2 files changed, 64 insertions, 33 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index f04d04af84f2..e8f65290e836 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -408,16 +408,13 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
                          * completion.
                          */
                         redirty_tail(inode);
-                } else if (atomic_read(&inode->i_count)) {
-                        /*
-                         * The inode is clean, inuse
-                         */
-                        list_move(&inode->i_list, &inode_in_use);
                 } else {
                         /*
-                         * The inode is clean, unused
+                         * The inode is clean.  At this point we either have
+                         * a reference to the inode or it's on it's way out.
+                         * No need to add it back to the LRU.
                          */
-                        list_move(&inode->i_list, &inode_unused);
+                        list_del_init(&inode->i_list);
                 }
         }
         inode_sync_complete(inode);
diff --git a/fs/inode.c b/fs/inode.c
index 0d5aeccbdd90..3bdc76f1653a 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -72,8 +72,7 @@ static unsigned int i_hash_shift __read_mostly;
  * allowing for low-overhead inode sync() operations.
  */
 
-LIST_HEAD(inode_in_use);
-LIST_HEAD(inode_unused);
+static LIST_HEAD(inode_unused);
 static struct hlist_head *inode_hashtable __read_mostly;
 
 /*
@@ -291,6 +290,7 @@ void inode_init_once(struct inode *inode)
         INIT_HLIST_NODE(&inode->i_hash);
         INIT_LIST_HEAD(&inode->i_dentry);
         INIT_LIST_HEAD(&inode->i_devices);
+        INIT_LIST_HEAD(&inode->i_list);
         INIT_RADIX_TREE(&inode->i_data.page_tree, GFP_ATOMIC);
         spin_lock_init(&inode->i_data.tree_lock);
         spin_lock_init(&inode->i_data.i_mmap_lock);
@@ -317,12 +317,23 @@ static void init_once(void *foo)
  */
 void __iget(struct inode *inode)
 {
-        if (atomic_inc_return(&inode->i_count) != 1)
-                return;
+        atomic_inc(&inode->i_count);
+}
 
-        if (!(inode->i_state & (I_DIRTY|I_SYNC)))
-                list_move(&inode->i_list, &inode_in_use);
-        percpu_counter_dec(&nr_inodes_unused);
+static void inode_lru_list_add(struct inode *inode)
+{
+        if (list_empty(&inode->i_list)) {
+                list_add(&inode->i_list, &inode_unused);
+                percpu_counter_inc(&nr_inodes_unused);
+        }
+}
+
+static void inode_lru_list_del(struct inode *inode)
+{
+        if (!list_empty(&inode->i_list)) {
+                list_del_init(&inode->i_list);
+                percpu_counter_dec(&nr_inodes_unused);
+        }
 }
 
 void end_writeback(struct inode *inode)
@@ -367,7 +378,7 @@ static void dispose_list(struct list_head *head)
                 struct inode *inode;
 
                 inode = list_first_entry(head, struct inode, i_list);
-                list_del(&inode->i_list);
+                list_del_init(&inode->i_list);
 
                 evict(inode);
 
@@ -413,7 +424,8 @@ static int invalidate_list(struct list_head *head, struct list_head *dispose)
                         list_move(&inode->i_list, dispose);
                         WARN_ON(inode->i_state & I_NEW);
                         inode->i_state |= I_FREEING;
-                        percpu_counter_dec(&nr_inodes_unused);
+                        if (!(inode->i_state & (I_DIRTY | I_SYNC)))
+                                percpu_counter_dec(&nr_inodes_unused);
                         continue;
                 }
                 busy = 1;
@@ -448,7 +460,7 @@ int invalidate_inodes(struct super_block *sb)
 
 static int can_unuse(struct inode *inode)
 {
-        if (inode->i_state)
+        if (inode->i_state & ~I_REFERENCED)
                 return 0;
         if (inode_has_buffers(inode))
                 return 0;
@@ -460,17 +472,20 @@ static int can_unuse(struct inode *inode)
 }
 
 /*
- * Scan `goal' inodes on the unused list for freeable ones. They are moved to
- * a temporary list and then are freed outside inode_lock by dispose_list().
+ * Scan `goal' inodes on the unused list for freeable ones. They are moved to a
+ * temporary list and then are freed outside inode_lock by dispose_list().
  *
  * Any inodes which are pinned purely because of attached pagecache have their
- * pagecache removed.  We expect the final iput() on that inode to add it to
- * the front of the inode_unused list.  So look for it there and if the
- * inode is still freeable, proceed.  The right inode is found 99.9% of the
- * time in testing on a 4-way.
+ * pagecache removed.  If the inode has metadata buffers attached to
+ * mapping->private_list then try to remove them.
  *
- * If the inode has metadata buffers attached to mapping->private_list then
- * try to remove them.
+ * If the inode has the I_REFERENCED flag set, then it means that it has been
+ * used recently - the flag is set in iput_final(). When we encounter such an
+ * inode, clear the flag and move it to the back of the LRU so it gets another
+ * pass through the LRU before it gets reclaimed. This is necessary because of
+ * the fact we are doing lazy LRU updates to minimise lock contention so the
+ * LRU does not have strict ordering. Hence we don't want to reclaim inodes
+ * with this flag set because they are the inodes that are out of order.
  */
 static void prune_icache(int nr_to_scan)
 {
@@ -488,8 +503,21 @@ static void prune_icache(int nr_to_scan)
 
                 inode = list_entry(inode_unused.prev, struct inode, i_list);
 
-                if (inode->i_state || atomic_read(&inode->i_count)) {
+                /*
+                 * Referenced or dirty inodes are still in use. Give them
+                 * another pass through the LRU as we canot reclaim them now.
+                 */
+                if (atomic_read(&inode->i_count) ||
+                    (inode->i_state & ~I_REFERENCED)) {
+                        list_del_init(&inode->i_list);
+                        percpu_counter_dec(&nr_inodes_unused);
+                        continue;
+                }
+
+                /* recently referenced inodes get one more pass */
+                if (inode->i_state & I_REFERENCED) {
                         list_move(&inode->i_list, &inode_unused);
+                        inode->i_state &= ~I_REFERENCED;
                         continue;
                 }
                 if (inode_has_buffers(inode) || inode->i_data.nrpages) {
@@ -620,7 +648,6 @@ static inline void
 __inode_add_to_lists(struct super_block *sb, struct hlist_head *head,
                         struct inode *inode)
 {
-        list_add(&inode->i_list, &inode_in_use);
         list_add(&inode->i_sb_list, &sb->s_inodes);
         if (head)
                 hlist_add_head(&inode->i_hash, head);
@@ -1237,10 +1264,11 @@ static void iput_final(struct inode *inode)
                 drop = generic_drop_inode(inode);
 
         if (!drop) {
-                if (!(inode->i_state & (I_DIRTY|I_SYNC)))
-                        list_move(&inode->i_list, &inode_unused);
-                percpu_counter_inc(&nr_inodes_unused);
                 if (sb->s_flags & MS_ACTIVE) {
+                        inode->i_state |= I_REFERENCED;
+                        if (!(inode->i_state & (I_DIRTY|I_SYNC))) {
+                                inode_lru_list_add(inode);
+                        }
                         spin_unlock(&inode_lock);
                         return;
                 }
@@ -1251,13 +1279,19 @@ static void iput_final(struct inode *inode)
                 spin_lock(&inode_lock);
                 WARN_ON(inode->i_state & I_NEW);
                 inode->i_state &= ~I_WILL_FREE;
-                percpu_counter_dec(&nr_inodes_unused);
                 hlist_del_init(&inode->i_hash);
         }
-        list_del_init(&inode->i_list);
-        list_del_init(&inode->i_sb_list);
         WARN_ON(inode->i_state & I_NEW);
         inode->i_state |= I_FREEING;
+
+        /*
+         * After we delete the inode from the LRU here, we avoid moving dirty
+         * inodes back onto the LRU now because I_FREEING is set and hence
+         * writeback_single_inode() won't move the inode around.
+         */
+        inode_lru_list_del(inode);
+
+        list_del_init(&inode->i_sb_list);
         spin_unlock(&inode_lock);
         evict(inode);
         spin_lock(&inode_lock);