On Mon, Dec 13, 2010 at 12:32:35PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> Introduce RCU freeing of XFS inodes so that we can convert lookup
> traversals to use rcu_read_lock() protection. This patch only
> introduces the RCU freeing to minimise the potential conflicts with
> mainline if this is merged into mainline via a VFS patchset. It
> abuses the i_dentry list for the RCU callback structure because the
> VFS patches make this a union so it is safe to use like this and
> simplifies and merge issues.
>
> This patch uses basic RCU freeing rather than SLAB_DESTROY_BY_RCU.
> The later lookup patches need the same "found free inode" protection
> regardless of the RCU freeing method used, so once again the RCU
> freeing method can be dealt with apprpriately at merge time without
> affecting any other code.
There are only two call sites that free into xfs_inode_zone. One of them
is initialization, before readers have access to the data strcuture,
and the other is covered by this patch. So looks good to me!
Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
> fs/xfs/xfs_iget.c | 14 +++++++++++++-
> 1 files changed, 13 insertions(+), 1 deletions(-)
>
> diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
> index cdb1c25..9fae475 100644
> --- a/fs/xfs/xfs_iget.c
> +++ b/fs/xfs/xfs_iget.c
> @@ -105,6 +105,18 @@ xfs_inode_alloc(
> }
>
> void
> +__xfs_inode_free(
> + struct rcu_head *head)
> +{
> + struct inode *inode = container_of((void *)head,
> + struct inode, i_dentry);
> + struct xfs_inode *ip = XFS_I(inode);
> +
> + INIT_LIST_HEAD(&inode->i_dentry);
> + kmem_zone_free(xfs_inode_zone, ip);
> +}
> +
> +void
> xfs_inode_free(
> struct xfs_inode *ip)
> {
> @@ -147,7 +159,7 @@ xfs_inode_free(
> ASSERT(!spin_is_locked(&ip->i_flags_lock));
> ASSERT(completion_done(&ip->i_flush));
>
> - kmem_zone_free(xfs_inode_zone, ip);
> + call_rcu((struct rcu_head *)&VFS_I(ip)->i_dentry, __xfs_inode_free);
> }
>
> /*
> --
> 1.7.2.3
>
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