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 <npiggin@xxxxxxxxx>
---
fs/dcache.c | 27 +++++++++++++++------------
1 files changed, 15 insertions(+), 12 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 23f6fed..4fa27b5 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -547,26 +547,29 @@ 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);
--
1.7.1
--
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