On Tue, Apr 20, 2010 at 11:26:08AM +0100, David Howells wrote:
> From: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
>
> Ensure that we correctly rcu-dereference the delegation itself, and that we
> protect against removal while we're changing the contents.
I queued both of these, thank you Trond and David!
Trond, if you would rather carry these in your tree, please let me know.
Thanx, Paul
> Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> ---
>
> fs/nfs/delegation.c | 42 ++++++++++++++++++++++++++++--------------
> 1 files changed, 28 insertions(+), 14 deletions(-)
>
> diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
> index 1567124..8d9ec49 100644
> --- a/fs/nfs/delegation.c
> +++ b/fs/nfs/delegation.c
> @@ -129,21 +129,35 @@ again:
> */
> void nfs_inode_reclaim_delegation(struct inode *inode, struct rpc_cred *cred, struct nfs_openres *res)
> {
> - struct nfs_delegation *delegation = NFS_I(inode)->delegation;
> - struct rpc_cred *oldcred;
> + struct nfs_delegation *delegation;
> + struct rpc_cred *oldcred = NULL;
>
> - if (delegation == NULL)
> - return;
> - memcpy(delegation->stateid.data, res->delegation.data,
> - sizeof(delegation->stateid.data));
> - delegation->type = res->delegation_type;
> - delegation->maxsize = res->maxsize;
> - oldcred = delegation->cred;
> - delegation->cred = get_rpccred(cred);
> - clear_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags);
> - NFS_I(inode)->delegation_state = delegation->type;
> - smp_wmb();
> - put_rpccred(oldcred);
> + rcu_read_lock();
> + delegation = rcu_dereference(NFS_I(inode)->delegation);
> + if (delegation != NULL) {
> + spin_lock(&delegation->lock);
> + if (delegation->inode != NULL) {
> + memcpy(delegation->stateid.data, res->delegation.data,
> + sizeof(delegation->stateid.data));
> + delegation->type = res->delegation_type;
> + delegation->maxsize = res->maxsize;
> + oldcred = delegation->cred;
> + delegation->cred = get_rpccred(cred);
> + clear_bit(NFS_DELEGATION_NEED_RECLAIM,
> + &delegation->flags);
> + NFS_I(inode)->delegation_state = delegation->type;
> + spin_unlock(&delegation->lock);
> + put_rpccred(oldcred);
> + rcu_read_unlock();
> + } else {
> + /* We appear to have raced with a delegation return. */
> + spin_unlock(&delegation->lock);
> + rcu_read_unlock();
> + nfs_inode_set_delegation(inode, cred, res);
> + }
> + } else {
> + rcu_read_unlock();
> + }
> }
>
> static int nfs_do_return_delegation(struct inode *inode, struct nfs_delegation *delegation, int issync)
>
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