fs-inode_rcu

RCU free the struct inode. This will allow:

- sb_inode_list_lock to be moved inside i_lock because sb list walkers who want
  to take i_lock no longer need to take sb_inode_list_lock to walk the list in
  the first place. This will simplify and optimize locking.
- eventually, completely write-free RCU path walking. The inode must be
  consulted for permissions when walking, so a write-free reference (ie.
  RCU is helpful).
- can potentially simplify things a bit in VM land. May not need to take the
  page lock to get back to the page->mapping.
- can remove some nested trylock loops in dcache code

todo: convert all filesystems

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>

1 files changed, 8 insertions, 1 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 5039ddf4f0e0..fd57c8371686 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -245,13 +245,20 @@ void __destroy_inode(struct inode *inode)
 }
 EXPORT_SYMBOL(__destroy_inode);
 
+static void i_callback(struct rcu_head *head)
+{
+        struct inode *inode = container_of(head, struct inode, i_rcu);
+        INIT_LIST_HEAD(&inode->i_dentry);
+        kmem_cache_free(inode_cachep, inode);
+}
+
 void destroy_inode(struct inode *inode)
 {
         __destroy_inode(inode);
         if (inode->i_sb->s_op->destroy_inode)
                 inode->i_sb->s_op->destroy_inode(inode);
         else
-                kmem_cache_free(inode_cachep, (inode));
+                call_rcu(&inode->i_rcu, i_callback);
 }
 
 /*