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/ext2/super.c b/fs/ext2/super.c
index f9cb54a585ce..d5f19f954fb7 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -157,11 +157,18 @@ static struct inode *ext2_alloc_inode(struct super_block *sb)
 	return &ei->vfs_inode;
 }
 
-static void ext2_destroy_inode(struct inode *inode)
+static void ext2_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(ext2_inode_cachep, EXT2_I(inode));
 }
 
+static void ext2_destroy_inode(struct inode *inode)
+{
+	call_rcu(&inode->i_rcu, ext2_i_callback);
+}
+
 static void init_once(void *foo)
 {
 	struct ext2_inode_info *ei = (struct ext2_inode_info *) foo;