And a followup patch for that, removing RCU locking from shrink_dentry_list().
I haven't tested any of this at this point, but I'll ask IBM to do some stress
testing.
Thanks,
Miklos
---
From: Miklos Szeredi <mszeredi@xxxxxxx>
Subject: dcache: don't need rcu in shrink_dentry_list()
Since now the shrink list is private and nobody can free the dentry while
it is on the shrink list, we can remove RCU protection from this.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---
fs/dcache.c | 29 ++++-------------------------
1 file changed, 4 insertions(+), 25 deletions(-)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -822,23 +822,9 @@ static void shrink_dentry_list(struct li
{
struct dentry *dentry, *parent;
- rcu_read_lock();
- for (;;) {
- dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
- if (&dentry->d_lru == list)
- break; /* empty */
-
- /*
- * Get the dentry lock, and re-verify that the dentry is
- * this on the shrinking list. If it is, we know that
- * DCACHE_SHRINK_LIST and DCACHE_LRU_LIST are set.
- */
+ while (!list_empty(list)) {
+ dentry = list_entry(list->prev, struct dentry, d_lru);
spin_lock(&dentry->d_lock);
- if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
- spin_unlock(&dentry->d_lock);
- continue;
- }
-
/*
* The dispose list is isolated and dentries are not accounted
* to the LRU here, so we can simply remove it from the list
@@ -854,7 +840,6 @@ static void shrink_dentry_list(struct li
spin_unlock(&dentry->d_lock);
continue;
}
- rcu_read_unlock();
if (unlikely(dentry->d_flags & DCACHE_DENTRY_KILLED)) {
bool free_it;
@@ -870,8 +855,6 @@ static void shrink_dentry_list(struct li
if (free_it)
dentry_free(dentry);
-
- rcu_read_lock();
continue;
}
@@ -879,17 +862,15 @@ static void shrink_dentry_list(struct li
/*
* If dentry_kill returns NULL, we have nothing more to do.
*/
- if (!parent) {
- rcu_read_lock();
+ if (!parent)
continue;
- }
+
if (unlikely(parent == dentry)) {
/*
* trylocks have failed and d_lock has been held the
* whole time, so it could not have been added to any
* other lists. Just add it back to the shrink list.
*/
- rcu_read_lock();
d_shrink_add(dentry, list);
spin_unlock(&dentry->d_lock);
continue;
@@ -903,9 +884,7 @@ static void shrink_dentry_list(struct li
dentry = parent;
while (dentry && !lockref_put_or_lock(&dentry->d_lockref))
dentry = dentry_kill(dentry, 1);
- rcu_read_lock();
}
- rcu_read_unlock();
}
static enum lru_status
--
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