[patch 24/35] fs: icache use RCU to avoid locking in hash lookups

[npiggin]

Signed-off-by: Nick Piggin <npiggin@xxxxxxxxx>

---
 fs/inode.c |   32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

Index: linux-2.6/fs/inode.c
===================================================================
--- linux-2.6.orig/fs/inode.c	2010-10-19 14:18:59.000000000 +1100
+++ linux-2.6/fs/inode.c	2010-10-19 14:19:22.000000000 +1100
@@ -646,27 +646,27 @@
 	struct inode *inode = NULL;
 
 repeat:
-	spin_lock_bucket(b);
-	hlist_bl_for_each_entry(inode, node, &b->head, i_hash) {
+	rcu_read_lock();
+	hlist_bl_for_each_entry_rcu(inode, node, &b->head, i_hash) {
 		if (inode->i_sb != sb)
 			continue;
-		if (!spin_trylock(&inode->i_lock)) {
-			spin_unlock_bucket(b);
-			cpu_relax();
-			goto repeat;
+		spin_lock(&inode->i_lock);
+		if (hlist_bl_unhashed(&inode->i_hash)) {
+			spin_unlock(&inode->i_lock);
+			continue;
 		}
 		if (!test(inode, data)) {
 			spin_unlock(&inode->i_lock);
 			continue;
 		}
 		if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
-			spin_unlock_bucket(b);
+			rcu_read_unlock();
 			__wait_on_freeing_inode(inode);
 			goto repeat;
 		}
 		break;
 	}
-	spin_unlock_bucket(b);
+	rcu_read_unlock();
 	return node ? inode : NULL;
 }
 
@@ -682,25 +682,25 @@
 	struct inode *inode = NULL;
 
 repeat:
-	spin_lock_bucket(b);
-	hlist_bl_for_each_entry(inode, node, &b->head, i_hash) {
+	rcu_read_lock();
+	hlist_bl_for_each_entry_rcu(inode, node, &b->head, i_hash) {
 		if (inode->i_ino != ino)
 			continue;
 		if (inode->i_sb != sb)
 			continue;
-		if (!spin_trylock(&inode->i_lock)) {
-			spin_unlock_bucket(b);
-			cpu_relax();
-			goto repeat;
+		spin_lock(&inode->i_lock);
+		if (hlist_bl_unhashed(&inode->i_hash)) {
+			spin_unlock(&inode->i_lock);
+			continue;
 		}
 		if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
-			spin_unlock_bucket(b);
+			rcu_read_unlock();
 			__wait_on_freeing_inode(inode);
 			goto repeat;
 		}
 		break;
 	}
-	spin_unlock_bucket(b);
+	rcu_read_unlock();
 	return node ? inode : NULL;
 }
 


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