[PATCH] prune_dcache comment fix

From: Maneesh Soni <maneesh@in.ibm.com>

Clarify some things which were confusing poeple...

diff --git a/fs/dcache.c b/fs/dcache.c
index 9191ec613174a02af9b28ea8b970de795c5bc013..4807b82cb0dc083b24effc921999091d441b43b8 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -384,7 +384,11 @@ static void prune_dcache(int count)
                dentry = list_entry(tmp, struct dentry, d_lru);
 
                spin_lock(&dentry->d_lock);
-               /* leave inuse dentries */
+               /*
+                * We found an inuse dentry which was not removed from
+                * dentry_unused because of laziness during lookup.  Do not free
+                * it - just keep it off the dentry_unused list.
+                */
                if (atomic_read(&dentry->d_count)) {
                        spin_unlock(&dentry->d_lock);
                        continue;
@@ -935,8 +939,9 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
  * rcu_read_lock() and rcu_read_unlock() are used to disable preemption while
  * lookup is going on.
  *
- * d_lru list is not updated, which can leave non-zero d_count dentries
- * around in d_lru list.
+ * dentry_unused list is not updated even if lookup finds the required dentry
+ * in there. It is updated in places such as prune_dcache, shrink_dcache_sb and
+ * select_parent. This laziness saves lookup from dcache_lock acquisition.
  *
  * d_lookup() is protected against the concurrent renames in some unrelated
  * directory using the seqlockt_t rename_lock.