From 89e6054836a7b1e7500cd70a14b5579e752c9250 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Fri, 7 Jan 2011 17:49:45 +1100 Subject: [PATCH] fs: dcache reduce prune_one_dentry locking prune_one_dentry can avoid quite a bit of locking in the common case where ancestors have an elevated refcount. Alternatively, we could have gone the other way and made fewer trylocks in the case where d_count goes to zero, but is probably less common. Signed-off-by: Nick Piggin --- fs/dcache.c | 27 +++++++++++++++------------ 1 file changed, 15 insertions(+), 12 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index a8f89765d602..195706374697 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -582,26 +582,29 @@ static void prune_one_dentry(struct dentry *dentry, struct dentry *parent) * Prune ancestors. */ while (dentry) { - spin_lock(&dcache_inode_lock); -again: +relock: spin_lock(&dentry->d_lock); + if (dentry->d_count > 1) { + dentry->d_count--; + spin_unlock(&dentry->d_lock); + return; + } + if (!spin_trylock(&dcache_inode_lock)) { +relock2: + spin_unlock(&dentry->d_lock); + cpu_relax(); + goto relock; + } + if (IS_ROOT(dentry)) parent = NULL; else parent = dentry->d_parent; if (parent && !spin_trylock(&parent->d_lock)) { - spin_unlock(&dentry->d_lock); - goto again; - } - dentry->d_count--; - if (dentry->d_count) { - if (parent) - spin_unlock(&parent->d_lock); - spin_unlock(&dentry->d_lock); spin_unlock(&dcache_inode_lock); - return; + goto relock2; } - + dentry->d_count--; dentry_lru_del(dentry); __d_drop(dentry); dentry = d_kill(dentry, parent); -- 2.20.1