relock:
if (!--cnt) if (!--cnt)
break; 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)) if (!list_empty(&referenced))
list_splice(&referenced, &sb->s_dentry_lru); list_splice(&referenced, &sb->s_dentry_lru);
spin_unlock(&dcache_lru_lock); spin_unlock(&dcache_lru_lock);
shrink_dentry_list(&tmp);
*count = cnt;
} }
/** /**
@ -805,7 +807,9 @@ void shrink_dcache_sb(struct super_block *sb)
spin_lock(&dcache_lru_lock); spin_lock(&dcache_lru_lock);
while (!list_empty(&sb->s_dentry_lru)) { while (!list_empty(&sb->s_dentry_lru)) {
list_splice_init(&sb->s_dentry_lru, &tmp); list_splice_init(&sb->s_dentry_lru, &tmp);
spin_unlock(&dcache_lru_lock);
shrink_dentry_list(&tmp); shrink_dentry_list(&tmp);
spin_lock(&dcache_lru_lock);
} }
spin_unlock(&dcache_lru_lock); spin_unlock(&dcache_lru_lock);
} }