From 2fd6b7f50797f2e993eea59e0a0b8c6399c811dc Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Fri, 7 Jan 2011 17:49:34 +1100 Subject: fs: dcache scale subdirs Protect d_subdirs and d_child with d_lock, except in filesystems that aren't using dcache_lock for these anyway (eg. using i_mutex). Note: if we change the locking rule in future so that ->d_child protection is provided only with ->d_parent->d_lock, it may allow us to reduce some locking. But it would be an exception to an otherwise regular locking scheme, so we'd have to see some good results. Probably not worthwhile. Signed-off-by: Nick Piggin --- kernel/cgroup.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/cgroup.c b/kernel/cgroup.c index eb7af39350c..7b4705b51d4 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -877,23 +877,31 @@ static void cgroup_clear_directory(struct dentry *dentry) BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex)); spin_lock(&dcache_lock); + spin_lock(&dentry->d_lock); node = dentry->d_subdirs.next; while (node != &dentry->d_subdirs) { struct dentry *d = list_entry(node, struct dentry, d_u.d_child); + + spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED); list_del_init(node); if (d->d_inode) { /* This should never be called on a cgroup * directory with child cgroups */ BUG_ON(d->d_inode->i_mode & S_IFDIR); - d = dget_locked(d); + dget_locked_dlock(d); + spin_unlock(&d->d_lock); + spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); d_delete(d); simple_unlink(dentry->d_inode, d); dput(d); spin_lock(&dcache_lock); - } + spin_lock(&dentry->d_lock); + } else + spin_unlock(&d->d_lock); node = dentry->d_subdirs.next; } + spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); } @@ -902,10 +910,17 @@ static void cgroup_clear_directory(struct dentry *dentry) */ static void cgroup_d_remove_dir(struct dentry *dentry) { + struct dentry *parent; + cgroup_clear_directory(dentry); spin_lock(&dcache_lock); + parent = dentry->d_parent; + spin_lock(&parent->d_lock); + spin_lock(&dentry->d_lock); list_del_init(&dentry->d_u.d_child); + spin_unlock(&dentry->d_lock); + spin_unlock(&parent->d_lock); spin_unlock(&dcache_lock); remove_dir(dentry); } -- cgit v1.2.3