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    Subject[PATCH 3.10 38/70] NFSv4: Fix races between nfs_remove_bad_delegation() and delegation return
    Date
    3.10-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Trond Myklebust <trond.myklebust@primarydata.com>

    commit 869f9dfa4d6d57b79e0afc3af14772c2a023eeb1 upstream.

    Any attempt to call nfs_remove_bad_delegation() while a delegation is being
    returned is currently a no-op. This means that we can end up looping
    forever in nfs_end_delegation_return() if something causes the delegation
    to be revoked.
    This patch adds a mechanism whereby the state recovery code can communicate
    to the delegation return code that the delegation is no longer valid and
    that it should not be used when reclaiming state.
    It also changes the return value for nfs4_handle_delegation_recall_error()
    to ensure that nfs_end_delegation_return() does not reattempt the lock
    reclaim before state recovery is done.

    http://lkml.kernel.org/r/CAN-5tyHwG=Cn2Q9KsHWadewjpTTy_K26ee+UnSvHvG4192p-Xw@mail.gmail.com
    Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/nfs/delegation.c | 23 +++++++++++++++++++++--
    fs/nfs/delegation.h | 1 +
    fs/nfs/nfs4proc.c | 2 +-
    3 files changed, 23 insertions(+), 3 deletions(-)

    --- a/fs/nfs/delegation.c
    +++ b/fs/nfs/delegation.c
    @@ -177,7 +177,11 @@ static int nfs_do_return_delegation(stru
    {
    int res = 0;

    - res = nfs4_proc_delegreturn(inode, delegation->cred, &delegation->stateid, issync);
    + if (!test_bit(NFS_DELEGATION_REVOKED, &delegation->flags))
    + res = nfs4_proc_delegreturn(inode,
    + delegation->cred,
    + &delegation->stateid,
    + issync);
    nfs_free_delegation(delegation);
    return res;
    }
    @@ -363,11 +367,13 @@ static int nfs_end_delegation_return(str
    {
    struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
    struct nfs_inode *nfsi = NFS_I(inode);
    - int err;
    + int err = 0;

    if (delegation == NULL)
    return 0;
    do {
    + if (test_bit(NFS_DELEGATION_REVOKED, &delegation->flags))
    + break;
    err = nfs_delegation_claim_opens(inode, &delegation->stateid);
    if (!issync || err != -EAGAIN)
    break;
    @@ -588,10 +594,23 @@ static void nfs_client_mark_return_unuse
    rcu_read_unlock();
    }

    +static void nfs_revoke_delegation(struct inode *inode)
    +{
    + struct nfs_delegation *delegation;
    + rcu_read_lock();
    + delegation = rcu_dereference(NFS_I(inode)->delegation);
    + if (delegation != NULL) {
    + set_bit(NFS_DELEGATION_REVOKED, &delegation->flags);
    + nfs_mark_return_delegation(NFS_SERVER(inode), delegation);
    + }
    + rcu_read_unlock();
    +}
    +
    void nfs_remove_bad_delegation(struct inode *inode)
    {
    struct nfs_delegation *delegation;

    + nfs_revoke_delegation(inode);
    delegation = nfs_inode_detach_delegation(inode);
    if (delegation) {
    nfs_inode_find_state_and_recover(inode, &delegation->stateid);
    --- a/fs/nfs/delegation.h
    +++ b/fs/nfs/delegation.h
    @@ -31,6 +31,7 @@ enum {
    NFS_DELEGATION_RETURN_IF_CLOSED,
    NFS_DELEGATION_REFERENCED,
    NFS_DELEGATION_RETURNING,
    + NFS_DELEGATION_REVOKED,
    };

    int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct nfs_openres *res);
    --- a/fs/nfs/nfs4proc.c
    +++ b/fs/nfs/nfs4proc.c
    @@ -1416,7 +1416,7 @@ static int nfs4_handle_delegation_recall
    nfs_inode_find_state_and_recover(state->inode,
    stateid);
    nfs4_schedule_stateid_recovery(server, state);
    - return 0;
    + return -EAGAIN;
    case -NFS4ERR_DELAY:
    case -NFS4ERR_GRACE:
    set_bit(NFS_DELEGATED_STATE, &state->flags);



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