From ec33679d78f9d653a44ddba10b5fb824c06330a1 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Fri, 7 Jan 2011 17:49:47 +1100 Subject: fs: use RCU in shrink_dentry_list to reduce lock nesting Signed-off-by: Nick Piggin --- fs/dcache.c | 46 +++++++++++++++++++++++++--------------------- 1 file changed, 25 insertions(+), 21 deletions(-) (limited to 'fs/dcache.c') diff --git a/fs/dcache.c b/fs/dcache.c index fe8f28a2878e..d1840b30c673 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -615,16 +615,16 @@ static void shrink_dentry_list(struct list_head *list) { 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 @@ relock1: * 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 @@ relock2: 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 @@ relock: 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 @@ void shrink_dcache_sb(struct super_block *sb) 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); } -- cgit v1.2.3-59-g8ed1b