Subject: Re: linux-next: manual merge of the vfs-scale tree with the xfs tree

From: Dave Chinner <[email-masked]>
Date: Thu, 6 Jan 2011 15:50:14 +1100

On Thu, Jan 06, 2011 at 12:10:56PM +1100, Stephen Rothwell wrote:
> Hi Nick,
> 
> Today's linux-next merge of the vfs-scale tree got a conflict in
> fs/xfs/xfs_iget.c between commits
> d95b7aaf9ab6738bef1ebcc52ab66563085e44ac ("xfs: rcu free inodes") and
> 1a3e8f3da09c7082d25b512a0ffe569391e4c09a ("xfs: convert inode cache
> lookups to use RCU locking") from the xfs tree and commit
> bb3e8c37a0af21d0a8fe54a0b0f17aca16335a82 ("fs: icache RCU free inodes")
> from the vfs-scale tree.
> 
> OK, so looking at this, the first xfs tree patch above does the same as
> the vfs-scale tree patch (just using i_dentry instead of the (union
> eqivalent) i_rcu.  I fixed it up (see below - the diff does not show that
> __xfs_inode_free has been removed) and can carry the fix as necessary.
> -- 
> Cheers,
> Stephen Rothwell                    [email-masked]
> 
> diff --cc fs/xfs/xfs_iget.c
> index 3ecad00,d7de5a3..0000000
> --- a/fs/xfs/xfs_iget.c
> +++ b/fs/xfs/xfs_iget.c
> @@@ -157,17 -145,7 +156,17 @@@ xfs_inode_free
>   	ASSERT(!spin_is_locked(&ip->i_flags_lock));
>   	ASSERT(completion_done(&ip->i_flush));
>   
>  +	/*
>  +	 * Because we use RCU freeing we need to ensure the inode always
>  +	 * appears to be reclaimed with an invalid inode number when in the
>  +	 * free state. The ip->i_flags_lock provides the barrier against lookup
>  +	 * races.
>  +	 */
>  +	spin_lock(&ip->i_flags_lock);
>  +	ip->i_flags = XFS_IRECLAIM;
>  +	ip->i_ino = 0;
>  +	spin_unlock(&ip->i_flags_lock);
> - 	call_rcu((struct rcu_head *)&VFS_I(ip)->i_dentry, __xfs_inode_free);
> + 	call_rcu(&ip->i_vnode.i_rcu, xfs_inode_free_callback);

The fixed up call_rcu() shoul dbe:

+	call_rcu(&VFS_I(ip)->i_rcu, xfs_inode_free_callback);

Cheers,

Dave.
-- 
Dave Chinner
[email-masked]