fs-inode_lock-scale-8

Make inode_hash_lock private by adding a function __remove_inode_hash
that can be used by filesystems defining their own drop_inode functions.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 28 insertions, 16 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 77dacd47b492..3ce2a15768dc 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -86,7 +86,7 @@ static struct hlist_head *inode_hashtable __read_mostly;
  */
 DEFINE_SPINLOCK(sb_inode_list_lock);
 DEFINE_SPINLOCK(wb_inode_list_lock);
-DEFINE_SPINLOCK(inode_hash_lock);
+static DEFINE_SPINLOCK(inode_hash_lock);
 
 /*
  * iprune_sem provides exclusion between the kswapd or try_to_free_pages
@@ -356,9 +356,7 @@ static void dispose_list(struct list_head *head)
 
                 spin_lock(&sb_inode_list_lock);
                 spin_lock(&inode->i_lock);
-                spin_lock(&inode_hash_lock);
-                hlist_del_init(&inode->i_hash);
-                spin_unlock(&inode_hash_lock);
+                __remove_inode_hash(inode);
                 list_del_init(&inode->i_sb_list);
                 spin_unlock(&inode->i_lock);
                 spin_unlock(&sb_inode_list_lock);
@@ -1261,6 +1259,20 @@ void __insert_inode_hash(struct inode *inode, unsigned long hashval)
 EXPORT_SYMBOL(__insert_inode_hash);
 
 /**
+ *      __remove_inode_hash - remove an inode from the hash
+ *      @inode: inode to unhash
+ *
+ *      Remove an inode from the superblock. inode->i_lock must be
+ *      held.
+ */
+void __remove_inode_hash(struct inode *inode)
+{
+        spin_lock(&inode_hash_lock);
+        hlist_del_init(&inode->i_hash);
+        spin_unlock(&inode_hash_lock);
+}
+
+/**
  *      remove_inode_hash - remove an inode from the hash
  *      @inode: inode to unhash
  *
@@ -1269,9 +1281,7 @@ EXPORT_SYMBOL(__insert_inode_hash);
 void remove_inode_hash(struct inode *inode)
 {
         spin_lock(&inode->i_lock);
-        spin_lock(&inode_hash_lock);
-        hlist_del_init(&inode->i_hash);
-        spin_unlock(&inode_hash_lock);
+        __remove_inode_hash(inode);
         spin_unlock(&inode->i_lock);
 }
 EXPORT_SYMBOL(remove_inode_hash);
@@ -1317,11 +1327,15 @@ void generic_delete_inode(struct inode *inode)
                 truncate_inode_pages(&inode->i_data, 0);
                 clear_inode(inode);
         }
-        spin_lock(&inode->i_lock);
-        spin_lock(&inode_hash_lock);
-        hlist_del_init(&inode->i_hash);
-        spin_unlock(&inode_hash_lock);
-        spin_unlock(&inode->i_lock);
+        /*
+         * i_lock not required to delete from hash. If there was a
+         * concurrency window, then it would be possible for the other
+         * thread to touch the inode after it has been freed, with
+         * destroy_inode.
+         * XXX: yes it is because find_inode_fast checks it. Maybe we
+         * can avoid it though...
+         */
+        remove_inode_hash(inode);
         wake_up_inode(inode);
         BUG_ON(inode->i_state != I_CLEAR);
         destroy_inode(inode);
@@ -1362,9 +1376,7 @@ int generic_detach_inode(struct inode *inode)
                 spin_lock(&inode->i_lock);
                 WARN_ON(inode->i_state & I_NEW);
                 inode->i_state &= ~I_WILL_FREE;
-                spin_lock(&inode_hash_lock);
-                hlist_del_init(&inode->i_hash);
-                spin_unlock(&inode_hash_lock);
+                __remove_inode_hash(inode);
                 atomic_dec(&inodes_stat.nr_unused);
         }
         spin_lock(&wb_inode_list_lock);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index fc4222374cd7..3551528a25f6 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2184,6 +2184,7 @@ extern int should_remove_suid(struct dentry *);
 extern int file_remove_suid(struct file *);
 
 extern void __insert_inode_hash(struct inode *, unsigned long hashval);
+extern void __remove_inode_hash(struct inode *);
 extern void remove_inode_hash(struct inode *);
 static inline void insert_inode_hash(struct inode *inode) {
         __insert_inode_hash(inode, inode->i_ino);
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 3e504f49753c..05479e576a77 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -11,7 +11,6 @@ struct backing_dev_info;
 
 extern spinlock_t sb_inode_list_lock;
 extern spinlock_t wb_inode_list_lock;
-extern spinlock_t inode_hash_lock;
 extern struct list_head inode_in_use;
 extern struct list_head inode_unused;