fs: use RCU in shrink_dentry_list to reduce lock nesting (ec33679d) · Commits · e / devices / android_kernel_fairphone_FP4

fs/dcache.c

+25 −21

Original line number	Diff line number	Diff line
		@@ -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 @@ static void shrink_dentry_list(struct list_head *list)
		* 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 @@ static void shrink_dentry_list(struct list_head *list)
		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 @@ static void __shrink_dcache_sb(struct super_block sb, int count, int flags)
		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);
		}