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, 4 insertions, 1 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index b86542c8d68c..9c595e725ee1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -726,7 +726,10 @@ struct inode {
 	struct hlist_node	i_hash;
 	struct list_head	i_list;		/* backing dev IO list */
 	struct list_head	i_sb_list;
-	struct list_head	i_dentry;
+	union {
+		struct list_head	i_dentry;
+		struct rcu_head		i_rcu;
+	};
 	unsigned long		i_ino;
 	unsigned int		i_count;
 	unsigned int		i_nlink;